It is necessary to keep all dry ice levels high in their respective containers. The 1-liter Dewar flasks each containing a 6/s-inch diameter trap held sufficient dry ice to last overnight but during runs were filled every hour or two. The Styrofoam cup was filled every half hour and the collector cup held sufficient dry ice to last for the 5-minute collection. It was discovered by accident that dusting the stoppers with flowers of sulfur reduced the water pickup t o virtually nothing during the water transfer step. Results and Discussion. Table I1 gives the results obtained when water was determined on the first eleven consecutive samples of barium chloride dihydrate t h a t were run on the apparatus described. T h e effectiveness of the water separation and the water transfer technique are
indicated by the average error of 2 pg. The greatest error appeared to be connected with a rapid change in humidity such as occurs with a n abrupt weather change. The blank a t the beginning of the afternoon was 5.7 pg. of water and at the end was 3.8 p g . During that time the weather cleared up and presumably the relative humidity dropped. If the relative humidity of atmosphere surrounding the water transfer aPParatus were controlled, the precision might well be improved. I n this method no purging of the is required to any serious interference by extraneous water from the air. The removal and collection of water from a sample can be carried out almost immediately after removing from an atmosphere of controlled humidity* Thus an accurate determination of the water of a solid in
equilibrium a t a known relative humidity is possible. LITERATURE CITED
(1) Armstrong, R. G., Gardiner, K. W., Adams, F. A m L . C m H . 32, 752
w.,
(1960). (2) Bastin, E. L., Siegel, H., Bullock, A. B., Zbid,, 31, 467 (1959). (3) Bruckenstein, S., Ibid., 28, 1920 (1956); 31, 1757 (1959). (4) Hiske 3 C. F., Zbid.1 21, 1440 (1949). (5) Keidef F. A., Ibid., 31, 2043 (1959). (6) Levy, G. B., Murtaugh, J. J., Rosenblatt, M., IKD.ENG.CHEY.,ASAL. ED. 17, 193 (1945). (7) &feYer, A. S.7 Jr., Boyd, C. hf., A N A L . CHEW 31, 215 (1959). (8) Mitchel,
