The lignin fraction of animal feeding‐stuffs. II—Investigation of lignin determination procedures and development of a method for ‘acid‐insoluble lignin’

Examination of humin residues obtained at various stages during lignin determination and of the alcohol‐soluble fraction of pre‐treated food materials has indicated the necessity for modifying the procedures used in lignin determination. Factors affecting the dispersion and hydrolysis of cellulose are reported, and it is shown that in order to determine as lignin only material insoluble in concentrated acid it is necessary to filter without dilution after the main treatment. A method for determining ‘acid‐insoluble lignin’ is proposed and shown to give satisfactory agreement between replicates.