ADDED WATER. 361 



This test, if carried out properly by competent witnesses, is 

 very reliable ; if the suspected sample were genuine, milk will be 

 yielded approximately of the same composition as the appeal to 

 the cow ; everything, however, depends on the competency of 

 the witnesses. 



Adulterations of Milk. The chief adulterations of milk 

 are 



(1) The addition of water, which is sometimes masked by the 

 use of a solid substance which is soluble. 



(2) The addition of skim or separated milk, or the removal of 

 cream. 



Calculation of Added Water. Watering is detected by the 

 depression of the solids not fat, total nitrogen, and ash ; if all 

 three are below the limits given above, the milk may be con- 

 demned as watered. The amount of water added is calculated 

 best from the solids not fat by the formula 



Water = 100 - ^ x 100, 



where S = solids not fat. 



This formula will give the minimum percentage of water 

 added. It is correct only if the original milk contained 8-5 per 

 cent, of solids not fat. 



The probable amount can be calculated by using the mean 

 figure for solids not fat 8-9, instead of 8-5 in the above formula. 



Another excellent method for calculating percentage of added 

 water is to use the sum of the degrees of specific gravity and the 

 fat as a datum ; thus 



Water = 100 - "3475- X 100. 



where G = degrees of gravity, and F = the percentage of fat. 



This likewise will give a minimum figure, and the probable 

 amount can be obtained by substituting 36 for 34-5. 



The latter formula has the advantage that it is applicable 

 without correction to milk which contains an excess or deficiency 

 of fat, while the percentage of solids not fat is affected to some 

 extent by variations in the fat; Table CXXV. will make this 

 clear. The solids not fat vary from 8 'IS to 9-08, a difference 

 of 0-30 or 3-3 per cent, of the solids not fat ; the sum of the 

 degrees of specific gravity and fat varies only from 36-11 to 36-35, 

 a difference of 0-24 or 0-7 per cent, of the sum. 



When milk contains either an excess of deficiency of fat, the 

 formula of L. J. Harris, 



Water = 100 - F - ~, 



o'O 



