such, that it was worth while to purchase platinum in other countries, and make coin of it, and then take it into that country and circulate it. The result was, that the Russian Government stopped the issue. The composition of this coin is—platinum, 97.0; iridium, 1.2; rhodium, 0.5; palladium, 0.25; a little copper, and a little iron. It is, in fact, bad platinum: it scales, and it has an unfitness for commercial use and in the laboratory, which the other well-purified platinum has not. It wants working over again.
Now, Deville's process depends upon three points,—upon intense heat, blowpipe action, and the volatility of certain metals. We know that there are plenty of metals that are volatile; but this, I think, is the first time that it has been proposed to use the volatility of certain metals—such as gold and palladium—for the purpose of driving them off and leaving something else behind. He counts largely upon the volatility of metals which we have not been in the habit of considering volatile, but which we have rather looked upon as fixed; and I must endeavour to illustrate these three points by a few experi-
