320 MILK AND CREAM TESTING 



Instead of using 18 grams as indicated, nearly, if not quite, 

 as accurate work can be done by adding only 9 grams of sample 

 and then by doubling the reading secured. This is economical 

 of both cream and acid. 



Adding Acid. — If 18 grams of cream are taken as sample 

 somewhat less than the usual measure of acid will be required. 

 If a 9-gram sample of cream is taken then less than half the 

 usual measure of acid will be needed. This is due to the fact 

 that so much of the sample is fat that there is not as much 

 solids to be dissolved as in the case of whole milk. The test 

 bottle should be canted so that the acid may flow down the side 

 of the neck as in the case of milk. Likewise it is preferable to 

 mix them thoroughly immediately upon the addition of the acid. 

 At this point it is necessary also to watch carefully the color of 

 the sample (Fig. 110). The reddish color soon changes to a 

 dark cherry-red, and may assume almost a black hue. The 

 sample must not be permitted to become fully black, for if this 

 has taken place considerable charring has been caused. To 

 prevent burning at this point, about half a teaspoonful of luke- 

 warm water should be added and shaken into the sample. This 

 small amount of water " kills " the acid. 



First Whirling. — As in the case of milk the test bottles 

 should be so placed in the machine as to balance. They are 

 then turned rapidly according to the size of the machine (Fig. 

 109), for fully five minutes, when the machine is gently stopped 

 or allowed to come to rest of its own accord. 



Adding Water. — Clean, soft water at a temperature of about 

 190 or 200 degrees may now be added. This is done simply 

 for the purpose of bringing the fat up into the neck of the bottle 

 where it can be read. In case of rich cream it may be necessary 

 to fill the bottle nearly to the top, otherwise, leaving a safety 

 space of about an inch unfilled. A single filling is found to be 

 sufficient in the case of cream, since the work cannot be carried 

 on with the same degree of accuracy as with milk in any case. 



Second Whirling. — This second whirling should be done 

 strongly for fully four minutes to insure the ascension of all 



