Ill 
on the colours used in painting by the Ancients. 
same substance as borax, because Pliny has mentioned that 
a preparation called by this name was used by goldsmiths for 
soldering gold ; * but nothing can be more gross than this 
mistake, which, however, has been copied into many elemen- 
tary books of chemistry. The material used for soldering 
gold consisted of carbonate or oxide of copper mixed with 
alkaline phosphates. This is evident from the description of 
Dioscorides “ m <txuXvikos Lib. v. c. 92, who says it was 
prepared from urine treated in brass mortars. Pliny says like- 
wise, that it was prepared from “ Cypria aerugine et pueri 
impubis urina, addito nitro/'-f The name of chrysocolla was 
probably derived from the green powder used by the gold- 
smiths, and which contained carbonate of copper as one of its 
ingredients.^ 
Amongst the substances found in the baths of Titus were 
some masses of a grass green colour. I at first thought these 
might be specimens of native chrysocolla ; they proved indeed 
to be carbonate of copper, but it had formed round longi- 
tudinal nuclei of red oxide of copper, so that probably these 
substances had been copper nails or small pieces of copper 
used in the building, converted by the action of the air, during 
so many centuries, into oxide and carbonate. 
The ancients, as it appears from Theophrastus, were well 
* Hist, de la Peinture ancienne, pag. 38. <e Nos droguistes la nomme Borax.” 
+ Lib. xxxiii. Cap. 5. 
J The commentators have been likewise misled by Pliny’s description, “ chryso- 
colla humor est in puteis per venam auri defluens. See.” Ibid; but this is merely an 
inaccurate account of the decomposition of a vein containing copper. We have no 
reason for supposing that the Greeks and Romans were acquainted with borax. 
Pliny, probably misled by the application of the same name to different substances, 
considered chrysocolla as the cement of gold in mineral veins. 
