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alumina. I n these experiments the oxides were ground to pass a 100-mesh sieve and were thoroughly mixed with the hydroxyapatite. The nature of the product obtained when hydroxyapatite is heated in the presence of water vapor and silica, alumina, or ferric oxide has not been determined. Inasmuch as all types of domestic phosphate rock contain small percentages of iron and aluminum, it seems likely that these constituents, a t least in so far as they are present in the form of the free oxides, contribute to the formation of citratesoluble phosphorus when phosphate rock is heated a t high temperatures in the presence of water vapor.
Literature Cited Bredig, M. A,, Franck, H. H., and Fiildner, H., 2. Elektrochem., 38, 158-64 (1932). Hill, W. L., Marshall, H. L., and Jacob, K. D., IND.ENQ. CHEM.,23, 1120-4 (1931). Jacob, K. D., Beeson, K. C., Rader, L. F., Jr., and Ross, W. H., J . Assoc. Oficial Agr. Chem., 14,263-83 (1931).
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(4) Jacob, K. D., Hill, W. L., Marshall, H. L., and Reynolds, D. S., U. 8. Dept. Agr., Tech. Bull. 364 (1933). ( 5 ) Jacob, K. D., Rader, L. F., Jr., and Ross, FV. H., J . Assoc. Oficia2 Aar. Chem.. 15. 146-62 (1932). (6) Jacob, K. D., Rader,’ L. F., Jr., and Tremearne, T. H., Ibid., 19,No.3 (1936). To be published. (7) Lapp, M. E., Ibid., 15, 66 (1932).
(8) Marshall, H. L., Reynolds, D. S.,Jacob, K. D.. and Rader. L. F., Jr., IND. ENQ.CHEM.,27, 205-9 (1935). (9) Reynolds, D. S.,J. Assoc. Oflcial A g r . Chem., 17,323-9 (1934). (10) Reynolds, D. S., Jacob, K. D., Marshall, H. L., and Rader, L. F., Jr., IND.ENQ.CHEM.,27, 87-91 (1935). (11) Reynolds, D. S., Jacob, K. D., and Rader, L. F., Jr., Ibid., 26. 406-12 (1934). (12) Schleede, A., Schmidt, W., and Kindt, H., Z . Elektrochem.. 38. 633-41 (1932). (13) Triimel, G . , M i t t . Kaiser-Wilhelm Inst. Eisenforsch. DQsseldorf. 14. 25-34 (1932). (14) Willard, H. H., and Winter, 0. B., IND.ESQ.CHEM., Anal. Ed., 5, 7-10 (1933). RECEIVED April 2, 1936.
GLASS PUMP for Circulation of G a s e s against Moderate Pressures J. C. BALSBAUGH, R. 0. LARSEN,AND D. A. LYON Massachusetts Institute of Technology, Cambridge, Mass.
V
ARIOUS modifications of all-glass, magnetically operated, piston-type circulation pumps have been used successfully by severa1 workers (1, I,3, 4). One similar to that described in the literature (3) was constructed for use in this laboratory. This pump proved to be unsatisfactory since it would not operate against the pressure required (about 70 mm. of mercury). The previous workers stated that 30 em. of water was the maximum head against which this type of pump would be effective. It was found possible to raise this maximum pressure somewhat, but a t the highest pressure the volume displacement was so small as to render the pump useless for the purpose in view, A new pump was constructed and it has been entirely successful. As now in use, it is capable of forcing air against a pressure of 210 111111. of mercury. Further improvements over the other pumps of this type were made by reducing the size, eliminating a troublesome commutator, dispensing with the need for cooling, and increasing the dependability of operation.
Apparatus The essential new feature of this double-acting pump is that the piston and cylinder wall are ground to fit as carefully as the parts of hypodermic glass syringes in common use. Thus the chief objection to the ordinary pump is completely eliminated-namely, leakage of gas between the piston and cylinder wall. ’ The second novel feature is that the usual series of solenoids alternately excited through a commutator is replaced by a single solenoid moving up and down mechanically. This arrangement permits operation a t smaller currents and thereby eliminates the need for cooling: The cylinder, A (Figure l), is made from heavy-walled, 25mm. Pyrex tubing, 18 cm. long and taper-ground at each end to
prevent the piston from sticking during rest periods. The glass piston, B, is 7.5 cm. long and holds a piece of soft iron, C, machined as indicated. The iron is packed in the glass piston with shredded asbestos before sealing. This packing effectively prevents the iron from making actual contact with the glass which might otherwise cause cracking during operation. The solenoid D, is wound with 3500 turns of No. 26 single cotton-covered enameled wire on a brass core with soft iron end plates. The solenoid is operated by a 0.05-horsepower motor, E , through a crank and a 3040-1 worm gear as shown. The stroke length is adjustable by means of a slot in the crank wheel. Mounting the pump vertically minimizes friction and wear on the piston. The valves, F , are emall glass bulbs about 10 mm. in diameter, blown on the end of 4-mm. Pyrex tubing and ground at the base into 7mm. tubing. About 15 mm. of the tubing is left attached to the bulb and drawn to a point. This acts as a guide to obtain effective seating of the valve. These valves are very responsive and will maintain a pressure of 100 mm. of mercury for several hours. The inlet and outlet tubes are connected at G and H, respectively.
Data Two variables control the capacity of the pump-the stroke length and the speed. The data given are for a speed of sixty-four strokes per minute and a stroke length of 55 mm. A current of 0.6 ampere is required to hold the piston in place during operation. The capacity of the pump operating against various pressure heads is as follows: Pressure
-Mm.H o 32 l6 46 58
Volume Cc./min. 2100 1900 1720 1570
’ Pressure
Volume
iMm. Ho 110 122 140 178
Cc./min.
900
740 560 200
Pressure Mm. Hg 190 202 210
Volume Cc./min. 120 60 16
The ratio of maximum inlet to outlet pressure attained by t h e pump is almost exactly the same as the ratio of the total dis-
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0
FIGURE 1. VIEWS OF
THE
GLASSPUMP
I /
I
r
i l l
I I
IJ
0
placement of the pump to that of the volume between the pump and the valves. Reduction of the end clearance and shortening the distance between the cylinder and the valves would thus increase the maximum pressure obtainable.
chusetts Institute of Technology, and the Utilities Coordinated Research, Inc., of the Association of Edison Illuminating Companies.
Literature Cited Acknowledgment This apparatus has been developed for use in connection with a research project on oxidation stability and electrical characteristics of electrical insulating oils carried on jointly by the Electrical Engineering Department of the illassa-
(1) Funnel1 and Hoover, J. Phys. Chem., 31, 1099 (1927). (2) Lehrer, Erwin, Chem. Fabrik,1932,33. (3) Livingston, Robert, J. Phys. Chem., 33,955 (1929). (4) Porter, Frank, IND.ENQ.CHEM., 18,1086 (1926). R E C ~ I Y EMaroh D 13, 1936.
