46 THE PKOTEINS. 



THE ALBUMINATES. 



These are called also acid and alkali albumins. They 

 are formed from the albuminous substances by the action 

 of acids or alkalies. They are soluble in water which con- 

 tains a small amount of acid or alkali, but are not in neu- 

 tral solution. Consequently they are precipitated when 

 their solution is neutralized. They differ from the glob- 

 ulins by being insoluble in dilute salt solutions. They are 

 not coagulated by boiling. The alkali albumin has the 

 properties of an acid, giving a slight acid reaction. Simi- 

 larly the acid albumin has a slight alkaline reaction. They 

 are named from the manner in which they are produced, 

 and not according to their reaction. 



ACID ALBUMIN. 



104. Prepare by adding dilute HC1 to a solution of 

 egg-albumin till it contains 0.1 per cent, of the acid. 

 Allow it to stand an hour, at about body-temperature, then 

 filter and neutralize with very dilute sodium hydrate, being 

 careful not to add an excess, as this would dissolve the 

 precipitated acid albumin. Wash the precipitate in water. 



105. Notice that the acid albumin is soluble in acids, 

 though insoluble in water. Make a solution in dilute HC1 

 and boil. It is not coagulated. 



106. Make acid albumin by the action of strong 

 HC1, HN"0 3 , or acetic acid on serum-albumin or egg-albu- 

 min, warming if necessary. It is formed very quickly. 

 Neutralize a portion with sodium hydrate. It is precipi- 

 tated. Show that it gives the xanthoproteic reaction and 

 biuret reaction, though it is not precipitated by boiling. 



