22—The Determination of Fatty Matter in Scoured Wool and Tops

The refractive index method for determination of percentage combing oil in solvent extracts from tops has been examined critically and a method which makes provision for the assessment of interference by other constituents has been developed. For accurate determinations, appropriate standards for each batch being processed must be available and the method cannot be applied to samples of unknown origin with confidence. The variation of refractive index of residual portions of wool grease remaining on the fibre has been examined and the effect of temperature considered.