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A, Figure 4, shows that the results are entirely reproducible. After one sample had been brought to constant weight at 100°, it was redissolved in benzene. Removal of the benzene by the same technique yielded the same weight of polymer. When this polymer was redissolved in benzene and the solvent removed by the distillation technique, the same weight of product was obtained if the heating time was sufficiently long (A, Figure 2), showing that moisture or solvent adsorption on the porous polymer was negligible.The following details should be of assistance in applying the frozen benzene technique.Pyrex Erlenmeyer flasks have been used because they give fairly large, flat cakes of polymer. Less than 1% of the 125-cc. flasks collapse under vacuum.

The increasing use of panthenol has emphasized the need for a more efficient assay method. Hence, the microbiological assay has been modified to eliminate the ether extraction for removal of pantoyl lactone or the separate assay required to correct for preformed pantoic acid. In the present procedure, these interfering products of hydrolytic cleavage of