US1298552A - Process of bleaching. - Google Patents

Description

CA'HON OF TEXTILES & FIBERS,

Concenfraflon in Millirnols per li'i'erQzndGramspcrhTer) G. ORNSTEIN.

PROCESS OF BLEACHING.

APPLICATION FILED use. 2. l9|6- Patented Mar. 25,1919.

60 7O 80 90 IOO Far cen'l" Hydrolyzed v INVENTOR;

4;, 'A TTORNEY cATToN OF TEXTILES & FIBERS,

uNrTEn STATES PATENT OFFICE.

GEORG ORNSTEIN, OF NEW YORK, N. Y., ASSIGNOB, TO ELECTRO BLEACHING GAS COMPANY, A CORPORATION OF NEW YORK.

PROCESS OF BLEAGI-IING.

Specification of Letters Patent. Patented 11 25, 1919,

Application filed December 2, 1916. Serial No. 134,749.

To all whom it may concern.-

Be it known that I, GEoRe ORNSTEIN, a citizen of the German Empire, residing at New York city, in the county of New Xork and State of New York, have invented certain new and useful Improvements in Processes of Bleaching, fully described and represented in the following specification and the accompanying drawings, forming a part of the same.

This invention relates to processes of bleaching; and it comprises a method of bleaching organic materials, such as animal and vegetable fibrous materials, and materials derived therefrom such as paper, cloth, pyroxylin, recovered viscose, etc.; wherein the bleaching is efiected by the immediate use of a solution of hypochlorous acid produced by introducing chlorin into water under conditions which result in substantially complete hydrolysis of the chlorin so that corrosive or attacking action of the chlorin as such on the material is prevented, all as more fully hereinafter set forth and as claimed.

Chlorin in various forms has been used in bleaching for a very long time. But the direct introduction of free chlorin into the bleaching solution was quickly abandoned in favor of bleaching preparations made by absorbing free chlorin in caustic alkalis, such as lime, producing the commonly used bleaching powder. This was for the reason that the action of free chlorin was considered too violent, irregular and uncontrollable. In contact with organic matter, such as that composing vegetable fibers, chlorin exerts many actions which should be avoided in bleaching. nate it), break it up into other things, or destroy it altogether. The bleacher wants no action on his material other than removal of coloring matters which may be present; he does not want his fiber changed in any way; and in particular, it must not be so attacked as to lose strength or be tendered.

The principle on which bleaching depends is that the organic bodies which constitute the coloring matters present with the fiber are in general more sensitive and attackable than the organic bodies (or carbon compounds) which constitute the fiber itself; and the bleachers problem is to provide means which will attack and. destroy the one, while not in any way affecting the other,

It may combine with it (chlori- Therefore, the violently acting chlorin solutions which had been tried were early substantially abandoned in favor of solutions of the more mildly acting hypochlorites produced by taking up chlorin by alkaline material such as lime and soda. Ghlorin is now used directly practically only in cases where it is desired to remove incrusting substances present with the fiber as well as to bleach the fiber.

In the ordinary bleaching operations with bleaching powder or neutral hypochlorites, the active bleaching agent is H001, the hypochlorites having no material bleaching action. Some HOCl is first liberated by the introduction of an acid, and as in the bleaching action the HOCl loses O which is takenu in the oxidation of the coloring matters, 1 Cl is formed and the H01 thus furnished sets free more HOCl, and so on.

In the present invention, while HOCl is the active bleaching agent, the intermediate ste of forming hypochlorites from chlorin an then using such hypochlorites to form the bleaching solution is avoided, and the HOCl is produced as and when wanted by the direct introduction of chlorin into water under conditions such that the hydrolysis of the chlorin is substantially complete, that is, substantially all of the chlorin introduced in the water disappears as such with the production of HOCl "and HCl.

