500 DIGESTION. 



strong sulphuric acid. A purple color is developed. To dis- 

 tinguish between the purples given by bile and by albumin, ex- 

 amine the test-tubes by the spectroscope. The bile acids give 

 four bunds; the first at D, the second and third between D and 

 E (the second being nearer D, the third close to E), the fourth 

 at F. If the solution is dilute, the third band is seen sharply, 

 the second less distinctly, and the other indistinctly. The col- 

 ored albuminous solution gives only one band between E and F. 

 Detection of Bile Acids in the Urine They are usually 

 present only in small quantities in the urine, even in severe 

 cases of jaundice. Various methods of applying Pettenkofer's 

 test have been proposed, one of which (Strassburg's) is applied 

 as follows: Add a little cane sugar to some urine containing 

 bile acids, dip a piece of filtering paper into it, let it dry com- 

 pletely, put a drop of pure sulphuric acid upon it, and allow 

 the acid partially to run off. In a quarter of a minute a beau- 

 tiful violet color appears, which is best seen by holding up the 

 paper to the light and looking through it. In all doubtful 

 cases, and whenever accurate results are required, the bile 

 ari'ls should be separated before applying the test, see 204. 



* 141. Crystallized. Bile. Mode of Preparation. 

 Evaporate bile to a quarter of its volume, mix it with a con- 

 siderable quantity of animal charcoal, rub them thoroughly 

 together, and then heat the mixture on a water-bath till it is 

 perfectly dry. Put it immediately, while still warm, into a 

 flask, cover it with absolute alcohol, cork the flask, and let it 

 stand for a good while, shaking it occasionally so that the 

 alcohol may dissolve out all the bile salts. Filter, and pour 

 the filtrate into a perfectly dry stoppered bottle, large enough 

 to hold four times as much. Add ether to it, until no further 

 precipitate is produced ; then replace the stopper, and put the 

 bottle aside for a few days. If the alcohol and ether are both 

 anhydrous, the precipitate which falls consists of microscopic 

 crystals, but generally it forms a resinous mass at the bottom 

 of the flask, which after several days, or weeks, begins to 

 ci -\>tallize, and groups of silky needles appear. 



To preserve the crystals, pour off the mixture of alcohol and 

 ether, wash them with pure ether, evaporate the adhering ether 

 from them in vacuo, and replace the stopper in the bottle. 

 The crystals, if left exposed, take up moisture, and form a 

 resinous mass, which is eventually converted into a syrupy 

 fluid. Crystallized bile is very soluble in water and in alco- 

 hol, but insoluble in ether. 



Composition of Crystallized Bile. Crystallized bile consists 

 of the sodium salts of glycocholic and taurocholic acids. To 

 separate these two acids from the base and from each other, 

 dissolve the crystals or the resinous precipitate in water, and 

 add first solution of neutral lead acetate, and then a little basic 



