5 



per cent, (by volume) of household ammonia. In the latter case the 

 results must be increased to ofifset the dilution by the factor of 1.05. 



Churned milk. In partly churned samples the lumps of butter 

 can be temporarily incorporated by heating and pouring, or by 

 dissolving in 5 per cent, (by volume) of ether. With the first method 

 it is necessary to pipette while the sample is warm and it is advis- 

 able to weigh the test. It is extremely difficult to secure an accurate 

 test of a badly churned sample. 



Separator cream containing more than 25 per cent, butter fat can- 

 not be pipetted directly with accurate results, for the reason that a 

 cream pipette (18 c. c.) will not deliver the requisite amount (18 

 grams) because of the lower specific gravity and greater adhesive- 

 ness of the liquid. The experiment station dctes not advocate the 

 use of 50 per cent, test bottles for rich cream, but prefers to use one- 

 half amount (9 grams) of the weighed sample in the 30 per cent 6 

 inch bottle where tests run over 25 per cent., multiplying the results 

 by two. In pipetting thin cream it is well to use two pipettes alter- 

 nately, allowing one to drain into the test bottle while the other 

 is in use. 



Sour cream can be suitably prepared by the use of a sieve but the 

 inclosed gas prevents satisfactory pipetting and makes weighing of 

 the test absolutely necessary, if accurate results are to be obtained. 

 Before mixing, the acid and the contents of the test 

 Adding Acid, bottle should be at a temperature of 60° — 70° Fahr. 

 When the acid is added the test bottle should be 

 turned so as to wash down all the sample adhering to the sides of 

 the neck, rotated at once and this continued until all the lumps of 

 curd are dissolved. The hand mixing should never be slighted, and 

 care should be taken not to throw the fat into the neck of the test 

 bottle. 



Cream of a high fat content and naturally a low percentage of 

 curd, requires slightly less than the regular quantity of acid (17.5 

 c.c.) and this is equally true of samples containing " an excess of 

 bichromate of potash (preservative). Skimmilk, containing slightly 

 more curd than whole milk, and samples preserved with formalin 

 which hardens the nitrogenous bodies (proteids), need relatively 

 more than the usual amount of acid. 



The machine should be balanced, provided there is 

 Whirling and not a full battery, by a suitable arrangement of the 



Filling. bottles. It should be run for at least five minutes 



at a speed equal to the theoretical demands for an 



inner disc of the given diameter. The diameter of the disc is 



