TOTAL FATTY AND RESIN ACIDS.
To the filtrate from the insoluble matter add 40 cubic centimeters of half normal sulfuric acid, all the acid being added at once. Boil, stir thoroughly for some minutes and keep warm on a water bath until the fatty acids have collected as a clear layer on the surface. Cool by placing the beaker in ice and syphon off the acid water through a filter. Should the fatty acids not readily congeal a weighed amount of dried bleached bees-wax or stearic acid may be added to the hot mixture. This fuses with the hot mass and forms a firm cake of fatty acids upon cooling. Without removing the fatty acids from the beaker, add about 300 cubic centimeters of hot water, cool, syphon off the water through the same filter used before and wash again. Repeat washing, cooling and syphoning processes until the wash water is no longer acid. When this stage is reached, dissolve any fatty acid which may have remained on the filter with hot 95 per cent. alcohol into the beaker containing the fatty acids. Evaporate the alcohol and dry the beaker to constant weight over a water bath. The fatty acids thus obtained represent the combined fatty acids, uncombined fat and hydrocarbons.