The Babcock Test. 39 



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. 



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. 

 There is this objection to the latter method that unless 

 carefully done, it is apt to weaken the bottles so that 

 they will easily break, and to both methods, that the 

 lead pencil marks made on such ground labels may be 

 effaced during the test if the bottles are not carefully 

 handled. Small strips of tin or copper with a number 

 stamped thereon are sometimes attached to a collar 

 around the necks of the bottles. They are, however, 

 easily lest, especially when the top of the bottle is 



1 A flat-bore test bottle and one with a brass collar and screw used 

 for opening and closing a small hole in the neck of the test bottle have 

 been placed on the market by an Eastern manufacturer. These have 

 been tried by us, and were not found to possess any particular advan- 

 tage over the round-neck bottles; in fact, are more subject to errors of 

 calibration. 



