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LORD RAYLEIGH AHD MRS. H. SIDGWICK OX THE 
chemists; but for our purposes the conclusion is that, for the present at any rate, 
platinum is preferable to silver. With suitable precautions, the platinum basins may 
be heated to redness without changing more than ^g milligrm. 
§ 20. In some of our later experiments ( e.g ., those on January 30, April 2) we 
included a voltameter, charged with a higher proportion of acetate, in order to 
exaggerate the errors that we had met with, in the hope of better detecting then' 
origin. When the nitrate solution is nearly saturated with acetate, the deposit is 
of a beautiful snow-white appearance, and almost always 5 or 7 milligrms. too heavy. 
On the second weighing, after heating to the verge of redness, a loss revealed itself, 
whose amount usually agreed fairly well with the view that the original excess of 
weight was due to nitrate, reduced to metal by the second heating. 
§ 21. In the hope of obtaining better evidence as to the cause of the anomalous 
weights, and also with the view of confirming our results by the substitution for 
nitrate of some other salt of silver, we have made several observations on deposits 
from chlorate of silver. The salt was prepared for us by Mr. Scott from chlorate of 
barium, and was found to give as good deposits as the nitrate. The chlorate was 
used in a nearly saturated 10 per cent, solution,* and also in a 5 per cent, solution. 
Voltameters charged with nitrate were included in the same circuit, so that the 
comparison was made under the most favourable condition. The results (Table II.) 
show an exceedingly good agreement, and constitute perhaps the most accurate 
verification which Faraday’s law of electrolysis has as yet received. 
But the second object which we had in view in using the chlorate has not been 
attained. The idea was to get a too heavy deposit by addition of acetate, and then 
after washing and weighing as usual, to dissolve up the metal with nitric acid and test 
for chlorine. If chlorate were present, and were the cause of the excessive weight, 
it should on strong heating be resolved into chloride, whose presence might be 
detected. Preliminary experiments showed that as little as -^g- milligrm. of silver 
chloride could be rendered evident. The deposits were dissolved in nitric acid, and 
strongly supersaturated with pure ammonia. After standing for some time with 
frequent stirring, the solution was diluted, and again rendered acid with nitric acid. 
The deposits from chlorate, which we had reason to regard as pure, stood the test 
almost perfectly, the amount of chloride of silver present being less than -Jg- milligrm. 
If one drop of the dilute NaCl milligrm.) were added to the solution in its alkaline 
condition, the cloud formed on acidification was perfectly evident after a minute or 
two when examined in Stas’ box. When a piece of fused silver chloride weighing 
3 milligrms. was added to the alkaline solution, it dissolved after about half an hour, 
and gave a dense milkiness on addition of nitric acid. 
The application of this method to deposits from chlorate and acetate, which the 
* The tendency to crystallise upon the anode is an objection to the use of the strong solutions, and 
probably makes itself the more felt in consequence of the paper wrapping, which impedes the free 
circulation of the liquid. 
