TESTING. 



Before beginning the test see that all the apparatus is per- 

 fectly clean, that everything is in its place, and that a test book, 

 headed as follows, lies open on the table : 



TESTING RESULTS. DATE 



19- 



When a large number of tests have to be made twenty-four 

 bottles should be used simultaneously. The first operation is 

 to run off into each bottle 10 c.c. of sulphuric acid, then by 

 means of the pipette provided for the purpose 11 c.c. of the 

 sample of milk mixed as described below is run into each bottle, 

 entering in the test book at once the number of the bottle and 

 the number oi the sample. 



[There is no part of the testing which needs closer attention 

 or more skill on the part of the operator than that of taking 

 a fair specimen of the composite sample of milk. The need 

 for care arises from several considerations. In the first place, 

 cream will have risen, and may have dried on the surface, ren- 

 dering difficult the getting it again thoroughly incorporated 

 with the bulk. In the second place the shaking, to secure 

 thorough mixing, gives rise to air bubbles which require a 

 certain time to escape. It is almost needless to point out that 

 if the milk be measured with air bubbles in it a quite inaccurate 

 result will be obtained. Accordingly, it is necessary, after the 

 composite sample has been thoroughly shaken, to allow it to 

 stand awhile ; but in the interval cream may have again risen, 

 and consequently some system must be adopted which ensures 

 thorough mixing, freedom from air bubbles, and a minimum 

 loss of time. To accomplish these ends the following procedure 

 has been found most satisfactory : Before commencing to shake 

 the samples look carefully for any in which the cream has dried 

 on the side of the bottle, and also for any in which churning has 

 taken place. In both these cases warm the sample to 38 C. 

 fco melt the fat, then shake vigorously, and cool under the water 

 tap, taking great care that no water enters the bottle. Now 

 arrange all the samples in numerical order, and commence to 

 mix the contents of each bottle by shaking vigorously, using 

 the palm of the hand as a stopper. After the first three 

 bottles have been shaken return to No. 1, which by this time 

 should be free from air bubbles. Gently invert bottle No. 1, 



