Alkali and Thio Lignins from Pine Bark

Lignin was recovered by acidification of the spent liquor from various cooks of pine bark in aqueous sodium hydroxide and Kraft cooking liquor, respectively. Processed data were collected and some properties of the lignin products determined. Product yields varied with the alkali bark ratio, but maximum recovery was of the magnitude predicted by the 72 percent sulfuric acid analysis method. The methoxyl and sulfur content and acetone solubility of the lignins varied with the changes of the chemical compositions of the cooks. The lignin content of the screened bark on an extractive-free basis was found to be 46.5 percent to 47 per cent. Yields of lignin from six cooks were greater than would be expected from similar cooks of the woods from the same species. The bark lignins are less soluble in aqueous alkaline solutions and organic solvents than are the wood lignins. It was thought that lignins from pine bark should sell at about the same price level as two commercial lignins and should be less expensive than the lignin solvents now on the market.

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