While this work was being done the manufacturer himself desired to check the mechanical centrifuge, and attempted to remove the air bubbles from the same samples by swinging the specific gravity cups by hand. He made a special effort to remove the air bubbles in this way, devoting nearly a day to the examination of the 17 samples. Notwithstanding his unusual care, his average specific gravity was 1.0318, while the centrifuge method gave 1.0328. It will be noted that the specific gravity as determined by the centrifuge method was .0013 higher than that obtained by the purchaser, though the latter used a more accurate method than has ordinarily been employed in this determination. This difference has ordinarily been regarded in the industry as insignificant. It is apparent that it is not negligible, however, when we consider that the difference in yield involved amounts to over 4.5 gallons in 100 gallons of pulp. It is true that all these results are lower than the specifications for which this particular pulp was sold, but the incident illustrates the importance of an accurate determination of specific gravity. EVAPORATION TO THE SPECIFIC GRAVITY DESIRED Manufacturers of tomato pulp have considerable difficulty in securing a product of uniform concentration and in determining at what point to stop evaporation. Some manufacturers turn off the steam when it is believed that the concentration has gone far enough and make a hasty determination of specific gravity. If it is found the concentration is not as great as is desired, heating is resumed for a time and the specific gravity again determined. Others make but one determination of specific gravity when it is believed that the desired concentration has been reached, and if it is found to be underconcentrated, continue the evaporation for a length of time which experience has indicated to be necessary. Neither of these methods of operating is satisfactory. They involve a great deal of work and the concentration of the product obtained is not sufficiently uniform. Moreover, the determination of specific gravity of hot pulp is very inaccurate (see p. 44). A method of employing a gauge stick is believed to be simpler and more practicable.