P latino, and Mercury upon each other. 107 
current of sulphuretted hydrogen gas through a mixed solution 
of platina and mercury. Their method was the following. 
They dissolved one hundred and fifty grains of platina with 
four hundred and fifty of mercury, and added a solution of 
hydrosulphuret of potash. They obtained a precipitate which, 
at first, was black, afterwards gray ; but the whole became 
black by being stirred. To be certain that all the metal was 
precipitated, they added an excess of sulphuret of potash, and 
perceived that a part of the precipitate was redissolved. The 
liquor was then filtered, and to that part of it, which contained 
the redissolved precipitate, an acid was added. From this pro- 
cess they obtained a yellow precipitate weighing ninety-one 
grains ; and fifty grains of this, exposed to a strong heat, left 
three-eighths of a grain of platina. They obtained no palla- 
dium from that part of the precipitate which had not been 
redissolved ; and the result of the experiment was complete 
failure. 
I shall not make any observation upon the issue of this 
process, since, in this case, the best conducted is but too liable 
to be unsuccessful, and that without any apparent fault in the 
operator. But as it has been given as a repetition of one-of 
mine, it may not be fruitless to examine how far the repetition 
was exact. 
I had passed a current of sulphuretted hydrogen gas through 
a mixed solution of platina and mercury, by which means they 
were precipitated together. My object was so intimately to 
combine sulphur with these metals, that when exposed to heat, 
they might (if I may be allowed the expression ) be in chemical 
contact with it at the moment of their nascent metallic state ; 
and as a low temperature suffices, as well to reduce those 
P 2 
