BabcocJc Test for other Milk Products. 



87 



to five minutes, keeping the tester as hot as possible the 

 whole time. 1 The readings must be taken as soon as the 

 whirling is completed, as owing to the contraction of the 

 liquid by cooling, the fat otherwise adheres 

 to the inside of the neck of the test bottle 

 as a film of grease which cannot be meas- 

 ured by the scale. 



99. The double-necked test bottle, (Fig. 

 36), suggested by one of us, 2 is made espe- 

 cially for measuring small quantities of fat 

 and gives most satisfactory results in testing 

 skim milk and butter milk. Each division 

 of the scale in these bottles represents five- 

 hundredths of one per cent., and the marks 

 are so far apart that the small fat column 

 can be easily estimated to single hundredths 

 of one per cent. In the first forms, now 

 out of use, the neck was graduated to hun- 

 dredths of one per cent. 



The value of the divisions of the scale on 

 the double-necked test bottles has been a FIG. 36. The 



double-necked 



subject of considerable discussion, and van- skim miik bot- 

 tle (sometimes 



ous opinions have been expressed whether called the Chi- 

 ron or B. & W. 

 they show one-tenth or one-twentieth (.05) bot tie.) 



of one per cent, of fat. By calibration with mercury the 

 value of the divisions will be found to be .05 or one- 

 twentieth of one per cent., but as shown above, the 

 results obtained in using the bottles for thin separator 

 skim milk often come at least .05 per cent, too low, so 

 that, practically speaking, each division may be taken to 



1 See Wis. exp. station, report XVII, p. 81. 



2 Farrington, and constructed by Mr. J. J. Nussbaumer, of Illinois. 



