Utilitjf ofVruJfiate of Copper as a Vigment. 359 



traiSted, but, on the contrary, if poffible, more completely 

 confirmed by the author's writings fince that period, I have 

 been lefs fcrupulous in applying thefe quotations to my pur- 

 pofe. Though another author has, in one folitary ieuieiKe, 

 apparently flatly contraditled C. Fourcroy, yet, on a cloioc 

 infpe6lion of the work, (2de edition conjidrahlement aug- 

 mejit e,)\s\v\c\\ I (hould call a /Z^zVf/ edition, it does not appear 

 that any one of thefe habitudes or anomalies has beeri clearly 

 demonllrated to exift. The fentence is, to fay no more of 

 it, evidently conditional, and no mention made either of con^ 

 centratian or dilution: " Tous les acides mineraux decom- 

 pofcnt ce fel," {meaning carbonate de bariie".) But my 

 doubts were completely removed, at leaft refpeiiing what I 

 have ftated at Nos. 3 and 4, when I read a whole pagef, 

 where we find detailed a molt circuitous proccfs for purifying 

 nitrous acid by litharge and nitrate of (ilver. 



I purpoielv forbear to mention any method I purfued to 

 accomplifli each combination; as it appears to me to be 

 within the limits of the meaneft capacity, and obvious to 

 every chemift to obtain the fame refults. 



No. loS, Long Acre, 

 January 44, 1K03. 



LXII. On the Utility of VrvJJiafe of Copper as a Pigment, 

 £y Charles Hatchett, EJq. F.R.S.X 



JL HE accidental difcoverv made by Diefbach of the pig- 

 ment called Berlin or Pruitian blue, about the year 1710, 

 and which afterwards was publiihed by Woodward in the 

 Pbilofophical Tranfaftions for 1724, was foon adopted by 

 artifts and manufacturers, fo that in a Ihort time the grpat 

 utility of this colour was completelv eltabliOied: it is there- 

 fore remarkable, that but little attention has been fubfequently 

 paid to the colorific properties of the other metallic pruiliiUes. 



The experiments made by Mr. Brown with the prulfic lix- 

 ivium on various metallic folutions do not merit particular 

 attention, as the refuli.i evidently fliow that a very laro,e por- 

 tion of the alkali remained unfaturaled with pruflic acid, and 

 thus the efTeCts appeared different when the lixivium was pre- 

 pared with blood or with mufclc §. 



Bergman has, however, more accurately examined the pro- 



• Analyfe, &:c. § 7. — " All tlic mineral acids decompofe this fait.*' 



t Manuel il'un L'ours dc Cliirriie. La G'-in^f. 



X From JournaU of the Royal Inltitution of Great Britain. 



§ Phiiolupliical Truiirddtiuiik i-'24, p. 17. 



Z 4 pcrlics 



