THE BILE. 213 



ture being allowed to remain at rest until the violet and purple colors 

 are developed. 



There are various other substances which yield a red, violet, or purple 

 color, when treated with sugar and sulphuric acid. Among these are 

 oleine, oleic acid, ethereal oil, amyl-alcohol, albuminous matters and the 

 salts of morphine and codeine. Albumen of the blood, white of egg, 

 and the opium alkaloids in the proportion of ten parts per thousand, if 

 treated with Pettenkofer's test, all produce a color un distinguishable 

 from that obtained with the biliary salts. These substances, however, 

 with the exception of morphine, may all be excluded by previously 

 treating the fluid as above described ; namely, evaporating to dryness, 

 extracting with alcohol, precipitating with ether, and dissolving the 

 precipitate in water. The salts of morphine might still remain, as they 

 are soluble both in water and in alcohol, and may be precipitated by 

 ether from their alcoholic solution. This substance, however, is very 

 unlikely to be present in an extract of the animal fluids, especially in 

 the proportion of ten parts per thousand. 



Pettenkofer's test is a very delicate one for either or both of the 

 biliary salts. A watery solution of pure sodium glycocholate, made in 

 the proportion of 1 part to 2000, yields, at the end of fifteen minutes, a 

 clear violet pink color, if the test be applied with care ; and a solution 

 of sodium taurocholate, in the proportion of 1 part to 3000, will give a 

 similar color at the end of an hour. The general characters of the test 

 are the same in both cases, as the reaction is really produced by cholic 

 acid, derived from the decomposition of either the glycocholic or tauro- 

 cholic acid of the original biliary salts. 



Fig. 71. 



SPECTBUM OF PETTENKOFER'S TEST, with the Biliary Salts in watery solution. 



The spectrum of Pettenkofer's test presents certain characters which 

 may be of service in distinguishing it from the reactions produced by 

 other organic substances. Jf either or both of the biliary salts, dis- 

 solved in water, be treated with sugar and sulphuric acid until a violet 

 or purple color is produced, and the colored fluid then placed before the 

 slit of the spectroscope, its spectrum shows a wide and dark absorption 

 band at E, extending usually from midway between D and E to a 

 quarter part the distance between E and F, the central parts of the 



