M. Berzelius on the Oa)ides of Platinum and Gold. 9 
composed, so that it forms potash and a sulphuret of potassium 
with more sulphur. When an acid is poured into it, this last 
converts the potassium into potash. The excess of sulphur in 
this last substance combines with the antimony, and the potas- 
sium, which can no longer oxidate itself at the expence of the 
oxide of antimony which remains undissolved, decomposes the 
water, and gives birth to the sulphuretted hydrogen. The 
quantity of sulphur auraturrt is greater, when the Kermes is pre- 
pared by the fusion of sulphuret of antimony with carbonate of 
potash ; for, on this occasion, it is formed of the antimonite of 
potash, and a part of the antimony is reduced to the metallic 
state. 
% Account of M. Berzelius'^s recent Experiments on the Com^ 
position of the Oxides (f Platinum and Gold. 
a. Oxides of Platinum. 
l)r Thomson, who has undertaken to correct analyses which 
have been made with the utmost care by other chemists, and 
who assures us, not without ostentation, that he has found the 
true results, at the same time that he commits serious mistakes 
whenever he does not follow in the track of a skilful predecessor, 
has, in the fifth edition of his System of Chemistry, (vol. i. p.501.) 
rejected the analyses of the oxides of platinum made by M. Ber- 
zelius, and substituted in place of them the analyses of a 
pretended prot-oxide by Mr Cooper. M. Berzelius having dis- 
covered the proto-muriate or proto-chloride of platinum, he de- 
composed it by heat, and determined the quantity of metallic 
platinum which remained. The proto-muriate is decomposed 
by the caustic alkalis, which take up the muriatic acid, and 
leave a black oxide, soluble in alkalis and acids, with a green- 
ish or rather black colour. M. Berzelius deduces in an incon^ 
trovertible manner the composition of this oxide from that of 
the proto-muriate. He afterwards decomposed the ordinary 
muriate of platinum with metallic mercury, and found that the 
metal was combined in it with two times as much oxygen as in 
the prot-oxide. Mr Cooper, who found these methods o5yVc- 
tionabUf precipitates a solution of muriate of platinum with 
nitrate of mercury, and heats the precipitate thus obtained at 
a temperature necessary to sublime the calomel, which forms 
