146 PHYSIOLOGICAL CHEMISTRY. 



PETTENKOFER'S lest for bile-acids is performed as follows. A 

 small quantity of bile in substance is dissolved in a small porcelain 

 dish in concentrated sulphuric acid and warmed, or some of 

 the liquid containing the bile-acids is mixed with concentrated 

 sulphuric acid, taking special care in both- cases that the temper- 

 ature does not rise higher than 60-70 C. Then a 10$ solution of 

 cane-sugar is added, drop by drop, continually stirring with a glass 

 rod. The presence of bile is indicated by the production of a beau- 

 tiful red liquid^ whose color does not disappear at the ordinary 

 temperature, but becomes more bluish violet in the course of a day. 

 This red liquid shows a spectrum with two absorption-bands, the 

 one at F and the other between D and E, near E. 



This extremely delicate test fails, however, when the solution is 

 heated too high or if an improper quantity generally too much 

 of the sugar is added. In the last-mentioned case the sugar easily 

 carbonizes and the test becomes brown or dark brown. The reac- 

 tion readily fails if the sulphuric acid contains sulphurous acid or 

 the lower oxides of nitrogen. Many other substances, such as al- 

 bumin, oleic acid, amylacohol, morphin, and others, give a similar 

 reaction, and therefore in doubtful cases the spectroscopic exami- 

 nation of the red solution must not be forgotten. 



PETTEJTKOFER'S test for the bile-acids depends essentially on the 

 fact that furfurol is formed from the sugar by the sulphuric acid, 

 and this body can therefore be substituted for the sugar in this test 

 (MYLIUS). According to MYLIUS and v. UDRANSZKY a 1 p. m. solu- 

 tion of furfurol should be used. Dissolve the bile, which must 

 first be purified by animal charcoal, in alcohol. To each c. c. of the 

 alcoholic solution of bile in a glass add 1 drop of the furfurol solu- 

 tion and 1 c. c. cone, sulphuric acid, and cool when necessary so that 

 the test does not become too warm. This reaction, when per- 

 formed as described, will detect ^5 ?V milligram cholalic acid 

 (v. UDRANSZKY). Other modifications of PETTEKKOFER'S test have 

 been proposed. 



Glycocholic Acid. The constitution of that glycocholic acid 

 occurring in human and ox bile, which has been most studied and 

 which is identical with the cholic acid of STRECKER and GMELIN, is 

 represented by the formula C^II^NOe. Glycocholic acid is absent 

 or nearly so in the bile .of carnivora. On boiling with acids or 



