482 
SECOND REPORT — 1832. 
Sulphate of copper. —The detection of copper in bread in 
several parts of France and the Netherlands has led to the dis¬ 
covery that in many places the bakers put sulphate of copper 
into their dough, for the purpose of improving the colour and 
lightness of their bread. The many analyses which have been 
made for the purpose of detecting it, however, have led to some 
interesting results. Meissner has shown that the detection of 
copper in grain is not always a proof of adulteration, for that 
copper exists in small quantity in many kinds of grain. This 
interesting result has been confirmed by other chemists, and 
M. Sarzeau in particular states* that he has found traces of it 
in two hundred vegetables, and that it exists in gelatine and in 
butchers-meat, in the proportion of one grain to every fifteen 
pounds, and in the cheese he has examined, in that of four 
grains and a half to fifteen pounds. 
Berthier f has lately analysed a native sulphate of copper, 
found in large quantities in South America. It occurs in the 
• • • 
form of a green powder, and is composed of 4 Cu + 3 S + 4 H. 
Red salts of manganese .—Mr. Pearsall J has published a 
very ingenious paper on the red colour occasionally developed 
in the salts and solutions of manganese. This he endeavours 
to show to be due at all times to the presence of permanganic 
acid. Allowing that in some instances the colour is due to the 
presence of this acid, it is sufficient to advert to the coloured 
salts of manganese to show that the colour is often wholly inde¬ 
pendent of any higher degree of oxidation than the protoxide. 
PfafF first drew the attention of chemists to the fact that there 
exist two sulphates of manganese, one of which is colourless, 
the other of a rose-red tint. Berzelius §, in his experiments to 
determine the atomic weight of this metal, obtained both the 
sulphate and the protochloride of this rose-red tint, and there¬ 
fore saturated the solutions with sulphuretted hydrogen to de¬ 
oxidize the permanganic acid which he supposed to colour them, 
but found it impossible by this process to render them colour¬ 
less. And lastly, Brandes|| has shown that the colourless and 
red sulphate have both the same composition;—we can there¬ 
fore explain the fact in no other way than by supposing that 
they are isomeric combinations of the same elements. 
Peroxalate of iron , action of light upon. —The peroxalate 
of iron kept in solution for several hours, at a temperature of 
* Journal de Pharmacie, November 1832, p. 653. 
f Annates de Chimie, i. p. 360. 
+ Journal of Royal Institution, ii. p. 49. 
§ Arsberdttelse, 1831, p. 190. 
jl Poggendorf’s Annalen , xx. p. 556. 
