IRG Documents Database and Compendium


Search and Download IRG Documents:



Between and , sort by


Displaying your search results

Your search resulted in 49 documents. Displaying 25 entries per page.


Comparison of Different Methods for Assessing the Performance of Preservatives in the BAM Fungus Cellar Test
1998 - IRG/WP 98-20149
The fungus cellar test is a common means to get reliable data on the long term performance of treated wood in soil contact. A constantly high humidity and a suitable of water holding capacity for a range of micro-organisms provide high decay rates in untreated wood and produce intensive microbial pressures on wood treated with biocides. Presently a range of biocides are under test in the BAM fungus cellar and the results will be presented for the following types of biocides: Tebuconazole in combination with copper and boron (5 years fungus cellar), quats with copper and boron (5 years fungus cellar) and Cu-organic compound combined with copper and boron (3 years fungus cellar). Figures will be shown on the development of the Modulus of Elasticity (MOE) over the years and on an assessment of the stakes according to EN 252.
I Stephan, M Grinda, D Rudolph


Migration of active ingredients from treated timber into fresh water
1991 - IRG/WP 3669
Spruce roundwoods and segments were treated with three different wood preservatives. Two of them containing copper and chromium the other one free of chromium. After fixation (3 weeks, 20°C) the specimens were leached by using artifical rain or by shaking the segments for one hour in contact with demineralized water. The water was analysed for the relevant elements of the preservative tested. Leachability of the components from the copper-chromate treated wood decreases. After 4-8 leaching cycles an almost constant migration of wood-preservatives, depending on the leaching method and the pH-value of water applied, was determined for the chromate containing preservatives. In the course of leaching cycles a constant rate of migrated copper from the preservative free of chromium was determined after 4 - about 17 leaching cycles. After 16 leachings of the segments the leached copper as calculated on the copper retention was determined to 1.6 - 5% for the chromium containing preservatives and about 22% for the tested variation of the new type of preservative.
H Klipp, H Willeitner, K Brandt, A Müller-Grimm


Inorganic wood preservative levels in soil near a noise barrier treated with different preservatives after 8 years in service
2005 - IRG/WP 05-50234
In March 1996 nine test sections of a noise barrier were installed near Stockholm Sweden. The test sections include untreated Scots pine, spruce and larch and Scots pine, treated with different wood preservatives. After 8 years in service, the untreated spruce, pine and larch boards in contact with the soil were significantly decayed, with an estimated service life of about 5-10 years, while the untreated wood above ground is stained but not visibly decayed. Some degradation was detected in wood in soil contact for some of the preserved pine sections treated to AB levels (i.e. use class 3, above ground). Soil samples were collected at three horizontal distances from the barriers (0, 7 and 14 cm) with the 7 cm sample representing the drip line under a protective wedge designed to keep water out of the joints. Samples were collected at two depths representing groundline and the depth of the barrier in the soil (7.5 – 13 cm) and directly under the barrier. Soil samples collected after 8 years showed highest contaminant levels close to the barrier and under the wedge dripline. Arsenic levels in some locations close to CCA treated panels exceeded Swedish and Canadian soil guidelines for agricultural use and copper levels were above residential/park guidelines for some locations near ACQ and Tanalith MCB treated panels.
P A Cooper, Y T Ung, M-L Edlund, J Jermer, O Söderström


Health hazards and environmental aspects when using Cu-HDO-containing wood preservatives in vacuum pressure plants
1993 - IRG/WP 93-50001-11
Apart from the biological efficacy of wood preservatives, the health and environmental aspects concerning the utilisation of wood preservatives, the use of treated timber and the disposal of impregnated wood are of high significance today. Therefore, information on a possible aerial concentration of wood preservatives, on the mobility of active substances in soil leached from treated timber in service and on the composition and toxicity of thermal decomposition gases releasing on combustion of impregnated wood, are of absolutely fundamental interest. Measuring procedures relevant for the practical application will be presented, and the results concerning the utilisation of Cu-HDO-containing wood preservatives will be described. With the proper use of Cu-HDO-containing wood preservatives, the aerial concentration at workplace falls distinctly below the maximum permissible limit. If vacuum pressure treated timber is used properly, no active substances will seep into the ground water as a result of the leaching process of impregnated wood in service. The composition measured and the acute toxicity of the thermal decomposition gases released on combustion of impregnated wood may axtually be compared to those of untreated timber.
W Hettler, S Breyne, M Maier


