USRE16279E - Separating process - Google Patents

Description

March 2 1926.

R- ELLIS SEPARATING PROCESS Original Filed April 15 gnvc'nroz @ida'clale Z7 Reissued Mar. 2, 19 26. Re.

UNITED S A ES PATENT OFFICE.

nmsnaLEnLLIs, or our Pang, ILLINOIS, ASSIGNOR T ELLIS FLOTATION COMPANY,

' IINQ, or NEW YORK, N. Y9, A CORPORATION or NEW YORK.-

snrannrme rnocnssori inal application filed April 15, 1918, Serial No. 228,623. Divided and application filed 11ml 2, 1919, Serial N0. 287,080. Original No, 1,425,186, datedAugustB, 1922. Application for reissue filed Augult 1, 1924. Serial No. 729,623. i 1

To all whom it may concern: in general to enhance the efliciency of con- Be it known that I, RIDSDALE ELLIS, a citicentrating processesas hitherto carried out zen of the United States, and a resident of to increase the percentage extraction and Oak Park, in the county of Cook and State rate of separation of the metalliferous conof Illinois, have invented certain new and stituents; to improve the grade of concenuseful Improvements in Separating-Proctratei and in particular to improve froth esses, of which the following is a spccificaflotation processes for the concentration of tion. ores and similar comminuted materials of My invention relates to processes for condlv rs h r h v i Q centrating "parts of masses of composite To thisend my invention contemplates character, such as metalliferous' ore, by the use of electrol tes of various types and t tin th in t d mass ith fl id the modification o the flotation processesas adapte to aid inthe separation of certain o ly ea e u o ena e the e fiof the comminuted particles from others @1111 1 1 f ch ele trolytes to be more 15 having difierent qualities. fully obtained This application is adivision ofmy co- Th effect. produced by electrolytes may di li atio s ial, N 228,623, fil d be conveniently classified according as they April 15, 1918, and a continuation in part of are due P r ly physical phenomenon or m ospending application Serial No, 75,430 to chemical reactions in which the electrofiled January 31, 1916. v j v lytcs added react chemically or electrochem- Broadly my i ntio i l d th use f ically with the constituents of the ore.

. means for p'roducin certain changes in the h p y q l action of electrolytes, more fl id d th -ti es f th mass h b particularly inorganic electrolytes, appears the se aration of certain of the comminuted to be dep ndent upon the v alence (and to a 25 t-i f th h i ldifi nt' hlesser extent on the. mob lity) of the ions ties is aided.' Preferably such means include P P l the S0111ti011 0f the electrolytes the use of substances adapted when dissolved n p g fluid and is conseq y e "in fluid, preferablyan. ionizing fluid, to bring tl'lcal ll about certain electrical changes, and to this I ve found that the eSu Q physb so 30 end to give polyvalent ion fo idi i cal. action may be modified bychanging the th ti f -mi f th rti l time of additlon of the electrolytes. Thus from others b means or a fluid having a 08113111 types 0 lectr lytes glYe improved preferential a ity'for'certain 'of-the. parresults en added p o o g and 1 9 other types better results when added after 35 More particularly, in its preferrcd form', g I l my invention relates to. processes for con There IS 3 yp a relatlon centrating metalliferous ores b means of. we -t phy l nq h 9- the combined action of gaseous ubbles and lytes f the slze of the P -1 Y oil, or other substances soluble or insoluble, W e effects produced by electrolytes adapted to aid in the formation of a froth of various types are readily demonstrable containing the metalliferous constituents of t c e of these eifeets s fa e co the ore. plex.

My invention is articularly adapted for In order, however, that the invention may the concentration 0 sulphide ores,- but is also be more fully understood I give a statement 45 applicable to the concentration of other ores, of the general principles underlying the forsuch as oxides, carbonates or hydroxides, mation of a froth and theactionof electroeitherunchanged-or after a sulpliiding or lytes in aiding or hindering the separation other treatment, native or precipitated copof metalliferous' matter by froth flotation per, gold, and for they concentration of processes. Y Y I 50 gra. bite and other similar materials. I Practice carried out by me has shown that fiie principal objects of my invention are results obtained by the use of electrolytes vary considerably according to the way in wh ch the gaseous bubbles are introduced to form a froth. Bubbles may be introduced in two general waysz-In the first place, the bubbles may be forced in fromwithout, and

secondly, the bubbles of gas may be generto involve both methods of introduction in varying degrees. The vortex of water roduced by the rapidly rotating prope lers draws into the ore pulp infinitesimally thin films of air which break up into minute air bubbles. As these minute air bubbles have a much higher solution tension than larger air bubbles, the water becomes supersaturated so far as bubble formation on a sulphide or oil surface is concerned and as a result air comes out ofsolution on the surface of the oiled sulphide particles. The result of the violent mechanical agitation is therefore two-fold, first, the introduction of air bubbles bodily from the external air and second, the generation of air bubbles ab initio on the surface of the oiled particles of sulphide; I

In the pneumatic agitation process the generation of bubbles in the pulp does not ap ear to takeplace to any great extent.

n' the formation of a froth where liquid oil is used, there appear to be two important operations, first the coating of the metalliferous particles with oil andsecond, the

formation ofa viscous bond between such oiled particles and the gaseous bubbles.

In these operations electrolytes may act in four amongst other-ways First in determining the readiness with which the oil can come into physical contact with the particles of sulphide.

Second in changing the readiness with which the oilafter contact with the particles of sulphide will spread over the surface of the latter and the tenacity with which the oil adheres to the sulphide surfaces.

Third in determin ng the readiness with which the gaseous bubbles can come into physical contact withthe oiled particles of sul hide,

ourth .in changing the readiness with which the oil after contact with the gaseous bubbles will spread over the surface of the latter.

The changes produced by electrolytes in any one or-more of. the above ways may be the result of either:

(a) Changesin the electrical conditions;

the particles to'be floated; Y

(6) Changes in surface tension due to ab' sorption of the electrolyte at theoll water,

(1;) Chemical changes at the surface of negligible and this is confir'm ed' by'the fact 7 that where the action of electrolytes does not follow certain laws based on the valency or number of electrical charges carried by thevions formed by the solution of the elec trolytes the deviation from these laws may be attributed in most, if-not 'all,instan.ces-, to chemical action between the electrolyte and the constituents of the ore.

With the majority of ores the most important function of electrolytes ,in aiding,

flotation appears to be the production of favorable electrical conditions.

In this respect it is not the molecules of the electrolyte which are active but the ions produced by the dissociation of the electrolyte when dissolved in an ionizing fluid such as water. i

All electrolytes, whether salts acids or alkalies, when dissolved in an ionizing fluid produce ions to an extent depending upon the degree of dissociationof the electrolyte.

