ANALYTICAL CHEMISTRY
86 The method was used for two years on several hundred compounds. Table I gives typical results on subtances of known purity. LlTERATURE CITED
(1) Ampt, G. A , , Australian Chem. Inst. J . Proc., 2, 10 (1935). (2) Brewster and Rieman, IND.ENG.CHEM.,.ISAL. ED., 14, 820 (1942). --, (3) Gibson, D. T., and Caulfield, T. H . , Anal& 60,522 (1935). (4) Hallett, L. T., and Kuipers, J. W., IXD.ENG.CHEM.,A X I L . ED., 12,360 (1940). (5) Ingrani, G., Analyst, 69,265 (1944). \
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Mercury Slug Flowmeter K. L. YUDOWITCB Gniversity of Missouri, Columbia, .llo.
C I D E X T A L t o other researches for the l I a n h a t t a n Pioject, I Sthe author developed \vith J. F. Bacon and othei associates a
(6) Manov, G. G., and Kirk, P. L., ISD. ENG.CHEM.,ASAL. ED.,9,
198 (1937).
( 7 ) Niederl, J. B., and Niederl, V., “Organic Quantitative Microanalysis,” 2nd ed., pp. 190-6, New York, John Wiley & Sons,
1942. ( 8 ) Ogg, C. L., Willits, C. O., and Cooper, F. J., A s a L CHEM.,20.,
83 (1948). (9) Sundberg, 0. E., and Royer, G. L., IKD.ENG.CHEM.,ASAL. ED.,18, 719 (1946). RECEIVEDJune 9, 1947. Presented before the Division of Analytical and Micro Chemistry a t the 111th Meeting of the AMERICASCHLYICAL SOCIETY, Atlantic City, N. J.
of a relay activated by the paasiage of the slug past the contacts shown in the illustration. This type of meter operates over a broad pressure range (2 t o 76 em. of mercury) and on a low pressure drop (2 t o 3 mm. of mercury). Its operation is independent of the physical properties of the gas being measured. It gives a n integrated or average flow rate rather than a n instantaneous rate. The advantages of this specific design are compactness, ruggedness, and higher flow rate attainable. More than a dozen of these meters have been used satisfactorily at SA11 Laboratories. They have held their calibrations t o ri-ithin from 1 t o lo%, over several months of regular use. AIost variations were probably due t o contamination of the mercury.
meter t o measure small gas f l o w a t various pressures. The iequirements of a n operating pressure drop of less than 3 mm of mercury and independence from t h e physical properties of the gas made capillary flowmeters, rotameters, and circuit-terminating flowmeters undesirable. Various designs of absolute displacement meters were investigated. Marsh’s ( 2 ) original design based on the displacement of a LITERATURE CITED bubble of amyl phthalate between scratches on a straight capillary (1) Appleby, IT. G., and Aver>-,W.H., IND.ESG. CHEY.,A s a ~ ED., . tube appeared unsatisfactory for several reasons. The range 15, 349 (1943). quoted was 0.25 t o 1 cc. per minute, much below requirements. (2) Marsh, ALE . L.. Trans. Faraday Soc., 36, 626 (1940). T h e accuracy of a straight tube meter varies as the distance beRECEIVED June 11, 1947. Based on v o r k performed under contract No. t w x n scratches, requiring a tube several feet long for reasonable. K-7405-eng-26 for the Manhattan Project. T h e information will appear in accuracy. Division VI11 of the Manhattan Project Technical Series a s p a r t of the Appleby and Avery ( 1 ) substituted mercury for amyl phthalate, contribution of the S;iM Laboratorieu, Carbide and Carbon Chemicals permitting the use of larger tubing and consequently higher flow Corp , New York, N. Y. rates. The range (up t o 25 cc. per minute) was still low and the delicacy of design incompatible with the need for portability a n d ruggedness. I n operation the mercury slug continuously ,--BYPASS traverses the spiral path as indicated. The spiral is made by winding 6-mm. Pyrex tubing in a plane, and allowing it t o set on a slightly convex carbon block. This fixes t h e spiral outlet 1 t o 2 mm. above the inlet. Sufficient mercury must be used in the meter, so t h a t a new slug will close the spiral entrance before the original slug completely leaves the spiral. The length of t h e slug and therefore t h e volume swept out per cycle were found t o vary somewhat with flow rate. This necessitates calibration over the range of flow rates t o be encountered. Below rates of about 25 cc. per minute, the volume swept out increases anomalously. I t is suggested t h a t the spiral be made of smaller tubing if it is desired t o measure rates below 25 cc. per minute. With the simple precautions of cleanliness and careful l e v e h g , rates of over 250 cc. per minute Tvere attained before the slug broke into several sections. It is not feasible t o use tubing much MERCURY SLUGlarger t h a n 6 mm., as the mercury will not then MERCURY WELLI ’ form a slug. The cycles may be counted by means
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