I have discovered that the attacking or corrosive action of chlorin in a solution of chlorin and water and the bleaching action of such a solution are by no means correlated, and that a solution may be produced by introducing chlorin directly into water which has practically no corrosive action, while the bleaching action is nevertheless highly effective. The advantage of a bleaching process founded on this discovery is obvious since it renders practical the direct use of chlorin as it comes from the generating apparatus or in the convenient commercial form of liquid chlorin without the annoyance, cost and inconvenience of an intermediate production of hypochlorites such as bleaching powder. And where the liquid chlorin is used, the operation is also made more exact and economical by reason of the ease with which the amount of chlorin used may be measured or weighed.

In its practical aspect, my invention comprises forming a bleaching solution simply extent it reacts with the water to form hy-' drochloric acid and hypochlorous acid in the sense of the following reversible or equilibrium react1on:

With suflicient water, the reaction will go entirely to the right, the chlorin as such dis- 15 appearing, being wholly hydrolyzed into hydrochloric and hypochlorous acids. WVith less water, the hydrolytic products tend to react upon each other'and limit the movement of the reaction to the right, that is, limit the disappearance of chlorin as such and the production of the hydrolytic acids.

I find that by increasing the dilution of a chlorin solution sufliciently to cause substantially all the chlorin to disappear, as such,

by conversion into its acid hydrolytic products, say, until 98 or 99 per cent. or more of the chlorin is so hydrolyzed, a solution is obtained which, while highly effective as a bleaching agent, has no harmful corrosive or attacking action on vegetable fiber. The

particular point of dilution where the corrosive action so disappears as to make the liquor practically non-corr0sive while still highly effective in bleaching, depends, to some extent, upon the particular fiber or fibrous material and on the coloring matters present, but as a general rule I aim not to leave unhydrolyzed more than one or two per cent. of the chlorin as a maximum. In

these dilutions, the two hydrolytic acids,

HCl and HOCl, can coexist to an extent impossible at less dilutions; or, in other words, the HCl does not destroy the E001 with formation of chlorin and the solution is permanent in this respect. And being acid with HCl, hypochlorites cannot form, and the main cause of instability is removed; that is, the reaction by which hypochlorites and free hypochlorous acid tend to form ehlorates with loss of bleaching power. The

highly dilute acid solutions used under the present invention are therefore relatively stable and permanent; being sufiiciently so to allow of use in bleaching with high utilization of chlorin.

The accompanying drawing illustrates diagrammatically by curves the influence of dilution on the hydrolysis of chlorin. In this diagram, or curve sheet, points on the ordinate represent the concentration in millemols (and in parenthesis, in grams) of added chlorin per liter of water, and points on the abscissa represent the percentage of the added chlorin which is hydrolyzed, the

first curve being based on results with the water at 0 0., the-next one with the water at 13.4: C., and so on as the curve lines are marked. As the diagrams shows, the hydrolysis increases with temperature as well as with dilution.

Since the degree of hydrolysis of chlorin with a given amount of water increases rapidly with an increase of temperature, any dilution shown by the first curve, which is for 0 (1, which would be safe at that low temperature would be safe at the higher temperatures used in actual bleaching practice. An increase in temperature will always increase the degree of hydrolysis with a given amount of water. Ordinarily I work with the bleaching solution at ordinary room temperatures or at the usual water supply temperature, but in some rather stubborn cases I have found that more satisfactory results both in quickness and quality of bleaching are secured by increasing the temperature of the bleaching solution, and I have found it best in some cases to have the temperature as high as 80 or C. The use of a solution which is too concentrated must be guarded 90 against even when hydrolysis is substantially complete since the bleaching effect of HOCl is well developed even in extremely weak solutions, while in stronger solutions both H001 and HCl exercise some tendering effect on vegetable fiber.

\Vhile the theories of the a1ti0n of HOCl in bleaching vary somewhat, the net result of the action is that HOCl loses O, which is taken up in the oxidation of the coloring matters, and HCl is formed; that is, as the bleaching action goes on there is a development of HCl, which is added to that formed in the hydrolysis of the chlorin. This affords another reason for workin at high 5 dilutions, thereby keeping the H61 concentration low.

