CHEMICAL TESTS AND ANALYSES 363 



Gravimetric Determination. 



Dilute a measured portion of a 40 per cent solution with an 

 equal volume of water, use 5 c.c. of the diluted mixture, correspond- 

 ing to 1 gram of the evaporated milk and proceed as directed under 

 "Milk." 



Ash. 



Ignite the total solids at very low redness, cool, weigh, see 

 "Milk/ 1 



Proteids. 



Use 5 c.c. of a 40 per cent solution, determine nitrogen accord- 

 ing to the Gunning method as directed under "Milk," and multiply 

 result by 6.38. 



Lactose. 



Dilute 10 grams of a 40 per cent solution to about 40 c.c. and 

 add .6 c.c. of Fehling's copper solution ; nearly neutralize with 

 sodium hydroxide, make up to 100 c.c., filter through dry filter, arid 

 determine lactose in an aliquot as directed under "Milk." 



Fat. 

 The Modified Babcock Method. 1 



Carefully weigh 4.5 grams of well-mixed evaporated milk into 

 the 8 per cent test bottle. Add one 17.6 c.c. pipetteful of water. Add 

 17.5 c.c. of sulphuric acid and shake until the curd in the test bottle 

 is completely dissolved. Whirl at usual speed (one thousand revo- 

 lutions per minute) for five minutes. Mix equal portions of water 

 and sulphuric acid in glass beaker. For one or two tests, one 

 pipetteful of water and one acid measure full of acid are sufficient. 

 Fill test bottle to slightly below the bottom of the neck with the hot 

 diluted acid. Whirl for two minutes. If the fat collected at the 

 base of the neck is not clear, shake the bottle until all the curdy 

 matter is completely dissolved, fill the bottle to about the 8 per cent 

 mark with hot_mater. whirl for one minute and read the test at 135 

 degrees F. The fat column must be read from the top of the upper 

 meniscus to the bottom of the lower meniscus. Multiply the reading 

 by 4. This gives the correct per cent of fat. 



Instead of weighing 4.5 grams into the test bottle, a 4.3 c.c. 



1 Hunziker and Spltzer, Indiana Agricultural Experiment Station, Bulletin 

 No. 134, 1909. 



