10 M. Berzelius on the Composition of the 
nearly four-fifths of it. The black powder which remains, Mr 
Cooper declares to be the true prot-oxide, which contains th 
hundreds of its weight of oxigen ; and what is very re- 
markable, which dissolves in the muriatic acid, and "gives the 
same muriate as is found in the nitro-muriatic solution of pla- 
tinum Dr Thomson adopts the accuracy of the results . 
of Mr Cooper, and with regard to the per-oxide, he reasons in 
the following manner “ Mr E. Davy, says he, has found, that 
100 parts of potassium combine with 11.86 of oxygen ; and M. 
Berzelius has found that 16.494 parts of oxigen combine with 
this same quantity of the metal. The mean of these two ana- 
lyses is 14.177, which is not very remote from 13.269, which 
would be the quantity of oxigen necessary, in order that the 
oxygen of the per-oxide should be three times that of the prot- 
oxide.” From this Dr Thomson sagaciously concludes, that 
the per-oxide of platinum is a trit-oxide. 
M. Berzelius has shewn, that the precipitate obtained by Mr 
Cooper is a mixture, or perhaps also a combination of per-oxide 
of platinum with the proto-muriate of mercury, from which the 
muriatic acid may extract the per-oxide. By the heat necessary 
for the sublimation of the proto-muriate of mercury, the oxide 
of platinum is decomposed, and the progress of this decom- 
position ought to vary both with the temperature employed for 
the sublimation of the calomel, and with the time during which 
the oxide is exposed to this high temperature. M. Berzelius 
has made a new analysis of the per-oxide of platinum, which 
coincides perfectly with the numbers which he has given in his 
Chemical Tables. He placed the double muriate of platinum 
and potash in a small ball, blown in the middle of a piece of 
barometer tube, and he afterwards passed a current of dry hy- 
drogen gas along the tube, heating the ball slightly with a 
lamp. The salt, which does not contain water, was decompos- 
ed ; the hydrogen gas was converted into muriatic acid gas, 
and when the muriatic acid was driven oW in this way, he weigh- 
ed the residue, which contained muriate of potash and metallic 
platinum. The loss was due to the oxy-muriatic gas or the 
chlorine of modern chemists. The muriate of potash was sepa- 
* Journal oftk6 Royal InsiityLtion^ Vol. iiu No. v. p. 122» 
