PROTEIN. 171 



ses. Scherer represents the constitution of protein by the for- 

 mula C 48 H 36 Az 6 O 14 = 65. This formula gives, 



48 atoms carbon, = 36* or per cent 55*38 



36 atoms hydrogen, = 4-5 ... 6-92 



6 atoms azote, 10'5 ... 16-16 



14 atoms oxygen, = 14-0 ... 25*54 



65-0 100-00 



This formula also comes very near the experimental quantity, 

 showing how difficult it is to determine by calculation the con- 

 stitution of such complicated compounds. 



Protein has the property of combining with sulphuric acid, 

 and of forming an acid to which Mulder has given the name of 

 sulpho-proteic acid. 



To prepare it, he mixed purified casein with concentrated sul- 

 phuric acid.* The solution was treated with ammonia, the ex- 

 cess of which was driven off by evaporation. Nitrate of silver 

 dropt into the liquid gave a precipitate of sulpho-proteate of sil- 

 ver, which was washed and dried at 266. He prepared another 

 sulpho-proteate of silver by treating albumen of eggs in the same 

 manner. 487 of the salt from casein gave 739 carbonic acid 

 and 231 water : 120 parts gave 22 of metallic silver, and 760 

 gave 140 of sulphate of barytes. Hence the constituents in 100 

 parts must be, 



Carbon, . 41-36 



Hydrogen, . 5-27 



Sulphuric acid, 6*35 



Oxide of silver, 19-68 



72-66 



What is wanting to make up the hundred parts must be azote 

 and oxygen. But protein contains five atoms of azote and twelve 

 atoms of oxygen. Hence the azote in 100 parts of the salt must 

 weigh 14-08, and of consequence the oxygen must be 13-26 ; 

 477 pf the salt containing the albumen gave 647 of carbonic 

 acid, and 200 water. Hence 100 parts contain, 



Carbon, . 37-08 



Hydrogen, . 4*66 



* Ann. der Pharm. xxxi. 127. 



