PHYSICAL AND CHEMICAL EXAMINATION OF MILK 



201 



with advantage to improve the product of their patrons. In the 

 opinion of some practical men the sediment test has done more 

 for cleanly milk production than any other single factor. The 

 dealer makes the test and records the results on a pledget of cot- 

 ton fastened to a card (Fig. 73). This is given to the patron, 



Fig. 73. — Sediment card. (Circular cf Information No. 41, September, 1912, 

 ITniv. of Wis. Agri. Exp. Sta.) 



who then actually sees the dirt which has been filtered out of his 

 milk, and a rivalry among producers is started which ultimately 

 leads to a greatly improved milk-supply. 



Reiss and Sommerfeld give the following average amounts of 

 visible dirt found in the milk-supplies of some European cities: 



AMOUNT OF DIRT IN MILK IN SOME EUROPEAN CITIES 



Berlin '. 10.9 mgrs. per liter. Helsinfors 1.79 mgra. per liter. 



Christiania 11.0 " " " Leipzig 3.8 



Halle 14.9 ' Munich 9.0 " " 



Hamburg 13.5 " " " 



The writer, in an investigation of Chicago milk, found that 

 the average amount of dirt in 108 samples of raw milk was 2.2 

 mgrs. per liter, and in 107 samples of pasteurized milk, 1.4 mgrs. 

 per liter. The amount in raw milk never exceeded 9 mgrs., and 

 in pasteurized milk 6 mgrs., per liter. 



It should be remembered in this connection that the intro- 

 duction of centrifugal clarifiers has in large measure reduced the 

 amount of visible dirt in market milk. 



Rough tests of the quantity of milk sediment can be made by 

 allowing the milk to stand for several hours in a conical glass vessel 

 so that the dirt accumulates in the apex; or by centrifuging a 

 small amount of the milk in a tube with a conical bottom. 



