November 15,1934
I N D U S T R IA L A N D E N G : N E E R I N G C H E M I S T R Y
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A mixture of 84.5 grams of A, 80.5 grams of B, and 46.5 grams of component C, which is in satisfactory agreement with the of C is shaken and on settling is found to give 122.5 grams of 46.5 grams actually taken. upper layer and 59.0 grams of lower layer. Point P in Figure 1 I n the present case the auxiliary lines IJ, etc., were so represents this over-all composition-namely 40, 38, and 22 per cent. drawn that they lay on either side of the tie line. I n case Now if I P J were the true tie line, the mass of B should be they had been so chosen that they all lay on the same side 0.01 ((89.0)(1) f (122.5)(62.5)] = 77.4 grams. Similarly K P L demands 80.9 grams and M P N 89.0 grams, whereas the true line of the tie line, this fact would have instantly appeared on ) , it would should give the amount of B originally taken, 80.5 grams. By graphing the expression O . O ~ ( ~ J B ~ J B since plotting these values against the percentage B represented by have been greater (or less) than m~ for all the lines instead the points J, L, and N , the percentage corresponding t o a value of greater for one and less for another. I n many cases the of 80.5 is found to be 64.7 (Figure 2). This percentage when graph could still be successfully extrapolated. If the extrapolocated on the curve of Figure 1 indicates that the upper layer obtained above is 3 per cent A , 64.7 per cent B, and 32.3 per lation seemed uncertain, then another line could be chosen cent C. By joining this point to P the tie line is obtained. so as certainly to lie beyond the tie line, and by adding this As a check on the work, the above process can be repeated on value to the graph the required value easily determined by component A , this time locating a point on the left side of the curve which when joined to P gives the tie line. If both times interpolation. the same tie line is obtained, one can feel sure of the accuracy LITERATURE CITED of the work. In the present case the percentage A is found to be 91, thus locating the oint on the curve 91 per cent A, 1.5 (1) Miller and Mopherson, J . Phys. Chem., 12, 710 (1908). r cent B, 7.5 per cent C! This also lies on the tie line secured (2) Roozeboom, H. W. B., “Die heterogenen Gleiohgewiohte,” Vol. computing on the basis of component B, thus checking the 3, Part 2, pp. 87-95, Friedr. Vieweg & S o h , Brauneohweig, previous work. Finally, using the values so obtained for the Germany, 1911. ercentage C in each layer, it is found that on this basis we should I U D22, 1934. gave started with 0.01 [(89.0)(7.5) (122.5)(32.3)] = 46.3 grams R ~ C ~ I V May
+
9”y
+
Chemical Studies of Wood Preservation 111. Analysis of Preserved Timber ROBERTE. WATERMAN, F. C. KOCH,AND W. MCMAHON,Bell Telephone Laboratories, New York, N. Y.
I
N T H E study of the preser-
e x p e n s i v e in order to permit Methods are given for analysis of preserved the examination of a substanvation of poles, one may distimber, creosoted or treated with inorganic tial proportion of all the poles tinguish s e v e r a l kinds of sails. The methods are in part adapted for a n d t h e d e l i v e r y of t h e res a m p l e s for chemical analysis aPPraisal O f freshly treated poles f o r quantity and sults of analysis within a few classified according $0 the purexcellence of distribution of preservatiw and in hours. pose of the study: I n order to d e t e r m i n e t h e part adapted to following the processes of deple1. Samples of freshly treated Penetration and retent of the timber taken for the purpose of tion during years of exposure. Recovery of d e t e r m i n i n g the quantity of a individual poles in any particuCmXote from old t h b e r (-2nd for the known preRervative and the lar charge, it w o u l d be necescharacter of its distribution. analysis and toximetry of creosote are described. sary to take s e v e r a l b o r i n g s 2. Samples from poles still around the circumference of each r e q u i r e d for service or further exposure in experimental plots. These samples may be used t o pole and perform an analysis on the composite borings from determine roughly the changes in quantity, distribution, and each pole separately. Except for very special purposes this is toxicit of preservatives with time. 3. gamples of poles which have been removed from service too laborious. A sing1e boring from each pole will suffice to lines or from experimental plots and are therefore available for give a fairly good appraisal, provided each boring is examined more thorough study of the changes in properties of preservatives for depth of sapwood and depth of penetration as well as with the lapse of years. preservative content. A great deal can be learned by sampling only a selected proportion of the poles. The borings It is the Purpose of the Present Paper to outline the analfli- may be split for analysis as described