258 0N THE ARSENATES OF COPPER AND TROtf; 



changes the nature of thefe fluids fo much, that their medical 

 properties are partly deftroyed. What happens to certain 

 pharmaceutical preparations, fuch as decoclions of medicines, 

 when white of egg and heat is ufed to clarify them, is well 

 known; for, in that cafe, they become almoft ineffectual, 

 if care, has not been taken (o double the proportion of in- 

 gredients which enter into their compofition. Lewis has ob- 

 ierved, that this operation deprives the fyrup of diacodium of 

 all its medical properties. 



Such are the obfervations which I have thrown together re- 

 fpecting clarification. JVTy defign in communicating them has 

 been to prove that this operation, though fimple in appear^ 

 ancc, cannot be praclifed without fome fkill and attention ; 

 and that among the number of proceflfes commonly ufed, feveral 

 afford remits lcfs fatisfaclory than others. It is neccflary, 

 therefore, to determine with regard to the choice of methods 

 . • according to the nature of the fubftances made ufe of. I have 



confined myfelf to a clear narration of the facts ; others may 

 direct their attention to the explanations of the mode in which 

 thefe fubftances operate. 



IV. 



On the Difcovery of the Arfeniates of Copper and of Iron. By a 

 Correjpondent. 



Difcovery of the AN article * of the Decade Philofophique (30 Nivofe), 



arfeniates of cop- giving an account of the firft trimeftre of the tenth year of the 



tributed to Vau- French Republic, fays, that Citizen Vauquelin has enriched 



quelin. the catalogue of mineral bodies by the difcovery of two new 



fubftances, arfeniate of copper and arfeniate of iron. I am 



far from imputing to this able analyft the defire of attributing 



to himielf any difcovery to which he has no title ; but the 



French chemifts, whether from ignorance or intention, pay fo 



little regard to the discoveries of others, that it becomes the 



duty of every friend of fcicncc to point out their violations of 



biftorical juftice. 



True itatement In the year 1786, Mr. Klaproth examined an ore from 



of their hiftory. Cornwall, and found it to be arfeniate of copper. Schlotheion 



-prow. publifhed a description of it in 1790. 



• ' *• By Cit. Lacepcde, Secfetaiy, 



