Vol. 14, No. 7
INDUSTRIAL A N D ENGINEERING CHEMISTRY
542
Britzke, E. V., and Dragunov, S. S., J . Chem. Ind. (U. S. S. R.), 4, 49 (1927). Courtois, J., J . pharm. chim., 23, 232 (1936). Dworzak, R., and Reich-Rohrwig, W., 2. anal. Chem., 77, 14 (1929). Gerber, A. B., and Miles, F. T., IND.ENG.CHEM.,ANAL.ED., 10, 519 (1938). Holt, A., and Myers, J. E., J . Chem. Soc., 99, 384 (1911). Kiehl, S. J., and Coats, H. P., J . Am. Chem. Soc., 49, 2180 (1927). Kiehl, S. J., and Wallace, G. H., Ibid., 49, 375 (1927). Lum, J. ,H., Malowan, J. E., and Durgin, C. B., Chem. &. M e t . Eng., 44, 721 (1937). Mellor, J. W., “Comprehensive Treatise on Inorganic and Theoretical Chemistry”, Vol. VIII, p. 987, New York, Longmans, Green and Co., 1928. Travers, A., and Chu, Y. K., Helv. Chim. Acta, 16, 913 (1933). Wurzschmitt, B., and Schuhknecht, W., Angew. Chem., 52, 711 (1939).
Summary A method has been worked out for the analysis of mixtures of phosphates in which hexameta-, trimeta-, pyro-, and orthophosphates are separated and determined. Polyphosphates are obtained from the difference between the total phosphorus pentoxide and the sum of the phosphorus pentoxide values of the other mentioned phosphates. Data on application of the procedures t o synthetic phosphate and carbonate and silicate mixtures, commercial phosphates, and “unknowns” are included.
Literature Cited (1) Aoyama, S., J . Pharm. SOC.J a p a n , No. 520, 553 (1925); 2. anal. Chem., 84, 31 (1931). (2) Boratynski, K., Ibid., 102, 421 (1935). (3) Bornemann, F., and Huber, H., U. S. Patent 2,174,614 (Oct. 3, 1939).
Pressure-Measuring Device for Moderate Vacua ERNEST R. KLINE University of Connecticut, Storrs, Conn.
T
HE increasing use of moderate vacua in distillations requires a pressure-measuring device having its maximum utility in the range of 0.05 to 2 mm. of mercury pressure. This range is below that at which the ordinary mercury-filled manometer is accurate and somewhat above that at which the conventional McLeod gage is designed to operate. Efforts to increase sensitivity by the use of lighter liquids of low vapor pressures in closed-end manometers yield unsatisfactory results, since such liquids wet glass and have a most persistent habit of sticking in the closed arm of the manometer. A serious objection to the use of mercury as the working liquid a t these pressures is that ‘a substantial amount of distillate vapor is present in the system and pressure variations eventually result in fouling the mercury surface. This is especially serious in McLeod gages where capillary lubes are used. These difficulties have been overcome in this laboratory by the use of the modified M c L e o d g a g e shown. T h e o p e r a t i n liquid which has been foun8 to give best results is olive oil which has been subjected to prolonged evacuation a t 100” C.-to remoye volatile solvents and moisture. This is introduced through the trap, T , to fill the reservoir. R1. and the b
