176 On the Definite Proportions in which the [March, 



acquired a slightly reddish tinge. The 97 parts of residue analyzed 

 by combustion left 91*3 per cent, of oxide of lead. Hence the 

 salt is composed of 



Acetic acid 570 100 



Oxide of lead 91-30 1G08 



Water 3*00 53 



Here the acid is combined with six times as much base as in the 

 neutral acetate, and the water of combination contains half as much 

 oxygen as the oxide of lead. 



1-06 parts of effloresced acetate of lead, equivalent to 0'333 of 

 acetic acid, produced by combustion 0"13 of water and 0^74 of 

 carbonic acid. Hence 100 of acetic acid are composed of 



Hydrogen 6*35 



Carbon 46*83 



Oxygen 46*82 



100-00 



Now 15'56 X 3 = 46-68. Hence it follows that acetic acid 

 contains three volumes of oxygen. The other numbers correspond 

 with four volumes of carbon and six volumes of hydrogen. Sup- 

 posing, then, acetic acid composed of 6 H + 4 C -f 3 O, its 

 composition will be as follows : — 



Hydrogen 6-195 



Carbon 46-871 



Oxygen 46-934 



100-000 



The real capacity of saturation of this acid is 15-63, instead of 

 15-56, determined by experiment. 



There is an approximation between the results of Gay-Lussac and 

 Thenard and mine. According to them, 100 acid are composed of 

 5-629 hydrogen, 50-222 carbon, and 44-147 oxygen ; but when we 

 consider that their experiments were made with acetate of barytes, 

 which, to judge from the quantity of barytes found in it, must 

 have contained a quantity of combined water, the oxygen in which 

 was equal to that in the barytes — when we consider this, it is obvious 

 that they must have obtained much more hydrogen and oxygen than 

 my experiments indicate, instead of a smaller quantity. Probably 

 their balls were so much dried as not only to dissipate all the 

 moisture, but likewise to oxidate a portion of the hydrogen of the 

 acid. 



6. Gallic Acid. — It is difficult to obtain pure gallic acid. What 

 I employed was obtained by leaving infusion of nutgalls exposed to 

 the influence of the air. The small crystals thus procured were 

 dissolved in water, and crystallized again. I tlicn exposed the 



