34 ANIMAL CHEMISTRY LECTURE II. 



properties are common to all the acids under consideration. They 

 are all volatile, inflammable, saponifiable, monobasic, and decom- 

 posible in a similar manner under the influence of the same 

 reagents. We are not in the habit of regarding vinegar in any 

 form as an inflammable material, but in reality strong acetic acid 

 is almost as inflammable as alcohol. It only requires to be heated 

 externally for a few minutes, wken it burns as you observe with 

 a large, lambent, feebly luminous flame. Neither are we in the 

 habit of regarding the acetates as soaps, yet solutions of acetates 

 possess the property of forming a persistent froth or lather to such 

 an extent as to be highly characteristic ; so that by searching out 

 for latent resemblances we can perceive that the different members 

 of the series, from the top to the bottom, are associated with one 

 another in a very intimate manner. 



(33-) ^he P r i mar y aromatic acids at present known are far less 

 numerous, and the series consequently is far more limited, as 

 shown in this table : 



Monatomic Aromatic Acid Series 



C 6 H 4 0, Collie ? 



C 7 H 6 2 Benzaic 



C 8 H 8 O a Toluic 



C 9 H I0 3 Picic 



C IO H ia O a Cuminic 



These acids correspond generally with the previously considered 

 fatty acids, in the reactions of which they are susceptible, and in 

 their mutual relationship. The first on the list, or collie acid, is 

 said to result from the artificial oxidation of albuminous matter, 

 but its existence is at any rate open to question. Next we have 

 benzoic acid, which is usually regarded as the representative in the 

 aromatic, of acetic acid in the fatty series. This is followed by 

 two acids of which at present comparatively little is known, 

 namely, the toluic and picic ; while the list is terminated by cu- 

 minic acid, a product formed by the spontaneous oxidation of the 

 chief constituent of oil of cumin. Now, just as the acetic, pro- 

 pionic, and butyric acids are associated each with their respective 

 hydrocarbons, alcohols, aldehydes, and more highly oxidised acids, 



