122 
Mr. Chenevix on the Action of 
obtained a precipitate weighing 102. He is surprised at the 
difference of weight between our results, which might be 
owing to his method of repeating the experiment ; but the real 
cause of this difference lies, as I suppose, in my having acci- 
dentally used nitrate instead of muriate of mercury. I had 
never observed that with mercury and silver this operation 
had failed, and it must have been, because, on account of the 
known effect of muriatic salts upon those of silver, I had 
naturally avoided using a muriate of mercury. 
But the state of the nitrate of mercury which is used with a 
solution of gold is not indifferent. As green sulphate of iron 
reduces mercury when dissolved in nitric acid, as well as gold, 
it is necessary to mix the solutions of those metals before the 
green sulphate of iron is added, in order that both may be 
acted upon together. If the nitrate be at the minimum of oxi- 
dizement, a precipitate is immediately formed upon mixing the 
solutions of gold and mercury. Calomel is produced by the 
muriatic acid of the solution of gold and the oxide of mercury ; 
whilst the gold is reduced to the metallic state by a portion of 
the oxide of mercury becoming more oxidized, and forming 
the soluble muriate. The precipitate consists of calomel, of 
metallic gold, and of a very small portion of mercury which I 
believe to be in the same state ; my reason for thinking so, is, 
that I have often observed, that a glass vessel in which I had 
sublimed some of it, was lined with a thin gray metallic coat. 
If, on the contrary, a nitrate of mercury be highly oxidized, 
no precipitate nor reduction of gold takes place until the green 
sulphate of iron is added. But at any rate the precipitation of 
gold and mercury, or of silver and mercury by green sulphate 