The valence of these ions may range from one to six and possibly, though not probably, even seven or more.-

The simplest combination of ions is M R where M. represents the cation or positive ion and R represents the anion or negative acid radicle ion. Now the valence of the cation or anion may each be increased separately or the valence of both may be increased simultaneously. These three changes may be represented graphically as follows:

As the valence of the ions increases their effect on the contact and frictional electrification of the oil, sulphide and gangue particles and. gaseous bubbles also increases, whether the ions are positive or negative, and these changes in the sign and magnitude of the electrification of the constituents of the ore pulp produce verymarked results in the formation of a froth and the separation of the metalliferous'ma'tter by such-means.

Solid or liquid particles of all kinds acquire a contact otential when suspended in pure water of rom 0.03 to 0.06 volts, the

particles being almost invariably (with the exception of oxides, hydroxides and some carbonates) negative with respect to the water. Gases, on the other hand, may be electrified in at least two different ways which are essentially distinct :first, fric tional electrification, and second, contact electrification. It air 'is blown thrrugh water it becomes electrically charged by friction with the water, and electricity may be collected from the air and also from the water. The potential of the water may reach several volts. If a bubble of air is in stationary contact with. Water, it acquires a contact potential of the same magnitude as that acquired by solid or liquiddrops suspended in water, namely, 0.03 to 0.06 volts.

In contact electrificationthe conversion of the original negative charge on a particle suspended in water (whether solid, liquid or gaseous) into a positive charge is brought about by means of polyvalent cations; thehigher the valence of the cations, the'smaller the concentration of the electrolyte required to bring about the reversal, and the greater the positive charge which can be produced thereby. 'If a polyvalent anion is present, the concentration required to produce reversal is increased, and also .the maximum positive chargewhich can be obtained is reduced. This inhibiting action of the anion increases as the valenceincreases. On the other hand, the original negative charge may be increased by p'olyvalent anions; the higher the valence of the anion the greater the increase in the negative charge which can be produced. Cations inhibit this increase in-negative charge in proportion to their valence.

In frictional electrification the valence of the ions appears to have exactly the-reverse efiect to what they have in contact electrification. In order to produce a strong posi-' tive charge polyvalent anions must be used.

The greater the valence of the anion, thesmaller the concentration required to pro duce reversal, and the greater the positive charged which is produced- Polyvalent ca tions have an exactly analogous efiect to polyvalent anions in the case of contact electrification as they increase the concen-' tration of 'polyvalent anions required to bring about the reversal, and the eflect of cations in this respect increases as the valence increases.

, While the spreading of a drop of oil over a sulphide or similar surface is no doubt .due .to differences in surface tension at the oil-water, oil-particle, and water-particle the oil must-first be brought into actual physical contact with the sulphide particle before it can spread. Now it is the electrical factors which; largely determine whether or .not such. physical contact takes place readily or diflicultly. U

In pure water an oil globule is strongly charged negatively, a sulphide particle very weakly negatively. Under these conditions there is a slight electrical repulsion; add a salt of the type of sodium pyrophosphate and the negative charge on both oil globule and sulphide particle will be increased so that the electrical repulsion is also increased. On the other hand if a small amount of acid is added the potential of the sulphide becomes positive; While reducing but not reversing the negative potential on the oil,

under these circumstances electrical attracoil and sulphide it will inhibit oiling, just as acid aids oiling by reversing the sign of the charge onthe sulphide.

Although any anion, particularly a high valent ion, tends to change the contact po tential of any solid or-liquid particles suspended inzan :ionizing fluid in the same direction there is a great difference in the natural tendency of various substances to acqulre and retain a negative or positive charge. Thus oil is' normally strongly negatively charged and a much higher concentration of acid is required to neutralize and reverse this charge than in the case of the much more weakly negatively charged sulphide particles.

Further with salts of the type of sodium pyrophosphate the negative contact potential of oil, sulphide and other substances in-. creases to *a maximum and then decreases and the position of this maximum point depends on the chemical nature of the substance. With oil this point is reached with a higher concentration of salt than with either sulphides or silica or silicates...

If'a salt is used which is adapted to give anions and cations both having a relatively high valence, such as aluminum pyrophosphate it is possible to. give the-sulphides a positive charge without (reducing the negative potential of the oil tothe same extent as when acid only is used to give the sulphides a positive charge. As oil acquires and retains ,a negative charge much more readily than do sulphides, a trivalent cation like aluminum has a much greater efiect on the sulphides than on the oil, while at the same time the quadrivale'nt pyrophosphate ion has amuch greater etfect on the oilthan on thesulphides.

In general, the higher the valence of the ions, the greater the electrical changes which can be produced and the greater the (litterences which can'be made betw een the electriis not the most eflicient type for oiling. Such a salt may, however, be used in relatively high concentrations to'take advantage of the diiference in the maximum potential points of oil and sulphide respectively. Further, a

- salt adapted to give both high valent cations and anions may be used to reverse the sign of the potential on the sulphides Without lowering the negative potential on the oil to the same extent as the acid alone. Again, oiling may be caused to take'place in plain water or acidified waterand the sodium pyrophosphate or similar salt addedafter oiling and immedi'ately'prior to flotation.

Delaying the'time of addition. of the sodium'pyrophosphate does not entirely eliminate its inhibiting efiect on the oiling forthe reason thatin the mechanical agitation process, and to a much smaller'extentin the pneumatic agitation process, the oiling, is in part at least, a reversible operation, possessing therefore a position of equilibrlum. With mechanical agitation, therefore, the fact that the oil originally adhered to the sulphides is not suflicient and it is desirable, if possible, that conditions during flotation should be as favorable as possible for reoiling.

. The greater the affinity of oil for the metalliferous particles the more tenaciously will the oil adhere once it has been brought into contact with the particles and the more irreversible will the operation become.

The. aflinity, of oil for sulphide parti: cles may be changed by salts, usually to reduce the adhesions (employed in preferential flotation) but in some cases to increase it. Such changes appear to be due to chemical rather than electrical causes.

The difference betwen the cnemical and the electrical action of sal 's is well illustrated by the action of potassium i'errocvanide on the flotation of copper ores; In neutral solutions this salt acts as a powerful poison ferrocyanide on the surfaces of the sulphide particles. .On the other handwith 'an alkaline solution of the same salt verv beneficial results are obtained since in the presence of alkali insoluble copper ,ferrocyanide is not produced so that the beneficial action of the qua'drivalent anion is obtained.

