202 Condensed Milk and Milk Powder 



Gravimetric Method. — "Heat from three to five grams of 

 milk at the temperature of boiling water until it ceases to lose 

 weight, using a tared flat dish of not less than 5 c.c diameter. If 

 desired, from fifteen to twenty grams of pure, dry sand may be 

 previously placed in the dish. Cool in a desiccator and weigh rap- 

 idly to avoid absorption of hygroscopic moisture." 



ASH 

 "Weigh about twenty grams of milk in a weighed dish, add 

 6 c.c. of nitric acid, evaporate to dryness, and ignite at a tempera- 

 ture just below redness until the ash is free from carbon." 



TOTAL NITROGEN 



Place about five grams of milk in a Kjeldahl digestion flask and 

 proceed, without evaporation, as described under "Gunning Method'' 

 for the determination of nitrogen. Multiply the percentage of 

 nitrogen by 6.38 to obtain nitrogen compounds. 



Gunning Method 



APPARATUS 



"(a) Kjeldahl flasks for both digestion and distillation. — These 

 are flasks having a total capacity of about 550 c.c. made of hard, 

 moderately thick, and well-annealed glass. When used for distilla- 

 tion the flasks are fitted with rubber stoppers and bulb tubes, as 

 given under distillation flasks. 



(b) Kjeldahl digestion flasks. — These are pear-shape, round- 

 bottomed flasks, made of hard, moderately thick, well-annealed glass, 

 having a total capacity of about 250 c.c. They are 22 cm. long and 

 have a maximum diameter of 6 cm., tapering gradually to a long 

 neck, which is 2 cm. in diameter at the narrowest part and flared 

 a little at the edge. 



(c) Distillation flasks. — For distillation a flask of ordinary 

 shape, of about 550 c.c. capacity, may be used. It is fitted with a 

 rubber stopper and with a bulb tube above to prevent the possibility 

 of sodium hydrate being carried over mechanically during distilla- 

 tion. The bulbs may be about 3 cm. in diameter, the tubes being of 

 the same diameter as the condenser and cut off obliquely at the 

 lower end, which is fastened to the condenser by a rubber tube." 



