CHAPTER XIV. 



THE ANALYSIS OF SOLID MILK PRODUCTS. 



Milk Powders. The sample should be ground and mixed 

 well to secure uniformity. Moisture is estimated by drying 

 about 1 gramme in the water-oven. 



Fat cannot be estimated by direct extraction, as the results 

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

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

 grammes, and proceeding as described on p. 126. The Werner- 

 Schmid method also may be used, and if there be 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 preferable 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- 

 metrically ; 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 be followed, 

 incomplete extraction of the sugar may result. The usual 

 method is then followed ; it is necessary to use phosphotungstic 

 acid to precipitate the last trace of proteins. 



Cane-Sugar may be conveniently estimated by the method 

 described by Harrison (p. 167). 



Proteins are calculated from the total nitrogen by KjeldahPs 

 method by the factor 6-39. 



Ash, Lime, and Phosphoric Acid as usual. 



Acidity and Aldehyde figure are estimated by grinding up 



about 1 to 2 grammes with hot water, and titrating with yy 

 strontia, using phenol-phthalein as indicator. 



The Proximate Analysis of Butter. The proximate analysis of 

 butter indicates, not whether the sample is genuine or otherwise, 



219 



