1007
V O L U M E 2 7 , N O . 6, J U N E 1 9 5 5 and the zero grid position changes markedly, zero grid p6sition is merely obtained as above and {vork with the unknowns iq continued. As the tube circuit is independent of the electrodc potentiometer circuit as shonn in Figure 1, replscement of the original reference buffer \till check within 0.01 p H unit of its origind position on P2. Beta-een determinations 8 4 is alternately switched from 1 to 2 positions, to make sure that the zero grid position is maintained. Instrument Housing. Figures 2 and 5 illustrate the instrument used routinely for blood p H measurements. The instrument is shielded by mounting on a suitable metal-lined (copper, 0.00.5 inrh thick) wooden bo.; using the usual care for ensuring a seal of the component parts within the shield. Batteries are either soldered at contacts or pressed in place at contacts with silver-plated brass screws. The sockets for inserting the electrocle plugs must be designed for high resistance to ground. Those shown in Figure 2 ere ohtained from Beckman Instrument Co.
LITERATURE ClTED
(1) Burr, H.
S.,Kims, L. F.. and Lane, C. T., Yale J . Biol. M e d . , 65
(Septembsr 1936). (2) Ellis, S.B., and Kiehl, S.J.. Rrr. Sci. Instr., 4, 131 (1933). (3) Garman, R. L., and Droz, AI. E., IXD.ESG. CHEU.,ANAL.ED.. 11, 398 (1939). (4) Goodhue, L. D., Iowa State J . Sci., 10, 7 (1935). ( 5 ) Hemingway. A,, and Brown, E. B.. Electronics, 23, 202 (May 1950), (6) Hitchcock, D. I., and Taylor, .L C., J . A m . Chem. Soc., 6 0 , 2710 (1938). (7) lIacInnes, D. A, Belcher. D.. and Shedlol-sky, T., I b i d . , 60, 1094 (1938). ( 8 ) AIorton, J . Chem. Soc., 1931, 2977 (9) Sims, L. F.. Yale J . B i d . Med., 10, 26 (1938). (10) Pugh, AI. D., Instrument Mfo.. 20, S o . 5 . 176 (1952). (11) Rider, J. F., "Vacuum Tube 1-oltmeters." 2nd ed., pp. 279-335. John F. Rider Publishers, New York. 1951. (13) Serfass, E. J.. IND.ENG.CHEM.,. ~ N A L . ED., 12, 536 (1940).
c..
RECEIVED for review April 12, 1954. Accepted Kovember 15, 1954. Presented before the Division of Biological Chemistry at the 125th Rleeting of tlie AMERICASCHEMICAL SOCIETY. Kansas City, >lo.
Rapid Determination of Perchlorates NATHANIEL L. CRUMP and NATHANIEL C. JOHNSON Research and Development Laboratory, Armament Division, Universal M a t c h Corp., Ferguson 21, Mo.
In connection with fundamental work on pjrotechnics, a need arose for the quantitative determination of a large number of perchlorate compounds. Because most
methods described in the literature are too time-consuming for routine anal?sis, work was undertaken to deyelop an accurate and rapid method that would not require the special nonoxidi7ing or inert atmosphere, the prolonged heating, or the hours of refluxing required b? many existing methods. This method involves the fusion of the perchlorate in a Parr bomb with sodium peroxide and subsequent volumetric determination of the chloride formed. 4n error of less than 1% is ohtained and the time for a complete duplicate determination need not exceed 1 hour. The method is applicable to all tjpes of perchlorates and adaptable for routine anal\ s i q .
T
111.; quantitative determination of chlorates by reduction to thp corresponding metal chloride can be carried out with little 01' no difficulty by any of the conventional methods drscribed i n a standard analytical test. However, perch1or:ttr ion does not lend itself to an easi- reduction. Sevrr:tl methods for the determination of perchlorates have been described in the literature, which may be classified as wet reducttion and reduction by thermal decomposition. Nost methods are of the n e t reduction t,ype. Haight (3) makes the perchlorate react with zinc amalgam and sodium molyhdate in acid solution, followed by boiling for 15 to 30 minutes to complete the reaction. I n another procedure, the perchlorate reacts with excess tin(I1) chloride or sulfate and sodium molybdate in acid media and this mixture is boiled under a nitrogen atmosphere for 15 to 30 minutes, and the excess tin(I1) ions are titrat ed with permanganate. Rothmund (.
