Lignin studies II. The lignin content and properties of lignin in different materials

In this investigation the lignin, the total of membrane substances, the crude protein and the methoxyl in lignin were determined in different materials. Some observations on the properties of lignin have been made. The lignin content, as calculated from the dry matter or from the total of the membrane substances, varies greatly in different materials, as can be seen in Table 1. This is the case even if one leaves out of consideration such materials as the bark of woods, sea-weeds, and mosses, the »lignin» of which scarcely is real lignin. In grasses and clover the content of lignin in the cell walls increases with the successive stages of development. The methoxyl content of lignin varies in different plants, in the same plant at successive stages of growth, and in the different tissues of the same plant. The solubility of lignin in hot diluted alkali solutions varies in different materials. Of the lignin in Gramineae plants even in an 0.1 N natrium hydroxide solution about 50 % dissolves, but of the lignin of softwoods only negligible amounts in a 2 N solution. The lignin preparations isolated by the usual acid methods contain, besides the real hydrolysis residue, also substances dissolved by the strong acid but precipitated by the succeeding dilution. The nitrogen content of the precipitated fraction is high. The high methoxyl content of its nitrogen free portion points to real lignin.