August10,1925
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Seventeen Fallacies about Wood 1 B Y L. F. HAWLEY F O R E S T PRODUCTS LABORATORY, MADISON.
The following aberrations about wood are, within the writer's observation, the most important or interesting from the chemist's point of view. Some are in well-nigh universal acceptance; others are used only for promotion purposes. Fallacy 1. A routine chemical analysis of a piece of wood will give information from which all its properties and peculiarities, both physical and chemical, can be determined. M a n y requests are received at laboratories for " a chemical analysis," when inquiry shows that the information wanted is not general but specific, as for instance: Will this wood contaminate food products in its vicinity? Will it m a k e a good storage b a t t e r y separator? How can it be bleached? Will it corrode metals? Is it resistant to acid? What is t h e coloring- matter in this wood? Why won't our X X waterproofing composition stick to this wood? Ordinarily, analyses of wood are expressed in such terms as cellulose, lignin, inethoxyl, water-soluble content, and pentosans. Therefore the most elaborate figures on such constituents obtained after much time and trouble may not answer a specific question about a particular piece of wood, when a simple practical test would meet the requirements. Fallacy 2. Wood contains " c o n s i d e r a b l e " q u a n t i t i e s of a l b u m i n , starch, pectin, sugars, a n d g u m s , which a r e " i m p o r t a n t " in connection with m a n y properties a n d uses of wood. Recent analyses indicate t h a t about 3 per cent starch, 1 per cent pectin, 1 per cent albumin, and 2 per cent sugar may exist in wood, although they are probably not all present in these quantities a t the same time. There is some doubt about even these determinations, since in a material so complex as wood the determination of these classes of extractive compounds, mostly by indirect methods, is difficult and may be rendered inaccurate by interfering reactions of the wood fiber itself. At a n y rate the quantities are far from "considerable" in the ordinary usage of that word. T h e term " g u m s " is so indefinite t h a t it will not be discussed here. N o doubt the other substances named are very " i m p o r t a n t " from the botanical-biochemical standpoint, but so far as concerns the properties and uses of wood they have little interest. The decay of wood and even the shrinking a n d swelling of wood with changes in moisture content are often attributed to these substances. Also the natural air-seasoning of wood is considered by some to be different chemically from artificial kiln-drying in t h a t the oxidation of various deleterious "gums, starches, sugars, resins, e t c . " occurs in the former process and not in t h e latter. As a matter of fact, short of actual burning no chemical difference between t h e results of t h e two processes can be detected. (The "brown stain" which sometimes appears in kiln-dried western yellow pine is a possible exception.)
Fallacy 3. Hardwoods have more lignin than softwoods, heavy woods more lignin than light woods, heartwood more than sapwood, and slowly grown wood more than rapidly grown wood. These statements m a y sound plausible, b u t there is no basis for any of them. In fact, the very opposite is true in t h e case of hardwoods vs. softwoods. T h e first two of these allegations are very good examples of attempts to explain in chemical language differences in wood t h a t are largely physical.
Fallacy 4- There is :i wide variation in the chemical composition and chemical properties of different species of wood. This is at best a half-truth, since the composition of the wood liber proper, which constitutes by far the largest part of any wood, varies but little between species. There is some variation between t h e two general classes of hardwoods and softwoods, but by chemical analyis of t h e liber no two hardwoods and no two softwoods can be distinguished. In t h e extractives, however, there may be a wide variation. 1
Received February 12, 1925. Presented before the Division of Cellulose Chemistry at the 69th Meeting of the American Chemical Society, Baltimore. Md.. April 6 to 10, 1920.
WIS.
Indeed, most of t h e striking differences in properties, such as color, odor, taste, and resistance to decay, are referable solely to the extractives. Fallacy 5. Sap-stained or blue-stained wood is weaker than similar unstained wood. This is a natural conclusion, since it is well known that fungus growth catises a decided decrease in strength. It has been shown, however, t h a t blue stain does not materially affect strength. The explanation is that the blue-stain organism lives principally on the extractives—the "sugar, starches, gums, etc.''—and does not affect the wood fiber. Similarly, the belief still persists that red hickory is weaker than white hickory of the same weight, although it was shown to be a fallacy several years ago. Here the difference lies in a natural coloration of the heartwood due to extractives and not in the wood liber. Hence, the strength cannot be affected by the coloration. Fallacy 6. "Wood can be so modified by t r e a t m e n t t h a t it no lunger absorbs moisture a n d therefore no longer shrinks or swells. The adherents of the sugar-starch-albumin-gum theory of wood drying claim that after the removal of these indefinite constituents the wood will no longer absorb moisture. As a matter of fact, the absorption is a physical property of the wood fiber and cannot be destroyed so long as the liber itself remains. This property may be modified as it has been shown t h a t the equilibrium between atmospheric humidity and the moisture content of wood changes after the wood has been completely dried. The modification is very slight, however, and so long as wood is wood it will shrink or swell with moisttire changes, indeed, the attraction of wood for moisture is so great t h a t there are very few coatings which are able t o do more than retard the process of absorption.