The particular manner of introducing the chlorin into the water to produce the bleaching solution, is not of prime importance. Ordinarily, I first dissolve chlorin in water, using the commercial liquid chlorin, or any other suitable source of chlorin, to form a solution which may be of greater or less strength, even up to that of a saturated so lution. In this solution some of the chlorin is hydrolyzed and some remains as dissolved free chlorin. This solution is then mixed rapidly with the larger amount of water, usually in the presence of the material to be bleached, the total amount of water being suflicient to cause substantially all the chlorin to be hydrolyzed. as before stated. And I consider it most desirable, ordinarily, to produce the preliminary stronger solution by passing the chlorin into a tower against a flow of water. In operating in this way, the amount of chlorin passed into the tower to be taken up by the flowing water is readily controlled and measured, so that any e tAcHTNs & erase; am TREATMENT & CHEMICAL MODTFT. 1

CATION OF TEXTILES & FIBERS,

desired amount may be introduced. into the bleaching vessel. A solution so formed is most desirably fed directly from the absorption tower into the water containing the material to be bleached in the bleaching vessel, the chlorin being thus introduced into the main body of water gradually and progressively and at such a rate that it may continue during a greater or less part of the bleaching operation. In operating in this way, the whole amount of hypochlorous acid will never be present at any one time in the solution, but more is formed progressively as that previously formed is used up in the bleaching operation. This permits of the use of a lesser amount of water, but it should be observed that because of the development of HCl from the E001 in the bleaching operation, the HCl concentration in the bleaching solution tends to increase, and as too great a concentration of HCl in the solution might have the effect of limiting the hydrolysis, it is desirable always to use a sufficient excess amount of water to avoid this result, unless some other expedient is resorted to, to prevent the accumulation of or increase in concentration of HCl in the solution. Instead of introducing the chlorin in the form of a relatively strong solution into the bleaching vessel, it may be introduced into the water in the vessel containing the material to be bleached as a gas, care being taken to secure a rapid distribution of the chlorin by suitable active circulation in the bleaching vessel, in whichever way it is introduced. Even though this distribution takes place in the presence of the material to be bleached, no harmful action results, since the hydrolysis, although requiring a certain time, is reasonably quick,quicker than the attacking action.

So, also, instead of introducing the chlorin, either as a gas or in a relatively strong solution, into the bleaching vessel in the presence of the material to be bleached, so

that a part or all of the hydrolysisv and production of H001 takes place in the actual physical presence of the material, the solution in its final dilution with substantially complete hydrolysis of the chlorin, may be formed away from the bleaching vessel, provided that it is used in the bleaching operation substantially at the time of its formation, this being of importance for the reason that HOCl solutions are not very stable. Of course, loss of HOCl in the solution is not a matter of absolute time, but also depends somewhat on conditions. For example, if the solution is kept in a closed vessel and light excluded, the loss of H001 will be retarded and substantially all of the introduced chlorin will remain in the solution in the form of IIOCl or P101 and its salts for a longer time. By using the solution for bleaching at the time, or substantially at the.

time, of its formation, or while it contains substantially all the introduced chlorin in the form of HOCl or HCl and its salts, I am enabled to make most efficient use of the chlorin, substantially all of the HOCl which the introduced chlorin is capableof supplying being utilized in the bleaching operation. This follows from what has been hereinbefore explained, and for the reason that the bleaching operation, although it takes some time, is relatively quicker than the possible reactions which might result in the loss of 11001 in a solution of the character of that used in the present invention.

