obS On ike Colours used in Painting by the Ancients. 



was pale grass green, had the character of carbonate of copper 

 mixed with ciialk ; and a third, which was sea green, was a 

 green combination of copper mixed with the blue copper frit. 



All the greens that I examined on the walls of the baths of 

 Titns were combinations of copper. From the extreme bril- 

 liancy of a green which I found in the vineyard to which I have 

 so often referred, I sUspectcd that it might contain arscnious 

 acid, and be analogous to Scheele's green ; but on submitting it 

 to experiments, it afforded no indications of this substance, and 

 proved to be a pure carbonate of copper. 



The greens of copper were well known to the Greeks ; the 

 most esteemed is described by Theophrastus and Dioscorides 

 under the name oi y^qimoxoKKu^ ^\ni is stated by both to be found 

 in metallic veins. 



Vitruvius mentions chrysoadla as a native substance found in 

 copper mines, and Pliny speaks of an artificial chrysocolla made 

 from the clay found in the neighbourhood of metallic veins, which 

 clay was most probably impregnated with coj)per. He describes 

 it as rendered green by the herb Inteum. There is everv reason 

 to believe, tliat the native chrysocolla was carbonate of copper, 

 and that the artificial was clay impregnated with sulphate of 

 copper rendered green by a vellow dye. 



Some commentators^ have supposed that chrysocolla is the 

 .'same suljstance as borax, because Pliny has mentioned that a 

 preparation called by this name was used by goldsmiths for sol- 

 dering gold* ; but nothing can l)e more gross than this mistake, 

 ivhich, however, has been copied into manv elementary 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 " Hsgt (cO 

 <rx:coXv]Koj," lib. v. c. 92, who says it was prepared from urine 

 treated in brass mortars. Plinv says likewise, that it was pre- 

 pared from " Cypria jeriigine ct pucr; impubis urina, addito ni- 

 trof." The name of clirysocoUa was probably Revived from tlie 

 green powder used by the goldsmiths, and which contained car- 

 bonate of copper as one of its ingredients J. 



Amongst the substances found in the baths of Titus were some 

 masses of a grass green colour. I at first thought these might 



* IJi'.t. dc la Printiire Jincionnc, png. 38. " Nos droguistes la noriime 

 Borax." f Lib. \x\iii. cap. 5. 



X The rommcntators have been likewisp inislrd by PliT\v'« description, 

 " cfirvsocolla humor est in puteis per venam aurrdefliiens, iVc " I hid.; hut 

 this is nieroiy an ii)acciiraie account of the decoinposition of a \cin coii- 

 t.-imins; copper. W(, have no reason for suppo>.ins£ that the (Jitclis ar.d 

 Konians were acquainted with borax. Plinv, probably misled bv the ap- 

 plication of" thf same name to ditVerent subitances, considered chrysocolla 

 as t!ic cement of gold in mineral veins. 



be 