Fallacy 7. Beech wood is necessary for the manufacture of " beech wood" creosote. The first medicinal creosote was made from beech wood, and t h e name "beechwood" has since been retained for all such creosotes. The term has become a misnomer, since U. S. P. creosote is now usually derived from the commercial hardwood tar oils, which may come from maple, birch, oak, or other species quite as well as from beech. T h e same kind of creosote has even been made commercially from pine t a r oils. The purity of t h e product is controlled by the refining methods used rather than by the wood furnishing the raw material.
Fallacy 8. Turpentined pine trees furnish a less resinous and weaker wood than unturpentined trees. This belief seems to be still fairly common, although competent investigators showed as long ago as 1893 t h a t there was no discernible difference either in strength or in resin content between "bled" and " r o u n d " m a t u r e longleaf pine. It hardly seems necessary to discuss the accuracy of those determinations now, when it is considered t h a t the heartwood of a tree is always deadwood and cannot be affected by changes in life processes. Turpentining may, of course, affect t h e resin content of heartwood formed afterward, but t h e result is more likely to be an increase than a decrease in resin.
Fallacy 9. Sapwood of longleaf pine contains more resin than the heartwood. This opinion would naturally be formed by one who had noted t h a t in the turpentining of longleaf pine the chipping was carefully limited to the sapwood, or who had seen the transparent beads of " g u m " form on a freshly cut sapwood surface (as after the felling of a tree) but not on the heartwood. However, although resin is manufactured in the sapwood it is stored mostly in the heartwood and will not Jloiv from the freshly cut surface of the latter. Fallacy 10. Resin in produced in longleaf pine wood after the tree is cut. This notion h a s been developed to explain the large amount of pitchy wood (lightwood and stumps) found in cut-over forests
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or abandoned turpentine orchards. It is shown to be incorrect by the* fact that heart wood is deadwood even before the tree is cut and can take no part in a life process such as the formation of resin, liven if the sapwood did continue to make resin after the tree were cut, its effect would not be noticeable because this "pitchy wood" is almost always heartwood. The simplest explanation, here as in most cases, seems to be the best: The old lightwood and stump wood, found many years after the cutting of the tree, existed in much the same form and with the same resin content in the living tree and is simply the undecayed residue of the original tree; the rest of the wood has rotted away. Fallacy 11. Wood from trees cut in t h e summer is much less resistant to decay than t h a t cut in the winter. There is no proof by comparative tests that this opinion is incorrect; nevertheless, it is quite certain that the apparent difference in durability is due to the more favorable conditions for decay during the summer than during the winter, and not to any seasonal difference in the chemical composition of the wood. The usual explanation offered is that in the summer the "sap is up" and t h e "sappy" wood is more liable to decay. There is no evidence of any chemical change in heartwood during the seasons, and any change in the sapwood would affect durability very little, since sapwood is not durable. Variation in durability is due to variation in amount and kind of substances that prevent decay and not of those that promote decay. Fallacy 12. Wood in construction is under all conditions more dangerous than steel in case of fire. It is true that wood will burn and that steel will not, and also that when wood is heated to about 280° C. it soon becomes charcoal, which has no structural strength, whereas the strength of steel is little affected at such comparatively low temperatures. Jint wood has one tremendous advantage. It is a very poor conductor of heat, so that the outside of large beams or thick planks may burn or char while the inside retains its strength. Steel in t h e same lire and carrying the same load would be very rapidly heated through, and not infrequently will lose its strength and drop its load sooner than the wooden member. Advantage is taken of the insulating property of wood in the so-called slow burning mill construction. Fallacy 18. Wood can be firoproofed so t h a t it will not burn or c h a r a t high temperatures. T h e so-called lireprooting of wood does not change its chemical nature, and if it is heated to 280° C. it will still decompose (char), giving off combustible tars and gases. The fireproofing only makes the wood ignite much less readily and slows down the speed of combustion. In this way it may render a very valuable service, but cannot keep the wood from charring at about 280° C. Fallacy l/h Hickory, or other h e a v y hardwood, h a s a higher fuel value t h a n pine. This m a y be true as between a cord of hickory and a cord of pine, as t h e cord of hickory weighs considerably more; but on a pound or ton basis the pine has the greater fuel value. On a weight basis there is not much variation between different woods except t h a t due to resin content, the resinous woods having in general t h e higher fuel value. This does not mean that for steady burning in a stove or a fireplace pine would be preferred to hickory, but that pound for pound the pine does give off more heat. I n considering the fuel values of woods it should also be kept in mind t h a t the moisture content, which varies between wide limits, is a s a rule the most important faotor. Fallacy 15.
