US1723853A - Titration apparatus - Google Patents

Description

Aug. 6, 1929.

J. E. s. HAN

TITRAIION APPARATUS Filed Sept. 30, '1927 WITNESS:

2 Sheets-Sheet l llil l l 3 Ja/m 527 6.6041 flan INVENTOR W BY 486's A'I TORNEY 6, 1929- J. E. s. HAN 1,723,853

' TITRATION APPARATUS Filed Sept. 30, 1927 2 Sheets-Sheet 2 I v I 1 3g. 6. 1 144. 4.

Johr} 'Sfiazz Han INVENIOR WITNESS: ATIORNEY Patented Aug. 6, 1929.

ururro STATES JOHN EN SHOU HAN OF SHANGHAI, CHINA.

TITRA'IION APPARATUS.

Application filed September 30, 1927. Serial No. 223,186.

This invention relates to improvements in titration apparatus which, at the present time, is composed of a reservoir for standard solution, a burette permanently connected thereto and a device for admitting a suitable gas into the said reservoir and burette. Such an apparatus is always permanently set up on a fixed shelf and is used in volumetric analysis for titrations and with standard solutions of sodium hydroxide, titanous chloride and other substances that cannot he exposed to ordinary air. Descriptions ot the present types of apparatus are found in the tollowing treatises and journal Treadvvell-lilall s Analytical Chemistry, 6th edition, (19%), Vol. H, pages 481 and 596. (John Wiley & Sons, line, New York city, puhlishers).

@uttons Volumetric Analysis, 11th edition, (19%) pages 12, l3 and 24151. (P. Blahistons don d: Co., Philadelphia, publishers). Scotts Standard Methods of Chemical Analysis, 3rd edition, (1923), Vol. II, pages loos-ameliorates. (D. Van Nostrand Co, New York city, publishers).

"llhronton and Woods Standardization of- 'litanous Sulphate Solutions, Journal ot ludustrial and Engineering Chemistry, vol;

, standard solution in the reservoir and that lctt over troin a previous titration in the hurette with the Water condensed (trout moisture formed hy spontaneous evaporation ot the standard solution) and remaining on the inside Walls ot the reservoir, the hurcttc and the gas passage hetvveen them.

Before using any standard solution, (even when lrept in a simple stoppered bottle), it is alivayscssential that it he thoroughly shaken up. Neglecting this, a slight change in the normality ot'the' standard solution will result, owing to the loss ot a small vol-- uine ot Water thereinwhich was evaporated, condensed and remaining on the inside Walls ot the container. This change "Willloe small it the container is nearly full with standard.

solution, but will he comparatively large it the volume of standard solution therein is small in relation to the capacity of the contamer. (See Suttons Volumetric Analysis, 11th edition, page 23, beginning with the third line from bottom).

' Standard solutions of alkalis cause the glass key to stick fast to the glass barrel of a stopcock. Rubber tubing in conjunction with pmchcock, glass bead or glass rod is at present time used instead of stopcocks with glass barrel and glass key Whenever standard solutions of alkalis are used in such an apparatus. (See Suttons Volumetric Analysis, 11th edition, page .9, first paragraph). This is objectionable because (a) the distention of rubber tubing is variable which causes error in the reading of the buret-te, and (b) it necessitates the exposure of an unnecessary length of rubher tubing to the action of the standard solution which, for accurate work, is to be avoided. (see Treadivelll-Ialls Analytical Chemistry, 6th edition, Vol. II, page 453, paragraph 2 regarding variable distention of rubber tubing and Thronton and Woods' Standardiza tion out 'litanous Sulphate Solutions, Journal 0t lndustrial and Engineering Chemistry, vol. 19, page 151, regarding harmful ettects of exposed rubber surface on the keep ing quality of standard solution).

For standard solutions other than allralis stopcoclrs, composed ct glass barrel and glass key, are used in certain types ot the present apparatus, hut the hydraulic pressure of the standard solution ahove gradually tends to loosen the stopcock-hey from the stopcoclr- 'harrel, resulting in the leaking out of solution and the leaking in of air. (See Thronton and Woods article ited ahove.)

