BABCOCK BOTTLE CERTIFICATION APPARATUS PERFORMANCE EVALUATION

The use and performance of a computer-controlled apparatus for certifi cation of Babcock bottles used for payment testing were evaluated. The apparatus delivered mercury into the bottle neck using a syringe moun ted on a motorized pump. Syringe movement and the collection and calcu lation of data were controlled by computer. The apparatus was evaluate d using four 8% milk bottles (total volume 1.600 mL; bottles rejected if deviation was greater than or equal to 0.008 mL) and four 50% short -neck cream bottles (total volume 5.000 mL; bottles rejected if deviat ion was greater than or equal to 0.050 mL). Six milk and 5 cream bottl e trials were conducted; each bottle was read 5 consecutive times for each trial, As a percentage of the rejection criteria, average repeata bility was 5-6% and reproducibility was 9-10%, These values were simil ar for both types of bottles, The evaluation of the apparatus demonstr ated acceptable within- and between-days performance in relation to th e rejection criteria and volumes measured. Because the apparatus creat es a closed system during certification, an additional experiment was conducted with 50% short-neck cream bottles to determine the effect of internal pressure within a bottle on volume estimates. Four trials we re conducted, as previously described, using 4 control and 4 experimen tal bottles, Volume between the 0 and 50% marks (5 mL) was determined, Holes were drilled in the experimental bottles to eliminate internal pressure for the final 2 trials, The estimated volume of bottles under pressure was 0.0054 +/- 0.0012 mL greater than without internal press ure (i,e., about 11% of the rejection criteria), We concluded that any pressure effect was small relative to other factors that affect volum e determination.