CLEA VAGE PRODUCTS OF THE BILE ACIDS. 379 



It crystallises in colourless rhombohedra, or in four-sided prisms, which have 

 a sweet taste and dissolve easily in cold water (1 in 4 '3) ; in alcohol and ether 

 they are insoluble. Glycocoll, like other amido-acids, can act chemically, either 

 as a base or an acid in forming compounds with acids and bases respectively. 

 As a type of these combinations with bases, the copper compound may be 

 taken. When freshly precipitated cupric hydrate is added to a warm con- 

 centrated solution of glycocoll, it dissolves to form a deep blue solution, which 

 is not reduced on boiling ; on cooling this solution, or on adding alcohol and 

 allowing to stand, fine dark blue needles crystallise out of the composition 

 (ra 2 .CH 2 .C0 2 ) 2 Cu,H 2 0. Glycocoll has been obtained synthetically by the 

 action of ammonia on monochloracetic acid thus : 



NH 3 + CH 2 .C1 COOH = CH 2 .(NH 2 ) COOH + HC1. 



Taurine is amido-isethionic acid, also called amido-oxyethylsulphonic 

 acid (NH^CgH^SOaOH). 1 It occurs in the body, apart from the bile, only 

 in minute and inconstant traces ; it has been stated to occur in the lungs 

 and kidneys of oxen, in some of the organs of cold-blooded animals, and 

 in inconstant traces, probably due to the decomposition of taurocholates, 

 in the intestine. The presence of sulphur in its molecule shows it to be 

 formed from proteids in the body; but the intermediate steps in its 

 formation are unknown. 



Taurine is very easily crystallised, and forms large colourless prismatic 

 prisms with a glassy glance, 2 without any taste, and gritty between the teeth, 

 neutral in reaction and very stable, not being altered by a temperature of 

 240 C. ; heated above this temperature they melt and decompose in so doing. 

 It is much less soluble in cold water than glycocoll, but still easily soluble 

 (1 in 15*5), and still more so in hot water; in alcohol and ether it is insoluble. 

 It is soluble in concentrated sulphuric and nitric acids without decomposition, 

 and the latter acid may even be boiled off, leaving it unaffected ; neither is it 

 affected by boiling with aqua regia. To alkalies also it is much more stable 

 than glycocoll ; it is not affected by weak alkalies, and only by continued 

 boiling in strong alkaline solution is slowly broken up into ammonia, acetic, 

 and sulphurous acids ; so that it is one of the most stable of the organic 

 compounds found in the body. Taurine is also a much more neutral substance 

 in its chemical behaviour than glycocoll j it does not combine at all with acids, 

 and its affinity for bases is very feeble. An amorphous mercury compound is 

 however obtained by boiling a solution of taurine with freshly-precipitated 

 mercuric oxide. 3 



The constitution of taurine is shown by its synthesis from chlorethyl- 

 sulphonic acid by the action of ammonia. 4 



/C^Cl /C 2 H 4 NH 2 



SO/ + 2 NH 3 = SO/ + NH 4 C1 



This synthesis, as well as the fact that taurine is not saponified by 

 dilute alkalies, shows that taurine is not an ester but a sulphonic 

 derivative ; that is, that the sulphur atom is united directly to carbon, 

 and not indirectly by oxygen. Taurine may also be obtained by heating 



1 The amido-oxyethyl radicle is directly united to sulphur in the molecule. 



2 Gmelin, " Ver darning uach Versuchen," S. 60. 



3 Lang, Jahresb. u. d. Fortschr. d. Thicr-Chem., Wiesbaden, 1876, Bd. vi. S. 74. 



4 Kolbe. Ann. d. Chem., Leipzig, 1862, Bd. cxxii. S. 33. 



