ihe Cofribincttimis of Allcdlks with Metallic Sulphur ets. "7 
atoms of sulphur and three atoms of the metallic sulphurets in 
general are required to separate entirely the two atoms of sul- 
phuretted hydrogen, together with one atom of proto-sulphuret 
of potassium. These decompositions are made even in the 
humid way. The sulphuret of arsenic pulverised, 
drives off at an ordinary temperature the sulphuretted hydro- 
gen gas from a solution of neutral and slightly concentrated 
hydrosulphate of potash) with the same force as if a liquid acid 
had been added to it. 
The proto-sulphuret of potassium combines equally with two 
atoms of the sulphuret of carbon = KS® -f 2 CS^ ; but when 
this combination is prepared in the dry way, it decomposes 
when dissolved in water ; the carbon separates from it entirely, 
and the solution contains only KS®. The proto-sulphuret of 
potassium dissolves the sulphuret of carbon in the humid way 
without separating from it the carbon. 
Besides these two double sulphurets, M. Berzelius has exa- 
mined the action of the alkalis and their sulphurets on the sul- 
phurets of Arsenic, Molybdena, Chrome, Tungsten, Titanium, 
Tantalium, Antimony, Gold, Platina and Rhodium. There are 
four methods of dissolving the metallic sulphurets dn an alka- 
line menstruum. 1. To dissolve the metallic sulphuret in a 
solution of the protosulphuret of potassium, or of the double 
sulphuret of. potassium and hydrogen, (hydrosulphate of pot- 
ash). 2 To dissolve the oxide of the metal by the double suL 
phuret of hydrogen and potassium. 3. To dissolve the metal- 
lic sulphuret by caustic potash ; and, 4. To melt together the 
metallic sulphuret and the carbonate of potash, and afterguards 
to dissolve the melted mass in water. The general result of all 
these ways of dissolution is, that it forms a combination of sul- 
phuret of potassium with the other metallic sulphuret, which is 
added. In the first method, this combination is made directly, 
or when we employ the hydrosulphate, the sulphuretted hydro- 
gen is disengaged by the other sulphuret, whicli replaces it, in 
the sulphuret of potassium. In the second, the sulphuretted 
hydrogen reduces the metallic oxide to the state of sulphuret, 
and the sulphuret thus produced combines with the sulphuret 
of potassium. In the third, a part of the metal is oxidated at 
the expence of the potash, (or the water,) and the metallic oxide 
