July 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
approximate 275 pounds per square inch (19 atmospheres) measured a t 22' C. The drop in pressure per mole of hydrogen is a linear function of the amount of liquid in the bomb, the slope of the line being dependent upon the space for gas in the bomb. The extent of hydrogenation may be approximated by observing the drop in pressure at the temperature of hydrogenation. However, such a value is in general much less accurate than that based upon a comparison made a t room temperature between the pressure before the bomb was heated up with that observed after the contents of the bomb have cooled to the original temperature. When the desired reaction is complete, the bomb may be pulled partially out of the heater in order to facilitate its cooling. Often it is advantageous then to place a water jacket around the bomb so that it may be more rapidly cooled to room temperature. When the bomb has cooled to room temperature, the pressure is slowly released by allowing the gas to escape through the outlet valve. The gas inlet is disconnected from the bomb, the latter removed from the heater, the cap screws loosened, and the bomb-head cover unscrewed. The head should then be gently loosened by tapping and attempting to rotate it. (If an attempt is made to lift it directly from the bomb, the gasket will probably be ruined.) The liner is then removed; opened, and the catalyst removed by filtering through a sintered glass filter. The bomb and liner may be washed out with a suitable solvent and this solution added to the reaction mixture. I n many cases it is advantageous to centrifuge the mixture before attempting to filter off the catalyst.
PRECAUTIONS The smaller bomb described above is intended for use at pressures up to 175 atmospheres and temperatures up t o 250' C., although the factor of safety under thes'e conditions is several hundred per cent. The larger bomb is intended for use a t pressures up to 400 atmospheres. The pressure of the hydrogen in the usual type of commercial cylinders is approximately 135 atmospheres, so that the maximum pressure obtainable (without the use of special equipment for compressing the gas) would be approximately 240 atmospheres a t 250 C. A gage should only be used over the lower 60 per cent of its range, so that 200 atmospheres is approximately the maximum pressure that should be used with the equipment suggested. The gage is the weakest point in the system, and it is well to replace the glass in it with celluloid and to have it so located that it is not faced directly but is read by means of a mirror. The temperature of hydrogenation should be carefully watched, and if the reaction is proceeding too rapidly, the shaker should be stopped for a time. ACKNOWLEDGMENT The author's experience with the apparatus and technic for carrying out the reaction of organic compounds a t temperatures up to 400' C. and pressures of several hundred atmospheres began in 1927 with apparatus purchased from the American Instrument Company. This equipment is still in use and it has never developed any fundamental defects. Since that time the bomb design, gaskets, etc., described in this paper have been developed as being more convenient and cheaper, and in general more satisfactory, The author is particularly indebted to W, H. Reynolds and Leopold Freedman of the American Instrument Company, and to Messrs. Hanson, Brockman, and Henke of the shops of the University of Wisconsin. The American Instrument Company have on the market an outfit for catalytic hydrogenation which includes the essential features of the unit described in
345
this paper. The Burgess-Parr Company of Moline, Ill., also have for sale an outfit patterned after the unit herein described. LITERATURE CITED
*
(1) Adkins and Cramer, J. Am. Chem. Soc., 52,4349 (1930); Adkins, Connor, and Cramer, Ibid., 5192 (1930); Adkins and Connor, Ibid., 53, 1091 (1931); Adkins and Folkers, Ibid., 1095 (1931); Adkins, Cramer, and Connor, Ibid., 1402 (1931); Adkins, Zartman, and Cramer, Ibid., 1425 (1931) ; Diwoky and Adkins, Ibid., 1868 (1931); Adkins, Folkers, and Kinsey, Ibid., 2714 (1931); Winans and Adkins, Ibid., 54, 306 (1932); Connor, Folkers, and Adkins, Ibid., 1138 (1932); Folkers and Adkins, Ibid., 1145 (1932); Covert, Connor, and Adkins, Ibid., 1651 (1932); Adkins and Covert, J. Phys. Chem., 35, 1684 (1931). (2) Ernst, IND.ENG.CHEM.,18, 664 (1926); Am. Instrument Co., Bull. 405 (1927); U.S. Dept. Agr., Circ. 61 (1929). R E C ~ I V EMaroh D 19, 1932.
A Modified Microburet R. B. DUSTMAN, West Virginia University Morgantown, W. Va.