Copper sulphate has a very marked chemical action. With zinc ores its use is very beneficial, with pyrite ores it is deleterious. lVith zinc ores it is more beneficial than the valency of the ions it forms would warrant and while copper sulphate and acid under certain circumstances appear to be more efficient than either alumlnum or sod um pyrophosphate and acid, a combination of the latter salts with acid and copper sulphate gives better results than copper sulphate and acid alone. v v

The next factor tobe considered isthe air-sulphide adhesion. At the first momentof adhesion-between the oiled sulphide particleand an air bubble there must be actual physical contactirrespective of the condi:

tionswhich occur afterwards.

of oil vapor process) and the sulphides receive their oil irom'the air bubbles.

(3) Both sulphides and air bubbles are oiled independently. The first of these is the method used in circulating mechanical agitation apparatus in which oil is added in liquid form. v a I As already indicated, a salt of the type vof sodium pyrophosphate gives the oil an increased negative charge and. the air a strong frictional positive charge (dependent upon the rate of movement of the air rela-J tively to the water) thereby producing an attraction between the oiled sulphide parv ticles and the bubbles of air.

The effectis to bring the air and oiled sulphide particles into contactmore rapidly and certainly, and thereby increase not only the extraction but also'the rate of separation, as is shown by actual practice to be the case.

As the negative potential of silica and silicates is also increased by a salt of the type of sodium'pyrophosphate, an increase in the amount of gangue floated would also be expected. Practice shows this to be the case.

If frictional electrification is an impor--' tant feature then sodium pyrophosphate will give higher extractions with the mechanical than with the pneumatic agitation process. owing to the much more Violent agitation in he former than in the latter case. This is also confirmed by practice. owing to th formation of insoluble copper present insolution, and at the same timegives the watera charge-of opposite sign. Now when polyvalent anions are present, the charge so produced on the water is of the same sign as that 'on' the metalliferous particles which it is desired to unite to the bubbles of gas and consequently it is desirable to get rid of the charge on the water as it.

appears to have a repellant action on the similarly charged metalliferous particles which prevents the union of these particles with bubbles of gas.- -I have found that the charge maybe advantageously eliminated,

preferably by ground-in the flotation ap aratus so as to connect t e water electriczfily with the earth.

I have also found that the action of electrolytes is greatly modified by the size of the particles in the ore pulp. With relatively cosirsefeed-say 8O to'lOO meshthe addition of sodium 'pyrophosphate even before oiling. greatly increases the extraction whereas with slimes thea-ddition of this salt before oiling may even decrease the extraction. i

This is due to the-fact that the smaller the particles the more important'become the electrical factors'in oiling;

In the pneumatic agitation process. unlike the mechanical agitation process, Iliave found that salts of the types of thorium chloride or aluminum pyro' hosphate' are,

under some conditions, distinctly deleteri='- ous, whereas a salt of the type of sodium pyrophosph'ate is very useful though not producing .as advantageous resultsv as in the mechanical agitation process. Further, while acidaids the action of salts in mechanical agitation alkali is preferably used in the pneumatic agitation process. There appear to be various reasons' for this difference between, the mechanical and pneumatic agitation processes.

Thus a reduction of the negative potential of the oiled sulphides is particularlydele terious inthe pneumatic agitation process as much less frictional electricity is generated on the air than in the mechanical agitation process, owing to the less violent agitation. This isdue to the fact that while the sign of" the charge on the air depends upon the ions present in solution, its magni- 'tude is largely dependent upon the speed at which the air bubbles are moved through the solution.'

Then the production of conditions advans tageous tooiling are more important .in the mechanical than in the. pneumatic agitation -proccss and such conditions are aided by acid or polyvalent cations. I

Further in the'mechanical a itation process some generation of gas bub les ab initio on the surface of the oiled'sulphides occurs.

The acquisition of a positive charge appears.

to favor the formation ofa bubble ab 'initio in water since it hasbeen shown that bubbles of gas are oftemif not, usually, positively ficharged when they have beengenerated I from a solution which would not give a posibubble. formation. [i5

tive charge to a bubble of gas introduced bodily'from'an external source. I

Apparently, therefore, hydrogen or high Forcarrying out my invention apparatus of well known types, may employedwitli such modifications in construction and arrangements as may be needed toenable my improvements to be employed to best advantage. As flotation apparatus of the type roposed for use with my salts'andv other improvements are so well known. to those skilled in the art detailed description will be unnecessary. Consequently in the accom panying drawing. I have given only a diagrammaticillustration of one construction and arrangement adapted'for carrying out my improvements.

In the draw ngs launder 2. -Oil and such reagents as may be employed to aid flotation and in particular theoiling of the metalliferous particles, for

2 example an acid solution containing such a quantity of sulphuric acid and aluminum or titanium pyrophosphate that the pulp containing the slimes after separationfrom the sands will contain in the case of copper sulphide ores about 4 lbs. of acid per .ton of 'drv slime ore (for an are which normally ,re-

, clamifier 6. As the ore is ordinarily. ground with a much smaller amount of water than.

is used for flotation the additional amount of water may conveniently be addedto the pulp in the classifier. vided -with an. inclined bottom 7 up which the sands which settle out are moved by means of rakes (not shown) until they pass over the lip or weir 8 into the pipe 9. At" the opposite end of the classifier an overflow lip or weir 43 is provided at a lower level than the lip 8 so that, the water in the classifier carrying the slime material in suspension will all flow over the lip 43' while the rakes in moving the sands over the lip will lift them out of the water and deliver them to the pipe 9 very largely dewatered. By

this arrangement the electrolytes employed in aiding oiling, which are more especially useful in the flotation of slimes, are removed from the sands and retained in the slimes.

The slimes pass from .the lip 43 into a. .pipe 10' which discharges into the agitation chamber 11 of a" machine which may conveniently be of the, mechanical agitation type. further additional quantities pyrophosphate, may be added or titanium v by means of pipe 12. In the agitation cham- 1' represents. the tube mill I towhich ore is fed by means of a chute or so the tube mill by means of 95 and oiled ore passes from the This classifier is pro- As the pulp flows into the pipe 10 of reagents, such for example as a solution of aluminum valent. cations are useful as either directly. or, indirectly providing positive nuclei for aerated ore pulp passes through the aperture I 15 into the spitzkasten 16 in which the bubmachine for retreatment.

bles of air carrying metalli-ferous particles form a layer of froth 17 while the sands fall soluble 'frothing agent. For this purpose the upper part of the agitation chamber 11 and spitzkasten 16 are enclosed by a-cover 21 at opposite ends of which pipes 22 and 23 are provided for ingress and egress of air carrying a frothing agent such as oil vapor.

Preferably the'machine just described is" employed merely. as a roughing cell and'the;

concentrates discharged by pipe are. re-

treated in a cleaning cell, as 24.

