CHEMICAL BASIS OF THE ANIMAL BODY. 117 



It may In- formed in the stomach as the result of fermentative 

 changes iu the food, and is frequently present in diabetic mine, as 

 also in traces in normal uriiie. In other organs and fluids it exists 

 only in minute tra 



With I'crru- chlnride it yields a blood-red solution, decolourised by 

 hydrocloric acid. (It differs in this last ivacti'in fmni siilphocyanide 

 Of iron.) Heated vrith alcohol and sulphuric acid, the characteristic 

 <>f acetic ether (ethyl-acetate) is obtained. 



Acetone. CH, . CO . CH,. 



This substance is the typical member of the general class known 

 as ketones, and may be prepared by the dry distillation of calrinm 

 or barium acetate. 



Ketoues are characterised by containing the group CO (carbonyl) in 

 the same way that the aldehyde- an- characterised by the group ('< 1 1. 

 and the acids by the group COOH. The ketones are closely related 

 to the aldehydes and may be regarded as derived from them 1>\- dis- 

 placing the H of the COH group by some monad (alcohol) radicle. 

 They are most usually prepared by the dry distillation of the calcium 

 .-alts of the appropriate acids. Ketones, like the aldehydes, unite 

 readily and directly with phenyl-hydrazin, yielding a class of com- 

 pound-. known as hydrazones. (Cf. p. lOii.) 



Acetone is a volatile liquid, soluble in water, boiling at 56, and 

 possessed of an agreeable ethereal odour. It may be obtained in 

 considerable quantity by distillation from the urine and blood of 

 diabetic patients and accounts for the peculiar ethereal odour which 

 these frequently evolve. 1 This symptom is of serious prognostic 

 importance, and it has been supposed by many authors that tin- 

 fatal diabetic coma which rapidly supervenes is caused by the pres- 

 ence of acetone. 2 The urine of diabetic patients frequently ex- 

 hibits a reddish-violet colouration with ferric chloride, supposedly 

 due to the presence of aceto-acetic acid (CH 8 . CO. CH 2 .('<>< >H > 

 which readily yields acetone by its decomposition. 



Acetone is also not infrequently 'found in the urine and 

 breath (?) of children in apparently normal health. 3 



Acetone gives a characteristic reaction with iodine in presence 

 of an alkali (formation of iodoform) and colour-reactions with 

 sodium nitro-prusside and fuchsin. 4 



Propionic acid. C 2 H 8 . COOH. 



This acid closely resembles the preceding one. It p..--. 

 a very sour taste and pungent odour; H soluble in water, boils 



1 Vim JukM-li. mirif n. fhnrrtiinr, Horlin, IS 1 - history ami 



liti-ratim- of the ubii>< t Cf '/.t . / /./,/.;/. CV,, , IM. vi. (1882), S. 541. 

 - cf. (Janice's />A ./W .r/,,,,, V,,! i 1880. p l'.- 



/ /'//(/.<"/. -Tali' 

 4 Consult IfeubMMr nd N'>t;'-l. // < >< 