The highest graduation on a Mohrs hurette'ot precision type and convenient sire mil. in 1/10 ml, suhdivisions) ivhen'permanently tired up is too high to be easily and accurately read Wllfilltllfi operatorstands on the tloor. A cha-niher hurette (description ot v"which is tound in l icott s titandardr dhaniher ill hil

tlti

burettes are intended for tit-rations requiringtrated in the accompanying drawings and more solution than what the chamber section delivers; therefore, in the. present arrangement of figures, the graduation above the chamber represents 0 and the first graduation below the-chamber marks the capacity of the chamber. No. direct reading can be made with such an arrangement of figures, if the titration requires a volume of solution'smalle'r than the capacity of the chamber section. Since ity .is preferable to have an apparatus rovided with a ,burette to g ve direct j rea ings of any volume of solution within its fullcapacity, a new arrangement of figures is needed.

The objects of this invention are, therefore, as follows To provide a device by which the solution in the reservoir and the burette can be merits of an ordinary stopcock, is meant that by its use no rubber tube has to exist between the stopcock and the barrel of the burette and that if any rubber tubes are used for connections beyond the stopcock, much less rubber comes into contactwith standard solution than in the case of a pinchcock or the bead or rod valves. The variable distention of rubber tubes that exists beyond the stopcock does not affect the accurate reading of the burette. a

To provide an adjustable and cushioned clamp that will serve to maintain sufiicient tightnessof the stopcock.

To provide a new arrangement of figures on chamber burette so that direct readings for volumes less than the capacity of the chamber can be made.

A further object of this invention is to provide an automatic tube closer so that the gas passage Within the glass and rubber tubes leading from the reservoir of standard solutionto the device for admitting a suitable gas into the said reservoir, canbe automatically 'closed when the said reservoir takes an inclined or inverted position during the mixing of the contents thereof. This deviceprevents any leakage of standard solution from thereservoir into the said glass and rubber tubes. i

With the above and other objects in view, the invention further includes the following novel features and details of construction, to be hereinafter more fully described, illusglass and that will not stick direction or the other.

I so that by ,with a cushion 22 two of these arms 23 and pointed out in the appended claims.

In the drawings:

Figure 1 is a front elevation of the apparatus. i

- Figure 2 is a plan view thereof.

Figure 3 is a side view.

Figure 4 is a section on.line 44 of Figure 3.

Figure 5 is a section ure 1.

Figure 6 is a section on line 6--6 of Figure 1.

Figure 7 is a. section 011 line 7-;-7 of Figure 3.

Figure 8 shows the cha'mber burette with the new arrangement of figures thereof and the solution tube attached thereto.

Figure 9 is a detailed view of part of the graduations on the lowermeasuring section of the chamber burette.

1 indicates an upright rod which is securely fixed to a. table A by the nuts 2 and 3 and the washer 4. Upper and lower journal blocks 5 are suitably fastened to the rod 1 and the stem 6 of a ring 7 is journaled in the upper block and a shaft having a crank handle 7 thereon is journaled in the lower block. The stem 6 and the shaft have each on line 55 of Fig- 'secured thereto a sprocket 8 over which passes an endless chain 9 so that when the shaft is turned by its handle, the stem 6 will also be turned to rock the ring 7 in one The stem 6 is normally held with the ring in horizontal position by the spring actuated latch 10 which engages a notch 11 in a disk 12 fastened to the stem, this latch being carried by a bracket 13 on the upper block 5.

A ring 14 fits in the ring 7 and the abutting edges of these rings are beveled, as shown in Figure 4. This ring 14 is suitably fastened to a ring 15 which rests upon the ring 7 and another ring 16 rests upon the ring 15 and is detachablv connected with the two rings 14 and 15 by the bolts 17 which are provided with the wing nuts 18, removing the nuts, the ring 16 can be lifted off the ring 15. As will be seen, the three rings which are connected together, are rotatably supported by the ring 7 and they may be rotated through means of the projections 14 on the ring 14. Curved arms 19 have their upper ends fastened to the ring 14 and these arms carry an annular seat 20 for the flask 21, the seat being provided of rubber or cork upon which rests a part of the flask. Curved arms 23 have their lower ends connected with the ring 16' and their upper ends are connected with a plate 24 which is formed with a semicircular recess 25. A rod 26 is carried by these rods support one-half of a sectional clamping collar 27, the other half being hingedly connected with ltl till

the first half and bein held in gripping position on the neck of t e flask by the turn screw 28 carried by another arm 23, the screw bein held in adjusted position by the nut 29.. T us the flask is firmlyheld'upon its seat between the rings by the collar gripping its neck, but the -flask can be easily removed by releasing the collar and removing the upper ring and its arms from the other rin s.