The effect of wood preservatives on the relation between the electric resistance and moisture content in scots pine (Pinus sylvestris L.) sapwood
1998 - IRG/WP 98-20142
The effect of two types wood preservatives (TBTO and CuHDO) on moisture content measurements with an electric resistance meter in pine sapwood is assessed. High and low concentration impregnated pine sapwood is climatized at different relative humidities. Once climatized the samples are weighed and the moisture content is measured with an electric resistance meter by fixed stainless steel, isolated measuring pins. Subsequently the wood is dried for 48 hours at 103°C and weighed to gain the correct climatized moisture content. The reading values of electrical moisture content measurements are compared to the actual moisture content. Compared to the original correction lines for pine, an increase in concentration of metal ions leads to a steeper slope, i.e. the conductivity of the treated wood increases. The change in conductivity is so small that electrical resistance measurements are still practicable. However, for precise measurements new correction lines, which depend on concentration and type of preservative, need to be established.
B W Holleboom, W J Homan


The fate of salt preservatives in facility yard soils and decontamination of soils and drainage waters
1993 - IRG/WP 93-50001-25
Extensive studies during the past 10 to 15 years revealed that noticeable amounts of preservative components may be released in the environment by dripping off or by rain prior to fixation unless adequate precautions are taken. Therefore, soil and groundwater contamination especially from chromium-VI compounds but also from other inorganic and organic constituents exist in impregnation plants, possibly endangering the soil and groundwater ecosystem. The actual risk potential originating from chromium-containing wood preservatives in a practical situation are to be studied in the frame of a comprehensive research programme sponsored by the German Ministry of Research and Technology (BMFT). Accompanying laboratory investigations are performed with the aim of assessing the various types of water-soluble wood preservatives with respect to whether or possibly which compounds remain mobile und thus bio-available in the soil. Special attention is drawn to the question as to which effective constituents are adsorbed to soil particles depending on the mineralogical-geological composition of the soil, and at what situation the retention capacity for effective components of different soils would be exceeded. The results of the pilot study and of parallel running laboratory tests serve as a basis of deterioration analyses for grading and assessing the endangering potential in the ecosystem and shall provide a basis for the choice of adequate remedial concepts and measures to avoid such environmental impacts.
R-D Peek, H Klipp, K Brandt


Formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) during the combustion of impregnated wood
1995 - IRG/WP 95-50040-19
Wood waste and industrial wood residues often contain various preservatives. The waste management for these residuals can be recycling, deposition or combustion. Among the three possibilities, combustion seems to be the most efficient way of disposal. To obtain detailed information about emissions of organic compounds with environmental impact, especially polychlorinated dibenzo-p-dioxins (PCDD) and furans (PCDF), different impregnated wood materials were incinerated in two furnaces after mixing with non-treated wood in a ratio of 1:4. The combustion process of residues containing organic or inorganic preservatives is influenced by the elementary composition of the preservative and the thermal and oxidative reaction paths in the flame. It was found that the concentrations of PCDD and PCDF in the exhaust gas can be kept low under good combustion conditions. However, a non-regular incineration process strongly supports increased emissions of PCDD and PCDF.
T Salthammer, H Klipp, R-D Peek


Determination of bis-(N-cyclohexyl-diazeniumdioxy)-copper in different matrices by photometer, thermal energy analyzer and HPLC
1999 - IRG/WP 99-20179
For the quantitative analysis of bis (N-cyclohexyl-diazeniumdioxy)-copper (Cu-HDO) three analytical methods are used. The employment of the different methods depends on the matrices involved. For several years now, the colorimetric determination of Cu-HDO by photometer has been applied to solutions and concentrates of wood preservatives. In principle, the technique consists of a quantitative conversion of Cu-HDO into a Fe-complex and the measurement by photometer compared to a calibration curve in a range of 20 to 220 mg Cu-HDO per liter. The colorimetric technique is unsuited to extracts of complicated materials such as soil or wood because of disturbances due to other ingredients of these matrices. Further, the method is not suitable for samples with a concentration below 10 mg Cu-HDO per liter. In the case of difficult analytical problems in the determination of Cu-HDO (e.g. soil or air from working areas) another technique, involving the detection by Thermal Energy Analyzer (TEA), is applied. In the first step of the method, Cu-HDO sets nitrogen monoxide (NO) free by a reduction reaction with NaI / acetic acid / sulphuric acid in a laboratory converter. A helium gas flow transfers the nascent NO into the TEA. There, NO is detected by chemiluminescence which originates from its reaction with ozone. The large expenditure of work and the high costs of the instrumental equipment are handicaps for a wide use of the analysis by TEA. A new technique based on the widespread analytical system HPLC was therefore developed to determine Cu-HDO in the important matrix wood. The chipped wood sample is first leached by a mixture of methanol p.a. and 0,05 M KH2PO4-solution at room temperature and the content of the active substance subsequently analysed in the filtered extract by HPLC with UV-detection. The concentration is calculated on the basis of external standard calibration. In studies carried out on impregnated pine samples (pinus sylvestris) in different laboratories, percentage recoveries for Cu-HDO of more than 80% were achieved.
J Wittenzellner, W Hettler, M Maier


