Effect of Heat on Cow's Milk. 



137 



gives striking color reactions with H 2 S0 4 , HN0 3 , KOH, CaOH 

 and other reagents. 



A solution to which a few drops of silver nitrate are added 

 gives a pink color changing quickly to a dull green. 



Iodine as Lugol's solution gives a pink color which quickly 

 fades. 



With ferric chloride a very dark blue or black changing to 

 brown. 



On the addition of Fehling's solution it turns green and on 

 boiling a slight reduction occurs. 



It does not reduce Fehling's solution in the cold on long stand- 

 ing even after it had been previously boiled with acid and again 

 rendered neutral. This leads to doubt as to its being a glucoside. 



With Millon's reagent it turns a port-wine color rapidly be- 

 coming darker which suggest the possibility of its belonging in 

 the group of the phenols. 



69 (1816) 



The effect of heat on the calcium salts and rennet coagulability 



of cow's milk.* 



By LEROY S. PALMER. 



[From the Section of Dairy Chemistry, Division of Agricultural 

 Biochemistry, University of Minnesota, St. Paul, Minn.] 



When milk is boiled a precipitation of a portion of the calcium 

 phosphates occurs, the amount of fixation being proportional in 

 general to the amount and duration of heat applied. Soldner 1 

 first called attention to this fact and his observations have been 

 confirmed by numerous investigators, among whom may be men- 

 tioned Boekhout and de Vries, 2 Purvis, Brehaut and McHattie, 3 

 and Grosser. 4 



It has been commonly believed, also, that some fixation of the 



* Published with the approval of the Director as Paper No. 288, Journal Series, 

 Minnesota Agricultural Experiment Station. 



1 Soldner, F., Landw. Versuchs., 1888, xxxv, 351. 



2 Boekhout, F. W. J., and de Vries, J. J. O., Landw. Versuchs., 1901, lv, 221. 



8 Purvis, J. E., Brehaut, A. H., and McHattie, A. C. N., Roy. Sanit. Inst. Journ % 

 Trans., 1912, xxxiii, 154. 



4 Grosser, Paul, Biochem. Zeitschr., 1913, xlviii, 427. 



