ON ANTIMONIU RETTED HYDROGEN, ETC. 
219 
15. If we dissolve kermes in a solution of caustic potassa, 
and add to it a solution of acetate of lead, and, finally, diluted 
sulphuric acid and zinc, antimoniuretted hydrogen will be 
disengaged. A similar reaction takes place when arsenic is 
used. 
It results from this comparative examination, that we have 
no good means of immediately distinguishing these two gases, 
especially if they exist in very small quantities, and that, con- 
sequently, the process of Marsh, for the detection of arsenic, 
should be rejected. 
I have tried the new processes for the detection of arsenic, 
and I have ascertained that the plan of Berzelius presents 
great advantages. This process consists, as is well known, 
in decomposing in a small tube, by means of a fragment of 
charcoal impregnated with carbonate of soda, the sulphuret, 
which is caused to pass over it in the form of vapor. This 
process possesses the great advantage of not giving rise to any 
uncertainty, as the sulphuret of antimony does not produce 
a similar reaction. We may likewise decompose the sul- 
phuret of arsenic by a mixture of caustic lime and charcoal. 
I added to a mixture of zinc and diluted sulphuric acid, 
salts of tin, platinum, silver, chromium, mercury, lead, and 
some other metals, but none of these metals gave combina- 
tions with hydrogen. 
Jinn, des Mines. 
