ANALYSIS OF MILK POWDER. 149 



Milk Powders. — The sample should be ground and well 

 mixed to secure uniformity. Moisture is estimated by drying 

 about 1 gramme in the water-bath. 



Fat cannot be estimated by direct extraction, as the results 

 are always low. The Gottlieb method is suitable, weighing out 

 OO to 0-7 gramme, making up with water to a weight of 5' 15 

 grammes, and proceeding as described on p. 119. The Werner- 

 Schmid method may also be used, and if there is no sugar except 

 milk-sugar, the fat, after drying, should be dissolved in petroleum 

 ether, and any residue weighed and subtracted from the total 

 weight. In the presence of much of any other sugar, it is pre- 

 ferable to mix the ethereal solution with an equal bulk of 

 petroleum ether, and shake out with water rendered slightly 

 alkaline with ammonia before the solution is evaporated. 



Milk-sugar may be easily and quickly estimated polari- 

 mctrically ; 10 grammes of milk-powder are ground up in a 

 mortar with sufficient hot water to make it into a paste, which 

 is gradually thinned with hot water, and the solution made up 

 to 100 c.c. ; a little ammonia may be added if the milk-powder 

 does not all go into solution. Unless this procedure is followed, 

 incomplete extraction of the sugar may result. The usual 

 method is then followed ; it is necessary to use phosphotunustic 

 acid to precipitate tlie last trace of proteins. 



Cane-sugar may be conveniently estimated by the method 

 described by Harrison (p. 103). 



Proteins are calculated from the total nitrogen by Kjeldahl's 

 method by the factor 6 "38. 



Ash, Iiime, and Phosphoric Acid as usual. 



Acidity and Aldehyde figure are estimated by grinding up 



N 

 about I to 2 grammes with hot water, and titrating with -rj 



strontia, using phenolphthalein as indicator. 