With most ores this cleaner cell 24 is preferably of the Callow or pneumatic agitation type having a porous bottom 25 through which air may be blown from pipe 26. This air may, if desired, be charged with a frothing agent such as oil vapor. To allow the unutilized ortions of the oil vapor to be conserved t e upper part of the cell is enclosed at 27 so that the air liberated by the breaking of the bubbles in the froth may be led away by pipe 28 for reintroduction through the'pipe 26 with such further additions of air and (or) oil vapor as may be required v As the concentrates only contain a small percentage of water additional water may be introduced into the cell 24 by means of pipe 36. The froth flows over weirs into launders along each sideof the cell in the usual way and the concentrates, and any froth'which' does not break down in the launders, passes out through the pipe'29.

The flow of the tails into the pipe 30 is controlled by a valve 31 operated in wellknown way by a float 32. These cleaner; tails contain considerable quantities of:

metalliferous matter and so they are preferably returned to the rougher cell by substantial means such as a centrifugal pump 33.

and pipe 34. The cells, particularly the rougher cell, are preferably electrically grounded in any suitable way as illustrated iagrammatically-at 35. I

The sand may conveniently be treated by a similar arrangement of mechanical agitation rougher and pneumatic agitation cleaner cells to those employed for treating the slimes, and in the drawing the same reference letters are used for corresponding parts in the two sets of cells.

'tothe sands and to sirable alkalinity.

than of slimesfor the reason that the sands are substantially dewatered by,the classifier and. fur-v ther, the tails are readil sands settle quickly. facilitate the operation of the rougher and dewatered as the cleaner cells on a closed cycle sofar as the circuit water is' concerned. This is particularly-advantageous with sand slnce for hese facts greatly particles of large size relatively large quantities of a salt of the t pe of sodium pyrophosphate is'employe for aidin in the in the ores,- In many cases it is desirable that oiling take place in acidified water.

production of a collective float of t 1e values a and flotation in alkaline water and the dcwatering of the sands by the'classifier r'educes the amount of alkali required to new tralize the acid'in the waterstill adhering. give the water 'the de- For copper sulphide ores a convenient concentration of 'sodium 6 lbs. per 'tonof ore andizf desired free alkali ma amount o alkali, such assodium hydroxide, may conveniently range from 0.01 to 0.2 lbs. per ton of ore in 'excess-ofthat required to neutralize any acid .adhering'to the particles of owes the i leave the classifier.

In the first p ace, ing-the tails from the pipe 18 to the tailing pond. they may to advantage betransferred to a settling cone 37, from, which the circuit water may be drawn off and returned to the system by pipe 38, centri-fugal pump 39 and pipe 40. A portion of'the circuit water passing throu h the pipe 40 may conveniently be iverted by pipe 41 to the cleaner cell 24. With this" arrangement flotation take place in the same solution in both rougher andcleaner cells. Additional quantities of water, salt and (or) alkali may be supplied as required byp p or purpose of illustration I give in detail the results of practice with a process of'the'mechanical agitation froth type.

The amounts of electrolyte employed are given merely as examples of concentrations found suitable for certain ores, since, as is wellknown to those skilled in the' art, the exact proportions of those substances which may be used in flotation processes vary somewhat according to the nature of the ore treated.

Asit is usually more convenient addth'e be considered first.

In the following examples of=-practice.

carried'out by' me the ore employed 'Was a be employed in addition. The I instead of dischargpyrophosphate is i cupriferous pyrite ore which contained about 42% of sulphide of iron and copper in a gangue of quartz and slate. v The ore was ground to pass 80 mesh and was therefore relatively coarse as compared with the slimes used in other practice which.

will bereferred to later.

For emulsification or oiling prior to fiotationseparation the ground ore was mechanically agitated with three times its weight of water, 0.3% to 0.4% of its weight of oil, and the desired quantity of electrolyte. The percentages of electrolytes used are based on the ore and not on the water. I

Using salts of a monovalent acid, i ..'e. hydrochloric acid, I 'io'undthat the highest recoveries were obtained with the following and still more so than that obta ned with sodium chloride, and, further,- the difference 'aluminum' chlori concentrations Aluminum phosphate percentages of sodium chloride, calcium chloride and aluminumchloride (each used alone without acid) respectively:' Sodium: chloride, NaCl 0. 40%

Calcium chloride,- CaGl 0. 27% Aluminum chloride, AlCl v0. 06%

This table clearlyshows that the higher the valence of the cation the smaller the quantity of salt required to give the best results for that particular salt. It'was-iu-rther found that not only didthe amount of salt required decrease as the valence of the cation increased, but also theamount of sulphide floated increased as the valence. of the cation increased. The froth obtained with aluminum chloride was not only thicker, but

also. much firmer, finer andcleaner than.

the froth obtained with calcium' chloride,

between thejfl'oats obtained with aluminum chloride andcalcium chloride, respectively,

was much. greater than between. calcium chloride and sodium. chloride, respectively;

articular, orequse'd, the

However, for the separation "of sulphides, even in the case of e tained with sulplniric acid both-as regards quantity and quality of concentrate.

-.Using salts of a trivalent metal with acid radicles of diflerent valence,.the highest recoveries were obtained with the following Aluminum chloride A1o1, 'AIPO, (small amount acid added to make salts soluble) Aluminum pyrophosphate Al;

(P 0 (small amount acid added to make salts soluble); 0.

Here again the efliciency of separation 'im proved as the valence increased.

Using salts-of a monovalent metal w th acid radicles or diiference valence, the high- ;Sodium chloride NaCl was inferior to that 019- est recoveries were obtained with the following concentrations a 0. 10% Sodium phosphate Na PO;(above) 0. 064% Sodium pyrophosphate Na P O, 0.016%

With'both sodium and aluminum salts increasing the valence of'th'e anion not only decreases the amount of salts required to produce the best results,but also increases the efiiciency of separation. It will be ob-" served that the smallest concentrations were obtained when the valence of both the ca'- tions and anionswas the greatest, namely,- when aluminum with sodium pyrophosphate was used. v I

In connection with sodium pyrophosphate I'have found that there are two'points of maximum extraction, one about 0.016% and theother above 0.3%. The contact potential ofoil steadily rises to a maximum obtained with concentration of sodium pyro phosphate above 0.3% so that the existence of the first maximum 'oint is probably due ifiiculty with which;

to the fact that-the oiling of the sulphide particles can occur Increases to a maximum and then decreases ,as the concentration of sodium pyrophos .phate is increased from zero to 0.3%. the two p oints of maximum extraction the higher concentration has been found by practice to be the most eflicient, and'this is probably due to the fact-that not only, is.

the contact potential on the oil much greater, which means that the oiled sulphide particles willhave a more .tion-for the positively (irictlona-lly) charged air, but also because at the higher concen tration the difliculty oi oiling appears to be less than at the lower concentration.

