HYDROXY-, KETO- AND DIBASIC ACIDS up 



Aceto-acetic acid is converted by reduction into -hydroxy- 

 butyric acid, and vice versa, /3-hydroxybutyric acid is converted by 

 oxidation into aceto-acetic acid. It seems most likely that aceto- 

 acetic acid, the keto acid, is the chief product of the oxidation of 

 butyric acid. 



The formation of aceto-acetic acid in the organism from fat when 

 carbohydrate is withheld from the food explains its formation in 

 diabetes. Here the organism has lost its power of utilising the carbo- 

 hydrate in the food, or its power of utilising carbohydrate is greatly 

 diminished. 



Aceto-acetic acid is very unstable and is readily converted into 

 acetone and carbon dioxide. This decomposition occurs spontaneously 

 in normal urine. 



The three closely related substances, /3-hydroxybutyric acid, 

 aceto-acetic acid and acetone are generally referred to in medical 

 literature as the acetone bodies. There is no basis for the older 

 statement that mild cases of diabetes excrete only acetone, that severer 

 cases excrete acetone and aceto-acetic acid, and that still severer cases 

 excrete /3-hydroxybutyric acid in addition. It seems to have been 

 due to a misinterpretation of the tests and to the inadequacy of our 

 methods of estimating these substances. 



The occurrence of acetone in the breath of diabetics can be ac- 

 counted for by the difference in the blood circulation. This is slow 

 through the systemic system and lung capillaries through which the 

 blood passes before it goes to the kidney. Venous blood is more 

 acid than arterial blood, so that the conditions for the decomposition 

 of aceto-acetic acid are most favourable. Acetone is very volatile 

 and if decomposition occurs during the passage of the blood through 

 the lungs it would pass into the expired air. 1 



Tests. 



The various tests for aceto-acetic acid were reviewed and sum- 

 marised by W. H. Hurtley in 191 3 in the " Lancet " for 26th April, and 

 the following preparation of a dilute solution of sodium aceto-acetate 

 was described : 



13 gm. of pure ethyl aceto-acetate are treated with 100 c.c. of 

 normal caustic soda and diluted to 500 c.c. The ester is almost 

 completely hydrolysed by allowing this solution to stand for 44'$ 

 hours. A solution containing I gm. of aceto-acetic acid is obtained 

 by diluting it to 5000 c.c., or better, by diluting 49-2 c.c. of this solu- 

 tion to I litre. This solution is conveniently used for the tests. 



'See the excellent account by Kennaway in the "Guy's Hospital Reports," Vol 

 LXVII. 



