24 Dr THOMAS THOMSON on some Experiments on Gold. 



The authority of these philosophers is deservedly of the greatest 

 weight, and has, I believe, induced chemists, so far as I have had 

 an opportunity of judging of their opinions, to consider the per- 

 oxide of gold as a ter-oxide. 



1. In order to determine the quantity of oxygen combined 

 with gold, when in the state of peroxide, I dissolved a known 

 quantity of pure gold in nitro-muriatic acid, and rendered the 

 solution as neutral as I could, by evaporating it to dryness in a 

 very moderate heat, and then dissolving the crystallised salt in 

 distilled water. 



It has been long known, that proto-sulphate of iron has the 

 property of precipitating gold from its solution in muriatic acid, 

 in the metallic state, and that the salt is at the same time con- 

 verted into persulphate of iron, obviously by uniting with the 

 oxygen previously in combination with the gold. 



I have shewn in my " Attempt" vol. i. p. 343, that an atom 

 of iron weighs 3*5, and that the oxides of this metal are compo- 

 sed as follows : 



Protoxide of 1 atom iron, + 1 atom oxygen, 

 Peroxide of 1 + H 



If the atomic weight of gold be 25, as I have shewn it to be, 

 and if peroxide of gold contain 3 atoms of oxygen, then, in or- 

 der to reduce 1 atom of peroxide of gold to the metallic state, it 

 is obvious that we must employ 6 atoms of protoxide of iron ; so 

 that to reduce 28 grains of peroxide of gold, we must employ 

 27 grains of protoxide of iron. To see how far this supposition 

 was well-founded, 50 grains of gold were dissolved in nitro-mu- 

 riatic acid ; 208'5 grains of newly crystallised protosulphate of 

 iron were dissolved in warm distilled water, and the two solu- 

 tions were mixed. 