Using sulphuric acid alone, the best rcowerful'attrae I sults were obtainedfwith'a concentration of lVhemhowever, mixture of salts and acid were used it was foundthat the amount oi acid which would give the bcs't. results in h conjunction with the .salts was approximately one-half that required when acid alone was used in the case-of salts; adapted to give trivalcntions, either positive or neg- I ative, or both'positive and negative, as will 'be seen from the table given below, In the case of saltsadapted to give quadrivalcnt ions, either negative or positive, itywa's I found that the amount of acid could be ad-I vantageously increased-beyond this amount (i. e. 0.060%) For instance, with titanium sulphate, increasing the concentration of acid up to 0.74%,gave a steadily increasing wield, so that the best results would be'obtained with the evenhigh'er' concentration of acid than that just referred to. Similarly with sodium pyrophosphate, the best resultswere obtained with a concentration of acid inexcessof 1%. v

1 Hiso, (above) When the valence of both cation and anion are. increased above two the amount of acid which can be usefully employed falls ofl' below 0.60%. The figures for the best concentration of the salt and acid, res ectively, ineach case are given in the fol owing table 0.74% H 80 (above) 1.00%

It will be seen that in each, of the above acidand salt mixtures there is a relatively much greater number of hydrogen ions than polyvalent ions produced by the dissociation of the salt, whether such ions are positive or negative.

In the above practice, both with and without acid, salts were used in the absence of heat and of material, such as bichromates adapted to inhibit flotation of certain sulphides. p

I have further found that anacid solution of sodium yrophosphate+0.3% Na P O, and 1.00% S0,,gives better results than the above acidsolution of sodium pyrophosphate, namely :-0.016% Na P O and 1.00% N SO It was found that the aluminum pyrophosphate either aluminum chloride or titanium sulphate. With most ores neutral sodium pyrophosphate gave higher extractions than aluminum pyrophosphate, and in ractically all cases a. strongly acid solution of sodium-pyrophosphate give much better results than either neutral sodium pyrophosphate or aluminum pyrophosphate.

I Conse uently it appears that of the foregoing so utions the one generally. most efficient for the mechanical agitation process is a strongly acid solution of sodium pyrophosphate.

Such a solution not only increases the extraction but also raises the grade of concentrate, shortens the time required for the flotation treatment and, especially where low pulp densities have been used to permit large amounts of oil to be 'used efficiently, enables higher pulp densities to be employed.

The ore employed in the foregoing practice was ground to pass 80 mesh but if the ore is ground to pass 200 mesh the results are markedly changed.

.the sands or larger ther use.

ave higher extractions than Ordinarily the finer the ore is ground the more readily it fioats but when a salt of the This difference is much more marked with zinc ores than with copper ores, doubtless due to the smaller afiinity of oil for blende than for sulphidesof copper.

Preferably, therefore, prior to flotation treatment the ore is classified in order that articles may be'oiled and floated in a di erent electrolyte than the slimes or fine particles. For the sands the electrolyte may be of the ty' e specially adapted to aid the flotation of t e particles when oiled, e. g. sodium pyrophosphate. In the case of the slimes the electrolyte may be of the type specially adapted to aid the oiling of the particles, eg. an acid solution of aluminum pyrophosphate.

This classification treatment has the further advantage thatitfacilitates' the recovery of the sodium pyrophosphate for fur- It is comparatively easy to dewater sands as they settle rapidly and can be. readily separated from water by means of drainage belts or the like. Slimes, on the other hand, require much longer time to settle and more careful treatment to separate the water. I

The amount of aluminum pyrophosphate required is so much smaller than the quantity of sodium pyrophosphate needed to.

give best results that the (la-watering of the slimes is not nearly as important as the dewatering of the sands.

In addition to classifying theoi'e according to size of particle I have found it useful with certain ores toemploy mechanical agitation rougher cells in combination with pneumatic agitation cleaners.

In practice using a low grade copper ore v ground with-oil and floated in the presence of 6 lbs. of sodiumpyrophosphate by the mechanical agitation process an extraction of 97.5% was obtained with a concentrate weighing 25% of the original feed. On the otherhand, using the pneumatic agitation -process and the same amount of such salt,

the extraction was only 93% instead of 97.5%, but the concentrate only weighed 16% of the original feed instead of 25%.

Accordingly, I propose to employ the two rocesses in con 'unct1on in order to comine the good eatures of each. I have found that the above concentrationof such salt gives very beneficial results in both forms of process so that the same solution mitly be used in both rougher and cleaner ce s..

Further, I may employ sodium pyrophosphate or other salt merely to improve the grade of concentrate. Thus in the case of zinc ores the beneficial effect of" sodium or aluminum pyrophosphate on the grade of concentrate may be as important as the effect of-these salts in increasing the extraction.

In practice with zinc ores I have found that a salt such as copper sulphate having a beneficial chemical or electrochemical action should be employed in addition to acid and pyrophosphate, whether sodium or aluminum.

The concentrations of sodium 'pyrophosphate found most beneficial with zinc ores appear to be very considerably lower than in the case of copper and other ores.

WVith relatively coarse feed a change in the time of addition has only a slight effect on the extraction. This was shown in the flotation of a copper ore assaying 1.00% Cu ground'16% on 80 mesh.

\Vhen the ore and oilwere both ground and subsequently floated in the presence of 0.10% Na,P,O., solution (on the water) the tails assayed 0.11% instead of 0.88% when ground with plain water and then floated in a solution of sodium pyrophosphate of that strength. The same ore, both ground and floated in plain water, gave a tail containing 0.25% Cu.

W'ith smaller concentrations of salt the effect is more pronounced. For instance, with a 0.003% solution (on the water) of Na,,P,O on a sample of ore assaying 1.92% Cu, the tails assayed 0.55% Cu when the salt was added prior to grinding and 0.42% Cu when the salt wasadded after grinding as compared with 0.47% Cu' for plain water. This is probably due to the maximum negative potential or the sulphides beingreached in much lower concentrations than 0.10% sodium pyrophosphate. If this is the case, then in a 0.10% solution, the negative potential of the sulphide will be brought to a value approaching zero.

The effect of changing the time of addition of'the sodium pyroph-osphate is much more marked in the case of slime-s.

In the case of a copper ore slime assaying about 0.92% Cu using acid alone (H SO 7 lbs. per ton) the tails contained 0.07% Cu.

When sodium pyrophosphate (10 lbs. per ton) Was added with the acid prior to oiling the copper in, the tails increased to 0.13% but when-added after oiling (acid added before oiling) it decreased .to 0.045%. This change in the time of addition also increased "the ade of rougher concentratefrom 8% Cu to 17% Cu as well. as very materially hastening the rate of separation.

