CHEMISTRY. 



57 





Acetic 

 acid. 



How ob- 

 tained. 



7f proper- 

 ties* 



ORDBR II. Crystallizable, not ivlatilizable. 



ORDER III. Not cryttallizable. 



ORDER IV. Calorific. 



SECT. I. Of Acetic Acid. 



This has been the longest known of all the acids. 

 It is obtained by causing trine or beer to undergo a 

 new Fermentation. They become sour, and are known 

 by the name of vinegar. When the vinegar is dis- 

 tilled, a transparent colourless liquid is obtained, call- 

 ed dittilled vinegar) or sometimes acetous acid. When 

 this substance is combined with oxide of copper, and 

 the dry mass distilled, a liquid is obtained, which 

 contains the acid in a much more concentrated state. 

 It was formerly called radical vinegar, and acetic acid, 

 by way of eminence. 



It is now known that the acid principle in all these 

 three liquids is precisely the same, and that they dif- 

 fer merely in the concentration of that acid, or in 

 consequence of containing small quantities of some 

 foreign ingredient. Hence, the term acetic acid is 

 now applied to the acid in all cases. 



Acetic acid is a liquid, transparent and colourless 

 like water. It has a peculiar and well known aro- 

 matic smell, when in the state of vinegar or distilled 

 vim-gar. In radical vinegar this smell is not so agree- 

 able, being mixed with a kind of empyreumatic 

 odour. When sufficiently concentrated, it may be ob- 

 tained in crystals; but the process is difficult, and re- 

 quires particular precautions to ensure success. 



The specific gravity of distilled vinegar varies from 

 1 .'X)7 to 1 .0095 : that of radical vinegar is 1 .080. 

 But the strength of the acid is not always propor- 

 tional to its specific gravity, owing to the presence 

 of foreign bodies, from which it is very difficult to 

 free it. It is very volatile, unites with water in any 

 proportion, and reddens vegetable blues. 



Neither oxygen, the simple combustibles, or incom- 



V0L. V|. PART I, 



bustibles, have any action on tliis acid. It oxidizes El 

 some metals ; but its action on thtse bodies is not 

 violent. It combines with metallic oxides, and forms 

 with every one a soluble salt. Indeed all the salts 

 that contain acetic acid are soluble in water. In this 

 respect it agrees with nitric acid. 



It combines with salifiable bases, and forms a class 

 of salts called acetate*. 



Sulphuric and nitric acids seem capable of decom- 

 posing it, but the action of the other acids is not 

 remarkable. It dissolves and combines with many 

 vegetable bodies, and is, in consequence, useful in ve- 

 getable analysis. 



It is composed of oxygen, hydrogen, and carbon, Compoei- 

 according to the experiments of Thenard and Gay- " OB * 

 Lussac, in the following proportions : 

 Oxygen, 44.147 

 Hydrogen, 5.629 

 Carbon, 50.224 



100 



SECT. II. OfBenzoic Ac'uL 



This acid is obtained, by sublimation, from a resi- fieazoic 

 nous substance called benzoin. acld> 



It is a fine light white matter in small needles. It Its proper- 

 is not brittle, but has a kind of ductility. Its taste t' 1 ' 5 - 

 is acrid, hot, and somewhat bitter. Its odour is 

 weak but aromatic. Its specific gravity is 0.667. It 

 reddens the most delicate vegetable blues. 



It is easily volatilized by heat. It burns when 

 kindled, and leaves no residuum. It is not altered 

 by exposure to the air. Cold water dissolves no sen- 

 sible quantity of it, but it dissolves readily in hot 

 water. 



It is not acted upon by oxygen gas, or by any of 

 the simple combustibles or incombustibles ; nor does 

 it seem capable of oxidizing any of the metals. 



It combines with the salifiable baaes, and form* a 

 class of salts called ttrnzoates. 



Several of the strong acids dissolve it ; but it is 

 precipitated again unaltered by the infusion of wateV. 

 Alcohol dissolves it copiously. 



SECT. III. Of Sebacic AciS. 



This acid was mentioned many years ago, but its Sebacic 

 nature and properties remained unknown till it was acld - 

 lately examined by Thenard. Berzelius has lately 

 added considerably to our knowledge of it. It may 

 be prepared by the following process. 



Distil hog's lard ; wash the product with hot wa- How pre- 

 ter, separate this water and drop into it acetate of pared- 

 lead. A flaky precipitate appears which is to be 

 washed and dried, mixed with sulphuric acid and 

 heated. A melted substance, like fat, swims on the 

 surface. This substance, i=. bebacic acid. 



Sebacic acid is white ; it has no smell ; its taste is a lu proper- 

 pleasant sour, leaving in the mouth a very slight im- tie 1 * 

 pression of bitterness. It r> ildens vegetable blues. 

 When heated, it melt* like tallow, and, ou cooling, 

 concretes into a crystallized mass. It may be volati- 

 lized, but requires a higher temperature than benzoic 

 acid. Bcrzelius bat shown that thu acid, in most of 



