CHemicar, Tests AND ANALYSES 357 
the tube 10 to 11 grams of a 40 per cent solution of the substance 
—add 1} c.c. of concentrated ammonium hydroxid (2 c.c. if the 
sample be sour) and mix thoroughly with the milk. .\dd 10 c.c. 
of 95 per cent alcohol and mix well. Then add 24 c.c. of washed 
ethyl ether and shake vigorously for half a minute, then add 25 
c.c. of petroleum ether (redistilled slowly at a temperature below 
60 degrees C. preferably) and shake again for. half a minute 
Let stand 20 minutes or until the upper quid is practically clear 
and its own lower level constant. Draw off of the ether solution 
as much as possible—usually 0.5 to O.8 c.c. will be left—into a 
weighed flask through a diminutive quick acting filter, of selected 
paper. The flask should always be weighed with a similar ore 
as counterpoise. 
“Re-extract the liquid remaining in the tube, this time with 
only 15 ¢.c. of each ether, shaking vigorously half a minute with 
each, and allow to settle. 
“Draw off the clear solution through the small filter into 
the same flask as before and wash the tip of the spigot, the funnel 
and the filter with a few c.c. of a mixture of the two ethers in 
equal parts (previously mixed and free from deposited water}. 
“For perfectly exact results the re-extraction must be re- 
peated. This extraction yields usually not more than about a 
iilligram of fat, if the previous ether-fat-solutions have been 
drawn off closely— an amount averaging about 02 per cent on 
a 4-eram charge. 
“TE vaporate the ether slowly on a steam bath, then dry the 
fat in a boiling water oven until loss of weight ceases. 
“Prove the purity of the fat by dissolving in a little pe- 
troleum ether. Should a residue remain, wash the fat out com- 
pletely with petroleum ether, dry the residue, weigh, and deduct 
the weight. (This should not often be necessary.) 
“Tnally deduct the weight obtained by blank determination 
on the chemicals used. 
“By this method practically absolute results can he ol- 
tained.” 
Sucrose. 
Determine by difference, deducting the milk solids (ash 
plus proteids plus lactose plus fat) from the total solids, or 
