Page:Popular Science Monthly Volume 80.djvu/434

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Similarly the charge carried by any captured ion is proportional to the change produced in this sum by the capture. Now the change in this sum produced by the capture of the ion which caused the time in column F to change from 34.8 to 84.5 was, as any one who wishes can verify, .00891 cm. per sec. and the successive values of this sum arranged in order of magnitude were .04456, .05347, .06232, .07106, .08038. If now electricity is atomic in structure all the different charges appearing in this experiment, those on the ions and those on the drop, should be exact multiples of the elementary unit of charge, which means that all of the numbers above given should be exact multiples of something. Dividing the above five numbers by 5, 6, 7, 8 and 9, respectively, gives .008912, .008911, .008903, .008883 and 008931, which are all seen to be within one fifth of one per cent, of the value of the change in the sum of speeds produced by the capture of the ion which caused the numbers in the column F to change from 34.8 to 84.5. Hence the charge carried by this ion was itself the elementary unit out of which all of the other charges which appeared in the experiment were built up. The results on another drop which was observed through a much longer time, namely, about four and a half hours, are given in the following table:

n 4.197 n Observed Charge n 4.197 n Observed Charge
1 4.917 —— 10 49.17 49.41
2 9.834 —— 11 54.09 53.91
3 14.75 —— 12 59.00 59.12
4 19.66 19.66 13 63.92 63.68
5 24.59 24.60 14 68.84 68.65
6 29.50 29.62 15 73.75 ——
7 34.42 34.47 16 78.67 78.34
8 39.34 39.38 17 83.59 83.22
9 44.25 44.42 18 88.51 ——

In this table 4.917 is merely a number obtained, precisely as above, from computing the change in the "sum of speeds" produced by the capture of a particular ion, while the column headed "observed charge" gives the successive values of the sum of speeds. It will be seen that during the experiment this drop carried all possible multiples of the elementary charge between 4 and 18, save only 15. No more exact or more consistent multiple relationship is found in the data which chemists have amassed on the combining powers of the elements, and on which the atomic theory of matter rests, than is found in the above numbers.

Nearly a thousand different drops have been examined in the manner indicated, some of them being of oil, a non-conductor, some of glycerine, a semi-conductor, some of mercury, a good conductor, and some of other substances, and in every case, without a single exception, the initial charge placed upon the drop by the frictional process, and all of the dozen or more charges which have resulted from the capture by the drop of a larger or smaller number of ions, have been found to be exact mul-