CHEMICAL TESTS AND ANALYSES 275 



1905, 9:531) or some similar apparatus and dilute with water in 

 the tube to about 10.5 c.c. or, if preferred, weigh into 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. Add 10 c.c. of 95 per cent 

 alcohol and mix well. Then add 25 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. pre- 

 ferably) and shake again for half a minute. Let stand 20 minutes 

 or until the upper liquid is practically clear and its own lower level 

 constant. Draw off of the ether solution as much as possible 

 usually 0.5 to 0.8 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 one as counterpoise. 



"Re-extract the liquid remaining in the tube, this time with 

 only 15 c.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 repeated. 

 This extraction yields usually not more than about a milligram of 

 fat, if the previous ether-fat-solutions have been drawn off closely 

 an amount averaging about -02 per cent on a 4-gram charge. 



"Evaporate 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 petroleum 

 ether. Should a residue remain, wash the fat out completely with 

 petroleum ether, dry the residue, weigh, and deduct the weight. 

 (This should not often be necessary.) 



"Finally deduct the weight obtained by blank determination on 

 the chemicals used. 



"By this method practically absolute results can be obtained." 



SUCROSE 



Determine by difference, deducting the milk solids (ash plus 

 proteids plus lactose plus fat) from the total solids, or invert the 

 sucrose, determine the total invert sugar, deduct from this the 