Inorganic preservative levels in soil under treated wood decks after 8 years natural exposure in Borås, Sweden
2005 - IRG/WP 05-50233
Inorganic preservative components (Cu, Cr and As) were measured to a depth of 150 mm under deck structures made with Scots pine lumber treated with several different wood preservatives and installed in Borås Sweden 8 years ago. Higher contaminant levels were observed mainly under the drip lines and in the top 50 mm of soil. Under CCA treated decks, soil arsenic concentrations increased from background levels of about 3.5 mg/kg to 6-15 mg/kg in this zone. Copper and chromium levels were only slightly elevated above backgrounds of about 10 mg/kg and 3 mg/kg respectively. Copper levels were also only slightly elevated under decks treated with Tanalith E, Impralit KDS and Wolmanit CX-S. The Wolmanit CX-8 treated wood had concentrations averaging about 45 mg/kg in the top soil layer under the drip line while the Kemwood ACQ treated deck had concentrations above 100 mg/g in this zone.
P A Cooper, Y T Ung, M-L Edlund, J Jermer


Detoxification of salt impregnated wood by organic acids in a pulping process
1993 - IRG/WP 93-50012
The paper descibes a novel method to detoxify pine wood (Pinus silvestris L.) treated with CCB-, CCF- CC-, and Cu-HDO-type salt preservatives. In the process of biological detoxification organic acids produced by strains of Antrodia vaillantii and other brown rot fungi are used for the dissolution of the previously fixed inorganic compounds. These findings are the basis for applying an acid pulping process (FORMACELL) developed by Nimz and Schone (1992) at the BFH, Hamburg, to detoxify salt impregnated wood waste with a mixture of acetic and formic acid. First results achieved with wood chips from treated poles after approximately 20 years of service life show that the obtained pulp contains less than 100 ppm of Cr and Cu. The pulp properties were neither influenced by the Cr and Cu ions nor by the age of the poles. The extracted quantities of Cr and Cu remain with the lignin whereas the acids are evaporated and recycled in the pulping process.
I Stephan, H H Nimz, R D Peek


Measurement of copper concentration in Cu-HDO treating solutions by handheld XRF
2022 - IRG/WP 22-20685
Copper based preservatives diluted in water dominate the wood preservative industry around the world. Periodically measurements and adjustments of the concentration of treating solutions must be performed as a part of the quality control at the treatment plant to achieve desired quality of the preservative treated wood. Many analytical methods are time consuming and must be performed under laboratory conditions, while others that are rapid and easy to apply at industry sites can be sensitive to impact from impurities, etc. The aim of this study was to evaluate handheld X-ray fluorescence (XRF) spectrometry as a tool for measuring copper concentration in CuHDO treating solutions. The material used in the study comprised samples of Wolmanit CX-8 (CuHDO) diluted in distilled water and samples from Wolmanit CX-8 treating solutions from Norwegian impregnation plants. All the preservative solution samples were analysed with a handheld Niton XL5 Plus XRF Analyzer. Atomic absorption spectrophotometry (AAS) was used as a reference method. The major advantages of portable handheld XRF spectrometry include: on-site immediate availability of analytical results, non-destructive analysis, a multielement capability, speed of operation and access to valuable/unique samples that otherwise would be unavailable or had to be transported to a laboratory for chemical analysis. The results from this study show that there is a good linear correlation with the XRF data and the corresponding laboratory results and that it is possible to use data measured with a handheld energy dispersive XRF-analyser for accurate calibrations and predictions of the copper concentration of treating solutions of Wolmanit CX-8.
P O Flaete


