5 1 8' Oxygeaation of Metals, — Difference hctivcen the Acetous and Acetic Acids. 



that the copper iu the green fand of Peru, ;uid in the native muriate of Chili, are in this 

 (late. 



It is of importance to remark, that the chemill might be induced to believe, that when 

 a metallic fubllance is difoxygenated in any manner whatever, whether by the applicatioa 

 of ftrong heat, or by the affinities of other metals for oxygen •, or, in the manner of Proult, 

 by hepatic gas, as happens in the difoxygenation of the tunitic and molybdic acids; the 

 chemifl might think, that thefc fubftances, at their tranfition to the violet blue, or black 

 colour, were reduced to the metallic ftate : but the effeft is, as he remarks, merely an incom- 

 plete difoxygenation. The metal is merely depreffed to the minimum, as happens with iron 

 and copper, when by various means diey are brought from their entire ftate of oxygenation, 

 to that in which the colour becomes blue, black, or red, more or lefs deep. There are no 

 metals b«t mercury, gold, and arfenic, in which a complete difoxygenation is obferved. 



But to return to tin : Prouft has found, with Bergman, that tin oxyded to the minimum 

 acquired no more than an addition of 30 parts in the hundred, and even in this ftate is not 

 exempt from marine acid. If it be ignited in a crucible it lofes weight, and emits the 

 vapours of muriate of tin ; and when the tin is oxyded to the maximum it is charged with 40 

 pci cent. But it is eafy to reduce it 30, in which ftate it is blueifli, and infoluble in acids. 

 The author here terminates his memoir, by remarking, that although Pelletier has not men- 

 tioned the white muriate of copper, he is not lefs perfuaded that it -Svas known to that 

 chemift ; and this more particularly, becaufe he has fpoken flightly of the difoxydation of that 

 metal by tin, as if he meant to fpeak more fully on another occafion. But while he renders 

 this juftice to Pelletier, he affirms with the open freedom of truth, that though his refults 

 coincide with thofe of that chemift, they were not undertaken fubfequent to his experiments. 



There are a great number of otlier fails and obfervations in the Memoir of Prouft which 

 defei-ve to be related ; but the abundance and denfity of thefe fa£ls are fuch, that tlie 

 attempt to communicate them would convert this abridgement into a memoir no. lefs ample 

 than the original. 



XV. 



Obfervations on the Dlffirences which exijl between the Acetous and Acetic Acids. By J. A. 



Chaptal.* 



T, 



H E acid of four wine prefents to our obfervation two very diftimSi ftates, which arc 

 known by the names of the acetous and the acetic acids. 



Chemifts have hitherto referred this difference to the varying proportion between the 

 oxygen and the radical, and it has generally been believed, that the acetic acid differs from 

 the acetous fimply in a ftronger dofe of the acidifying principlef. 



Citizen Adet has refumed this interefting refcarch, and has prefented to the foeiety a courfe 

 of experiments, from which he concludes : 



• Annales de Chimie, XXVIII. 113. 

 t We may except Citizen Peres, who, in the Journal des Pharmaciens, has anntunced, that the difference 

 Wtween the acetous and acetic acids confifts in the proportion of cirbone.— C. 



I. That 



