to give perfectly satisfactory results from all points of view, on a tip with a diameter of 4.5 I millimeters ; while, excluding carbon tetrachloride, and possibly a few other similar liquids, characterized by a very small surface tension and a large density, which then form drops of minimum volume, equally satisfactory results are obtained on all tips with diameters between 4.51 and 5.50 mm.; and higher, for many liquids. In other words, it is shown that when the drop profile is not abnormal to the eye, and the control of the drop is perfect, "ate's first law-the weight of a falling drop is proportional to the diameter of the tip from which it falls-holds rigidly. Surface tensions in dynes, calculated from the benzene constants and the drop weight from the tip employed (i. e. , by aid of the proportion r : w : : K, : k,) are found to agree on all tips from 1.51 to 5.50 mm., independent of the diameter of the tip, as long as the drop profile is normal and the control of the drop is perfect; in other words, for all liquids except carbon tetrachloride, which gives perfectly satisfactory results on tips around 4.5 mm. in diameter only, owing to its exceedingly small drop volume. Surface tensions in dynes for these liquids are also calculated a t 27.8' by aid of the formula r=w/o.o63g7 X (2~) 7 r , which is also found to lead to results independent of the diameter, and which agree with the values calculated from the above proportion. It is to be concluded from this investigation that the Morgan drop weight apparatus will give satisfactory results when the tip diameter lies between 4.51 and 5.50 millimeters, although if such a liquid as carbon tetrachloride is to be used it would be necessary to reduce the tip diameter to 4-51 mm., which will probably gi-,.e satisfactory results for every known liquid. 4. 5 .
ALTHOUGH several publications {2, 3, 5, 7) have dealt with the interferences encountered in the determination of sodium by the zinc uranyl acetate method of Barber and Kolthoff (2, 5), no reference is found to the effects of molybdenum. Molybdate interferes by the formation of a precipitate with the zinc uranyl acetate reagent. This precipitate, which is a yellow, amorphous material, is apparently the uranyl molybdate, UO2M0O4, described by Lancien (6).The interference of the molybdate may be either positive or negative. If the precipitate is retained on the filter and weighed with the sodium, the results will be high. If the
I353 an alpha particle which captured an electron before it reached the cathode would have a value e/m = a g x ICP. This value was actually determined for the particles which produced patch c. There still remains the probability that a considerable number of alpha particles would combine with two electrons and form neutral helium atoms before reaching the cathode, and these would be undefleeted in the space back of the cathode and would form the central bright patch. On the whole, then, it seems established within the limits of error,of the experiment that alpha particles were given off from the anode and formed an important part of the Kanalstrahlm. This explanation will also account for the sometimes unaccountable appearance of helium in vacuum tubes through which an electric charge has been passed. A striking example of this is given by Soddy in Proc. Roy. Soc., London (A) , 80, 94, and while the explanation which he there oiTers may be the correct one it seems not impossible that the one here suggested may be the true one, instead.
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