.5 pair of -depending arms 30 have their upper ends connected with the lower ring it and their lower ends are connected to a support 31 for the clamps 32 and 33, each clamp com risinga stationary plate 34 and a hinged p ate 35, with a screw 36 hinged to.

the stationary plate and adapted to pass througha notch in the hinged plate, with a wing nut 37 on the outer end of the screw for holding the hinged plate in clamping position. The clamp 32 1s adapted to sup port the burette B and the clamp 33' engages the solution tube 38 which has its upper and connected by a short tube 39 with the outlet ot the flask and its lower end is connected by a short rubber tube 40 with the inlet 41 of the burette. The portions of the clamps which engage the burette and tube are provided with a suitable lining, such as cork or rubber. Theinlet 41 is connected with the stopcock barrel or casing 42 which is formed at the lower end of the burette and this casing is provided with the nozzle 43. The key ot the stopcock is shown at 44: and is provided withthe handle 45 and said key is rovided with the port46 for connecting the inlet 41 with the bottom of the burette and with the port 47 for connecting said bottom with the nozzle 43. These ports are so arranged that when the key is in one position,

the inlet 41 will be in communication with the burette and the nozzle will be closed, and

this end carries areinforcing block 49 which is threaded, as is also the bent end, to receive.

a turn screw 50 and said screw has ablock 51 of resilient material at its inner end for engaging the small end of the stopcock barrelor casing. "Thus by turning the screw 50 to force its block 51 against the end of the casing, the platewill be moved to cause its slotted end to firmly engage theouterend of the plug and thus the plug will be held against loosening.

A gas washing bottle 0 is supported from the upright 1 by the clamp 52 and this bottle is connected by a tube 53 with the capillary tube 54v of the flask, this tube 54 passing through the opening 25 in the plate 24:. The

upper part of the tube 53 passes through an automatic-tube closer which is supported on i .in a partition in the casing and throu h holes in the bottom of the casing and tie plate. These rods carry a plate 61 and the tube passes through holes 62 in the casing and between'the partition and the plate 61 so that the tube is compressed by being pressed by the plate 61- against the partition. When the flask holding means are turned, however, to bring the ball 56 under an arm 63 carried by the top of the rod 1, said arm will press upon the ball 56 and thus cause said ball to lower the rods and the plate 61 against the action of the springs 59, so that the tube can expand and open. If the flask supporting means are turned to move the closer to a position where the ball 56 will not be in contact with the arm 63, the springs will move the parts upwardl and thus close the tube, and when the ask supporting means are rocked, by turning the handle 7,

as soon as the closure passes from under the arm 63, during this rocking movement, the springs 59 will move the parts upwardly and close the tube.

A bulb 64 is connected with the bottle G and then by turning the handle, the chain 9 will communicate the movement of the shaft, which is connected with the handle,

to the stem 6 and thus the rings and the parts carried thereby will be rocked. By

providing the handle and its associated parts, the supporting means for the flask can be placed at a considerable height.

The automatic tube closer automatically closes the gas passage between the interior of the flask and the gas washing bottle as soon as the ball is not directly under the arm 63 or ball presser, or-in other words, as

soon as the apparatus begins to invert. This arrangement prevents the. solution in the tlask'from entering the capillarytube (gas inlet) during the inversion of the apparatus. The capillary tube has a very small inner diameter and is short. The rubber tube is of small size and the section between capillary tube and the pressing plate 61 is also short. The volume of gas in the capillary tube and this section of the rubber tube is very small, so there is no chance" for the standard solution to compress the gas in the capillary tube andthis section of the rubber tube to give room for any of the solution to enter them when the gas passage is closed.

The air passage in rubber tube can .be kept closed when the apparatus stands in an upright position by pushing the revolvable rings until the automatic tube closer reaches the left side. In this position, the automatic tube closer is not directly under the ball presser, so the ball is released.

