v m U. S. Department of Agriculture, Forest Service FOREST PRODUCTS LABORATORY In cooperation with the University of Wisconsin MADISON, WISCONSIN EXTRANEOUS MATERIALS IN WOOD B y GEORGE X. BITTER Chemist S. DEPOSITOR R |03$ I Or mm II! i>T\i^.J m$M GF n Published in THE ANNUAL CRUISE 1934 Digitized by the Internet Archive in 2013 http://archive.org/details/extrteriOOfore EXTRANEOU S MATER IALS IN WOO D GEORGE J. RITTER, Chemist All species of woods contain materials other than wood sub- stance and water. Although, such materials are not an integral part of the wood structure, nevertheless, they affect the properties of the wood as a whole. They are referred to under the all-inclusive term, extraneous materials. These materials vary over a wide range both in amount and composition among the different species of woods, among different trees of the same species, and even among the various parts of the same tree. Consequently, an infinite amount of painstaking chemical work would be required to describe and identify all the compounds included in this group of substances. In this short article a general account of only a few of them is given. In general, except for some dyes that require oxidizing treatments to remove them from wood, most of the remaining extraneous materials can be divided into two classes: (1) those soluble in water and (2) those soluble in such neutral organic solvents as ether, alcohol, or mixtures of alcohol-benzene. Among the water-soluble materials is a class of compounds known as tannins. Some of these are toxic toward wood-destroying fungi and thus, when present in sufficient quantities, act as natural wood preservatives. Although tannins are present in only minute quantities in most woods, in a few, such as hickory, oak, and redwood, they are more plentiful; their main source of supply for commercial use is chestnut wood and hem- lock bark. They are extracted from the wood or the bark by means of water which is subsequently evaporated to obtain a concentrated tannin liquor or a dry powder, depending on the process employed. These concentrated tannins are used in the leather and fur industry as they have the property of reacting with the proteins in hides, making them resistant to putre- faction. Another water-soluble extraneous material is galactan. It occurs in large quantities in western larch and can be converted by hydrolysis to a sugar, galactose, which in turn can be converted to mucic acid. This acid is adapted for use in the manufacture of baking powder, self-rising flours, effervescent salts, and soft drinks. Still another water-soluble extractive is pinite. This sugar-like substance has been found in a few conifers. In sugar pine it is plentiful enough to concen- trate as a white powder on the surface of the lumber during seasoning in the kiln and the yard. Then, too, sugar maple is known to contain sugars and esters which are concentrated from the sap to form such well-known products as maple syrup and maple sugar. R1038 Under certain conditions water-soluble extractives produce un- desirable effects in wood, whereas under others they increase its value. Some of them darken on prolonged exposure to the atmosphere or to elevated temperatures. During the seasoning of some species of lumber, especially by improperly controlled artificial means, these materials produce, near the surface of the stock, intense discolorat ions which cause heavy degrades to otherwise select stock. On the other hand, some extractives in conjunction with the natural dyes impart harmonious colors to wood and thereby enhance the value of lumber. A knowledge of the changing of these colors during natural or artificial aging of wood is invaluable to the architect in selecting the woods best suited, from an artistic point of view, for the innumerable types of wood construction. Compounds found in the class of extraneous materials that are soluble in neutral organic solvents, in general, are resins, oils, fats, and waxes. In most of the pines the resinous materials consist of a mixture of oils and rosin. However, in Jeffrey and digger pines the oily portion is principally normal heptane which belongs to a different class of compounds than do turpentine oils. There is aiso present in the oily portion minute amounts of aldehydes which are thought to impart a fruitlike odor, but the rosin is similar to that in the other pines. Thus far, turpentine oils and oils belonging to the heptane class have been found only occasionally in the same species. The crude distillate of oleoresins from Jeffrey and digger pines was early known as abieiene, and it has been used locally in California as a cleans: ng agent, an insecticide, and as a constituent of chewing gum, cough syrup, and other medicinal preparations. A recent new use has arisen for heptane as a constituent of a standard fuel for the measurement of "knock" in automo- bile engines. A high resin content in lumber is undesirable because it inter- feres with the proper surfacing of the stock and with the pleasing appearance and the wearing qualities of surface finishes. In one process developed for removing the excess resin, the lumber is stacked on trucks which are pushed into a fairly air-tight shed. The lumber is then sub- jected to a treatment with turpentine fumes which condense on thp stock and dissolve the resin on and near the surface of the lumber. The resin solution then trickles to the floor from which it is conveyed by gravity to a heated retort. There the turpentine is again vaporized and con- ducted to the lumber , leaving behind the concentrated rosin for use in paper sizing and other commercial processes. A process for recovering resins from wood waste having a high resin content has been used extensively. In this process the turpentine is recovered by steam distillation of the wood waste and the rosin is then dissolved by means of gasoline from which it is recovered by vapor- izing the solvent. Turpentine and rosin obtained from conifers by this procedure supplement the gum oleoresins obtained from living trees as sources of supplies for naval stores. R103 8 -2- Fats are also present in the ether extractives of woods. Some of them are similar to the solid fats that occur in lard whereas others are oils at ordinary temperatures. Both fats and oils are formed by the combination of fatty acids and glycerine. Another class of compounds closely related to fats and oils are waxes. These materials are formed by the combination of free fatty acids and sterols which are classed as alcohols having a high molecular weight. Research studies have shown a general distinction between the ether extractives of the young; second-growth sapwood and the heartwood of southern pines. The content of the sapwood extract is considerably less than that of the heartwood extract. Moreover, the major portion of the sapwood extract consists of fats, waxes, and fatty acids and is semiliquid in nature. In contrast the major portion of the heartwood extractives consists of resins and is solid in character It is likely that the lower ether-soluble extractive content and the more liquid state of the extractives in the sapwood than in the heartwood account for the difference in the pulpirg qualities of the two types of wood. These differences in the extractives would seem to explain why the sap- wood can be pulped by the sulphite process, whereas the heartwood requires an alkaline process for its successful conversion into pulp. From this brief discussion it is evident that wood is both a finished raw product and a storehouse of raw materials. A knowledge of the chemical composition of the extraneous materials in conjunction with that of the wood itself offers a direct aid in the silvicultural control of wood and its properties. Such knowledge forms a scientific basis for selecting, handling, seasoning, surfacing, finishing, preserv- ing, and converting wood into pulp and other products — in short, it affords a rational cooperative means by which our forests can be more economically utilized than at present. R103S -J>~ UNIVERSITY OF FLORIDA 3 1262 08925 4501