1226 ACIDS OF THE ACETIC SERIES. 



Acetic acid. CH 3 . COOH. 



Is distinguished by its characteristic odour ; its boiling- 

 point is 118 C. ; the anhydrous acid solidifies at about 17. 

 It is soluble in all proportions in alcohol and in water. 



It may be formed in the stomach as the result of fermenta- 

 tive changes in the food, and is frequently present in diabetic 

 urine, as also in traces in normal 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 sulpho- 

 cyanide of iron.) Heated with alcohol and sulphuric acid, the char- 

 acteristic odour of acetic ether (ethyl-acetate) is obtained. 



Acetone. CH 3 . CO . CH 3 . 



This substance is the typical member of the general class 

 known as ketones and may be prepared by the dry distillation 

 of calcium or barium acetate. 



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

 and possessed of an agreeable ethereal odour. It may be ob- 

 tained in considerable quantity by distillation from the urine 

 and blood of diabetic patients and accounts for the peculiar 

 ethereal odour which these frequently evolve. This symptom 

 is of serious prognostic importance, and it has been supposed 

 by many authors that the fatal diabetic coma which rapidly 

 supervenes is caused by the presence of acetone. The urine of 

 diabetic patients frequently exhibits a reddish-violet colora- 

 tion with ferric chloride, supposedly due to the presence of 

 aceto-acetic acid (CH 3 . CO . CH 2 . COOH) which readily yields 

 acetone by its decomposition. 



Acetone is also not infrequently found in the urine and 

 breath (?) of children in apparently normal health. 



Acetone gives a characteristic reaction with iodine in pres- 

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

 with sodium nitro-prusside and fuchsine. 



Propionic acid. C 2 H 6 .COOH. 



This acid closely resembles the preceding one. It possesses 

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

 at 141 C., and may be separated from formic and acetic acid 

 by taking advantage of the superior solubility of its lead salt 

 in cold water. 



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 fermentation. 



It is stated to have been found occasionally in normal urine. 



