THE AROMATIC OXY-ACIDS. 279 



to the common methods of analysis. To estimate the amount, the 

 final distillate is neutralized with barium hydrate, evaporated to dry- 

 ness, and the residue weighed. This weight less that of the barium, 

 which is in combination, and which can be determined as barium 

 sulphate, after incineration and extraction with dilute hydrochloric 

 acid, indicates the amount of the fatty acids in general. 



/9-Oxybutyric Acid. 



This acid is never found in the urine under normal conditions. 

 It is principally met with in the severer forms of diabetes, when it 

 is associated with the presence of diacetic acid and acetone. It may, 

 however, also be found in other diseases, as in the continued fevers, 

 in cachectic conditions, inanition, etc. As a general rule it is found 

 in combination with the common alkalies of the blood, but when it 

 is produced in especially large amounts a corresponding quantity of 

 ammonia is furnished by the body to effect its neutralization. It 

 may happen, however, that the acid formation exceeds that of am- 

 monia, and in such cases the free acid occurs in the urine, and can 

 also be demonstrated in the blood as such. Symptoms of acid in- 

 toxication then exist, and it is noteworthy that in such cases the 

 amount of carbonic acid in the blood has been found markedly 

 diminished, showing that the alkaline salts are not present in suffi- 

 cient amount to remove the carbonic acid from the tissues. 



As regards the origin of the /9-oxybutyric acid, there is evidence 

 to show that it may originate from the albumins, but it is question- 

 able whether this is its only source. Some writers claim that it may 

 also originate from the fats, and they adduce as proof the observa- 

 tion, that the amount of acetone which, as seen below, is a deriva- 

 tive of /9-oxybutyric acid, is increased by a diet rich in fats, even 

 though there may be no increased destruction of tissue-albumins. 

 On the other hand, it may be said that no proof has been offered 

 to show that an increased destruction of tissue-fat increases the 

 production of acetone, and it is quite likely that the increased 

 elimination on a diet rich in fats is referable to an increased produc- 

 tion in the alimentary canal as the result of bacterial action, and 

 resultant absorption and elimination in the urine. More plausible 

 is the supposed origin of /9-oxybutyric acid from the carbohydrates. 

 During tke katalysis of the latter, and notably the hexoses, accord- 

 ing to Magnus-Levy, lactic acid is formed, which is readily decom- 

 posed into formic acid and acetic aldehyde. Through a condensation 

 of two molecules of the latter /9-oxybutyric aldehyde would then be 

 formed, which on oxidation yields /9-oxybutyric acid, as shown by 

 the equations : 



(1) C 6 H 12 6 = 2 CH 3 .CHOH.COOH 



(2) CH 3 .CHOH.COOH == H.COOH + CH 3 .CHO 



(3) CH 3 .CHO + CH 3 .CHO = CH 3 .CHOH.CH 2 .CHO 



(4) CH 3 .CHOH.CH 2 .CHO + O = CH 3 .CHOH.CH 2 .COOH 