Influence of different fixation and ageing procedures on the leaching behaviour of copper from selected wood preservatives in laboratory trials
2003 - IRG/WP 03-20264
The paper focuses on the role of different parameters, such as fixation, sample size, wood species, and leaching in internationally standardized ageing procedures for wood preservatives from Europe, Japan and the United States. The leaching protocols used were EN 84, JIS K 1571 and AWPA E11 protocols. The wood species were Scots pine, Sugi and Southern Yellow Pine respectively. Three types of commercially important copper-based wood preservatives were used as model formulations, namely copper/copper-HDO, ammoniacal copper/quat and CCA. The most important factors determining the extent of copper leaching in the different lab trials were the sample size (volume/surface ratio) and the fixation conditions prior to leaching. On the other hand, the wood species and the leaching protocol itself were found to have only minor influence on the copper leaching rate in the test methods included in this study.
J Habicht, D Häntzschel, J Wittenzellner


Collaborative soft rot tests: PRL tests of Cu/Cr/As preservative using method of Document No: IRG/WP/208
1973 - IRG/WP 223
These tests were undertaken as a preliminary to the next series of collaborative soft rot tests. An interim report has already been presented at Berlin in 1972 as Document No: IRG/WP/211
J K Carey, J G Savory


Cu, Cr and As distribution in soils adjacent to CCA treated utility poles in Eastern Black Sea Region of Turkey
2004 - IRG/WP 04-50214
In this study, the main objective was to asses the distribution of Cu, Cr, and As in soils adjacent to CCA treated utility poles in Eastern Blacksea Region of Turkey (Trabzon, Rize and Artvin ) and determine the influence of soil composition. Surface (0-5cm), subsurface soil samples (30-40cm) were collected near CCA-treated utility poles and control soil samples away from CCA-treated utility poles were also collected. Water holding capacity, pH, mechanical properties of soil samples were determined for both depth levels. Results showed that Cu, Cr and As concentration in soil samples taken from all three cities in 0-5cm depth was higher than soil samples taken from 30-40cm depth. Cu, Cr and As concentrations were much higher in soil samples taken from city of Rize.
E D Gezer, Ü C Yildiz, A Temiz, S Yildiz, E Dizman


Leaching of Active Components from Preservative Treated Timber. Stage 1: Semi-Field Testing
2004 - IRG/WP 04-20302
The project is aiming at finding realistic leaching rates from preservative-treated wood in use class 3 (above ground). The project focuses on developing a field trial method for investigating leaching. Panels are subjected to outdoor exposure under natural weather conditions at a test field at the Danish Technological Institute. The leachate is collected and monitored by chemical analysis of the active ingredients. The project is ongoing and the paper presents results from approximately 12 months’ of exposure. The study includes commercially available organic and inorganic fungicides using 4 different application methods: vacuum-pressure-, double-vacuum-, flow coat and supercritical treatment. Different test set-ups examine the influence of a number of different parameters. The results obtained from outdoor exposure will be compared with a laboratory test method (proposal of CEN/OECD, DOC TC38 WG 27 N039). The method investigated has proved to be useful in characterising the leaching behaviour from preservative-treated wood. The results from the present project are intended to serve as part of the basic documentation according to Directive 98/8/EC (The Biocidal Products Directive, BPD) for leaching of active ingredients in use class 3.
N Morsing, B Lindegaard


Collaborative soft rot tests: Interim report on PRL tests of Cu/Cr/As preservative using method of Document No: IRG/WP/208
1972 - IRG/WP 211
Preservative: Tanalith CT.106 - Results obtained with beech are given in the table and indicate a toxic limit of 16.7-19.2 kg/m³ - The initial soil moisture content was adjusted to 27.8% (the water holding capacity). Noticeable drying out has occurred in some of the test bottles.
J G Savory