in a previous paper (Q), cal methods used for the examination of the foregoing classes though for some purposes the whole boring may be analyzed of samples. While these studies are primarily concerned with and an empirical correction or an arbitrary standard of creosote, the authors have examined many other preserva- preservative content may be applied. tives Inore O r less thoroUghlY. For this Purpose it has been I n the case of freshly creosoted poles the following method necessary to devise special analytical methods in certain cases. of determining creosote has been found convenient: ANALYSISOF FRESHLY TREATED TIMBER The purpose of a n examination of freshly treated timber is usually to secure some measure of the excellence of a treating process at a particular plant or by a particular method. this case a sample of the original preservative is available for thorough examination of its physical and chemical properties as well as toxicity. Since i t is unnecessary to recover the preservative from the samplesin its original state, one has a freer choice of analytical methods. It iS Often highly deskable that the method of analysis of wood be rapid and in-
The heartwood and untreated sapwood are broken off the borings, and the samples thus obtained are chipped up and placed in a tared brass container provided with a screen bott,om and weighed. This container is then placed in the apparatus shown in Figure 1. The solvent, which may be either toluene or xylene, is boiled, and as the vapors extract the wood, the water is carried UP into the condenser and drops into the calibrated trap, The extraction is continued until the solvent dripping from the cage is colorless and water ceases to drop into the trap. The solvent is evaporated from the extracted wood, which is then brought to constant weight at approximately 105’ C. The water content i8 read directly in the trap. The weight of water plus the dry weight of wood subtracted from the original weight
410
ANALYTICAL EDITION gives the creosote content. Using the weight of creosote t h u s found, the retent per unit volume is calculated from tho diameter of the boring, the radius of the pole, and the number of borings taken.
This method involves ignoring the weight of natural extractives derived from the wood. Air-dried untreated s a p w o o d of s e v e r a l s a m p l e s of southern Dine has been extracted and never f o k d to contain more than 0.2 pound per cubic foot (0.32 gram per 100 cc.) of t o l u e n e - or xylenes o l u b l e m a t e r i a l s u c h a s resins. The a m o u n t is u s u a l l y even less and has therefore been neglected in all this work. Care must be taken in sampling poles which have been felled only 2 or 3 days before treatment. Such wood may still contain very v o l a t i l e c o m p o u n d s such as t e r p e n e s which may lead to falsely high results for c r e o s o t e c o n t e n t . Steam conditioning lessens the chance for this error, but it is w e l l a f t e r splitting the borings to leave them in the open for a few minutes before weighing in the case of poles which were treated when extremely green. C r e o s o t e l o s s e s from the exposed b o r i n g s a r e s m a l l , a s t h e y cool FIGURE 1. APPArapidly. R A T U S FOR D E TERMINING CREOIJ.Iorder to indicate experimentally SOTE the accuracy of the toluene extraction method, a weighed amount of creosote was added to a given weight of sawdist in a tared metal extraction thimble and extracted as described above with the results recorded in Table I. An adaptation of this method of retent determination has been in use for some time in the Bell System for c r e o s o t e d Douglas fir poles. The chips from an ordinary wood bit are used for analysis and an arbitrary standard of creosote content is chosen. Aside from the creosote content, the depth of penetration in relation to the depth of sapwood is a very important index of efficiency of impregnation. It is well to record these figures for statistical examination. W h e n t h e l i n e of demarcation between the sapwood and heartwood is not clearly evident in the case of southern pine, use is made of a staining test. The test is performed as follows: The boring as it comes from the increFIGURE 2. APment borer is often smeared with oil. It PARATUS FOR INis therefore split longitudinally to provide DIRECT DETERa clean surface. The edge of the face of M I N A T I O N OF the split boring is brought in contact with CREOSOTE the surface of a water solution of nigrosine black or cotton blue, so that t)he rate of absorption as well as intensity of the discoloration of the wood can be readily observed. As a rule the dye solution is absorbed readily by the sapwood, but not by the heartwood. Any dark dye which is not actually adsorbed by the wood and hence taken out of solution would probably be satisfact,ory. Experience is necessary.in interpreting the results when abnormal or irregular conditions are encountered.
