A careful consideration of the question of temperature leads one to the conclusion that the practice of placing a thermometer through the roof of the chamber does not enable one to determine the temperature correctly. In the same way a thermometer suspended behind the observation window cannot indicate the temperature of the rubber, as in both of these positions the thermometer must be influenced by radiation from the walls of the chamber. The only position in which the correct temperature could be indicated is between the folds of crepe. This can be arranged easily so as to enable one to read the temperature from the observation window.
COLOMBO COMMERCIAL COMPANY'S DRIER.--The drier of the Colombo Commercial Company consists in principle of a number of small chambers or units in which crepe rubber is placed, and through which hot air is passed. As in the case of vacuum drying, a great deal depends upon the preliminary treatment of the rubber. If the crepe is not rolled thin enough drying will be unduly prolonged, with a possibility that the rubber will become tacky. The temperature usually obtained is about 150° F., and if the rubber is thin the production of an installation of two chambers should be at the rate of 1 lb. of dry rubber per minute. The usual period of drying is under two hours. One advantage which this drier has over the vacuum drier is that the chamber can be opened at any time for a short period to withdraw or insert trays. The thin crepe is folded several times, as in the case of vacuum-drying.
Figures obtained from the actual working of a drier in Ceylon are given below:
-------------------------------------------------+----------------------- CHAMBER 1.--TEMPERATURE 160°-180°F. | -------------------------------------------------|CHAMBER 2.--TEMPERATURE _NO. OF | _DRYING | _WEIGHT OF | _WEIGHT OF | 150°-165°F. Tray._ | Period._ | Wet Rubber._ | Dry Rubber._ | --------+----------+--------------+--------------+----------------------- |Hrs. Mins.| Lbs. | Lbs. | 1 | 1 22 | 7-1/2 | 6 |Worked similarly 2 | 1 42 | 7-1/2 | 6 |to No. 1. Yielded 3 | 1 57 | 7-1/2 | 6 |in 2 hrs. 23 mins. 4 | 1 57 | 7-1/2 | 6 |70-3/4 lbs. dry rubber, 5 | 1 57 | 7 | 5-3/4 |from 87-1/2 lbs. wet 6 | 1 57 | 7-1/2 | 6 |rubber. 7 | 2 0 | 7-1/2 | 6 | 8 | 2 0 | 7-1/2 | 6 | 9 | 2 11 | 6-1/2 | 5 | 10 | 2 11 | 7-1/2 | 6 | 11 | 2 11 | 7-1/2 | 6 | 12 | 2 18 | 7-1/2 | 6 | --------+----------+--------------+--------------+----------------------- | | 88-1/2 | 70-3/4 | --------+----------+--------------+--------------+-----------------------