Page:Popular Science Monthly Volume 11.djvu/90

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THE POPULAR SCIENCE MONTHLY.

brought in succession into the action of the spark until the lines of the substance were clearly visible," If a skeptical person refuse to believe the results of Cappel, who tells us that 1/600 of a milligramme (1/38800 of a grain) of nickel will just write the signature of that metal, what will he say when, glancing at Table B, appended hereto, he finds the statement that 1/60000 of a milligramme (1/3880000 of a grain) will sign its name in brilliant characters! And yet the writer does not hesitate to say that even a smaller amount of this metal will show a spectrum, for in these experiments a much stronger spark was used than was necessary to show a visible spectrum. When reduced to a minimum, by means of a miniature Leyden jar, improvised out of a test-tube, which still gave a distinct spectrum, the loss in weight, after passing 3,000 sparks, was absolutely inappreciable on the balance. The tables show another curious and unexpected result, viz., that the loss in weight of the volatile metals very slightly exceeds, and in some cases does not equal, the loss of the less volatile metals. Thus, in three different experiments of 3,000 sparks each, copper loses but 1/10 milligramme, while gold loses 5/10 milligramme."[1]

In one experiment the number of sparks was increased to 10,000, and the loss in weight was nearly proportioned to the increased number. In this case the sparks were passed at the rate of about 250 per minute.


TABLES.

The first column shows weight of metallic electrodes (in milligrammes) before passing the sparks.

The second column shows weight after passing 3,000 sparks.

The third column shows total weight of metal volatilized (in fractions of a milligramme).

The fourth column shows the amount of metal volatilized by each spark (in fractions of a milligramme).

The fifth column shows the amount of metal volatilized by each spark (in fractions of a grain troy).

TABLE A.
1. 2. 3. 4. 5.
Upper pole, gold 16.6 15.9 .7 1/4286 1/277000
Lower " " 16.7 16 .7 1/4286 1/277000
Upper " copper 18.5 18.4 .1 1/30000 1/1940000
Lower " " 18.5 18.4 .1 1/30000 1/1940000
Upper " gold and copper 24 23.4 .6 1/5000 1/324000
Lower " " 24 23.4 .6 1/5000 1/324000
Upper " tin 20 19.6 .4 1/7500 1/486000
Lower " " 20 19.4 .6 1/5000 1/324000
Upper " silver 24.8 24.6 .2 1/15000 1/976000
Lower " " 25.1 25 .1 1/30000 1/1940000
Average lead 91.6 90 1.6 1/1870 1/121000
  1. "The Spectroscope in its Application to Mint-Assaying." Journal of the Franklin Institute, October, 1874. Reprinted in the Quarterly Journal of Science, January, 1875.