ANALYSIS OF MILK-PRODUCTS 49 



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}-5 c.c. -- soda solution, and this mixture again dis- 

 tilled ; the final distillate is made up to the original 

 bulk, and the specific gravity estimated. The difference 

 in degrees of gravity between the specific gravity and 

 1000 multiplied by 0.977 gives the percentage by 

 weight of milk sugar converted into alcohol. 



Volatile Acid. Ten grammes of milk are neu- 

 tralised to the extent of one-half, and a little 

 phenolphthalein added; the mixture is evaporated 

 to dryness on a water-bath with frequent stirring, and 

 after the addition of 20 c.c. boiling distilled water, 

 soda solution is added till a pink colour just appears! 

 The difference between the number of c.c. of soda 

 solution used in this experiment, and that required for 

 the original acidity of 10 grammes of milk, is multi- 

 plied by 0.0255 to give the percentage of milk sugar 

 converted into volatile acid. 



Ammonia. Two grammes of milk are diluted to 

 100 c.c. and filtered clear. Ten c.c. of the filtrate made 

 up to 50 c.c. with distilled water are compared in tint 

 with a solution of ammonium chloride solution (i c c 

 - o.oi milligramme (NH 3 ) in 50 c.c. water containing 

 10 c.c. of a solution of 2 grammes fresh milk acidified in 

 100 c.c. after the addition of 2 c.c. of Nessler solution 

 (see Appendix) to each. The number of c.c. of ammonia 

 solution required to produce the same tint multiplied 

 by 0.026 gives the percentage of casein converted into 

 ammonia. 



The three amounts are added together, and constitute 

 the total correction for solids lost by fermentation. 



Milk Powder. Moisture is estimated by drying i to 2 

 grammes in a basin to constant weight, and the ash is 

 estimated in the same portion. 



The estimation of fat should be made by the Gottlieb 

 method, 0.6 to 0.7 gramme being weighed out and 

 water sufficient to make up to 5.15 grammes; after 



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