52 DAIRY ANALYSIS 



By Clause 4 of the Sale of Food and Drugs Act, 

 1899, ^ ne President of the Board of Agriculture is 

 empowered to lay down limits below which a pre- 

 sumption is raised that milk is not genuine, and he 

 has fixed 8.5 per cent, of solids not fat and 3.0 per 

 cent, of fat. The effect of this is that the onus of 

 proving that milk taken under the Sale of Food and 

 Drugs Acts falling below these limits is genuine lies on 

 the vendor, and for most practical purposes milk below 

 these limits is taken as adulterated. 



It is generally, though not invariably, found that, in 

 milk falling below 8.5 per cent, of solids not fat, the 

 deficiency lies chiefly on the milk sugar, and that the 

 proteins and ash are normal ; a percentage of total 

 nitrogen above 0.5 and a percentage of ash above 0.7 

 in a milk below 8.5 per cent, of solids not fat will 

 afford strong evidence that the milk is genuine, while 

 figures for total nitrogen and ash low proportionately 

 to the solids not fat will strengthen the conclusion 

 that the milk is watered. 



There appears to be no chemical means of dis- 

 tinguishing between fat naturally low and fat lowered 

 by the abstraction of cream ; the most numerous 

 instances of fat below 3.0 per cent, naturally occurring 

 have been found in April, May, June, and July, and 

 they are especially rare in October, November, and 

 December. 



The percentage of added water may be calculated 

 by the formula : 



o _ a 



Added water -~ - X 100. (S = solids not fat.) 



A formula which gives a nearer approach to the 

 probable amount is : 



Added water = - - ^ ' x 100. 

 36 



(G = degrees of gravity. F = fat.) 