As the addition of alkali to a solution containing a salt of the type of sodium pyrophosphate greatly aids the latter in increasing the negative charge on the oil I may, especially after oiling 1n acidified solution, make the solution alkaline by the addition of caustic alkali simultaneously with the introduction of sodium pyrophosphate. Caustic alkali in very small concentrations (up to' about 0.001 normal) itself increases the negative potential of oil as well as increasing the amount of high valent anions produced by the dissociation of the sodium pyrophosphate. I

The use of various salts adapted to give high valent ions has been referred to, and in particular, sodium-and aluminum pyrophosphates. Other similar salts might be. used although these two appear to be the most readily available.

As in general the anion appears to be more importantthan the cation the available salts capable of giving anions-having a high valence will be considered first.

As examples of hexavalent anions the tetraphosphates such as Na P O and hexametaphosphates such as Na P O may be referred to. As instances of salts capable of giving quadrivalent anions may be mentioned the pyrophosphates such as Na,P O,, ferrocyanides such as K Fe(CN) pyroai-senates such as Na As O and pyroantimonates such as I ,Sb O,. trivalent anions phosphates such as Na PO ferricyanides such as K FefllN). or arsenates Na Aso might be used.

If valence were the only factor to be considered the tetraphosphates and hexametaphosphates would be superior to salts which give quadrivalent or trivalent anions. However, another, almost equally important factor is the extent to which the salt and the corresponding acid dissociates, as this determines the number of high valent anions furnished by a given amount of salt. Any.

polybasic acid or salt of such acid dissomates in stages. In other words, cat ons are of negative ions of increasing valence. For instance yrophosphoric acid (11 F 0 dissociates tain number of which then split up'to form H P O," ions, a certain number ofwhich split up to form HP,O.,"' ions, a num-' ber of which split up to form P,O.,"" ions. The dissociation constants of the first, second, third and fourth hydrogen ions of pyrophosphoric acid are respectively 1.4 10' 1.1X10' 2.9 1O' and 3.6X10' Consequently the amount I of quadrivalent P,O ion formed is much less'than the amount of the trivalent ion, which in turn is very much less than the amount of the divalent ion which in turn is less than the amount of the monovalent ion. The first given off progressively with the formation rst to form H P 'O; ions, a cer-' and second dissociation constants are less tion constant for the first, second and third hydrogen ions being 1.1 10', 2X10 and Comparing these constants with those for pirophosphoric acid it will be seen that p QSPl'lOIlC, acid only gives as many monovalent ions as pyrophosphoric ac1d gives divalent and as many divalent as the latter ives trivalent ions. Consequently even t ough pyrophosphoric acid dld not give a quadrivalent ion while phosphoric acid can only give a trivalent 1on pyrophosphoric acid would be much superior to phosphoric acid on account of the much larger number of diand trivalent ions it gives on dis sociation.

The dissociation of the acid corresponding to the salt added is very impo tant since, particularly when the electrolyte is added prior tooiling, acidified solutions in general give better results than neutral so lutions. Especially after oiling, and this, of course, includes the cleaning of rougher concentrates, the solution may to advantage be made slightly alkaline. .Not only do hydroxyl ions tend to increase the negative charge on the oil but also the addition.

of alkali greatly increases the concentration of high valent anions.

This latter effect results from the fact thatthe product of the concentrations of the hydrogen and hydroxyl ions is always 10'.

In a solution containing only 0.05% of sulphuric acid the hydrogen ion concentration (assuming complete dissociation is 1X10. In a solution containing 0.05% of sodium hydroxide the hydroxyl ion concentration (assuming complete dissociation) is 12x10" so that the hydrogen ionv concentration will be less than 10*.

The change from acid to alkaline solution involves a change of hydrogen ion concentration from 1X10 to .-1 1O which will result in greatly increasing the dissociation of the H P O,", HPQO, and similar ions.

In view of the importance of the hydrogen ion concentration and the dissociation constants of the first, second, etc., hydrogen ions of. .the acid corresponding to the salt used it is usually advisable to employ salts of inorganic acids in preference to those of organic acids as the dissociation of the acids formed in the presence of sulphuric acid is much greater in the case of inorganic acids than of organic acids.

Relatively little is known of tetraphosphoric acid, but the fact that it has been found that over ten times the amount of sodium tetraphosphate is needed to produce the same efiect on flotation as a given amount of sodium pyrophosphate indicates that the salt and acid dissociate far less cnnpletely than do the pyrophosphates.

Ferroc 'anic acid is a strong acid and its salts 'suc as potassium ferrocyamde glve very good results in flotation where the formation of insoluble ferrocyanides can be avoided. 'In' view, however, of the fact that pyrophosphoric acid does not readily form injurious insoluble compounds its use is ordinarily to be preferred.

So far as trivalent salts are concerned, these would be superior to pyrophosphates only if they dissociated to an unheard of degree. Phosphates have been shown to be far inferior to pyrophosphates and prob-.

ably the same is true of the arsenates.

The ferricyanides 'are .in general open to the same objection as the .ferrocyanides namely the formation of insoluble compounds'which poison flotation.

'Itappears therefore that the pyrophosphates are the most suitable source of high valent anions for flotation. Sodium pyrophosphate, which appears to be the most generally usefulpyrophosphate can be very cheaply and easily prepared from the common' phosphate of soda of commerce (Na i-IP0 by simply heating it to drive oil water. a

Since in connection with some ores and slime material in-particular it may be found advisable to use a salt adapted to give cat1ons and anions, both of high valence, the availability of suitable high valent cations will be considered.

\Vhile in the case of polyvalent anions the dissociation constants. of the corresponding acid appears to be one of the most important factors, in the case of polyvalent cation the mobilityfof the ions appears to be a very important factor. For instance, the, aluminum ion has a greater mobility than the ferric ion, and it isfound that aluminum salts are much more'-eifective in flotation than are ferric salts. For instance when ferric sulphate was used in conjunction with acid, the best results were obtained with a concentration of 0.16% of the salt as compared with 0.060% of aluminum sulphate. This difference between the mobility of the aluminum and the ferric ions is in part if not entirely due to the smal er atomic ing to the kinetic theory the velocity of movement of the ions in solution is inweight of the aluminum ion, sin: e accordversely proportional to the square root of their masses, consequently since the atomic Weight-of aluminum is 27 and that of iron is 56, We should expect a greater mobility of the aluminum as compared with iron which is exactly the case.

