The Country Gentleman* s Magazine 



385 



W^t ^airg anil Poitltrg-^arii. 



THE ADULTERATION OF MILK. 



AT the first general meeting of the 

 Manchester Farmers' Club, the follow- 

 ing report on the adulteration of milk, com- 

 piled by Dr Leach, of the Manchester and 

 Salford Sanitary Association, was read : — 



A large portion of the milk supplied to the 

 inhabitants of Manchester and Salford is 

 adulterated, but this adulteration consists of 

 the addition of water, and not, as is popularly 

 supposed, of the introduction of such sub- 

 stances as chalk, starch, and brains. In 

 only one out of a large number of specimens 

 of milk purchased in this city and examined 

 was any foreign ingredient found. In this 

 instance common salt was present in con- 

 siderable quantity, but as the milk from the 

 same dealer did not afterwards contain it, 

 the impurity was possibly accidental. Be- 

 sides adding water, however, the vendors 

 still further deteriorate the milk which they 

 sell by abstracting the cream. For all 

 practical purposes it is found that the purity 

 of a milk may be determined by ascertaining 

 the percentage of cream and solid matter 

 which it gives. It has been found that 

 genuine milk gives 10 per cent, of cream, and 

 contains not less than 12 per cent, of solid 

 matter. A milk having sensibly less per- 

 centage of cream and solid matter than this 

 has been skimmed, or watered, or both. 

 But the analysis requisite to estimate the 

 quantity of solids present, though readily 

 performed in a laboratory, cannot be under- 

 taken in an ordinary household, and a more 

 simple yet fairly reliable test is therefore 

 required. An instrument called the lacto- 

 meter has long been used for estimating the 

 purity of milk by means of its specific gravity. 

 The results obtained are not very reliable 

 however — firstly, because instruments bought 

 at different places do not give the same indi- 

 cations as to purity; and, second!-', because 



VOL. IX. 



an excess or deficiency of cream may alte 

 the results which the lactometer gives. A 

 rich milk if it contains a very large percent- 

 age of cream may appear from the lactometer 

 to have been adulterated, whilst a milk which 

 has been deprived of cream may appear from 

 the lactometer to be good, even though in 

 addition to abstracting cream some water has 

 been added. The specific gravity of cream 

 varies much — the average, however, is about 

 950, that of water being taken at 1000. 

 Therefore, the presence of cream or the addi- 

 tion of water will produce similar results as far 

 as specific gravity is concerned. If a cream 

 measurer be used in addition to a lactometer, 

 the chances of a correct result being obtained 

 are markedly increased ; if a large quantity 

 of cream be present a somewhat lower specific 

 gravity will be looked for, and vice versa. 



It is not very easy, in any case, to cal- 

 culate to what extent the specific gravity 

 ought to be affected from the amount of 

 cream contained — the effects of the removal 

 of cream do not seem quite uniform in 

 different milks. The best plan seems to be 

 first to ascertain the quantity of cream present 

 by means of a cream measurer, and then to 

 take the specific gravity of the milk 

 after the cream has been removed. By 

 adopting this plan a test is obtained suf- 

 ficiently accurate for the ordinary purposes 

 of seller and buyer, enabling the former to 

 judge whether he is distributing poor or 

 adulterated milk, whilst the latter can tell 

 whether he is receiving that for which he 

 pays. If milk yields not less than 10 per 

 cent, of cream, and when this is removed 

 has a specific gravity of not less than 10.31, 

 it is good, though the milk from some cows 

 gives more cream and has higher specific 

 gravity. The best milk tested gave 15 per 

 cent, of cream, and had a specific gravity, 



6 B 



