232 



ature must be constant from 100 to 105 degrees C. Two and 

 one-half hours drying is usually sufficient. The coil is known 

 to be dry when a cold watch-glass being held over one end of it, 

 immediately after it is removed from the bath, does not show 

 a deposit of moisture. In making this test the coil must be 

 held in a vertical position. The dry coil is placed in an 

 extracting apparatus, the form known as Knoefler's being 

 preferred, connected with an upright condenser and a tared 

 flask, and extracted with a pure anhydrous ethyl ether for 

 two hours. The ether is distilled and may be used again, the 

 flask placed on water bath until all odor of ether has disap- 

 peared, then in air bath having a constant temperature of 

 100-105 degrees C.for one-half hour or until fat is of constant 

 weight. The coil should be re-extracted until there is no 

 longer a gain of fat. The weight of fat is calculated in the 

 usual way. The flask used above should be dried in air bath 

 and cooled in air-bath before weighing. A flask containing 

 the fat should be cooled in the same way. Care must be taken 

 not to electrify the flask by rubbing the same when dry. The 

 ether used must be free from residue, water and alcohol. 

 Fat-free paper (commercial) must be proved to be free from 

 extractive matter." 

 The Total Solids may be determined as follows: 

 "Five grams of milk (thoroughly mixed by gentle agita- 

 tion) are weighed in a dry, tared, flat- bottom, 'lead-tin ' or 

 platinum capsule (diameter If inches, and f of an inch deep; 

 it is important that the dish is no smaller than this). This 

 dish is placed on a water bath, a piece of clean fllter paper 

 being m contact with the bottom, and when the water has 

 app.ireutly all evaporated is transferred to an air bath (care- 

 fully regulated to maintain a temperature of from 100 to 105 

 degrees C.) and allowed to remain for 2^ hours. After cooling 

 in a dessicator dish, and the contents are weighed, return to 

 air bath for one-half hour and again weigh. If necessary this 

 reheating and reweighing are repeated until solids cease to 

 lose in weight. From this final weight calculate total 

 solids." * 



* New York City Board of Health Report, 189G, p. 168. 



