Determination of Free Carbon in Rubber Goods

The carbon black analysis should not be made without a consideration of the nature of the original stock. The size of the sample must be related to the black content. To lessen time consumed in this analysis, preliminary extraction of the sample should be omitted. The correction factor for clay must be applied. By the revised method greater accuracy is obtained, although there is still a tendency for the results to be higher than calculated. Precision in this method seems to depend mainly upon accuracy of weighing and avoiding the loss of small particles of black.