The Babcock Test. 39 



tenth, or even five-hundredths, of one per cent, of fat 

 in the samples tested. 



In the best kinds of Babcock bottles the per cent, 

 marks are complete circles and the half per cent, 

 marks are semi-circles. This greatly aids in making 

 correct readings. 



As the necks of Babcock test bottles vary in diame- 

 ter, each separate bottle must be calibrated by the manu- 

 facturers ; the length of the scale is not, for the reasons 

 given, apt to be the same in different bottles. 1 



If the figures and lines of the scale become indistinct 

 by use, the black color may be restored by rubbing a 

 soft pencil over the scale, or by the use of a piece of 

 burnt cork after the scale has been rubbed with a little 

 tallow. On wiping the neck with a cloth or a piece of 

 paper the black color will show in the etchings of the 

 glass, making these plainly visible. 



Special forms of test bottles used in testing cream 

 and skim milk are described under the heads of cream 

 and skim-milk testing (89, 90, 99). 



443. Eight-per-cent. bottles. Milk test bottles with 

 scale graduated from to 8 per cent, have come into 

 general use of late years, having been adopted in 1911 

 by the National Dairy Instructors' Association as 

 " standard." The specifications for this bottle and 

 other Babcock 'glassware are given in par. 307. 



45. Marking test bottles. Test bottles can now be 

 bought with a small band or portion of their neck or 

 body ground or "frosted," for numbering the bottles 

 with a lead pencil. Bottles without this ground label 

 can be roughened at any convenient spot by using a wet 

 fine file to roughen the smooth surface of the glass. 



