96 GUIDE TO DAIRYING IN SOUTH AFRICA 



the machine at a good speed for three minutes. 

 The bottles are then taken out and replaced in a 

 hot- water bath and then each bottle read. If, 

 however, the layer of fat is not sufficiently high in 

 the bottle the cork should be pushed in a little more, 

 which will bring the fat layer completely within the 

 division marked on the bottle. Each of these 

 divisions is equal to 0*1 per cent. If the sulphuric 

 acid used is too weak, particles of curd will remain 

 undissolved and will accumulate during the whirling 

 at the bottom of the fat layer ; this must not be read 

 in with the fat when determining the percentage. If 

 the acid used is too strong, charring of the curd will 

 take place, and the fat layer will be of a dark brown 

 colour and be nearly impossible to read correctly. 

 The sulphuric acid should have a specific gravity of 

 1*825 to be the correct strength for this test. 



If froth accumulates on the top of the fat layer, 

 the bottles should be placed in hot water for four 

 or five minutes and then whirled in the machine 

 once more. 



If an odd number of tests are being made, the 

 bottles must be arranged in the machine so that 

 they will balance ; if necessary, a bottle filled with 

 water may be used to make an even number. 



If separated or butter milk is being tested, place 

 the bottles in hot-water bath for five minutes after 

 whirling, then whirl them a second time, after which 

 the fat may be read as with milk. 



