Introduction. 9 



milk samples are tested every day, as, for instance, in milk control 

 stations, the butyrometer may be preferable to the Babcock test; 

 but it requires more skill of the operator and does not work satis- 

 factorily in case of sour, loppered, or partially churned milk. 



14. Fjord's centrifugal cream tester 1 (fig. 3) is exten- 

 sively used in Denmark and is mentioned in this connection as it 

 furnishes, as a rule, a reliable method for comparing the qual- 

 ity of different lots of milk. ' The method was published in 1878, 

 by the late N. J. Fjord, director of the state experiment station 

 in Copenhagen, through whose exertions and on whose authority 

 it was introduced into Danish creameries in the middle of the 

 eighties. No chemicals are added in this test, the milk being 

 simply placed in glass tubes, seven inches long and about two- 

 thirds of an inch in diameter, and whirled for twenty minutes 

 at a rate of 2000 revolutions per minute at 55C (131F.). 

 The reading of the cream layer thus obtained gives the per cent 

 of cream, and not of butter 

 fat, in the sample tested. One 

 hundred and ninety-two sam- 

 ples of milk can be tested 

 simultaneously. Within the 

 limits of normal Danish herd 

 milk, the results obtained cor- 

 respond to the per cents of fat 

 present in the samples, one per 

 cent, of cream being equal to 

 about 0.7 per cent, of fat; FIG. 3. Fjord's centrifugal cream 

 outside of these limits the test 



is, however, unreliable, especially in case of very rich milk and 

 strippers' milk. Only sweet milk can be tested by this method. 

 Milk tests proper, like the Gerber, Babcock and De Laval tests, 

 have during recent years been introduced into Denmark and 

 are used in some creameries. 2 



1 State Danish experiment station, Copenhagen, sixth and ninth re- 

 ports, 1885-7. 



2 Among foreign milk tests in use abroad should also be mentioned 

 the Lindstrom ~butyrometer and the Wollny refractometer, both of 

 which, in the hands of trained chemists, may prove better adapted for 

 use where a very large number of samples are to be tested at a time, 

 than any other available milk test. 



