THE BILE A CIDS. 3 7 5 



The different solubilities of the lead salts of the two acids provides 

 another means of separating glycocholic acid; the separation of pure 

 taurocholic acid from the mixture by this method is more difficult. 



Glycocholate of lead is thrown out of solution on the addition of neutral 

 acetate of lead to a solution of a mixture of the bile salts ; the remainder of 

 the glycocholate and all the taurocholate are thrown down on the addition of 

 ammonia or of basic acetate of lead to the nitrate. 



Fresh ox bile is treated with alcohol to precipitate the pseudo-mucin. 

 The alcohol is evaporated off, and neutral acetate of lead added as long as a 

 precipitate forms ; this precipitate is collected and decomposed by warming 

 with a solution of sodium carbonate, whereby sodium glycocholate is formed ; 

 the mixture is next evaporated to dryness, and extracted with alcohol, in which 

 the sodium glycocholate dissolves. This alcoholic solution is filtered, the 

 filtrate is evaporated to dryness, and the residue is dissolved in water. The 

 watery solution of sodium glycocholate so obtained is decolorised with animal 

 charcoal, and the glycocholic acid thrown out of solution by adding a mineral 

 acid. Finally, it can be recrystallised, either from boiling water, or by the 

 addition of ether to its alcoholic solution. Taurocholic acid can be obtained 

 from the filtrate from neutral acetate of lead, by fractional precipitation with 

 basic acetate of lead, as the remaining glycocholate unprecipitated by the 

 neutral acetate is precipitated by the portion of basic acetate first added. 1 

 Basic acetate of lead is stirred into the filtrate from the neutral acetate, until 

 the precipitate commences to gather into a sticky mass, when the addition is 

 discontinued, and the solution decanted off from the precipitate. More basic 

 acetate solution is now added, and throws down a plastic mass, consisting of 

 fairly pure taurocholate of lead. This precipitate is dissolved in boiling 

 alcohol, filtered warm into water, and the resulting reprecipitated mass, after 

 being purified by kneading, is dried, dissolved in a small quantity of alcohol, 

 decomposed with sulphuretted hydrogen, filtered from lead sulphide, and 

 dried at first in the air, afterwards in a vacuum over sulphuric acid. 



Taurocholic acid is, however, best prepared from dog's bile, as 

 described by Parke. 2 



The bile is evaporated down, extracted with alcohol, decolorised with 

 animal charcoal, evaporated to dryness, dissolved in absolute alcohol, and 

 treated with excess of ether. After some time the crystalline precipitate of 

 sodium taurocholate so obtained is dissolved in water, and the solutions 

 precipitated with acetate of lead and ammonia. The precipitate is collected, 

 washed, suspended in alcohol, or dissolved therein by boiling, and decomposed 

 by sulphuretted hydrogen. The filtrate from sulphide of lead is evaporated 

 to a small volume, and mixed with excess of ether, when the taurocholic acid 

 is precipitated as a syrup, in which, after some time, small crystals appear. 

 These are in the form of fine needles which deliquesce in the air. 



Glycoclwlic acid (C 26 H 43 N0 6 ) is a monobasic acid, crystallising in 

 long fine needles, which fell together into a light, voluminous mass 

 when first formed from a solution, and on drying form a loose, snowy 

 white mass with a silky glance. These crystals melt at 100 C., losing 

 water in so doing and forming glycocholonic acid ; they are very 

 sparingly soluble in cold water (1 in 300), somewhat more soluble in 

 boiling water (1 in 120), and so can easily be recrystallised from hot 

 water ; they are easily soluble in alcohol and in acetic acid, but soluble 

 in ether with great difficulty. Glycocholic acid and its salts in solution 



1 Lieberkiilm, Jahresb. ii. d. Fortschr. d. ges. Med., Erlangen, 1852, Bd. i. S. 113. 



2 Hoppe-Seyler's Mcd.-cliem. Untersuch.. Berlin, S. 160. 



