48 THE VEGETABLE PROTEINS 



SPECIFIC ROTATION OF VEGETABLE PROTEINS (continued). 



Solvent (a) D 



Hordein, barley, Lindet and Ammann (226), 70 % alcohol \ _ ,, 7 ..o 



rye, ,, ,, / 



Zein o, maize, ,, ,, - 2g - 6 



,, 0, ,, ,, - 40-0 



,, ,, Osborne and Harris (352), go / alcohol - 28'o 



Kjeldahl (igo), 75 / - 35'o 



,, ,, glacial acetic acid - 28-0 



Alexander's determination of the rotation of edestin was made on 

 edestin chloride and therefore contained some combined acid, but the 

 result was the same as that obtained by Osborne and Harris for a pre- 

 paration free from combined acid. Alexander concluded that the specific 

 rotation decreased with decreasing concentration of the edestin solution, 

 and his result which is given in the above table is that calculated for a 

 i per cent, solution of this protein. Osborne and Harris, however, 

 found that differences in concentration had no effect, while differences 

 in temperature appeared to have but slight effect on the specific rotation 

 of edestin. Alexander found a slightly lower rotation for edestin dis- 

 solved in sodium sulphate solution, and an intermediate value when 

 dissolved in one of ammonium sulphate. The addition of alkali to the 

 sodium chloride solution raised the rotation to about -64 and the 

 addition of acid raised it to about -8 5. Alexander also found that 

 the specific rotation of excelsin was increased by the action of alkali 

 to - 58 and that of the globulin of the flax-seed to- 54-5. 



Lindet and Ammann concluded from the results of their determina- 

 tions of the rotation of gliadin and zein that preparations obtained in 

 the ordinary way were a mixture of two proteins. Their results, how- 

 ever, are not in accord with the experience of other investigators. It 

 is possible that the differences which they noticed in rotation were 

 caused by the presence of small quantities of acid. From rye and 

 barley they obtained an alcohol-soluble protein which could be separ- 

 ated into two parts of different rotation, one of which with a rotation 

 of- 87-8 they called gliadin, the other with a rotation of- 137*5 they 

 called hordein. This latter name, therefore, does not designate the same 

 substance as that to which the writer had previously applied this 

 name. 



B. Heat of Combustion of Vegetable Proteins, 



Few determinations of the heat of combustion of vegetable proteins 

 are to be found in the older literature. The earliest were those made 

 by Danilewsky (86), Stohmann (527), Berthelot and Andre (31), and 

 Stohmannand Langbein (528). 