Vol. 6, No. 6
TABLEI. TOLUENPEXTRACTION OF CREOSOTE CREOSOTIU CREOSOTIU ADDmD FOUND No. Grams Grams 10.379 10.596 11.538 11.499 10.876 11.117 11.593 11.547 10.483 10.138 10.795 10.235 11.213 11.968 Sawdust equilibrated over water prior to addition of creosote. SAWDUST Grams 55.675 55.705 55.487 54.234 46.671O 45.413a 55.607"
ERROR % ._
4-2.09 -0.34 +2.2a -0.40 -3.29 -5.19 -6.31
(I
ANALYSISOF SAMPLES FROM STANDINQ POLES When examining creosoted poles which have been exposed for some months or years, it is desirable to use a nontoxic solvent, so that the toxicity of the extract can be determined a s well as the retent in the pole a t the time of sampling. This excludes the use of benzene, toluene, etc., as extractants, as the low-boiling cyclic hydrocarbons in general are extremely toxic and difficult to remove completely from creosote. Ether is preferred on account of its low toxicity, but i t also is so difficult to remove completely that the determination of amount of creosote is best made indirectly. The borings from the test poles, usually eight per pole, taken from the region of special interest] are split diagonally and the heartwood and untreated sapwood discarded. The rest is cut up into small pieces, placed in a small tared wire basket, and put over calcium chloride until at constant weight. This requires from 2 t o 4 weeks. Usually scores of these determinations are run in parallel] so that the time required is not serious. The basket is then suspended from a water-cooled condenser in a tall form flask over boiling ether (Figure 2). The extraction is continued until the drip from the basket is colorless. The basket is then removed, and after the ether has evaporated is replaced over calcium chloride until again at constant weight. The difference in wei ht before and after extraction thus represents the extractive. %he step of bringing the wood back to equilibrium over calcium chloride a second time may be dispensed with by merely drying in an oven at 105" C . and applying a suitable correction factor based on the moisture content of the wood in equilibrium with calcium chloride. This has been found from experience to average 1.39 per cent, dry weight basis, for southern pine sapwood, The ether extract obtained in this process is reserved for tests of its toxicity by methods referred to below. The accuracy of the ether extraction method is indicated by experiments involving the addition of a weighed amount of creosote to an appropriate weight of sawdust and subjecting the samples to extraction (Table 11). TABLE11. ETHEREXTRACTION OF CREOSOTE No. 1 2 3 4 5 6
7 8 5
SAWDUST Grams 8.267 8.890 8.600 8.136 7.324a 7,446" 8.162a 7.456a
CRBO~OTE ADDED Grams 2.193 2.146 2.164 2.072 2.269 2.172 2.317 2.026
CRBOBOTE FOUND Oroms 2.091 2.090 2.114 1.947 2.261 2.163 2.258 2.002
ERROR % -4.66 -2.47 -2.31 -6.03 -0.35 -0.41 -2.66 -1.18
Samples equilibrated over water prior t o addition of creosote.
ANALYSISOF DISCARDEDPOLES During the past few years scores of creosoted poles which presented some feature of special interest, such as early failure or outstandingly good performance, have been available for examination. In addition many pole sections have been removed from test plots for dissection and analysis. I n such cases a more liberal sampling is possible, as there is no necessity for keeping the pole intact for further exposure or observation. Such examinations are for the purpose of qualitative information regarding the kind of changes which have occurred. Quantitatively, they are often of limited value on
November 15,1934
INDU STRIAL AN D E N GI N E E R I N G C H E M I STR Y
account of uncertainty as to the representative character of the pole chosen for examination. The procedure is to cut a cross-sectional slab about 1 inch (2.5 cm.) thick from the above-ground portion of the pole and another from below ground for determination of sapwood depth,
411
Samples of the substances under test (usually ethereal solutions in the case of creosote) are weighed or measured and introduced into a hot mixture of malt, agar-agar, and water in glass-stoppered bottles. The bottles are shaken vigorously and the agar is poured into Petri dishes, or the whole operation may be carried out in glass-stoppered Erlenmeyer flasks or preferably Petroff
