METAPROTEINS. 



51 



2. It is important to add exactly the amount of acetic acid mentioned, 

 that is, one per mille above the amount required to give a faint permanent 

 precipitate. 



3. The same method can be employed for the crystallisation of serum- 

 albumin from the perfectly fresh serum of a horse, ass or mule. 



H. The Metaproteins. 



The metaproteins are derived from the albumins and 

 globulins by hydrolysis. This can be effected rapidly by 

 dilute acids and alkalies at temperatures over 60 C. (see 

 Exs. 29 and 30) : more slowly at body temperature. They are 

 formed immediately by the action of strong mineral acids 

 at room temperature. They are insoluble in water, strong 

 mineral acids, and all solutions of neutral salts, but are 

 soluble in dilute acids or alkalies in the absence of any 

 large amount of neutral salts. They are not thrown out 

 of solution (in acid or alkali) by boiling. But if such 

 a solution be neutralised or precipitated by the addition of 

 an excess of a neutral salt, the suspended metaprotein is 

 coagulated on boiling, so that it will no longer dissolve in 

 acid or alkali. 



Preparation. Egg white or serum is diluted with ten times its volume 

 of either 0-4 per cent, hydrochloric acid or o-i per cent, sodium hydroxide and 

 the mixture placed in a water bath or incubator at 40 C. for about twenty-four 

 hours. The albumins and globulins are hydrolysed to metaprotein. 



43. Neutralise about 25 cc. with 2 per cent, sodium carbonate, 

 or 0-4 per cent. HC1, depending on the original reaction of the 

 fluid. A bulky precipitate of metaprotein forms. The acid or 

 alkali should be added until the maximum amount of precipitate is 

 produced. The reaction then will probably be very slightly acid 

 to litmus. Filter. The nitrate generally comes through very 

 slowly. When as much as possible of the fluid has been removed in 

 this way transfer the fluid on the paper to a small beaker, open the 

 paper, and add the precipitate to the fluid that has been poured off, 

 dilute with a little water, and divide the suspension into six equal 

 portions and with them perform the following six exercises. 



44. Add some 0-4 per cent. HC1. The precipitate dissolves. 

 Neutralise with sodium carbonate: the precipitate reappears. 



