338 On a cheap Snbjtdulc for Oil Taint, 



If any doubt fhould ftill remain, that an addition of oxy- 

 gen is indifpenfably neccflary to convert acetous into aCTtfc 

 acid, the following experiment mutt, in my opinion, en- 

 tirely remove it. 



Exper. IV. Equal parts of di (tilled vinegar, concentrated 

 by freezing, and of oxide of manganefe in powder, mixed to- 



f ether and diddled to drvnefs, gave me the following pro- 

 ucts. There firft paffed about one half of the vinegar, 

 which had not experienced the leaft alteration. 1 then 

 changed the receiver, and the acid which I obtained had ac- 

 quired the odour which characterizes the acetic acid. When 

 it was thus proved that the addition of oxygen is indifpen- 

 fably neccflary to convert acetous into acetic acid, it re- 

 mained for me to examine how the oxygen effects that 

 change, — whether by taking from it a portion of its carbon, 

 as Chaptal fuppofes, or rather by combining with it, as the 

 following experiment will prove. 



I repeated the fecond experiment in a mercurial appa- 

 ratus, that I might collect the carbonic acid gas, which 

 would necefTarily be difengaged if the acetous acid parTed 

 to the ftate of acetic acid only in confequence of lofing a por- 

 tion of its carbon, which in this operation muft have com- 

 bined with the oxygen of the manganefe. When the opera- 

 tion was terminated, lime water did not mow the lead atom 

 of carbonic acid. 



From the above experiments I think myfelf authorized to 

 conclude, 



i ft, That there is a difference between the acetous and 

 the acetic acid. 



2d, That this difference is owing to a greater proportion 

 of oxygen in the acetic than in the acetous acid. 



3d, That the acetous may be converted into acetic acid, 

 by combining it with a new quantity of oxygen. 



4th, That the acid, in what is now called acetate of potafh, 

 is in the ftate of acetous acid. 



5th, That the acetic acid obtained from the decompofition 

 of that fait, by the means of fulphuric acid, is owing to a 

 portion of oxygen which it takes from the latter acid. 



LI 1 1. On a cheap Subjiitute for Oil Faint. 



V>». Cadet de Vaux has lately publiihed a memoir, on 

 what he calls painting in diftemper with milk. His pro. 

 eel's, which is nearly fnnilarto that of Ludic, given in the 

 tii ft volume of this Magazine, is as follows : 



Take 