depth of penetration, and amount of creosote still present. The slabs are cut into several sectors as nearly as possible representative of the entire cross section and the average sapwood and penetration are measured. The wedge-shaped pieces may be divided into an outer and inner treated part, an untreated sapwood portion when present, and the heartwood. The volume of each section is measured by mercury displacement in a graduated cylinder. When it is desired to determine only the quantity of oil present, the selected treated parts are cut up into slices approximately 1 inch wide by 0.063 inch (2.5 X 0.16 cm.) thick and extracted with toluene or xylene as outlined under “analysis of freshly treated timber.” Calculations are made of creosote content of the entire sector or of the different parts of the cross section, according to the information desired. In order to et some indication of the t y of oil originally present and to 8nd how it has changed t h r o u z t h e years, several cross-sectional slabs cut from the pole both above and below ground are separated into an outer and inner treated section; the wood is sawed and split into pieces roughly 0.75 X 0.75 X 2 inches (1.9 X 1.9 X 5 cm.), and put through a hog to reduce it to sawdust. The sawdust, usually 2 to 10 lbs. (1 to 5kg.), de ending on the operator’s judgment of the oil content, is placefin the extractor shown in Figure 3. The sawdust is contained in the false bottom cage which is 15 inches (37.5 cm.) high and 11.5 inches (28.75 cm.) in diameter and ether is poured in from the top. The ether is boiled by circulation of water at 45” C. and is condensed by the water-cooled coils attached to the hinged cover. Flexible hose is used to connect the cold water supply with the condenser. During the extraction the cock on the side
CONDENSER
DRIP
OJ:
i
CLOSED WHEN RUNNING. OPEN WHW RECLAMINC ’TOM
FIGURE4. BATTERY OF FOUREXTRACTORS
flasks sealed with gelatin bottle caps. After the agar cools and gels, the medium is inoculated with a pure culture of a wooddestroying fungus. If no growth has taken place after an incubation period of 4 weeks, the inoculum is removed and placed on nontoxic agar to determine whether it has been killed or merely inhibited by the act,ion of the toxic substance.
At present the fungi most in use in this laboratory are Fomes annosus, Lentinus lepideus, Poria incrassata, and Coniophora cerebella, all obtained originally through the courtesy of the Forest Products Laboratory. A more extended discussion of various toximetric methods, results, and interpretations will appear in a later paper. is closed, allowing the ether to drip down through the sawdust. When extraction is complete, usually in less than 2 days. this cock is opened to reclaim the ether. The residual oil after being further freed of ether by gradually bringing to steam bath temperature is available for analysis as in the case of new creosote.
A battery of four such extractors is illustrated in Figure 4. They are operated in a small room separated from all other laboratory operations and provided with vigorous ventilation and sa,fety devices on electrical outlets.
METHODS OF GENERAL APPLICATION TOXIMETRY. The toxic potency of preservatives has usually been determined in essentially the same manner as a t the Forest Products Laboratory, Madison, Wis. ( 7 ) .
CREOSOTE ANALYSIS Whenever possible the methods of the American Wood Preservers’ Association (1) are followed in creosote analysis. The manual of the association does not include a method for sulfonation residue. For this purpose 37 N sulfuric acid is used as the sulfonating agent and the unsulfonated residue is read after centrifugalizing in Babcock milk-test bottles. The authors prefer for the sake of expedition to determine tar acids by extracting the oil in benzene solution with sodium hydroxide, followed by liberation of the acids from the aqueous solution with sulfuric acid, rather than to use the American Wood Preservers’ Association method. A rapid method for determination of water in creosote is sometimes needed. For example, in the empty cell treatment
412
ANALYTICAL EDITION
of green wood, some water accumulates in the creosote. To facilitate control of this feature, the following method was developed : The apparatus as shown in Figure 5 is similar to that used in water-content determinations for various organic compounds utilizing a solvent lighter than water, but with a higher boiling point. Toluene, xylene, or naphtha are boiled vigorously in the apparatus; w when no further traces of water appear at the end of the condenser, the sto cock on the trap is opened momentariry toremove any traces of water which may have collected. The creosote is added slowly through the separatory funnel and after a few minutes’ boiling all water present has passed into the graduated trap and the quantity is read directly. This water can be drained out of the trap, and the apparatus is ready for another determination without recharging with toluene.
