32 



Testing Milk and Its Products. 



neck thus cleared of adhering milk. By pouring the 

 acid into, the middle of the test bottle, there is also 

 a danger of completely filling this with acid, in which 

 case the plug of acid formed will be pushed over the 

 edge of the neck by the ex- 

 pansion of the air in the bot- 

 tle, and may be spilled on the 

 hands of the operator. 



The milk and the acid in 

 the test bottle should be in 

 two distinct layers, without 

 any black portion of partially 

 mixed liquids between them. 

 Such a dark layer is often fol- 

 lowed by an indistinct separa- 

 tion of the fat in the final 

 reading. The cause of this 

 may be that a partial mixture 

 of acid and milk before the 

 acid is diluted with the water 

 of the milk may bring about 

 too strong an action of the 

 acid on the milk, and the fat 

 in this small por- 

 tion may beslightly 

 charred by the 

 strong acid. The 

 appear an ce of into test bottle. 



black flocculent matter in or below the column of fat 

 which generally results, in either case renders a correct 

 measurement of fat difficult and at times even impos- 



FIG. 8. The wrong way of emptying pipette 