Solutions of H001 are much more stable in the absence of any neutral hypochlorites. In the present invention where the hydrolytic products of chlorin are used in their natural state, hypochlorites cannot of course be present, all hypochlorites being at once broken up by HCl. Where hypochlorous acid and hypochlorites coexist in the same solution, a reaction sets in whereby chloric acid or chlorates, as the case may be, are developed at the expense of the E001 and the hypochlorite. Since chlorates and chloric acid have no bleaching power their formation represents a waste; a waste which has been more or less inevitable in the methv ods of bleaching now in use. In the present invention this source of loss does not exist; partly because the bleaching liquor is always acid and partly because it is used too rapidly to permit formation of chlorates. The chlorate reaction is one which requires a relatively long time. This non-formation of chlorates in the present invention is probably one of the main reasons for the great economy in operation which it displays.

After bleaching, the goods may be treated with the usual antichlores and given such other treatment as may be desired.

In its broader aspect, I regard the present invention as covering the bleaching of organic materials by HOCl produced directly from chlorin and utilized as fast, or substantially as fast, as formed for the bleaching action; the conditions of production being such as to obviate the presence of any substantial amount of chlorin as such or of hydrochlorite. That is, whatever these conditions may be, they are such as to cause a substantially complete conversion of the chlorin with its disappearance as such. In this conversion of the chlorin, as shown in the reversible equation hereinbefore given, half the chlorin becomes HOCl, which is a useful body in bleaching, while the other half forms HCl which has little or no direct utility. And while I have hereinbefore more specifically described this conversion of chlorin as-eifected by extreme dilution, a dilution such that there is enough water present to allow conversion of substantially allthe chlorin into its acid hydrolytic products,

HCl and IIOCl, producing a bleaching liquor which is acid in its nature, yet I wish it to be understood that extreme dilution is notthe only expedient or condition which may be used. As stated, I regard my invention, considered broadly, as covering any way of bleaching organic materials with HOCl pro duced directly from chlorin and in the substantial absence of chlorin as such. And in such production the liquor need not be necessa-rily acid in the sense of containing free I-ICl; it may be substantially neutral, or partly acid. In this connection, it may be noted that while HOCl is technically an acid, since it will combine with bases, yet it is actually hardly acid in its nature at all; it will only combine with a few bases. On the other hand, I-ICl is one of the strongest acids known and combines with all bases, and is taken up by many bodies, such as sulfate of soda which are not strictly basic bodies.

When chlorin is brought into the presence of water and of a base, hydrolysis or conversion may be made complete in the presence of a relatively small amount of water, for the base is converted into a chlorid, no free I-ICl being formed, and the reaction is enabled to go' entirely to the right. It is only the presence of tree HCl together with HOCl which. tends to drive the equilibrium of the reaction to the left. If the base is one which combines with both HCl and H001, the amount used and the circumstances of addition of base, should be such as to neutralize only the HCl, or a portion thereof. There are only a few bases which will combine with HOCl. Most of the basic bodies will combine with HCl but not with HOCl; and any of these latter bases may be used in any quantity which may be desired, great or little, without neutralizing the HOCl. I may therefore within the limits of the present invention use bases of any kind provided that the amount or nature of such base shall be such as to prevent any substantial neutralization of, or combination with, the HOCl Which is the active agent in my bleaching process. As stated, in the present invention I am bleaching with HOCl produced from chlorin without the intermediate production of hypochlorites as is done in the usual methods of bleaching, as hereinbefore outlined.

For example, I may pass chlorin into water in the presence of calcium carbonate (chalk), or zinc white (zinc carbonate), and the goods to be bleached. Under these circumstances the HCl is taken up by the basic body as fast as it is formed while the I-IOCl is unaffected. Or I may add chlorin, or

'chlorin Water, to the bleaching vessel as a slow stream and simultaneously introduce a slow stream of water containing a dissolved or suspended base. For example, I may lead in chloriii thus, and may at the same time introduce water carrying suspended calcium carbonate. I may so use bases which could combine with HOCl on condition that no more, or substantially no more, of the base is used than is necessary to combine withthe I-ICl as it is produced. Here, again, the HOCl is unaffected by the base.

