CHAP. IV.] GLYKOCHOLIC ACID. PETTENKOFER'S REACTION. 297 



Products of When subjected to long continued boiling with 

 decomposition, diluted hydrochloric or sulphuric acid, or when heated 



for X . 2 hours in a sealed tube with a coventrated 

 solution of barium hydrate in a water bath, glyko- 



FIG. 18. SODIUM GLYKOCHOLATE. 



cholic acid combines with a molecule of water and splits up into 

 glycocoll and cholalic acid, thus : 



Ca.H4.NO. + H 2 = C M H0. + CH 2 (NH 2 )COOH 



Glykocholic acid Cholalic acid Glycocoll 



Cholonic acid. According to Hoppe-Seyler 1 , when a solution of 



C 26 H 41 N0 5 glykocholic acid in concentrated sulphuric acid is 



warmed, an amorphous precipitate separates consisting of cholonic 

 acid (cholonsaure) ; this acid is insoluble in water, but readily 

 soluble in alcohol. Cholonic acid has not been obtained in a 

 crystallised condition. It is dextrogyrous and its specific rotation 

 is approximately the same as that of glykocholic acid. It is distin- 

 guished both from glykocholic and cholalic acids by the insolubility 

 of its barium salt in water. Cholonic acid, it will be observed, differs 

 from glykocholic acid in containing one molecule less of H 2 O. 



Pettenkofer's Glykocholic acid, as indeed cholalic acid and all 



reaction. ^ s immediate derivatives, exhibit the reaction known 



by the name of its discoverer 2 ' Pettenkofer's reaction.' 

 In its original form the test is performed as follows : the solution of 

 the substance to be tested is (after the separation of albuminous 

 substances) placed in a test tube or in a porcelain capsule and to 

 it are added 2 or 3 drops of a 10 per cent, solution of cane sugar. 

 When the contents of the tube have been shaken, strong and pure 

 sulphuric acid is added drop by drop, care being taken that the 



1 Handbuch der physiologisch- und pathologisch-chemischen Analyse. Sechste 

 Auflage neu bearbeitet von F. Hoppe-Seyler und H. Thierfelder. Berlin, 1893. See 

 p. 211. 



2 Pettenkofer, 'Notiz iiber eine neue Reaction auf Galle und Zucker.' Annal. d. 

 Chemie u. Pharmac., Vol. LII. (1844), p. 9096. 