Sawdust has no value as a fuel.
This opinion is probably a survival of the former custom of sawmills t o burn "slabs" for fuel and to waste sawdust in trying to build mountains or fill lakes. Both slabs and sawdust were not needed for fuel requirements, and in those days neither was good for anything else; hence the slabs, being handiest, were fed under the boilers. Later, as other uses for the slabs were developed, it was found that by using special fire boxes and grates sawdust could be burned as a fuel. Anyone who has tried to burn sawdust in a stove or on a grate designed for coal is perhaps justified in the opinion t h a t it has little or no fuel value; but the Dutch oven lire box has rendered sawdust a really valuable fuel. Fallacy 16. Wood waste can be obtained free, or a t a n y rate at a very small cost. T h e t r u t h of this statement depends on the definition of waste. If t h e statistician's definition of waste is used—namely, "all the
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wood brought to the sawmill and not made into timbers or boards" •—the fallacy is almost self-evident. There are many other uses for wood, not so high-grade perhaps, yet giving the materials a definite value; laths, shingles, box shooks, dimension stock, and fuel are examples. No man, not even a lumberman, is going to give away material suited to such uses. On the other hand, if waste be defined as the wood that is actually unused for any purpose and may even cause an expense for disposal, still it cannot be obtained for nothing—for the very human reason that material with a zero or even a minus value immediately takes on a plus value when someone else wants it. This point should be kept in mind by anyone contemplating the promotion of a project requiring ''waste" wood as a raw material. Fallacy 17. With regard to t h e removal of s t u m p s there are three fallacies t h a t ought to be uprooted. (a) S t u m p s can readily he burned by saturating t h e m with kerosene or other combustible and setting fire to t h e m . Those who suggest this method seem to forget that the stump itself, when dry, is combustible enough and for better burning needs more air, not more combustible. There is nothing much more combustible than a fat pine stump, provided it is in small enough pieces so that the air can get at it; and yet the stumps do not burn, although grass fires frequently char the surface a little. So kerosene will hardly do the work. (b) S t u m p s can readily be burned by boring a vertical 1-inch hole 6 inches deep in t h e center of t h e t o p of t h e s t u m p and filling it with saltpeter, waiting a few days, and setting fire to the s t u m p . This method takes cognizance of the need for oxygen, but like most purely theoretical suggestions it will not work. Even if the holeful of saltpeter could distribute itself throughout the stump it would not give off enough oxygen to burn its own weight of the wood. (c) S t u m p s can be obliterated b y boring a hole in t h e t o p of t h e s t u m p a n d p u t t i n g in " s o m e t h i n g " t h a t will " r o t " t h e wood. The word " r o t " is used here in the sense of "soften" or "chemically decompose," since the "something" is at times more nearlyspecified as "an acid." Moreover, this is often not the chemist's acid at all, but the layman's favorite catalyst, a "strong corrosive chemical" which will " e a t " the wood. If " r o t " were meant in the sense of decay as a result of fungus attack, the suggestion is unnecessary, since any wood t h a t can be made to rot will do so without help or compulsion.
Owed to the Chemist The chemist, they say, isn't getting his due; his salary checks are too meager and few\ Not seldom the business depends on his skill; without him the earnings would be about nil. Yet while he's inventing new things by the score, the credit is left at the president's door. "The chemist? Oh, yes, he plays 'round with his smells, but executive 'pep' is the factor that tells." The chemist works out a new process or two, saving millions that formerly went up the flue. Do they therefore promote him and double his pay, and give him a big block of stock, if he'll stay? More likely they tell him that business is bad, t h a t profits are minus, and prospects are sad; but if he'll continue to work his poor head off, they possibly might stave the ruin they dread off. For in spite of the moralists, all of us know that many earn less than the service they show, and an income that runs to the millions oft comes from a Jack-Horner-habit of grabbing the plums. The men with the test-tubes need more self-esteem; they must show they are not as content as they seem. For they'd like to get more than an office boy's pay, and know that their training was not thrown away. And it isn't for lucre alone they are yearning, although they would like to receive wdiat they're earning; but they want to be valued at what they arc worth, and then they will feel more content with their berth. If chemistry's really important to us, we can't leave the chemists to chafe and to cuss. For virile young men, when they see how they fare, will go into law or take up cutting hair. Now a dearth of trained chemists will leave such a gap, it would mean to the country a big handicap. Employers and chemists and public at large, for the sake of the future, consider this charge. Ignoring the scientist, sooner or late will bring the whole craft to an ignoble state. And so, if we wish to see science advance, we all must assist its prestige to enhance. So here's to the chemists, and high may they climb; may they win aii the credit thc> merit in Lime:. The Nucleus.
