164 MODERN METHODS OF TESTING MILK 



tion, (2) by centrifugal machine, (3) by ordinary set- 

 tling. 



Filtration test for dirt. This can be carried out 

 in a very simple form by packing a funnel with some 

 absorbent cotton and pouring a pint of milk on this. 

 Most of the dirt will collect on the top of the cotton 

 if it is not packed too loose. 



The Wisconsin experiment station (Bulletin 195) 

 has made a special device (Lorenz sediment-tester) 

 for the application of this principle, which furnishes 

 a convenient and effective means for filtering or strain- 

 ing dirt from milk. The details of construction are 

 shown in Fig. 40. In operating the test, a cotton 

 disc is placed in the cap over the wire gauze and then 

 fastened in place. A pint of milk is .then poured into 

 the cylinder or funnel (A). When the milk has run 

 through the filter, the cotton disc is removed and 

 placed on a piece of white, clean paper to dry. Then 

 another disk can be inserted and another sample of 

 milk tested and the operation repeated for any desired 

 number of samples. When many samples are tested 

 in rapid succession, a numbered cap should be pro- 

 vided for each test. 



The rapidity of testing many lots of milk depends 

 on (i) the temperature of the milk while filtering 

 and (2) on the character of the cotton filtering-discs. 

 The milk filters more rapidly if it is kept hot; the 

 apparatus provides for this condition. The cotton 

 discs should be made of absorbent cotton that is en- 

 tirely free from starch or similar material. The discs 

 should be about one-eighth inch thick and cut out 

 to fit the cap and wire gauze. When properly made, 