ANALYSIS OF WOOD PRESERVED WITH INORGANIC MATERIALS For the purpose of d e s t r o y i n g organic matter t o permit determination of m e t a l i o n s i n w o o d , the authors have found the method of Bateman (2) very useful. This consists in digesting a known volume or weight of wood with a saturated solution of potassium chlorate in concentrated nitric acid, adding sulfuric acid, and boiling down to fumes, with repeated additions of a few drops of concentrated nitric acid if necessary to destroy the last traces of organic matter. This method has the adFIGURE5. APPAvantage over leaching of insuring the RATUS FOR DETERcomplete recovery of all metal ions. MINING WATER IN CREOSOTE In some instances, there is reason to suspect that certain metal ions become fixed in the wood in such a way as to become inoperative in a preservative sense. This is notably true of certain copper, zinc, and chromium preparations. When this is suspected a leaching method may be used for determining the “available” metal ion in which case the organic matter in the evaporated extract may be destroyed in the manner above described. The matter of determination of effective metal ions present as distinguished from the total metal ions has not yet been thoroughly studied. ARSENIC. Determination of small amounts of arsenic is made by the Sanger Black method (8) with slight modifications upon an aliquot of the solution prepared according to Bateman. Determination of large amounts of arsenic is made by distillation of a solution of 5 grams of wood prepared in the same manner. For this purpose the digestion flask is attached to a thistle tube and connected to a condenser after addition of 2 grams of hydrazine sulfate and 5 grams of potassium bromide to reduce the arsenic to the arsenous form. Sixty to 70 cc. of concentrated hydrochloric acid are added through the thistle tube and distillation is carried on until the volume is reduced to 15 to 20 cc.; hydrochloric acid is again added and distillation repeated as before. This is continued until the final distillates are free from arsenic, as shown by a test with hydrogen sulfide. Distilling off two portions of acid is usually sufficient. The combined distillates are neutralized with ammonia, treated with 5 grams of sodium bicarbonate, and titrated with 0.1 N iodine using starch as indicator. A blank correction is made. The precision of this method may be judged from analyses which were made of mixtures of sawdust and arsenic trioxide in known proportions (Table 111).
Vol. 6 , No. 6
TABLE 111. DETERMINATION OF ARSENIC -SAMPLE-
Arsenic trioxide
Gram 0.0502 0.0502 0.0251 0.0251 0.0100 0.0100
Wood Grama 3.0 3.0 3.0 3.0 3.0 3.0
A R S ~ N ITBIOXID~ C FOUND Gram 0.0486 0.0483 0.0241 0.0221 0.0095 0.0095
ZINCIN PRESENCE OF ARSENIC. Determination of zinc in the presence of arsenic is performed upon the residue from the arsenic distillation. Iron is usually present in appreciable amounts and must be removed. This is done by oxidizing with ammonium persulfate, adding ammonium chloride and ammonia, and filtering off the ferric hydroxide. The solution is then evaporated to dryness and brought down to fumes with sulfuric acid. The resulting solution is titrated with potassium ferrocyanide using diphenylamine as indicator to an apple green end point (3). This titration is also applicable to the determination of substantial amounts of zinc when present as residues from zinc chloride treatments-that is, in the absence of arsenic. If only minute amounts of zinc are present, an aliquot of the solution after destruction of organic matter is freed of iron and recipitated in a Nessler tube with otassium ferrocyanide. Tge final determination is made nepherometrically. COPPERIN PRESENCE OF ZINC. Copper is determined in the presence of zinc by precipitation as copper sulfide after destruction of organic matter. The filtrate from the copper sulfide is used for the zinc determination as above. The copper sulfide is dissolved in a solution of bromine in hydrochloric acid, brought down to fumes with sulfuric acid, and copper is determined colorimetrically as the ferrocyanide. MERCURY.Determination of mercury in wood subjected to mercuric chloride treatments has been the source of some difficulty. It was found that some mercury is volatilized if organic matter is destroyed by Bateman’s