1821. J of the Atoms of Copper, Zinc, Iron, Manganese, Sfc. S42 



most admirably as far as the bodies at present under our review 

 are concerned. 



I. Copper. 



It will be seen from the preceding table that Dr. Wollaston 

 and Dr. Prout consider the weight of an atom of copper to be 4, 

 while I make it 8. Both the numbers of these gentlemen and 

 my own are deduced from the sulphate of copper, or blue vitriol, 

 the crystals of which, by a careful analysis, 1 have found cona* 

 posed as follows : 



'l; Sulphuric acid lO'OO \ 



Peroxide of copper lO'OO ** 



Water 11-25 "''^ 



31-25 



From this it appears that the salt contains equal weights of 

 racid and base, and that 9-25ths of its weight is water. Now 

 the weight of an atom of sulphuric acid being 5, it is obvious 

 that if we consider blue vitriol a compound of one atom acid and 

 one atom base, an atom of peroxide of copper will weigh 5 

 (exactly the same as sulphuric acid), and consequently an atom 

 of copper will weigh 4. This is the reasoning which led Wol- 

 laston and Prout to fix upon 4 for the atomic weight of copper. 



On the other hand, I am of opinion that blue vitriol is abisul« 

 phate of copper, or a compound of two atoms of sulphuric acid 

 and one atom of peroxide of copper, and that its composition 

 may be thus stated : 



2 atoms sulphuric acid = 10*00 



1 atom peroxide of copper = 10-00 



10 atoms water = 11*25 



31-25 



if diis constitution be admitted, it is obvious that an atom of 

 peroxide of copper must weigh 10, and consequently an atom of 

 copper 8. Now the reasons that lead me to conclude that blue 

 vitriol is a bisulphate of copper are the following : 



(1.) It is well known that copper forms two oxides with oxy- 

 gen, the red and the black, and that the oxygen in the black 

 oxide is precisely double that in the red oxide. Hence I think it 

 likely that the protoxide is a compound of one atom copper + 

 one atom oxygen, and the peroxide of one atom copper -+■ two 

 atoms oxygen. If this be admitted, an atom of copper must 

 weigh 8, and the composition of the oxides will be as follows : 



Protoxide 8 copper + 1 oxygen 



Peroxide 8 +2 



Dr. Wollaston and Dr. Prout must consider the black oxide 



q2 