The gas washing bottle C is adjustably attached to the rod 1 by the clamp 52. If the standard, solution is caustic alkali, a strong solution of sodium hydroxide could be used for washing the air that enters the apparatus. The bulb 64.- is provided to prevent the washing solution (sodium hydroxide, etc.) from being pushed out by ex pansion of gas in the flask, owing to a rise in room-temperature. For standard solution of titanous chloride, ferrous sulphate,

etc., a small carbon dioxide or hydrogengenerator is to be used and the gas washed by bubbling through water or other suitable solution in the gas washing bottle. If it is desired to admit moisture-free gas, dehydrating agents' can be placed in-the gas washing bottle All the parts below the lower ring, including the two depending arms, the flask cushion support, the solution tube and the clamps for theburette and the solution tube, are arranged in such positions as not to shade off any li ht from the graduations on the burette w en the apparatus is read before a window. i

The spherical shape of the flask is preferred, because it insures the exposure of a minimum areaof glass to the attack of the standard solution. The flask outlet-fits directly into the rubber tube. the use of a rubber stopper, as the exposure of rubber surface should also be minimized. For the same reasons, the neck of the flask is made short and narrow so as to expose less glas surface and at the same time to take a smaller rubber stopper.

The device worksas follows Standard solution isdrawn into the bufl rette through the solution tube by turning v plug or key 44 of the two-way stopcock.

Upon entrance of solution into the burette, gas therein escapes into the flask through the gas tube 73 which connects the upper This avoids end of the burette with the flask. The gas tube is of moderately large inside diameter which equals that of the upper section of the burette. The comparatively large bore avoids capillary attraction and allows anydrops of solution adhering to it to drain down freely.

The solution tube 38 is of smaller size than the gas tube, but sufficiently large to insure a quick filling of the burette.

The burette is of the chamber type, but possesses a new arrangement of figures which increases its usefulness. It has two measuring sections of equal delivery capacity, namely, the upper measuring section 74. and the lower measuring section 75. Each section may deliver a volume of 15 -ml., 25 ml. or any other volumes according to the size of the burette. The lower measuring section has subdivisions of 1/5, 1/10 or 1/20 ml. For the convenience of explanation, let us refer to a 50 ml. burette. The upper section is similar in construction to a transfer pipette and delivers 25 ml. The lower section takes the form of a precision burette and also delivers 25 ml. It is graduated in ml. andl/lO ml. There are two rows of figures; on the right hand side the graduation above the chamber 74 is marked 0, the first graduation below the chamber marked 25 ml. and thelast graduation marked 50 1111., while on the left hand side the graduation above the chamber is not marked, the first graduation below the chamber marked 0 and the last graduation marked 25 ml. Suppose the titration requires more than 25 m1. of solution, the burette is filled to the graduation above the chamber and the final reading taken from the figures on the right hand side row of the lower measuring section. If the titration requires less than 25 ml. of solution, the burette is filled to the first graduation belowthe chamber (0 on the left hand row of figures) and final read ing taken from-the figures onthe left hand row. With a 50 cc. burette graduated only with one row of figures, direct reading for titration using less than 25 ml. of solution is impossible. Similar arrangements of figures can be applied to chamber burettes of other ca acities.

The cham or type of burette is preferred because a 30 ml. or 50 ml. size one with the lower measuringsection graduated to l/lO or 1/20 ml. subdivislons can be made comparatively short to allow the highest graduation to be conveniently and accurately read without detaching it from the apparatus while the operator stands on the oor.

The two-way stopcock or valve has a barrel or casing of glass. Each stopcock is furnished with two double-bored stopcockkeys of the same design, one of glass and the other of silver or gold. The smaller end of the stopcock key or plug does not project beyond the end of the sto cock barrel. The glass stopcock key is to be used in connection with standard solutions -that do not cause glass key to stick to the glass barrel of a'stopcock. With standard solutions of caustic, caibonate and other alkalis that the fourth line from top 0 cause stopcock-key to stick vfast onto the glass barrel of a stopcock, the silver or gold key or plug is to be used.

