io8 MILK AND DAIRY PRODUCTS PART 



Observed A. Water, per cent. Observed A. Water, per cent. 



0-53 3-63 0-44 20 -00 



0-52 5-45 0-43 21 -81 



0-51 7-27 0-42 23 -63 



0-50 9-09 0-41 25-45 



0-49 10-90 0-40 27-27 



0-48 12-72 0-39 29'09 



0-47 14-54 0-38 30 '90 



0-46 16-36 0-37 32 -72 



0-45 18-18 0-36 34 -54 



This method of determining the amount of added water 

 is very simple, and perfectly reliable if carried out carefully. 

 It is remarkable that it has not found more general application, 

 for it not only shows that water has been added, but gives also 

 the amount with accuracy. 



The author l has experimented \vith this method, and is quite 

 satisfied that the results are reliable, and that, in agreement 

 with Winter and Parmentier, 2 Schnorf, 3 and others, pure 

 unadulterated milk never has a higher freezing-point than 

 0'54 C. This is independent of breed, individuality, food, 

 stage of lactation, sexual excitement, amount of fat, &c., but a 

 very small addition of water at once raises the freezing-point. 



5. Determination of the Refractive Index of Milk Serum. 



With a refractometer it is also possible to detect added 

 water, but if accurate results are to be obtained exactly the 

 same method must be used in obtaining the serum. It is 

 of importance to remember that the serum will vary according 

 to whether it is got from milk that has soured naturally, or that 

 which has been treated with acetic or other acid or acted upon 

 by rennet. In all these cases the results vary somewhat, and 

 the serum obtained in these ways must be separated by filtra- 

 tion, which is always difficult and takes time. Ackermann's 4 

 method, which is carried out in the following manner, gives the 

 best results : 



Thirty c.c. of the milk to be examined are placed in a 

 glass tube provided with a reflux condenser, and then 0'25 c.c. 

 of calcium chloride solution added. This solution of calcium 



1 Revue Generate dn Lait, Vol. IV, p. 505. 



2 Loc. cit. 



3 Neue physikalisch-chemische Untersuchungen der Milch, Zurich, 1905. 



4 Zeilschr. fur Unt. der Nahr- und Genussmittel, Vol. XIII, 1907, p. 186. 



