Chemical Analysis of Milk and Its Products. 229 



263. Specific gravity of butter milk. The specific gravity 

 of butter milk (as well as of sour or loppered milk) is deter- 

 mined by Weibull's method; a known volume of the milk is 

 mixed with a certain amount (say 10 per cent.) of ammonia of 

 a definite specific gravity, and the specific gravity of the liquid 

 determined after thorough mixing and subsequent standing for 

 an hour. If A designate the volume of butter milk taken, B that 

 of ammonia, and (7 that of the mixture; and if furthermore S 

 designate the specific gravity of the butter milk, s t that of the 

 ammonia, and s, that of the mixture, we have 



"Cs 2 -Bsi 



Klein 1 has modified this method by weighing the liquids, thus 

 securing greater accuracy; 22 to 24 per cent.-ammonia is used, 

 one-tenth as much being taken as the amount of milk weighed 

 out. The results come uniformly .0005 too high, and this correc- 

 tion should always be made. The following formula will give 

 the specific gravity of the milk, which in case of careful work 

 will be accurate to one-half lactometer degree; if the letters 

 given above designate weights (instead of volumes as before) 

 and specific gravities of the liquids, respectively, we have 



jC ._ JB 



S2 " Si 



264. Condensed milk. The same methods are, in gen- 

 eral, followed in the analysis of condensed milk as with 

 whole milk. Condensed milk is preferably diluted with 

 five times its weight of water prior to the analysis, both 

 because such a solution can be more easily handled 

 than the undiluted thick condensed milk, and the errors 

 of analysis are thereby reduced, and because the fat is 

 not readily extracted except when the milk has been 



1 Milchzeitung, 1896, p. 656 ; see also De Koningh, Analyst, 1899, 

 p. 142. 