method. Accordingly, a sample of the wood is reduced to sawdust by means of a ras and a weighed amount ( 5 to 10 grams) is suspended in 150 cc. ofwater and 50 cc. of concentrated nitric acid in which is dissolved 1 gram of potassium permanganate to maintain an oxidizing condition in the solution. The suspension i s then electrolyzed for 2 hours with a current of 1 ampere, using a rotating platinum electrode. The cathode is raised from the solution and washed with distilled water before interrupting the current. The mercury is now dissolved with about 30 cc. of concentrated nitric acid at 45’ to 50’ C. The electrode is washed in water and the solution is diluted to 100 to 125 cc., filtering if necessary to remove any particles of sawdust which have adhered to the electrode. The mercury is oxidized with a slight excess of potassium permanganate solution and any excess permanganate is quantitatively removed by addition of dilute hydrogen peroxide. Ferric sulfate is added as indicator and the solution is titrated with 0.01 N ammonium thiocyanate. In order to insure that no mercury has been left in the ori inal sawdust residue the electrolysis should be repeated in case of uncertainty and any additional mercury obtained is oxidized and titrated as before. TABLB IV. DETERMINATION OF MERCURY -SAMPLHIMercurio chloride Gram 0.0050 0.0100 0.0100 0.0050
Wood Groms 3.0 3.0 3.0 3.0
MERCURIC CHLOIUDE FOUND Gram 0.0049 0.0099
0.0093 0.0047
BORAX. Determination of borax is made by a modification of the Thompson method (5). The wood is first extracted with hot water in a Soxhlet-type extractor, concentrated to a small volume, and the Thompson method followed except that mannitol is used in place of glycerol in the titration. FLUORINE. Determination of fluorine in wood treated with sodium fluoride alone presents no especial difficulties, The finely divided sample is ignited in a platinum crucible; the ash is dissolved in hot water and any insoluble material filtered off. From this point on, t>helead chlorofluoride method outlined by Hawley ($) is followed. Determination of fluorine in the presence of arsenic or chromium or both reauires sDecial methods. The method outlined below gives approiimate rksult,s. The chipped sample in a crucible is moistened with sodium hydroxide and sodium carbonate solution, dried, and ignited a t 800’ C. ( A 50’) until all organic matter has been destroyed. The residue is dissolved in hot water and filtered; the solution is cleared of chromium and arsenic with excess silver nitrate. The
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IN D U ST R I A L A N D E N G IN EE R I N G CH E M IS TR Y
excess silver is removed with sodium chloride and the fluorine in the filtrate is determined as follows (6): Ammonium hydroxide is added in excess and the solution boiled down to 40-50 CC. A 7.0-em. ashless filter paper is added and thoroughly macerated and 10 cc. of 2 N calcium nitrate are added t o the hot solution t o precipitate the fluorine. The solution is cooled, filtered, and washed (filtrate and washing should not exceed 100 cc.). The residue is ashed in a platinum crucible and weighed as calcium fluoride. Data on the accuracy of such fluorine determinations are given in Table V. TABLEV. DETERMINATION OF FLUORINE --SAMPLE-
Sodium fluoride Gram 0.0125 0.0153 0.0216
Wood Grams 3.8 5.0 5.0
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LITERATURE CITED (1) Am. Wood Preservers’ Assoc., “Manual of Recommended Practice,” Washington, D. C. (2) Bateman, E., INn. ENG.C H ~ M6, . , 17 (1914). (3) Cone, W. H., and Cndy, L. C., J. Am. Chem. Sac., 4 9 , 3 5 6 (1927). (4) Hawley, F. A., INn. ENG.CHEW,18, 573 (1926). (5) Leach, A. E., “Food Inspection and Analysis,” 4th ed., p. 886, John Wiley & Sons, N. Y . , 1920. (6) Pflaum, D. J., and Wenzke, H. H., IND. ENG.CHQM.,Anal. Ed., 4, 392 (1932).
(7) Richards, C. A., Proc. Amer. Wood Preservers’ Assoc., 127 (1923).
Gram 0.0110
(8) Treadwell, S. P., and Hall, W. T., “Analytical Chemistry,” 7th ed., Vol. 11, p. 203, John Wiley & Sons, pu’. Y . , 1929. (9) Waterman, R. E., and Wells, C. O., IND. EXG.CHEM.,Anal. Ed., 6, 310 (1934).
0.0114 0.0183
RIPCEIVED April 14. 1934.
Sonrnai FLUORIDE FOUND
IV. Small Sapling Method of Evaluating Wood Preservatives ROBERT E. WATERMAN AND R. R. WILLIAMS, Bell Telephone Laboratories, New York, N. Y.
