THE BILE ACIDS. 375 
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 filtrate. 
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. 
Glycocholic acid (C 2G H 43 X0 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 Lieberkithn, Jahresb. ii. d. Fortschr. d. ges. Med., Erlangen, 1S52, Bd. i. S. 113. 
- Hoppe-Seyler's Mcd.-cliem. Untcrsuch., Berlin, S. 160. 
