Studies on the Acetone Extraction of Raw Rubber. V. The Influence of Heating at 100° C. and Storage of the Acetone Extract on the Saponification Value

Abstract (1) When the acetone extract was heated at 100° C., the saponification value (AT) first diminished and then increased. (2) When the acetone extract was stored, the saponification value (AT) first increased and then diminished and returned to the original value. (3) The determination of the saponification value was carried out as follows: The sample was extracted for the required time, the acetone was evaporated off as rapidly as possible and the flask was dried in a steam bath for as short a time as possible. The drying time must not be over 15 minutes, and usually 5 minutes is sufficient. The dried flask was cooled and weighed, after which 20 cc. of 0.2 N alcoholic KOH was added and the flask heated on a water bath for 60 minutes. The excess alkali was titrated with 0.1 N HCl solution, using phenolphthalein as indicator.