100 HOW CROPS GROW. 



(one to one and one-half parts potash to 1000 parts of water), and the 

 liquid, after standing some days at rest, may be poured off from any 

 residue of starch. On adding acetic acid in slight excess, the purified 

 albuminoids are separated in the solid state. By extracting succes 

 sively with weak, with strong, and with absolute alcohol, a form of 

 casein (gluten-casein, of Rl ithausen) remains tmdissolved, which is perhaps 

 identical with the iasein (legumin) of the pea. 



On evaporating &quot;he alcoholic solution to one-half, there separates, on 

 cooling, a brownish-yellow mass. This, when treated with absolute al 

 cohol, leaves vegetable-fibrin nearly pure. 



Vegetable-fibrin is readily soluble in hot alcohol, but 

 slightly so in cold alcohol. It does not at all dissolve in- 

 water. It has no fibrous structure like animal fibrin, but 

 forms, when dry, a tough, horn-like mass. In composition 

 it approaches animal-fibrin. 



Casein* Animal casein is the peculiar ingredient of 

 new cheese, It exists dissolved to the extent of 3 to 6 

 per cent in fresh milk, unlike albumin is not coagulated! 

 by heat, but is coagulated by acids, by rennet, (the meml 

 brane of the calf s stomach), and by heating to boiling 

 with salts of lime and magnesia. 



EXP. 50. Observe the coagulation of casein when milk is treated 

 with a few drops of sulphuric acid. Test the curd with nitrate of 

 mercury. 



EXP. 51. Boil milk with a little sulphate of magnesia (epsom salts) 

 until it curdles. 



When casein is separated from milk by rennet, as in 

 making cheese, it carries with it a considerable portion of 

 the phosphates and other salts of the milk ; these salts 

 are not found in the casein precipitated by acids, being 

 held in solution by the latter. 



The casein of milk coagulates spontaneously when it 

 stands for some time. Casein has recently been detected 

 in the brain of animals. (Hoppe-Seyler, Med. Chem. Un- 

 ters., II.) 



Vegetable casein. This substance is found in large pro 

 portion (17 to 19 per cent) in the pea and bean, and in 

 deed generally in the seeds of the so-called leguminous 

 plants. It closely r sembles milk-casein in all respects. 



