RECENT WORK IX AGRICULTURAL SCIENCE. 



CHEMISTRY. 



The behavior of paracasein toward rennet, O. Hammarsten 



{ZUvhr. physioJ. Chem., 2^> {1800), Xo. 2, pp. 103-l:J6).—l\\ 1894 E. Peters' 

 published investigations including among other things a study of the 

 action of rennet on the proteidsof milk. He concluded from these studies 

 that when the paracasein resulting from the action of rennet on casein 

 was dissolved in the smallest possible amount of lime water it could be 

 reprecipitated by rennet, and that this dissolving in lime water and 

 curdling with rennet could be repeated many times. This was contrary 

 to the previous work of the author, who further investigated Peters' 

 conclusions. It was found that the rennet extract used by Peters con- 

 tained considerable common salt, whereas the author had used rennet 

 free from salt; and the author's experiments showed conclusively that 

 salt was callable in a marked degree of curdling solutions of paracasein, 

 both in presence and in absence of soluble lime salts. Eennet free 

 from salt invarial)ly failed to curdle lime water solutions of paracasein, 

 but the extract used by Peters always curdled the solutions, even 

 though the extract was heated to destroy the ferment. Hence it was 

 clear that the curdling action observed by Peters was due entirely to 

 the salt in the rennet extract which he used rather than to the rennet 

 itself. 



Paracasein prepared under varying conditions was found to have 

 somewhat difl'erent i)roperties, but all ijreparations of it agreed in not 

 being capable of reprecipitation with rennet enzym. This property the 

 author regards as the most pronounced difference between casein and 

 paracasein. 



Solutions of casein in lime water which failedto curdle with rennet 

 on account of a deficiency of soluble lime, gave a voluminous precipitate 

 of paracasein when the proper amount of lime- free common salt was 

 added. This action of salt is confined within rather close limits, and 

 depends upon the concentration of the casein solution, and also the 

 temperature. 



On the peculiar relations of solubility of barium sulphate, 

 E. Fresenius and E. Hintz {Ztschr. analyt. Chem., 35 {1S96), Xo. ^-', pp. 

 170-183). — From 6 series of experiments the authors found that — 



(1) [a) One part barium sulphate remains in solution after 24 hours' 

 standing in 100,000 jiarts of \}w.ve water, (b) Barium chlorid or free 

 sulphuric acid decreases considerably the solubility of barium sulphate 



'UntersnchuDgeii iiher das Lab nud die labiihulichen Fermente. Rostock, 1894. 

 454 



