APP.] CHEMICAL BASIS OF THE AXIMAL BODY. 735 



Heated with sulphuric acid it yields carbonic oxide and water ; with 

 caustic potash it gives hydrogen and oxalic acid. 



Acetic acid. C 2 H 3 O . OH. 



Is distinguished by its characteristic odour; its boiling point is 

 117C. ; it solidifies at 5 and is fluid at all temperatures above 15C. 

 It is soluble in all proportions in alcohol and water. 



It occurs in the stomach as the result of fermentative changes in the 

 food, and is frequently present in diabetic urine. In other organs and 

 fluids it exists only in minute traces. 



With ferric chloride it yields a blood-red solution, decolourized by hydrochloric 

 acid. (It differs in this last reaction from sulphocyanide of iron.) Heated with 

 alcohol and sulphuric acid, the characteristic odour of acetic aether is obtained. It 

 does not reduce silver nitrate. 



Propionic acid. C 3 H 5 O . OH. 



This acid closely resembles the preceding one. It possesses a very 

 sour taste and pungent odour; is soluble in water, boils at 141C., 

 and may be separated from its aqueous solution by excess of calcic 

 chloride. 



It occurs in small quantities in sweat, in the contents of the stomach, 

 and in diabetic urine when undergoing fermentation. It is similarly 

 produced, mixed however with other products, during alcoholic fermen- 

 tation, or by the decomposition of glycerine. It partially reduces silver 

 nitrate solution on boiling. 



Butyric acid. C 4 H 7 O . OH. 



An oily colourless liquid, with an odour of rancid butter, soluble in 

 water, alcohol, and aether, boiling at 162C. Calcic chloride separates 

 it from its aqueous solution. 



Found in sweat, the contents of the large intestine, faeces, and in 

 urine. It occurs in traces in many other fluids, and is plentifully 

 obtained when diabetic urine is mixed with powdered chalk and kept at 

 a temperature of 35 C. It exists, as a neutral fat, in small quantities 

 in milk. 



This is the principal product of the second stage of lactic fermenta- 

 tion. (See Dextrose.) 



Valerianic acid. C 5 H 9 O . OH. 



An oily liquid, of penetrating odour and burning taste ; soluble in 

 30 parts of water at 12C., readily soluble in alcohol and sether. Boils 

 at 175 C. Possesses, in free and combined form, a feeble right-handed 

 rotation of the plane of polarisation. 



