1824.] the Metallic Sulphates by Hydrogen Gas. 335 



residual oxidum manganoso-manganicum weighed 0*425 gr. It 

 dissolved completely in muriatic acid, and the solution was not 

 rendered turbid by muriate of barytes, and was found to contain 

 no foreign body, except a trace of iron. 0494 Mn S 2 are pro- 

 portional with 0434 Mn -f 2 Mn ; which does not much exceed 

 the experimental result. We may conclude from this experi- 

 ment that manganglanse is a compound of one atom manganese 

 with two atoms sulphur. That the loss of weight was a little 

 greater than it ought to have been was a necessary consequence 

 of the protocarbonate of manganese mixed with the ore, which 

 could not be completely separated, notwithstanding every possi- 

 ble care. Even when we rind pieces which appear quite pure, 

 if we heat them in a little glass capsule, they always become 

 spotted with small brown flocks of decomposed carbonate. 

 These may always be easily perceived if we examine the matter 

 through a glass. 



Reduction of Sulphate of Zinc by Hydrogen Gas. 



The zinc vitriol employed in these experiments was prepared 

 by dissolving pure oxide of zinc in distilled sulphuric acid. The 

 salt was moderately heated to render it anhydrous without 

 driving off any of the acid. It was then treated with hydrogen 

 gas exactly in the same way as the protosulphate of manganese. 

 At the same temperature in which that salt was reduced, the 

 sulphate of zinc began likewise to be decomposed ; sulphurous 

 acid and water were given out ; and in a short time the reduc- 

 tion was completed. A little before that period, the matter 

 swelled up and acquired a motion ; at the same time its temper- 

 ature augmented, in consequence of which a small portion of 

 metallic zinc was sublimed, and attached itself to the upper part 

 of the apparatus. 



The reduced substance was pulverulent and straw-yellow. 

 When treated with sulphuretted hydrogen gas a considerable 

 portion of water was formed. It dissolved in muriatic acid with 

 the evolution of sulphuretted hydrogen gas, and the solution was 

 not rendered turbid by muriate of barytes. Hence it was 

 evidently a mixture of sulphuret and oxide of zinc. 



The loss of weight during the reduction of the salt was in three 

 careful experiments as follows : In one experiment 0*544 gr. of 

 zinc vitriol left 0*305 gr. or 56*07 per cent. In the next 2*933 

 gr. of the salt left 1*708, or 58*23 percent; and in the third 

 1*106 gr. of salt left 0*664, or 56*95 percent. 



The quantity of oxisulphuret here obtained is greater than it 

 ought to be if the compound were analogous to the oxisulphuret 



of manganese ; that is to say, Zn + Zn S- *, for 100 parts of 



sulphate of zinc correspond by calculation with 52*52 Zn + Zn 

 S 9 , a quantity which deviates considerably from that actually 