However, the atomic weight is not the only, and in some cases not even the principal factor which determines the mobility of the ion. This is due to the fact that practically all ions are hydrated to a greater or less extent. For instance, the hydrogen ion has two waters of hydration, the ot-assium ion averages 9.6 water of hydration, while the lithium ion has 24 waters of hydration. This attached water has, of course, the efiect of slowing up the action of the ions in solution, so that whereas the hydrogen ion with an atomic Weight of 1 has a mobility of 318, and the potassium ion with an atomic weight of 39, a mobility of 65.3 the lithium ion with an atomic weight of 7, has a mobility of only 33.4. Other things being equal, therefore, ions havin a high mobility should be selected in pre erence to those having a, low mobility.

Aluminum has an atomic weight smaller than any other tri-valent metal, and since with the exception of iron its salts are cheaper than those of other trivalent metals, its salts are particularly suitable for use in flotation.

There are a number of metals which under certain conditions are quadrivalent, the most common being titanium and tin. Some of the rare earth metals also give quadrivalent cations, such as germanium, thorium, vanadium, uranium and zirconium. Of all these metals the cheapest is titanium, since the oxide, rutile or ilmenite is found in considerable quantities. Titanium has also the smallest atomic weight as its atomic weight is only 48 as compared with 118 for tin and 230 for thorium. Titanium sul hate producin only a divalent anion was ound to be in erior to aluminum plyrophosphate and when titanium pyrophosp ate was prepared it was found to be largely'colloidal in character, so that, although therorctically it should be superior to aluminum Cpyrophosphate, the number of positive an negative quadrivalent ions produced was apparently not suflicient to enable it to give superior result to aluminum pyrophosphate. The pyrophosphate of other quadrivalent metals might possibly be used to advantage if their cost is not prohibitive.

There are also a number of metals which form pentavalent salts, the principal of these being tungsten. This metal is also hexavalent under certain conditions. However, man of these salts do not ap ear to exist in t e presence of water, at' east to any appreciable extent. For instance tungsten pentachloride on treatment with large quantities of water is at once decomposed almost entirely into blue oxide W 0 and hydrochloric acid with the evolution of heat. 1

, While I have referred to the employment of o'ilas a frothing agent, I may use a soluble organic frothing agent such as amyl alcohol either alone or in conjunction with oil. I

Further, although oleic acid and similar fat acids and resinous acids might be use I prefer not to employ such substancesas are capable of forming insoluble compounds with the aluminum or other similar salts used for aiding flotation.

With certain ores the use of an organic frothing agent may be wholly dispensed with and av froth formed by the aid of inorganic material, more particularly salts of the type of sodium pyrophos hate.

Although in the foregoing, escription of actual-practice air only was employed in other ractice carried out by me other gases have een employed and in particular air with additions of readily condcnsable gases. As a general rule, the readiness with which a gas will condense upon'a surface depends on the ease with which the gas can be liquefied. For instance, carbon dioxide condenses to a greater extent on a sulphide surface than does air for the reason that-the critical temperature of carbon dioxide is same series. Further, in place'of oil vapor,

I may use the vapor of a soluble organic compound such as amyI alcoholw.

Such oil or, vapor may be employed either in substitution for or in-addition to the use of oil in the liquid state or the introduction of a soluble organic frothing agent independently of the air or other gas required to operate the process.

Electrolytes are preferably added to the ore pulp to aidthe separation of the metalliferous constituents vapor is used.

I claim: 7 1. The process of concentrating ores which includes mixing the comminuted 'ore with oil in the resence of an acid, then when such frothing aerating the so-oi ed o're pulp to form a oollective froth and se aratmg the froth from' the remainder by ther' includes the addition subsequent to the oiling treatment of material adapted to otation' and which -furchange the contact potential of the oil-to a.

potential more negative than before for aiding the formation of a collective froth.

2. The process of concentrating ores which includes mixing the oomminuted. ore with oil in the presence of material adapted to change the contact potential of the articles of ore to a potential more ositive than before, then aerating the so-oiled ore pulp to form a collective froth, and separating the froth from the remainder by fiota tion and which further includes the addition Y f .two for aiding the-iormationof afroth.

iroth v ,7 J

3.1 of concentrating ores which ,inc-ludes'imixing the comminutedl ore andwhich -further'includes aci ifying the ore'pri or lto oiling and the addition withwateuand an oily liquid, aerating the mixture tojiorm a froth, and se aratingf thejiroth fro'm the remainder b otation,

si lbsequent topiliugof material adapted to 'educ'e the: hydrogen 1 ion concentration and to give anions having. a greater .valenceith'an 4. The pron-42$.) of concentratingflores which;includes-"mixing the comminute'd. ore

Z ticles, thenfa erating the-mixture to form a with, wa'ter'and an oily liquid in the presence of acid: to ;oiI, =the metalliferous' parfroth. andeeparating the froth from the remainder. by flotation, andzwhich .further I includesithe additionint'ermediate the oiling and aeration treatments offsodium' pyrophosphate. --g f5. The process of concentrating ores which includes mixin the comminuted ore ,with water and an oi y liquid,- aeratlng the mixture to'form a'fi'oth and-5e 'arating the froth'from' the remainder by otation and which furtlienincludes acidifying the ore [pulp prior to oiling andthe addition of .a' froth'. 6. Theprocess of concentratlng oreswhich alkali intermediate the oiling and aeration treatments includesmixing the comminuted ore with water and an oily li uid in thepresence of acid to. coat the meta liferous particles with ".oil', then adding an electrolyte adapted to give highervalent anions than cations to aidin theflotation'of the particles so oiled,

subsequently aerating the mixture to form a froth and separating the froth from the remainder by flotation.

7; The, process of concentrating comminuted masses of composite character which" includes the treatment of the mass .withan ionizing liquid and a as, said liquid con taining in solution substances adapted to I .from those of different characterto a; v

- tional electrical charge on the gas and which change the contact potential of the constitucuts of the composlte mass to be separated tential more negative than before and a apted simultaneously to produce ajpositive fricfurther includes the movement of the gas relatively to the liq'uid and the substantial elimination of the electric charge produced on the liquid by suchmovement.

8. The process of separating composite comminuted masses which includes a preliminary flotation treatment by mechanical agitation, separation of the froth produced for aiding-in the formation of by such agitation and a secondary recleaning flotation treatment of such froth by fluid a solution adapted to change-the contact pressure agitation,and .whichfurther ineludes-the usein each agitation treatment of potentialof the valuable constituents of the {fore 9. The process of concentrating commi- 'nuted masses of composite character which includes the treatment of the mass with an ionizing; liquid and a as, said.- liquid cont'ro th to a-potential more negative than betaining in solution su tances adapted to produce an electrical charge on the gas otopposite sign to that on the constituents of the composite mass to-be separated from those of different character, and which further includes'the movement of the gas relatively to theliquid and the substantial elimination of the electric charge produced on the liquid by such movement.

