the Combiiiations (^‘Alkalies with Metallic Sulphurets. B 
When the hepar is prepared in a solution, there is only a 
single degree which can be observed between the maximum and 
minimum ; and it is this which forms, when a hydro-sulphate of 
potash is exposed for a sufficiently long time, till its hydrogen is 
oxidated. It is, therefore, KS^. The hepar, which is formed 
by a complete saturation of a lixivium of caustic potash, which 
is boiled with sulphur, contains three-fourths of potash, convert- 
ed into KS^ or into a sulphuretted hydro-sulphuret of potash 
corresponding to it, and one-fourth of potash combined with a 
quantity of hypo-sulphurous acid, which contains three times as 
much oxygen as itself*. When potash is added to it, the state 
of neutrality of the hypo- sulphite changes first, and afterwards, 
by new additions, that of the sulphuretted hydro-sulphuret. 
Among the sulphurets of other alkaline bases, M. Berzelius 
has examined only those of Calcium. The protosulphuret of 
this metal is formed, by passing a current of sulphuretted hy- 
drogen gas over pure lime in a porcelain tube, in a state of in- 
candescence. It forms water and sulphuret of calcium, of a 
light rose colour. It contains no trace of sulphuric acid. The 
sulphuret is not altered by pure water even when boiling. M. 
Berzelius has preserved it under water in flasks, full and well 
corked, during whole months without suffering any alteration. 
A small portion of this sulphuret is soluble in water. This so- 
lution, when evaporated in vacuo, yields a white crystalline mass, 
which, when heated, with the exclusion of air, yields its water 
of crystallization, and becomes sulphuret of calcium. This sul- 
phuret has then a great analogy with the cyanurets, and the sul- 
pho-cyanurets of alkaline radicals which appear soluble in water ; 
whence M. Berzelius concludes, that this may probably be the 
case with the sulphurets of the same radicals. The protosulphuret 
is the only sulphuret of calcium which can be obtained in the dry 
way. In the humid way we can obtain two others of them, one of 
which is CaS*, examined a long time ago by Bucholz and Bern- 
hardi, and more recently by Mr Herschel ; and the other, the 
persulphuret which is obtained pure by digesting the 
protosulphuret with water and sulphur in excess. 
Nearly KS® SKSio. 
