CHAP. IV.] THE MUCOID NUCLEO-ALBUMIN OF THE BILE. 337 



Two methods are available for the separation of the nucleo- 

 albumin in a, pure and unaltered condition, of which the second is 

 the best : 



Firstly. Bile is subjected to dialysis in running water for many 

 days, thymol being added to prevent putrefaction ; in this way the 

 bile acids and the greater part of the bile colouring matters are got 

 rid of. The contents of the dialyser, which possess a neutral reaction, 

 a pale yellow colour, and are opalescent and somewhat viscid, are 

 precipitated by the addition of a few drops of hydrochloric acid. 

 The precipitate is washed, dissolved in the smallest available quantity 

 of solution of sodium hydrate and the solution is purified by dialysis. 



Secondly. Bile, which must have previously been filtered, is 

 mixed with five times its volume of absolute alcohol and, immediately 

 thereafter, is centrifugalised. In 10 minutes the precipitate, which 

 has aggregated into a coherent mass, is taken from the tubes, freed 

 from adhering liquid by pressing between layers of filter paper, and 

 is then broken up and suspended in water. It gradually dissolves, 

 yielding an opalescent, greenish-yellow, slimy liquid. In order to 

 purify it further, it is once, or even twice, again precipitated as 

 above, centrifugalised, and dissolved in water, the ultimate solution 

 being viscous ; it is, however, an essential condition to success 

 that the substance should remain in contact with alcohol for as short 

 a time as possible. 



Reactions of The neutral viscid solution does not coagulate on 

 a solution of boiling, but becomes opaque. If a trace of acetic acid 

 not sufficient to produce a precipitate be, however, 

 added to it and the solution be then heated, an 

 albumin like coagulum is obtained. When acetic acid is added to 

 the solution of nucleo-albumin at ordinary temperatures, it produces 

 a precipitate which is soluble, though with some difficulty, in an 

 excess of the precipitant. In the presence of salts of the bile acids, 

 the precipitate contains considerable quantities of the latter and is 

 not soluble in excess of acetic acid. Thus is explained the fact that 

 the precipitate of the nucleo-albumin, obtained by treating bile with 

 acetic acid, is insoluble when the latter is added in excess, whilst it 

 is obvious that all determinations of the nucleo-albumin made in this 

 manner cannot be relied upon. 



A solution of the nucleo-albumin in acetic acid is precipitated 

 by potassium ferrocyanide, iodohydrargyrate of potassium, mercuric 

 chloride, and tannic acid. Aqueous solutions are precipitated when 

 treated with a very small quantity of hydrochloric acid, the flocculent 

 precipitate, thus produced, being readily soluble in excess of hydro- 

 chloric acid. The aqueous solution is precipitated by all the general 

 reagents which precipitate the albuminous substances. 



The following reactions are of special importance, as distinguishing 

 the mucoid nucleo-albumin from the other groups of albuminous 

 substances, on the one hand, and from the mucins, *on the other : 



G. 22 



