Acids. 163 



bonat ; and thus the tube speedily increases to a 

 stalactite. The atmosphere contains about one- 

 hundredth part of carbonic acid gas diffused in it. 



There are yet several acids referable to the 

 vegetable kingdom, some of which are native, 

 others artificial, products. These are the acetic, 

 tartar ic, citric, gallic (acid of nutgalls), oxalic 

 (acid of sorrel), malic (of apples), benzoic (of 

 gum benzoin). I shall notice in particular the 

 four first. 



The acetic acid, commonly called vinegar, is 

 (as its name expresses, vin aigre, sour wine) any 

 proper vinous liquor rendered acid by oxygen 

 absorbed from the atmosphere. In this country 

 the infusion of malt after fermentation is made 

 into an impure vinegar, which being distilled 

 becomes a clear colourless liquid, moderately 

 acid. By freezing, and by chemical processes, 

 this may be deprived of its water to such a de- 

 gree as to constitute a very strong acid of a 

 pungent smell, and crystallizable at 22 of the 

 thermometer. 



This acid is a production of most extensive 

 utility, not only in diet and medicine, but in the 

 arts. Combined with copper it forms verdigris, 

 and with lead the salt improperly called sugar 

 of lead. There are acetats of copper and some 

 other metals. 



If this acid is exposed to a red heat, there are 

 soon no remains of it to be seen, unless it is 

 united to a fixed alkali, in order to repress its 

 volatility. If the neutral salt also produced by 



