1822:} Composition of the Alkaline Sulphurets. 349 
Four atoms of sulphur would be 82°12 ; there is in this case 
the difference of 6°43. { took this combination at first for K S*, 
but having mixed a portion of the solution with nitrate of cop- 
per, it formed to my great surprise a precipitate of sulphuret of 
copper. Other metallic salts produced a similar effect ; conse- 
quently the solution contained more sulphuretted hydrogen than 
had been formed by the oxidation of the potassium. Mixed with 
an acid, it became turbid and milky ; but the precipitated sul- 
phur formed only a very small deposit ; and the remainder of this 
substance escaped in the form of sulphuretted hydrogen gas. 
It was then evident that the combination effected in the dry 
way was composed of sulphuret of potassium and sulphuretted 
hydrogen; or if we suppose it to be a double sulphuret K S$? + 
2 H? S; that is to say, that the potash and hydrogen combine 
with an equal quantity of sulphur, it follows that 100 parts of 
potassium combine with 82°12 of sulphur, and with 2°60 of hydro- 
gen, making together 84°72 parts. The excess was undoubtedly 
derived from access air, which, by oxidizing the hydrogen at its 
expense, occasioned a higher degree of sulphuration, the preci- 
pitate produced by acids. 
It became then interesting to discover if the neutral hydrosul- 
phuret of potassium is similarly constituted. With this view, I 
saturated a portion of pure potash with sulphuretted hydrogen 
gas, and heated the mixture to ebullition, passing a current of 
hydrogen gas through the apparatus until all the excess of sul- 
phuretted hydrogen gas was expelled. One part ofthis solution 
was precipitated by muriate of copper added drop by drop. The 
precipitate was collected on a filter, well washed, dried, and 
heated in a retort, until nothing but sulphuret of copper at a 
minimum remained; it weighed 1°82 gramme. After the 
remainder of the copper had been separated by sulphuretted 
hydrogen from the solution, it was evaporated to dryness, and 
gave 1*7] gramme of muriate of potash: there were, therefore, 
2 atoms of copper to 1 atom of potash. It is evident from this, 
that to form a neutral hydrosulphuret, the potash takes such a 
quantity of sulphuretted hydrogen, as that the hydrogen is 
double the quantity which is required to form water with the 
oxygen of the potash, and that this hydrosulphuret i its dry 
state may be represented, like the preceding combination, by 
KS? + 22S. 
It is well known that the composition of sulphuret of potas- 
sium at a minimum is such, that when it 1s destroyed by water, 
an hydrosulphuret is formed in which the potash is half saturated 
with sulphuretted hydrogen when compared with the above 
compound. We here meet with the two degrees of saturation 
which M. Gay-Lussac has mentioned, but the composition of 
which he has not described. We shall in the sequel examine, 
whether they are actually what they appear to be ; that is to 
say, whether they are hydrosulphurets. 