10. The process ofconcentrating commiincludes the treatment of the mass with an .ionizin-gliquid and a gas, said li uid contaming in solution negative 10I1S 1B,V1Ilg a valence greater than two, said gas having an electrical charge of opposite slgn to that on theconstituents of the com site mass to be separated from those of di erent character, and which further includes the movement of the gas relatively to the liquid and the substantial elimination of the electric charge produced on the liquid by such movement.

11. The process of concentrating comminuted masses of composite character which includes the treatment of the mass with an ionizing liquid and a. gas, said liquid containing in solution negative ions having a valence greater than three, said gas having an electrical charge of opposite sign to that on the constituents of the composite mass to be separated from those of diflerent character, and which furtherincludes the movement of thegas relatively to the liquid and the substantial elimination of the electric charge produced on-the liquid by such movenent.

12. The processiof concentrating composice, comminuted masses of composite character which includes the treatment ofvthe mass'with a gaseous fluid adapted to aid in the movement of certain of the comminuted particles relative to others having diflferent qualities, and which further includes the use of a solution containing a salt of pyrophosnuted'masses of composite character which. I

, violent mechanical agitation whereby thesulphide particles are separated "from the gauge the substantial absence of violent mechani cal agitation whereby' certain of h com-f minuted particles fare jseparate.d from others having different qualities. I,

14. The process of concentrating sulphide ores which comprises mixing the comm nuted ore with oil and a solution containing anions havinga'valeiice' greater than three and passing bubbles of airupwardly; through the mixture in the substantial a sence of 15. The proce s of concentrating sulphide ores which comprises mixing the comminuted ore withvoil and a solution containing anions having a valence reater than three and passing a gaseous flui through the mix ture in the substantial absence of violent mechanical agitation whereby the sulphide particles are separated from the particles of v gangue.

16. The process of concentrating comminuted' masses of com osite character which comprises the formation of a non-permanent froth by mixing the mass w th an ionizing liquid, and passing bubbles of gas through the mixture to form a relatively non-permanent froth with certain of the comminuted particles having a preferential affinity for such gas bubbles and separating the froth so formed from the remainder of the ore, and which further includes the use of anions having a valence greater than three for-increasin the said preferential aflinity.

17. e rocess of which inclu es mixing the comminuted ore with oil, then aerating the oiled pulp, forin-- se arating theing a collective both and froth from the remainder by otation, and which further includes the addition subsequent to the oiling treatment of material adapted to change the contact potential of oil to apotential-more-negative than before for aiding in the formation of said collective froth. I

18. 'The process of concentrating ores which includes mixing the comminuted ore with oil, then aerating the oiled pulp, forming a collective froth and se arating the froth from the remainder by otation, and which further includes the addition subsequent to the oiling treatment. of alkali for aiding in' the formation of said collective froth. r p

19. The process of concentrating ores which includes mixing the comminuted ore with oil, then aeratin the oiled pulp, forma collective frot and se arating the froth from the remainder by otation, and which further includes the addition subsequent to the oiling treatment of alkaline material adapted to give hydroxyl' ions and anions having a greater valence than one with oil, then aerating the oiled pulp, form-' 'ing a collective froth'and separating the terial adapted to give hydroxyl ions and concentrating" ores for aiding in" the formation of said collective froth.

.20. The process of concentrating ores which includes mixingthe comminuted. ore

froth from the remainder by otation, and

which' further. includes the addition subsequent to the oilingtreatment of alkaline maanions having a greater valence'than two 76 for aiding in the formation of said-collective froth. I i I 21. The process of concentratingores by 1 flotation which includes mixing the ore wit a inodifyingagent, aerating-to form a collective froth and separating the froth from the remainder by flotation, and which further includes the addition of alkali under such conditions-as to aid in the formation of said collective froth without inhibiting the coating of the metalliferous particles of said ore by the modifying agent.

22. The process of concentrating ores b flotation which includes mixing the ore with a modifying agent, aerating to form a collective froth and separating the frothfrom the remainder by flotation, and which further includes the I addition of alkaline material adapted to give hydroxyl ions and anions having a greater valence than one, under such conditions as to aid in the formation of said collective froth without inhibitin the coating of the metallif'erous particles 0 said ore by the modifying agent. 4 23. Theprocess of concentrating commi nuted masses of composite character which includes the'treatment of the mass with an ionizing liquid and agas, said liquid containing in solution substances including hydroxyl ions in excess of those produced by hydrolysis'and adapted to change the contact potential of the constituents of thecomposite mass to be separated from those of different character to a potential more nega: tive than before and adapted simultaneously to produce apositive frictional electrical charge on the gas, and which further includes the movement of the gas relatively to the liquid and the substantia elimination-of the electric charge produced on the liquid by such movement.

24. The process of concentrating comminuted masses of composite character which includes the treatment of the mass with an ionizing liquid and a gas, said liquid containing in solution added substances includin the salt of a weak polybasic acid and by oxyl ions in excess of those produced by hydrolysis and adapted to change the contact potential of the constituents of the composite mass to be separated from those of different character to a. potential more negative than before and adapted simultaneously to produce a positive frictional electrical charge on the gas, and which further includes the movement of the gas relatively to the liquid and the substantial elimination of the electric charge pro duced on the liquid by such movement.

25. The process of concentrating comminuted masses of composite character which includes the treatment of the mass with an ionizing liquid and a gas, said liquid containing in solution substances including anions having a valence greater than two and hydroxyl ions in excess of those produced by hydrolysis and adapted to change the contact potential of the constituents of the composite mass to be separated from those of different character to a potential more negative than before and adapted simultaneously to produce a positive frictional electrical charge on the gas,

and which further includes the movement of the gas relatively to the liquid and the substantial elimination of the electric charge produced on the liquid by such movement.

26. The process of concentrating ores by flotation which includes mixing the ore with a modifying agent, aerating to form a froth and separating the froth from the remainder by flotation, and which further includes the use of an added salt of a weak polybasic acid and hydroxyl ions in excess of those produced by hydrolysis for aiding in the formation of the froth.

27. The process of concentrating ores by flotation which includes mixing the ore with a modifying agent, aerating to form a froth and separating the froth from the remainder by flotation, and which further includes the use of an added salt of a polybasic acid. and hydroxyl ions in excess of those producedby hydrolysis for aiding in the formation of the froth.

28. The process ,of concentrating ores by flotation which includes mixing the ore with a modifying agent, aerating to form a froth and separating the froth from the remainder by flotation, and which further includes the use of anions having a valence greater than two and hydroxyl ions in excess of those produced by hydrolysis for aiding in the formation of the froth. I

In testimony whereof I hereunto aifix my signature.

RIDSDALE ELLIS.

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