P
ERMANEXCE and
I n order to expedite tests of the permanency effective ratio perhaps to 9 or 10. However, other factors, notably toxicity are probably the of Pole preservatives, use is made of groups of longitudinal diffusion from below most necessary characsmall pine saplings treated with the preservative ground upward, further compliteristics of a wood preservacate the comparison and prohibit in question and set in the ground as miniature an exact treatment of it.) The tive. E a s e of injection, freesaplings are easy t o obtain, and telephone poles, In these specimens weathering dom from corrosive properties, are better than turned sticks in cleanliness, cost, and the like is relatively rapid on account of the large ratio of that they approximate a pole in are all important, b u t no surface to volume, and poorly preserved material which the grain runs parallel t o material can be considered unthe surface. The saplings rarely, begins to decay in ‘i or 2 years. Analyses and if contain any heartwood less it displays a high degree of toxicity tests as well as observations of decay and a r e easily impregnated resistance to wood-destroying throughout. are made periodically. Seven years’ experience fungi and u n l e s s t h i s toxic The usual procedure has been potency persists when t h e indicates that the comparative preservative values to inject three dozen a i r - d r i e d treated wood is exposed to the of various salts, creosotes, oils, etc., may be ~~~~~~~~~~~~~~~~~~~~i~~ w e a t h e r f o r l o n g periods of estimated relatively cheaply, quickly, and with ture treating plant using the full time. The problem under discell process. After discarding the considerable reliability by this method. cussion is that of appraisal of butt 3 inches (7.62 em.), the next 3 inches (7.62 cm.) are cut off for wood preservatives f o r t h e s e analysis, or for extraction and toximetry. (The preservative contwo characteristics within a reasonably short time. tends to be higher in the upper part than in the butt. The Methods are gradually becoming standardized for toxi- tent same is significantly true for full-sized poles However, in both metric determinations and if this were the sole considera- case8 we are interested chieflv in rates of dedetion at the ground tion, judging preservatives would be greatly simplified. line which is nearer the butt.“) A dozen of fhe saplings c h t o a However, permanence is equally important and is more length of 30 inches (76.2 cm.) are set in the ground, butt down, in each of three test plots which are maintained at Limon, Colo.; difficult to estimate. It may be measured to a degree by Chester, N. J.; and Gulfport, Miss. Such quick and consistent laboratory determination of the evaporation and leaching results are obtained at the last-named location that the other rates of oils and salts, respectively, but a true measure of the test plots are now less used for this particular work. Comparautility of a preservative should include something closely tive data at the three plots have, however, furnished a rough calibration of climatic influence on the test. Untreated saplings resembling outdoor exposure and a measurement of the rate at Gulfport have always failed completely within a year either of decline in amount and potency of the preservative. Prefer- by rot or termite attack or both. All tests reported herein were ably these observations should be extended till actual rotting made at the. southern test plot. occurs, a t least in the case of less satisfactory products. The sapling form of specimen and its method of exposure I n dealing with such a complicated chemical, physical, and biological process, laboratory tests have definite handicaps is clearly imitative of a telephone pole. The contact with and it is always possible that some vital factor has been the soil and consequent leaching effect below ground and missed. A complete life observation within a short time is the exposure of the upper part of the sapling to the evaporathe end to be desired and the use of small specimens exposed tive effects of the air are both essential features of the exposure. The data so obtained provide a well-rounded picture to a warm moist climate permits an approach to this ideal. of the virtues and shortcomings for pole preservation purposes The method chosen makes use of small saplings of southern of each preservative. Naturally, the effects of ground water yellow pine about 0.5 inch (1.27 cm.) to 0.75 inch (1.94 om.) in extend up into a sapling farther in proportion to its total diameter and 30 inches (76.2 cm.) long. The ratio of surface length than is the case with a pole, so that one must be caret o volume, expressed in inches, in the average pole in use in the Bell System is approximately 0.467. In a sapling of 0.75 inch ful not to carry the parallelism too far in interpreting ground(1.94 cm.) diameter this ratio is 5.33. Hence for a given unit line effects. of volume the sapling has a surface available for evaporation The specimens are examined for rot and insect attack a t or leaching 11.42 times as large as the average pole with a diam- least once a year. On each inspection one or more from each eter of 8.56 inches (21.7 cm.) and accordingly tends to rot much sooner. (The treated volume of wood in a pole is normally group may be removed for laboratory examination. Chemisomewhat smaller than the total volume, thus reducing the cal or biological assay of these saplings affords evidence
