MILK AND MILK PRODUCTS 33 



milk the proportion would remain unchanged, but in abnormal 

 milk it has been found to vary. 



Richmond states that the determination of the amount of 

 water that has been added to milk is best calculated from the 

 figures obtained by adding the difference between the specific 

 gravity of the sample and looo to the figure representing the 

 percentage of the fat. Thus, if a milk have the specific gravity 

 of 1029.2 and contain 3.27 per cent, of fat, the figure from which . 

 the water is calculated is 29.2 + 3.27 = 32.47. The mean figure 

 from unadulterated milks was found to be 36.0, but 34.5 is con- 

 sidered to be a safer limit. Accepting this figure, the percen- 

 tage of added water in the sample given above will be found by 

 the proportion 34.5 : 23.47 : 100 :: 94.1, i. e., the sample contains 

 5.9 per cent, of water. Experiments on milks which had been 

 diluted with known proportions of water showed that this method 

 of calculating the added water gave nearer approximations to 

 the truth than by calculating from the figure for non- fatty solids. 



It is stated that the watering of milk can be detected by the 

 lowering of the freezing-point. The freezing-point of whole 

 milk ranges from — 0.55 to — 0.57. Bomstein claims that as 

 little as 5 per cent, added water can be detected by this method. 

 The special apparatus devised for these determinations (known 

 as "cryoscopy") must be used, and the data must be determined 

 by each observer in order to be safely comparable. 



For ordinary milk control it will suffice to take the specific 

 gravity by the lactometer (see page 9) and the fat by the 

 Leffmann-Beam method. From the figures thus obtained the 

 total solids can be ascertained from the table or Richmond's 

 slide- rule. 

 Coloring 



Annatto, turmeric, and some coal-tar colors are much used. 

 Caramel is occasionally used, saffron and carotin but rarely. 

 Annatto may be detected by rendering the sample slightly alka- 

 line by acid sodium carbonate, immersing a slip of filter-paper, 