Silver and gold are more resistant to alkalis than glass and crucibles made from such metals are used for caustic alkalifusions. Gold is the most resistant to fused caustic alkali, even more so than platinum, and undoubtedly is the ideal metal to use for the construction of the said stopcock key, butas at room temperature alkali solutions, of normal and weaker strengths exert practically no corrosive action on silver, the cheaper metal can be used to 've satisfactory results. (See Roscoe and So or-- lemmers Treatise on Chemistry, 6th edition,

( 1923), Vol. II, page 261,

When thestopcoc is allowed toremain under a comparatively high column of solution, the hydraulic pressure radually loosens the key or'plug from the arrel of the stopcock and results in a leakage of solution. This ispr'evented by the locking device or clamp shown in Figure 7. During titration, the clamp also helps to maintain sufficient tightness of the stopcock to prevent leakage of solution from the burette inlet 41 directly into the burette nozzle 43.

The burette may be. provided with two stopcocks with two single bored keys. The stopcock-clamp can be. applied to each of these stopcocks equally well.

of "paraflin to provide *further 'protection,'-;

which is essential for the maintenance of a constant titer of the standard solution- All glass parts, with the exception of the gas washing bottle and bulbs and tubes thereof, are preferably made. of highly resistant chemical lass. The inner surface of the flask is preferably. coated with a layer therein.

The standard solution in the flask and the burette is mixed with the water condensed and still remaining on the inside walls of the said flask, the said burette and the gas passage between them in the following manner: Turn the stopcock key until the wa'ybetween the burette inlet 41 and the burette barrel is open and let it remain frame for the 'frameis rotata ly mount in that position. When the burette is filled with the standard solution, turn handle 7 clockwise'so that the flask descends behind the apparatus. Let the burette, which at this time rises in front of the apparatus, remain at a higher position than that of the flask so that the standard solution therein completely flows back into the flask, which at the same time carries with it all the water that has been condensed on the inside walls of the said burett-e and the gas tube 73. Then turn the handle 7 counter-clockwise so that the flask descends in front of the apparatus, and continue to turn until the solution tube 38 nearly touches the side of the ball presser arm 63. Turn the apparatus around the other way and let the burette rise in front of the apparatus again. Re

peat the process a few times to efiect a thorough mixing. If the volume of'the standard solution in the flask is small and cannot reach certain parts of the flask during inversion, then push the lower ring 14 through an angle of (or any other suitable angle) and repeat the inversion.

The mvention is susceptible of various changes in its form, proportion and minor details of construction and the right is herein reserved to make such changes as properly fall within the scope of the appended claims.

Having described the invention, what I claim to secure by Letters Patent are 1. A titration apparatus comprising a reservoir for standard solution, a burette permanently connected to the reservoir and a revolvable and invertible support for the reservoir and burette.

, 2. A titration apparatus comprising a reservoir for standard solution, a burette permanently connected to the reservoir, a sup porting frame for-the reservoirand burette, a support in which the frame is rotatably mounted and means for moving the support about a horizontal axis to invert the parts.

3. A titration apparatus comprising a reservoir for standard solution, a burette permanently connected thereto, a supporting arts,,a supcport in which the e means for turning the support about a horizontal axis to invert the parts, a as washing bottle, a

rubber tubing connecting the bottlewith the reservoir, means permitting gas to be introduced into the bottle and automatic means for closing the rubber tubing as the reservoir begins to invert or to revolve and to open-the gas passage in the rubber tubried by the frame, a burette carried by the frame, tubing connecting the lower end of the bure'tte with the outlet. of the reservoir, tubing connecting the top of the burette with the top of the reservoir, means for removably holding the reservoir in the frame, a rotary handle supported by the upright, means for communicating the movement of the handle to the stem, a gas Washing bottle supported by the upright, a tube connecting the same with the top of the reservoir and means permitting gas to be introduced into the bottle, means for closing a part of the tube automatically when the reservoir is being inverted or revolved and for openingthe tube when the reservoir is in its original position.

are mounted onto a revolvable and inverti- I ble support by movements of which support the said reservoir-burette combination can be made to turn around horizontally (that is, from left to right, etc.) and to turn up and down vertically so as to effect a thorough mixing of the standard solution in the combination with the water that has been condensed and still remains on the inside walls of the said combination substantially as described.

In testimony whereof I affix my signature.

JOHN E. S. HAN.

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