100 Inquiry into the Lanvi of Jffimty. 



is formed, the precipitation is capable of continuing by the mere force of cohefion of the 

 gold to itfelf. 



7. What Ihave juft dated is verified in the precipitation of copper "by iron. When a 

 folution of copper is decompofed by a plate of iron, and the copper attached to the plate is 

 feparated, it is perceived by the brown colour of the interior furface, that the copper is not 

 there pure, and that it contains fome iron. After this firft flratum the copper continued to 

 precipitate, by contrafting an adherence with itfelf, and afterwards with thofe coats which 

 are fucceffively formed ; fo that the affinity for the iron began the effeft, which was conti- 

 nued by that of the copper for itfelf. 



8. Phofphorus precipitates feveral metallic folutions, as has been explained by Sage and 

 Bouillon*. Though it has a ftrong affinity with oxigen, yet what has juft been explained 

 relative to precipitation by the metals, ought to be applied to its a£tion. 



Pelletier has proved, that phofphorus has the property of combining with metals, fo that 

 a part of that which is put in aftion is capable of combining with oxigen, while the other 

 ac\s equally upon the metal. 



Among the metallic folutions there are fome which are not affefted by phofphorus ; in 

 others the metal is precipitated in oxide, which doubtlefs retains part of the acid of the 

 folution, or of the phofphoric acid which is formed ; in others the metal is at length re- 

 duced. Gold, Giver, copper, and mercury, are among thofe whicb refume the metallic 

 ftate. 



On conGdering the obfervations which have been made on this precipitation, it appears 

 that copper and filver are precipitated by combining with a fmall portion of phofphorus; 

 thus, to precipitate twelve grains of filver, three grains of phofphorus are confumed. But 

 only about three grains of phofphoric acid, in a gelatinous ftate, were obtained: now, one 

 grain of phofphorus only would be neceflary to produce this quantity of acid ; there con- 

 fequently remain more than two grains, which muft have combined with the filver. , 



A part only of mercury thus treated refumes the metallic ftate ; the reft preferves the 

 ftate of an oxide, and combines with the phofphoric acid. Here the force of cohefion is 

 weak } and no combination is made with the phofphorus : hence the efFe£l is but partial, as 

 when iron is ufed. (No. IV.) 



Though the affinity of gold for oxigen is very weak, and much inferior to that of cop- 

 per, its precipitation is not fo quickly efFefted, and a portion is precipitated in the ftate of 

 oxide } this doubtlefs happens becaufe it has little difpofition to combine with phofphorus ; 

 and it is by the combination of copper with phofphorus, that the precipitation of the lattes 

 ^netal is determined. 



Some of the obfervations which I have here prefented require the accuracy of experiment 

 for their entire explanation : but all appear to me indubitably to prove, that it is the force 

 of cohefion which tends to recombine the particles of a one individual metal, and it is the 



• Journal de Phyfique, 178 1. 



mutual 



