GASTRIC DIGESTION. 43 



of ammonium sulphate, separated from the solution, and this 

 second solution then thrown away. 



It is now necessary to free the albumose precipitate from 

 the ammonium sulphate clinging to it and inclosed in it. For 

 this purpose dissolve it in water and boil the tolerably dilute 

 solution (best in an enamelled-iron dish) with barium car- 

 bonate, replacing the water which evaporates by hot water. 

 By boiling with barium carbonate the sulphuric acid is com- 

 bined with the barium and the ammonia escapes. Continue 

 the boiling until the fluid no longer smells of ammonia and 

 a filtered portion gives no cloudiness with barium chloride 

 solution and therefore all the sulphuric acid is united to the 

 barium. Then filter. 1 The albumose solution thus obtained 

 very frequently, perhaps always, contains barium, often in 

 considerable amount (shown by adding dilute sulphuric acid 

 to a small portion of the solution). To separate the barium 

 add ammonia and ammonium carbonate as long as a precipi- 

 tate is formed, heat, and filter from the barium carbonate, 

 best after allowing to stand for some time. Evaporate the 

 filtrate on the water-bath to a small volume and precipitate 

 with 95 per cent, or absolute alcohol. The albumoses pre- 

 cipitate in the form of a viscous mass. Let stand for some 

 hours under the strong alcohol, best with renewal of the 

 alcohol, until the mass has become hard and brittle, pour off 

 the alcohol, grind the residue in a mortar with absolute alco- 

 hol, bring the whole mass into a vessel which may be closed, 

 let stand in this for twenty-four hours, filter, and wash with 

 ether. We thus obtain a fine white or yellowish-white pow- 

 der, which according to Kiihne is a mixture of four substances : 

 dysalbumose, protalbumose, heteroalbumose, and deutero- 



1 The filtrate should be clear ; however, a slight cloudiness does not 

 matter in case the solution is afterwards to be treated with ammonium 

 carbonate, as the precipitate of barium carbonate thereby formed carries 

 down with it the remainder of the barium sulphate. 



