BY H. S. HALCKO WARDLAW. 817 



century, an enormous number of analyses has been carried out, 

 both by the authorities responsible for the control of the food- 

 supply, and by the producers who wish to know the value of their 

 product. 



The standards set by the authorities were considered by them to 

 he such as would be complied with by any normal, unadulterated 

 milk. These standards, of course, were based on extensive series 

 of investigations, and, for a time, all milk not complying with the 

 standards was regarded as adulterated. Those engaged in the 

 dairying mdustry, however, soon found that, even under normal 

 conditions, the composition of cows' milk sometimes varied between 

 wider limits than those prescribed by the standards. This fact has 

 been somewhat tardily recognised, in some cases, by the authorities 

 controlling the sale of foods, but a distinction is now made in most 

 countries, between the sale of adulterated or pathological milk, and 

 the sale of milk which may be simply below standard in some of 

 its constituents. 



The question whether milk lias been adulterated with water, or 

 is naturally deficient in solids, is one which is extre.nely difficult to 

 settle by chemical means alone. The early investigations of Beck- 

 mann (1894), Winter (1895), Carlinfanti (1897), and others, on 

 the freezing point of milk showed that, in the measurement of this 

 property, lay a convenient means of detecting the addition of 

 water. They showed that the freezing point of milk remains 

 extremely constant, no matter liow the composition may vary. The 

 work of subsequent investigators, notably that of Brownlie 

 Henderson and Meston (1913, 1914), in Queensland, has con- 

 firmed and extended these results. This method, however, does not 

 detect the addition of solutions which do not alter the osmotic 

 pressure of the milk. 



The relatively large variations to which the composition of nor- 

 mal cows' milk is subject, and the consequent fluctuations in its 

 butter-value, have induced dairy farmers to carry out numerous 

 investigations with the object of determining the cause of the 

 variations. The possession of this knowledge would be of use in 



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