I do not, however, in the present case claim specifically the embodiments of my invention wherein a base is employed to neutralize I-ICl; these embodiments being more particularly described and specifically claimed in another and co-pending application Serial No. 13%,748, filed December 2, 1916. In the present case I present broad claims to bleaching with free HOCl directly produced from chlorin and in the substantial absence of chlorin itself, while more specifically I claim bleaching with the acid liquid produced by using chlorin in connection with sufficient water to cause substantially complete hydrolysis of the chlorin; that is, a liquid containing substantially all of the tree HCl formed from the chlorin.

In the case of many materials to be bleached. as with rag pulp made by the soda process, the material may contain a noticeable amount of alkali. In the practical operation of the present process, however, this residual alkali, if present, simply combines with some of the H01 produced in the hydrolysis of the chlorin and does not otherwise afi'ect the process. The quantity of alkali even in soda pulp is rarely enough to neutralize all the HCl formed in hydrolysis of the chlorin used in bleaching. Where its quantity is too great the material may be treated with a little acid.

Irrespective whether alkali be present in the material to be treated or not, and as stated it is rarely present in any large amount, I consider my invention as herein claimed as covering any process wherein bleaching is effected by the direct use of chlorin in the presence of water sufiicient in amount under the existing conditions to preclude any substantial amount of chlorin remaining as such. The invention in a narrow aspect contemplates the direct introduction of chlorin, as gas, or dissolved in water, into the presence of the goods to be bleached and in the presence of sufficient water; the conditions being such as to preclude chlorin remaining in the free state. In so far as any small amount of alkali is present in the goods to be bleached, it simply reinforces the converting action of the water. It is obvious that the method of preparing the hypochlorous acid bleaching liquor by bringing together in a continuous or continuing manner regulated amounts of chlorin and absorbing liquor may be employed with any absorbing liquor, whether containing water without any base or water with bases which do not aitect HOCl,

uLLfluuuru u:. u l LIHQU, ILUIU but is most important, if not necessary, with bases which will combine with and might neutralize the H001. This particular method is claimed specifically in my copending application Serial No. 134,829, filed December 4, 1916.

In the bleaching action of HOCl, hydrochloric acid may be formed, HOCl losing 0 and becoming HCl. In the specific claims in this case, I do not mean to include only this HCl, which may be called secondary HCl, as the acid of the said liquor; but in tend to cover also what may be called the primary I-ICl; the HCl which is produced in the direct hydrolysis of the chlorin; that is, bleaching with a substantially unneutralized dilute solution of chlorin in water.

For most materials I find. that at ordinary temperatures a bleaching solution representing a ratio of about 0.1 gram of chlorin to the liter (a ratio of 1:10,000) is effectively strong for bleaching and has no substantial corrosive properties. This ratio of course is that of the added chlorin to the actual liquor in the bleaching vessel. IVhere a chlorin solution is used for adding the chlorin to the chlorin vessel, its strength may be, and usually is, much greater than this, but it is diluted by the liquor in the vat. Such a bleaching solution will contain only about one per cent. of the chlorin added as such. For many purposes, even weaker solutions containing a still less proportion of unhydrolyzed chlorin are desirable. A solution containing chlorin and water in the ratio of 20 milligrams of chlorin to a liter (a ratio of 1:50,000) is amply strong for many bleaching purposes. and in such a solution the chlorin is hydrolyzed to an extent of about 99.9 per cent, only about 0.1 per cent. remaining as such. In this dilution, there is no corrosive action due to chlorin, while the HOCl and HCl are in such low concentration that no effect by either on the fiber is to be feared. The action of H001 is purelv that of bleaching.

Where gaseous chlorin, either from an electrolytic cell, or from a container of the commercial liquid chlorin, is introduced directly into the bleaching vessel, in order to insure quick dilution and the prevention of local over-concentration of the solution, it is best to introduce it as very minute bubbles under the surface of the liquid, such liquid of course being in active circulation. Such minute distribution may be easily effected by using porous plates of one kind or another. Those made from fritted kieselguhr or alundum are cheap, convenient and suitable. Baked porous clay diaphragms may be employed.

