ISOLATION AND PREPARATION 21 



temperature up to the boiling-point of the solvent, for, if the alcohol is 

 sufficiently concentrated, the proteins which dissolve in it are entirely 

 unchanged. At higher temperatures the proteins dissolve more quickly 

 than at lower. The dissolved protein can be separated from the filtered 

 extract either by diluting with water or by concentrating, best under 

 diminished pressure and at a temperature below 50, whereby the 

 alcohol is removed to such an extent that the protein separates from 

 the nearly aqueous residual solution. It is important in carrying out 

 this concentration to avoid high temperatures toward the end of the 

 process, for in the presence of relatively much water the protein is easily 

 coagulated at high temperatures, and when a part has been thus 

 rendered insoluble the subsequent filtration of the extract becomes 

 exceedingly difficult, if not impossible, although but little insoluble 

 matter may be present. From concentrated alcoholic solutions the 

 protein may also be separated by adding absolute alcohol, for none 

 of these proteins is soluble except in alcohol containing some water. 

 The precipitation by absolute alcohol can be made more complete by 

 adding ether, and this method affords an excellent means for separat- 

 ing from the protein the fats and oils which are invariably extracted 

 from the seed together with it. 



