126 PROTO-ALBUMOSE. [BOOK II. 



The aqueous solution which has been dialysed and 

 thus separated from heteroalbumose, possesses, as do, 

 according to Kiihne, all solutions of albumoses, an alkaline reaction. 



In order to obtain proto-albumose in a state of purity, the solu- 

 tion is saturated with NaCl, the precipitate dissolved in water, and 

 the process of precipitation and solution repeated four times. 



From the watery solution of this purified proto-albumose, the 

 solid substance is obtained by precipitating directly with alcohol, or 

 by first concentrating the solution in the water bath and then adding 

 alcohol to the concentrated solution. The alcohol precipitate is 

 washed successively with alcohol and ether, after treatment with 

 which, proto-albumose is obtained in thick, snow-white masses. The 

 substance is highly soluble, and although its solution is not effected 

 immediately, the quantities dissolved are so great, that a solution of 

 syrupy consistence can be obtained. The solutions are colourless, 

 not perfectly, although almost perfectly, transparent, and have an 

 alkaline reaction. 



When nitric acid is added, drop by drop, to a pure solution of 

 proto-albumose, a white precipitate falls which at first disappears 

 when the fluid is mixed by shaking, a fresh precipitate occurring on 

 addition of more acid. The precipitate which persists after adding 

 a sufficient quantity of acid, disappears on heating, but is deposited 

 again as the liquid cools. An excess of nitric acid, even in the cold, 

 dissolves the precipitate at first formed, the solution assuming a 

 yellow colour ; sodium chloride added to it throws down a precipitate 

 which is entirely dissolved by heat, and deposited again on cooling. 



Solutions of proto-albumose are precipitated by acetic acid and 

 potassium ferrocyanide. If the quantity of acetic acid be small 

 the precipitate is undissolved by heat ; if, on the other hand, strong 

 acetic acid be added to the solution, a larger quantity of ferro- 

 cyanide is required to produce a precipitate, but this is dissolved on 

 heating the liquid, which becomes turbid on cooling. 



Solutions of proto-albumose if saturated w r ith NaCl and filtered, 

 become a little less transparent when boiled, and the turbidity con- 

 tinues when they are cooled. The addition of a trace of acetic acid to 

 such solutions causes them to become very turbid. 



Cupric sulphate, mercuric chloride, and basic lead acetate, cause 

 heavy precipitates, which in the case of the first and third of these 

 reagents are soluble in excess of the precipitant. These precipitates are 

 only partially dissolved when the liquid in which they occur is boiled. 



Treated with a trace of copper sulphate and a large quantity of 

 solution of sodium hydrate, solutions of proto-albumose exhibit the 

 beautiful red- violet so-called 'biuret' reaction. When boiled with 

 lead acetate and alkali, solutions assume a dark colour due to the 

 formation of PbS 2 . 



Proto-albumose is laevogyrous. Kiihne and Chittenden deter- 

 mined the specific rotation of five different preparations of the sub- 

 stance and obtained the following results : 