In a specific embodiment of the present invention in bleaching rag paper pulp, a saturated chlorin water was made in an absorption tower and the chlorin water thus prepared was gradually run into a heater, introduction extending over a period of 1% hours, the beater containing paper pulp equivalent to about 500 pounds of dry material and a quantity of water equivalent to about 9.500 gallons. The amount of chlorin and water so added as saturated solution corresponded to about 6 milligrams of chlorin per liter of the final amount of liquid in the beater. The paper pulp was bleached as well as it could be with bleaching powder or better and was apparently not in any way tendered or weakened, while the total consumption of chlorin for effective bleaching was about 30 per cent. less than was necessary for the same degree of bleaching with chlorin used in the form of bleaching powder.

In the employment of the present invention it is best to use measured or weighed quantities of chlorin calculated on the amount of water in the bleaching vessel. This gives a more accurately controlled operation than possible in other ways. However, it is found that after a period of use of this process the workmen are able to approximate to some extent the safe limits by the odor of the bleaching liquor. In the presence of any substantial amount of unhydrolyzed chlorin the odor of the chlorin is noticeable. Within safe limits of operation, only the rather different sweetish smell of hypochlorous acid is noticeable. A more delicate test is afforded by leading a current of ammonia vapor into proximitv to the surface of the bleaching liquor. WVhen any substantial amount of chlorin is present a distinct cloud or fog is noticeable. In the dilution here contemplated neither the HOCl or HCl will give such a cloud. The best way to use the test is by fitting a cap illary tube to a bottle of ordinary water of ammonia and placing the end of the capillary just above the surface of the liquor. The amount of ammonia given off from ammonia water at ordinary temperatures is suffi ient for the test.

What is claimed is;

1. The pro ess of bleaching. which comprises producing a dilute solution of HOCl by introducing chlorin into water under conditions which cause substantiallv complete hydrolvsis 0f the chlorin with production of a solution containing free HCl, and submitting the material to be bleached to the action of such solution at the time or substantially at the time of the production of the 11001.

2. The process of bleaching, which comprises producing a dilute solution of HOCl by introducing chlorin into a sufiicient amount of water to cause substantially complete hydrolysis of the chlorin without substantially any of the HCl formed being removed, and submitting the material tobe bleached to the action of such solution at the .time or substantially at the time of the production of the HOCl.

3. The process of bleaching with the aid of chlorin, which comprises submitting the material to be bleached to the action of a bath comprising both acid products of the hydrolysis of chlorin and substantially free of chlorin as such, said material being brought into contact with said products at the time, or substantially at the time, of their formation.

at. The process of bleaching with the aid of chlorin, which comprises dissolving chlorin in water and exposing the material to be bleached to the resulting solution, the amount of water relative to chlorin being sufiicient to cause the reversible reaction,

to go substantially entirely to the right.

5. The process of bleaching with the aid of chlorin, which comprises dissolving chlorin in water and exposing the material to be bleached to the resulting solution, the amount of water relative to chlorin being sufficient to cause the reversible reaction Cl +H Oz- I-ICl H001 to go substantially entirely to the right, the amount of chlorin remaining as such being not over one to two per cent. of that introduced.

6. The process of bleaching with the aid of chlorin, which comprises dissolving chlorin in water in the absence of suflicient base to neutralize all the HCl resulting from hydrolysis and exposing the material to be bleached to the resulting solution, the conditions of solution being such as to cause the reversible reaction 01 H Or HCl H001 to go substantially entirely to the right.

7. The process of bleaching fibrous material with the a d of chlorin and water, which compr ses subiecting the material to the action of a solution produced by introducing chlorin into water and which contains substantially allthe chlorin in the form of HOCl and chlorid, such chlorid including hydro' en chlorid.

