The Babcock Test. 



47 



cock through which the acid passes has a diameter of at 

 least one- eighth of an inch, as is generally the case. We 

 have used or inspected some half a 

 dozen other devices, which have 

 been placed on the market by vari- 

 ous dealers for delivering the acid, 

 but cannot recommend them for 

 use in factories or outside of chem- 

 ical laboratories. 



52. Instead of measuring out the 

 acid, Bartlett 1 suggested adding it 

 directly to the milk in the test bot- 

 tles, till the mixture rises to a mark 

 on the body of the bottle at the 

 FIG. 19. Swedish acid bot- point where this will hold 37.5 cc.. 



tie; the side-tube is made f 



to hold 17.5 cc. of acid. j. 6t? the total volume of milk and 

 acid (89). This method of adding the acid is in the line 

 of simplicity, but has not become generally adopted. If 

 the method is used the marks should be put on by the 

 manufacturers, as the operator in attempting to do so 

 will be apt to weaken or break the bottles. 



CALIBRATION or GLASSWARE. 



Test bottles. The Babcock milk test bottles are so 

 constructed that the scale or graduation of the neck 

 measures a volume of 2 cubic centimeters, between the 

 zero and the 10 per cent marks (44). The correctness 

 of the graduation may be easily ascertained by one of the 

 following methods: 



53. (A.) Calibration with mercury. 27.18 grams of 

 metallic mercury are weighed into the perfectly clean 



i Maine experiment station, Bull. No. 31. 



