The determination of water in glycerols

Abstract

Water in concentrated glycerols may be satisfactorily determined directly by the Bidwell-Sterling distillation method, using toluol as the boiling liquid. A variable but very small amount of glycerol is carried over with the water. In no case in our analyses did this glycerol carried over amount to as much as 0.10 gram, and the correction to the apparent per cent of water in the sample did not exceed 0.15% in any of the glycerols containing up to 10% of water. The use of a solvent like xylol boiling appreciably above 100°C is not advisable since it causes considerably more glycerol to be carried over and does not markedly shorten the time of distillation. An analysis made by this method on a 25.00 gram sample of dynamite glycerol to which 2.80 grams of water was added, producing a sample containing 10.37% water, gave a recovery, corrected for 036 grams of glycerol carried over, of 10.39% water. On the A. O. C. S. Standard Crude Glycerine sample, Mr. Church reports that four laboratories found an average of 4.90% moisture by the P2O5-vacuum method. We found 4.99% moisture by direct distillation in this same sample.