8. The pro ess of bleaching, which comprises forming a solution containing HOCl and HCl from chlorin in the presence of water under conditions precluding existence in the solution of substantial amounts of chlorin as such, and directly bleaching the goods therewith.

9. The process of bleaching, which comprises directly producing HOCl from chlorin in the presence of water under conditions precluding existence in the solution of substantial amounts of chlorin as such, and in the presegice of the goods to be bleached.

10. The process of bleaching fibers, which comprises submitting the same to the action of a dilute solution of chlorin and containing free HCl substantially free of unhydrolyzed chlorin.

11. The process of bleaching fibers, which comprises submitting the same to the action of a solution of H001 and HCl, said solution being sufliciently dilute to preclude any substantial formation of chlorin by the mutual action of said HCl and H001.

12. The process of bleaching, which comrises producing a dilute solution of HOCl y introducing chlorin into a sufficient amount of water to cause substantially complete hydrolysis of the chlorin without substantially any of the HCl formed being removed and increasing the hydrolysis {by heating the liquid, and submitting the material to be bleached to the action of such solution at the time or substantially at the time of the production of the HOCI.

13. The process of bleaching, which comprises roducing a. dilute solution of H001 by introducing chlorin into water under conditions which cause substantially complete hydrolysis of the chlorin, such conditions including heating the liquid, and submitting the material to be bleached to the action of the HOCl in such solution at the time or substantially at the time of the production of the HOCl.

14. The process of bleaching, which comprises hydrolyzing chlorin in the presence of water to form a solution containing HOCl all in the free state, and treating the material to be bleached with such solution at or substantially at the time of production thereof, the solution being sulficientlv dilute to insure the presence of all the HOCl originallv formed at the time of contact of the solution with the material to be bleached.

15. The process of bleaching, which comprises hydrolizing chlorin in the presence of water to form a solution containing HOCl, all such HOCl being in a free state and the dilution being suificient to give a content of chlorin of the order of magnitude not greater than about 0.01 per cent, and treating the material to be bleached with such solution.

16. The process of bleaching fibrous materials, which comprises hydrolyzing chlorin in the presence of water to form a dilute solution containing HOCl and under circumstances precluding combination of said HOCl with base. and treating the material to be bleached with such solution at the time or substantially at the time of the production of the HOCl.

17. The process of bleaching, which comprises introducing chlorin directly into water containing the goods to be bleached under conditions which result in the substantially immediate disappearance of the sLEACHING a crane; time :iEATMENT chlorin as such with production of H001, whereby the material to be bleached is subjected to the action of substantially all the HOCl produced and at the time of its production.

18. The process of bleaching, which comprises supplying ameasured flow of chlorin to water under conditions which result in the substantially immediate formation of H001 and disappearance of chlorin as such, producing a solution containing in the free state all the HOCl so formed, and subjecting the material to be bleached to the action of the solution so produced, the introduction of chlorin being a gradual introduction and continuing during at least a part of the bleaching operation.

19. The process of bleaching, which comprises utilizing gaseous chlorin, converting substantially half of all the chlorin used into free hypochlorous acid, and maintaining the desired strength of the bleaching solution during at least a part of the bleach- Gopies of this patent may be obtained for ing operation by supplying the gaseous chlorin in a measured flow during such part of the bleaching operation.

20. The process of bleaching, which comprises utilizing gaseous chlorin, converting substantially half of all the chlorin used into free hypochlorous acid, and continuously regulating the bleaching by the measured [low of the chlorin introduced.

21. The process of bleaching with free chlorin, which. comprises permitting a regulated inflow of chlorin into the bleaching apparatus, the inflow of chlorin being con-: trolled so as to be proportional to the ob served rate of bleaching effect in the bleaching zone.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

, GEORG ORNSTEIN. Witnesses:

A. L. KENT,

PAUL H. FRANKE.

five cents each, by addressing the Commissioner of IPatents, Washington, D. G.

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