The isolation of pectic substances from softwoods.

Branfoot (1) has summarised the early work on pectic substances. Bonner (2), Norman (3), and Hirst and Jones (4) have reviewed later work on the structure of these substances. Pectic materials that approximate the composition and have some of the properties of pectic acid are widely distributed but in small amounts in mature hardwoods. In 1925 O’Dwyer (5) isolated such a material from beechwood, and in 1931 Preece (6) reported 0.4 per cent of pectin in boxwood. Since then pectic materials have been isolated from mature wood of black locust (7), lemon, mesquite, and white pine (8), and from cottonwood (9). In mature woods peetic materials are mixed or combined with large amounts of cellulose, lignin, hemicellulose, and often with other carbohydrate materials. Although they have been isolated from mature hardwoods and from one softwood, it is far more difficult to isolate them in appreciable amounts from softwoods. This possibly is due to the greater solubility of the hemicelluloses of softwoods than of hardwoods and to the greater amount of other soluble carbohydrates that dissolve with the pectic materials in the extraction of softwoods. No satisfactory procedure for isolating these materials from mature woods and for separating them from the accompanying substances is known. The methods now used are not quantitative. They require large amounts of wood if sufficient pectic material is to be obtained for complete purification. Undoubtedly the pectic materials so far isolated from wood have undergone considerable hydrolysis in the process of isolation and purification. As a result, pure pectic materials from mature woods have not been studied sufficiently for their properties and composition to be accurately determined.