22 PHYSIOLOGICAL CHEMISTRY. 



Synopsis 01 the Most Important Properties of the Different Chief 

 Groups of Albuminous Bodies. 



Albumins. These bodies are insoluble in water and are not 

 precipitated by the addition of a little acid or alkali. They are 

 precipitated by the addition of large quantities of mineral acids or 

 metallic salts. Their solution in water coagulates on boiling in the 

 presence of neutral salts, but a weak saline solution does not. If 

 NaCl or MgS0 4 is added to saturation to a neutral solution in 

 water at a normal temperature or at -j- 30 C. no precipitate is 

 formed ; but if acetic acid is added to this saturated solution the 

 albumin readily separates. When ammonium sulphate is added 

 in substance to saturation to an albumin solution a complete pre- 

 cipitation occurs at ordinary temperature. Of all the albuminous 

 bodies the albumins are the richest in sulphur, containing from 1.6 

 to 2.20. 



Globulins. These albuminous bodies are insoluble in water, 

 but dissolve in dilute neutral salt solutions. The globulins are 

 precipitated unchanged from these solutions by sufficient dilution 

 with water; and on heating they coagulate. The globulins dis- 

 solve in water on the addition of very little acid or alkali, and on 

 neutralizing the solvent they reprecipitate. 



The solution in a minimum amount of alkali is precipitated by 

 carbon dioxide, but the precipitate may be redissolved by an excess 

 of the precipitant. The neutral solutions of the globulins contain- 

 ing salts are partly or completely precipitated on saturation with 

 NaCl or MgS0 4 in substance at normal temperatures. The globu- 

 lins contain an average amount of sulphur, not below 10. 



A sharp line between the globulins on one side and the artificial albu- 

 rn in ates on the other can hardly be drawn. The albuminates are, indeed, 

 as a rule insoluble in dilute common-salt solutions ; but sin albuminate may 

 be prepared by the action of strong alkali which is soluble in common-salt 

 solutions immediately after precipitation. We also have globulins which are 

 insoluble in NaCl after having been in contact with water for some time. 



Nucleoalbumins. These bodies are found widely diffused in 

 both the animal and vegetable kingdoms. They form one of the 

 chief constituents of protoplasm, while the albumins and in part 

 also the globulins are special constituents of the animal juices. 



