ALBUMIN. 41 



Purified egg-albumin may be prepared by the following 

 method: 



84. Separate the white from the yelk and cut it for some 

 time with scissors or beat it up to a strong foam. Allow this to 

 subside; filter or press it through clean, unsized muslin; mix it 

 with an equal volume of water, and, after the precipitate has sub- 

 sided, filter it. Saturate the filtrate at about 20 with very finely 

 powdered magnesium sulphate, added in small portions with con- 

 tinual stirring. When it is saturated filter off the precipitated 

 globulins and dialyze the filtrate until a portion gives only a faint 

 turbidity with barium chlorid. The solution will increase in vol- 

 ume during the operation. It should be concentrated in flat dishes 

 at 40 to 50, again dialyzed, and finally evaporated to dryness at 

 the above temperature. It still contains 1 to 3 per cent, of ash. 



85. To obtain purified serum-albumin the blood must be 

 drawn into a dry vessel and the fibrin coagulated by beating. 

 Filter this out through muslin and separate the corpuscles from 

 the serum by a centrifugal machine or by allowing it to stand in a 

 tall cylinder until the corpuscles have settled. Horse-blood, if 

 obtainable, is best for this purpose. Then draw off the clear 

 serum with a siphon, dilute it with three volumes of a saturated 

 solution of ammonium sulphate, and add gradually, stirring con- 

 tinually, finely powdered ammonium sulphate until the liquid is 

 saturated. Filter off the precipitate, which contains serum- 

 albumin and paraglobulin, and wash it with a saturated solution 

 of ammonium sulphate. It will be purer if it is dissolved in a 

 small quantity of water and the precipitating and washing are 

 repeated. Dissolve the precipitate while it is still moist in the 

 smallest possible quantity of water and dialyze it. The para- 

 globulin separates out as a white flocculent precipitate, while the 

 albumin remains in solution. Filter out the globulin and wash 

 it with water. It is insoluble in water, but soluble in dilute 

 solutions of neutral salts. It is precipitated by neutral salts like 

 ammonium sulphate, magnesium sulphate, or sodium chlorid. Its 

 sodium chlorid solution coagulates at about 75. 



If the solution of serum-albumin contains no globulin, it will 

 not be made turbid by adding to a small portion magnesium sul- 

 phate to saturation. In that case it is to be carefully neutralized 

 with ammonia, the salts dialyzed out, the contents of the dialyzer 



