96 MILK AND DAIRY PRODUCTS PART 



equally good results and has the advantage of being easily 

 carried out. One hundred c.c. of milk are precipitated with 

 200 c.c. of alcohol, the mixture well stirred, and the precipitate 

 allowed to settle. When this has taken place the precipitate is 

 filtered off and the filter and precipitate placed in the cartridge 

 of a Soxhlet extraction apparatus, and extracted for at least 

 thirty hours with chloroform. The alcoholic filtrate is evaporated 

 at 50-60 C., the residue extracted thoroughly with chloro- 

 form, and the extract added to that obtained from the extraction 

 of the filter and precipitate. The united chloroform extract is 

 then allowed to evaporate in a platinum dish, and the residue 

 carefully ignited with a mixture of sodium carbonate and 

 potassium nitrate. After ignition the mass is exhausted with 

 water, the phosphoric acid precipitated with ammonium molyb- 

 date, and from the phosphomolybdate the magnesium pyro- 

 phosphate is prepared in the usual way. On multiplying the 

 amount of phosphoric acid by 7 '27 there is obtained the 

 quantity of lecithin present in the milk. Using this method, 

 Nerking and Haensel found 0'0364-01163 per cent, lecithin 

 in cow's milk, the average being 0'0629 per cent. 



VIII. To DISTINGUISH RAW AND HEATED MILK. 



When it became necessary to require milk coming from herds 

 of cattle suffering from diseases such as foot-and-mouth disease, 

 anthrax, &c., to be pasteurised, the need of a test which would 

 quickly and simply show whether a given milk had been heated 

 to a certain temperature or not was soon felt. Very numerous 

 indeed have been the methods proposed for this purpose in the 

 last few years, and a very large class of literature l dealing with 

 this subject has accumulated. It is not necessary to discuss all 

 these different methods, particularly as one of the first to be 

 proposed that by Storch satisfies all reasonable demands, 

 and for exactness and simplicity is not surpassed by any 

 other. 



The methods which have been suggested for the purpose of 

 distinguishing raw and heated milk fall into two main 

 groups : 



1 An almost complete record of the early literature is to be found in Weber's 

 " Die zur Unterscheidung roher und gekochter Milch dienenden Untersuchungs- 

 methoden, u.s.iv" Inaug. Diss., Leipsic, 1902. 



