26 Director's Report of the 



stuffs and other materials. This work occupies quite a large portion 

 of the time and energy of the department. 



The effect of mixing lime-sulphur solution with lead arsenate. — This 

 is an important question which has been raised many times by 

 orchardists. It is desired to use the arsenate as an insecticide in 

 connection with the lime-sulphur for controlling the San Jose scale 

 and apple scab, but it has been asked whether the efficiency of the 

 arsenate is diminished by the combination, or whether it, in any 

 way, becomes dangerous to foliage. It was found that with lead 

 arsenates containing the compound known as di-lead arsenate, 

 some arsenic is made soluble; with lead arsenates containing only 

 tri-lead arsenate, much less arsenic becomes soluble. The amounts 

 made soluble are scarcely sufficient to harm foliage under ordinary 

 conditions. 



For some years, the Station has been engaged in a study of the 

 changes taking place in milk when it is converted into cheese. This 

 subject has never been satisfactorily understood and much remains 

 for investigation. As fundamental to these studies, it has been 

 necessary to get at certain underlying technical facts; among these 

 it has been found necessary to investigate the solubility of casein in 

 dilute acids. This work has an important bearing upon the methods 

 used in determining the amount of casein in milk. It was shown 

 that the volumetric method for determining casein (which was 

 devised in this laboratory and which has been described in Technical 

 Bulletin No. 10) admits of quite wide variations in the amount of 

 acid used without impairing its accuracy. 



Further study has been made of the action of rennin (this being 

 the enzym contained in rennet extracts and powders) upon casein 

 and an explanation has been offered as to why the ammonium, 

 sodium and potassium compounds, known as casemates, are not 

 curdled by rennet, and also why some calcium casemates are curdled 

 by rennin and others are not. 



New compounds of magnesium caseinate have been prepared 

 similar to the compounds of calcium described in Technical Bulletin 

 No. 26. 



These preliminary studies are time-consuming, but are essential 

 as a basis for further investigations. 