s
OME Years ago the Department of Agricultural Chemistry became engaged in analyses necessitating the use of a microburet. Fkkrence to several SuPPlY house catalogs a t hand revealed only the Folin type available. One of these was purchased and put into use, but it did not meet the needs in a satisfactory manner. Consequently a buret was designed as illustrated in the accompanying sketch. The advantage of this type of buret lies chiefly in its increased capacity without sacrificing any of the conveniences of the ordinary single-tube type, The short length of the graduated tube affords convenient reading throughout its entire range without undue elevation or lowering of the level of the eyes. For titration with small withdrawals of liquid, this part of the buret may be used exclusively if desired. When titrating from the graduated tube, the bulb side furnishes a convenient outlet for excess solution run into the buret from the stock bottle and adjusted to the zero graduation. However, when considerable quantities of solution are r e q u i r e d , the bulbed tube is more suitable. When titrating from the bulb side, the titration is completed by manipulation of the lowest stopcock, t h e s t o p c o c k on the left remaining open. After the titration is finished, the stopcock on the right is opened and the liquid in the partially emptied bulb allowed to rise to the nearest graduation mark above. It may he noted that the zero graduation on the top bulb stands slightly below the level of the 3-ml. graduation on the uniform-bore tube. This permits the refilling of any one of the four bulbs on the left hand side with liquid drawn from the main tube on the right. The total quantity is then read off by a d d i n g t o t h e FRONT SIDE volume of the e m p t i e d b u l b s the sKETCH OF M ~ volume withdrawn from the graduBURET
~
ANALYTICAL EDITION
346
ated tube. All titrations are best controlled by the use of the lowest stopcock. This buret delivers approximately 26 drops per ml. and is suitable for work with blood and urine in addition to the more general analytical procedures. The graduation interval is 0.02 ml., but readings are easily possible to 0.01 ml. Because of the relatively small bore of the graduated t,ube, some time must be allowed for afterflow if the tube has been emptied rapidly and readings of greatest accuracy are desired. This seldom requires a total of more than 1.6 to 2 minutes, and ordinarily most of this drainage will have taken place during the time necessary for the withdrawal of the last few drops. Two of these burets have been made a t moderate cost by E. Machlett & Son of Long Island City, N. Y., the first of which has been in constant use over a period of 2 years. They are of rugged construction and excellent workmanship. The calibration is highly accurate, the volumes being adjusted well within the tolerances required by the U. S. Bureau
Vol. 4,No. 3
of Standards for measuring pipets. The approximate dimensions of the buret are as follows: Total length.. ................................... Length of graduated main tube from 0 to 5 m l . . ..... Height of side tube with bulbs.. . . . . . . . . . . . . . . . . . . . Distance from 5-ml. graduation to point of curved tip Length of tip below stopcock.. .................... Diameter of graduated main tube (outside). . . . . . . . . . Diameter of bulbs (outside). .......................
.
Total capacity., . , , ............................. Capacity of graduated main t u b e . . . . . . . . . . . . . . . . . . . Capacity of single bulb.. .......................... Subdivisions,, ...................................
Cm.
60 38 23 15 4
0.8 1.4
MI. 17 5 3 0.02
These dimensions give a small unit convenient both for general laboratory use and for certain specialized procedures. Manipulation is rapid and easy, total capacity large, and accuracy adequate for exact measurements. RECEIVED January 11, 1932. Published with the approval of the Director of the West Virginia Agricultural Experiment Station, as Scientific Paper 106.
Pressure Control with Automatic Liquid-Leveling Device J. V. VAUGHEN,E. I. du Pont de Nemours & Co., Wilmington, Del.
THERE
is often a need in the laboratory for a device which will automatically control liquid levels in the leveling bulbs of gasometers and combustion pipets and in mercury reservoirs in such a way as to give constant pressure or c o n s t a n t l i q u i d flow. Figure 1 represents a variation of the a r r a n g e m e n t used by Stone ( 1 ) that has been used in this laboratory f o r m a i n t a i n i n g a constant flow of mercury to displace liquids at a constant rate into a r e a c t i o n vessel. T h e mercury reservoir, C, is s u s p e n d e d b y a suitable spring, B, which lifts the r e s e r v o i r a distance e q u a l to the fall in mercury level in the bulb when m e r c u r y flows out. The s p r i n g and reservoir are matched by measuring the e l o n g a t i o n , X , of the spring with a load of 100 cc. of m e r c u r y . The appropriate diameter, D, of the reservoir is then calculated according to the formula D = 2
stance two springs 27 em. long were used together to support a mercury reservoir. Together these springs stretched 6.8 cm. for 100 cc. of mercury. The calculated diameter of the reservoir was 4.32 em. The reservoir was made with a diameter of 4.5 em. and further adjustment of the apparatus was accomplished by shortening the spring. A volume of 200 to 300 cc. of mercury could be emptied from the reservoir with a change in mercury level of less than 3 mm. I n applying this scheme to the maintenance of constant pressure in gasometers and combustion pipets with leveling bottles, the following equation gives the relationship between the radius, r, of the gasometer or combustion pipet, the radius, R, of the leveling bottle, and the elongation, X, of the spring, for a volume, Ti, of confining liquid:
I n one instance a leveling bottle for a gas-combustion pipet was suspended by two springs 42 cm. long. They elongated 8.0 em. with a load of 100 cc. of mercury. Since the diameter of the pipet was 4.8 em., the leveling bulb should measure 7.2 em. LITERATURE CITED (1)
Stone, Engineering, 100, 554 (1915).
RECEIVEDFebruary 16, 1932. Contribution 91 from the Experimental Station, E. I. d u Pont de Nemours & Company.
-
WORLDPOTASHPRODUCTION. According to the estimate of the general director of the Kaliwerke Aschersleben, reported The reservoir is made of to the Department of Commerce by the trade commissioner at t u b i n g of approximately Berlin, potash salts representing 1,457,400 metric tons of potash were produced in the world in 1931 In 1930 world production this diameter, and further of potash was 2,018,000 tons, and in 1929, 2,118,000 tons. OF m a t c h i n g is accomplished Germany is first in volume of potash produced, with 964,000 LEVELINGDEVICE by c h a n g i n g the length of tons; France (Alsace) second with 340,000 tons' the United States third with 60,000 tons; and then Poland, kpain, Russia, the spring. in the order named. A decline from over 1,300,000 tons in 1930 Brass springs have been found more suitable than steel is shown in German production, and a drop of 16 per cent for ones, and they are generally made by winding No. 16 B. & S. the first five months of 1932 over the corresponding period in brass wire on a 0.25-inch (0.62-em.) mandrel. I n one in- 1931, in sales of German potash.
1
