344 CHEMICAL TESTS AND ANALYSES 
L, = Quevenne lactometer reading. 
f= per cent of fat. 
Example: Lactometer reading is 32; per cent fat is 4. 
27 
ee 
Total solids = r +1.2x%4= 12.8 per cent. 
Gravimetric Method.--"Ileat 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 rapid- 
ly to avoid absorption of hygroscopic moisture.” 
Ash. 
“Weigh about twenty grams of milk in a weighed dish, add 
6 cc. 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 percent- 
age 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 
distillation 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 cc. ‘They are 22 c.m. 
long and have a maximum diameter of 6 c.m., tapering gradually to 
a long neck, which is 2 ¢.m. 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 
