As already noted on page 13, the heating of milk causes an 

 alteration in the milk sugar. In The Analyst for June and July, 

 1893, H. D. Richmond and L. K. Bosely note that heating to 

 the extent to which milk is subjected in the preparation of con- 

 densed milk may reduce the rotatory power of the sugar suffi- 

 ciently to cause serious error, if the polarimeter be used for the 

 determination. The reducing power with Fehling's solution is 

 not seriously affected. 



In the examinations made by us, we have not noticed so great 

 an alteration in the milk sugar, but in view of the liability to 

 error from this cause, the cane sugar is best determined by 

 the difference in polarimetric reading produced by inversion, 

 (pp 60-62) and the milk sugar gravi metrically (p 62). 



The albumin ^of condensed milk is partly coagulated by the 

 heat employed in its manufacture. When magnesium sulfate 

 is added, therefore, to precipitate the casein, the coagulated al- 

 bumin will be carried down at the same time and only the solu- 

 ble albumin will be found in the filtrate. Faber ( Analyst, 1889) 

 has applied this fact to the detection of the previous heating of 

 a sample of milk. Usually, only about one-third of the albu- 

 min is found uncoagulated in condensed milk. The soluble 

 albumin of unheated milk ranges from 0.35 to 0.50 per cent. 



laicuiauoii meiuuu, ^o 



Calf's brain in milk, 43 T/JELDAHL-GUNNING 



Cane-sugar, 43, 6l J\ Method, 30 

 Casein in milk, 10, 33 



butter, 65 I ACTOCRITE, 24 



cheese, 77 L Lactodensimeter, 16 



91 



