Mobilities of Ions in Air, Hydrogen, and Nitrogen.

Preliminary communication. s The paper will appear shortly in Science, New York, N. S., 1918. All the precautions mentioned in this account were carefully observed in the present investigation. 3 The methods previously used in studying the photosynthesis of aquatic plants are not as accurate as the one here described, nor do previous experiments afford the kind of data needed for our purpose. Cf. Blackman, F. F., and Smith, A. M;, Proc. Roy. Soc., London, (B) 83, 1911, (389). 4 All matching of shades was done under a 'Daylight' lamp, so that uniform conditions were assured throughout the experiments. Cf. Science, New York, N. S., 42, 1915, (764). A clear space was left in the tube below the Ulva to facilitate comparison of colors. In any single experiment the buffer may be dispensed with by using as a standard the pink solution produced by the first exposure. The first exposure should be as short as is consistent with obtaining a definite standard. Experiments showed that the trace of alcoholic phenolphthalein had no injurious effect. s In experiments on fresh water algae a small amount of sodium bicarbonate was added to the water.