Temperature corrected ready-reckoner chart for determination of dry rubber content in Hevea latex using the metrolac

Rubber latex is collected by periodic excision of a thin shaving of the bark of Hevea tree. In addition to the volume, its value is determined by the dry rubber content (DRC) of latex. Dry rubber content of latex varies usually in the range of 20-45% and depends on several factors such as clone, season, climate and weather condition, stimulation program, tapping system, soil condition etc. Hydrometry (using the Metrolac) is the most widely used method in the determination of DRC in the Sri Lankan rubber industry. Metrolac measurements are highly vulnerable to temperature of the latex/water mixture. Existing ready-reckoner for Metrolac readings is valid only at 290C, hence the present study was aimed at developing a Metrolac ready-reckoner chart corrected for temperature variation in latex. Under natural and adjusted conditions, the new ready-reckoner chart showed an accuracy level of 84% on average in the estimation of dry rubber content whilst the average accuracy by the existing chart was below 50%. The Metrolac estimated DRC differed in the range of -12.69% to 9.25% from the actual under existing ready reckoner whilst that was limited to -7.56% to 5.31% with the use of new ready-reckoner chart.