The deviation from the mean velocity of the ram during the day, and from day-to-day, was no greater than f1.2%.
ful to Mary V. Buell for her criticism of the manuscript. LITERATURE CITED
(1) Bray, R. C., Biochem. J . 81, 189
ACKNOWLEDGMENT
The authors are grateful to Graham Palmer and William E. Hauser for their advice and to Howard S. Mason who suggested the servo motor. We also acknowledge the services of Robert F. Sutton who fabricated the ram and contributed to the engineering and John C. Drake who fabricated some of the experimental rams. We are also grate-
(1961). (2) Bray, R. C., “Rapid Mixing and Sampling Techniques in Biochemistry,” B. Chance, R. H. Eisenhardt, Q. H. Gibson, K. K. Lonberg-Holm, eds., p. 195 Academic Press, New York, 1964. (3) Chance, B., “Investigation of Rate and Mechanisms of Reactions,” S. L. Friess, E. S. Lewis, A. Weissberger, eds., Part 11, p. 728, Interscience, New York, 1963. (4) Gibson, Q. H., Jlilnes, L., Biochem. J . 64, 161 (1964).
(5) Palmer, G., Beinert, H., “Rapid Mixing and Sampling Techniques in Biochemistry,” B. Chance, R. H. Eisenhardt, Q. H. Gibson, K. K. Lonberg-Holm, eds., p. 205, Academic Press, New York, 1964. (6) Palmer, G., Bray, R. C., Beinert, H., J . Biol. Chem. 239. 2657 (1964). ( 7 ) Roughton, F. J. W.; “Investigations of Rates and llechanisms of Reactions,” S. L. Fries>, E. S. Lewis, A. Weissberger, eds., Part 11, p. 704, Interscience, New York, 1963. RECEIVED for review September 8, 1965. Accepted December 13, 1965. Supported by XIH grant GN-12394 and Research Career Program Award Gl\I-K6-18, 442 (H.B.).
Analysis of Hydrazine-Ammonia Mixtures SIR: I n a recent study of the kinetics of the thermal decomposition of hydrait was necessary to zine vapor (4, analyze mixtures containing N?H4,SH3, H2, N2,and -4r. Typically, a sample might consist of approximately equal partial prei.sures (-1 Torr each) of the first four components, highly diluted with argon (-400 Torr), in a volume of 300 cc. An essential feature of the research problem was the determination of the overall decomposition stoichiometry. Hence, a quantitative analysis for each species was required; i t was very desirable not to obtain any component by difference. -I novel analytical technique a a 4 developed to meet this particular problem. The main purpose of this communication is to des m b e this method, in the hope that the principle involved will be of use to analytical chemists. hIany of the details of the technique are unique to individual applications of it, and for this reason a somewhat generalized description is presented here. Initially, a direct analysis of the mixtures in a mass spectrometer was attempted. This method failed completely because the hydrazine (and most of the NH3) was adsorbed on the walls of the inlet system and analyzer tube, and none could be detected. The possibility of substituting a gas chromatograph for the maqs spectrometer seemed to raise more problems than it would solve. Methods for analyzing hydrazine by GC have been reported (2, S), but these are not applicable to the type of samples encountered here.
However, the Hz, Nz,and d r were amenable to mass spectrometric analysis, if they could be separated from the N2H4and NHa. A freeze separation was effected using a slush of 2-methylpentane, which freezes at - 154’ C. Liquid nitrogen could not be used to condense the NzH4 and S H s because it also partially condensed the argon, which has a vapor pressure of 209 Torr at -196’ C. (At -154’ C., the vapor pressure of SHs is