Evaluation of wood treated with copper-based preservatives for Cu loss during exposure to heat and copper-tolerant Bacillus licheniformis
1999 - IRG/WP 99-20155
Copper-based wood preservatives need to be effective against exposure to all types of microorganisms. Wood treated with six copper-based preservatives was exposed to 121°C and 20 psi pressure for 15 minutes under standard autoclave conditions and the copper-tolerant bacterium, Bacillus licheniformis CC01, for 10 d at 28°C and 150 rpm. Sixteen to 37 percent of the copper was released from the wood during autoclaving, with copper citrate demonstrating the highest percent loss. Forty-four to 82 percent of the copper remaining in the samples following autoclaving was removed during exposure to the bacterium in liquid culture; copper naphthenate in oil and ACQ-D had losses of eighty percent or greater of the remaining copper. The bacterium removed as much or more total copper in 4 of 6 gas-sterilized samples (85-94%) than the cumulative effects of steam-sterilization and the bacterium on treated samples. Copper loss from in-service treated wood compromises the efficacy of copper-based wood preservatives.
D M Crawford, C A Clausen


An appraisal of methods for environmental testing of leachates from salt-treated wood (2)
1998 - IRG/WP 98-50110
For wood preservatives for use in hazard class 4 information on the ecotoxicity of preservatives and ingredients as well as on the effect of losses from impregnated timber is needed for a proper environmental risk assessment. In the evaluation of a suitable test procedure the leaching behaviour of copper-based formulations was studied using analytical and ecotoxicological test methodology. These studies included an analytical comparison of end grain sealed and not sealed wood blocks. Using sensitive bioindicators in ecotoxicological studies, real effects of the leachates gained from EN 84 were measured. The possibility to use a laboratory test procedure based on the leaching according to EN 84 is shown and discussed for the risk assessment of treated timber.
H W Wegen, A Platen, G M F Van Eetvelde, M Stevens


EPR investigations of interactions between ammoniacal Cu(II) octanoate and wood
1996 - IRG/WP 96-30110
Ammoniacal solutions of copper(II) octanoate [ C u . h l f . 2 . r h l f.(O2CC7H15)4], interactions of these solutions with wood and wood components, and leaching of copper(II) octanoate from impregnated wood samples, have been studied by electron paramagnetic resonance (EPR) method. It is still not clear if in the Cu(II) octanoate - water - ammonia system, Cu(II) remains in a (copper(II) octanoate - ammonia) complex. The majority of leached Cu(II) with distilled water and a solution simulating acid precipitations was washed out in the first five hours of leaching procedure (up to 35% of initial Cu(II)). Time dependence studies of interactions of ammoniacal Cu(II) octanoate with wood, cellulose and brown rotted lignin showed, that the fastest and most significant was the reaction with lignin. Cu(II) is immobilised also on cellulose. A significant contribution of ammonia evaporation to the fixation mechanism of the preservative was observed as well.
F Dagarin, M Petric, F Pohleven, M Sentjurc


The course of fixation of Cu-Cr-As wood preservatives
1972 - IRG/WP 307
Copper-chrome-arsenic (CCA) preservatives in contact with wood result in an instant extensive increase of pH, because of ion-exchange and adsorption reactions with the wood. During precipitation of the active elements the pH continuously increases but reaches a maximum, when all chrome is consumed. Some of the early reaction products are unstable and slowly convert via dissolution into stable compounds. The conversion proceeds by proton liberating as well as proton consuming reactions. The pH therefore alternatively decreases and increases until the reactions cease after several months. The final equilibrium fixation products are: ion-exchange fixation of Cu to the wood CrAsO4, Cu(OH)CuAsO4 and Cr(OH)3. The chrome fixation is 2nd order with respect to hexavalent chrome in the liquid phase, four regions with distinct chrome fixation rate constants were found. A hypothesis is given for the mechanism of fixation.
S-E Dahlgren


Long-term protection of stored lumber against mould, stain, and specifically decay: A comparative field test of fungicidal formulations
1984 - IRG/WP 3281
The problem of decay in packaged, unseasoned lumber stored for many months has become of major importance in recent years. Large financial claims have resulted from decay in Canadian lumber stored at length in seaports and storage yards of distributors. For decades acceptable protection from moulds and sapstain was readily achieved with chlorinated phenols applied at appropriate treating levels. However, in recent years, the use of chlorinated phenols in sawmills has become controversial, out of concern for its persistance in the environment and because of its broad spectrum of toxicity to practically all organisms. Although it was realized that this toxicity to humans had been over-emphasized, the discovery of traces of chlorinated dibenzodioxins as a minor impurity of some chlorinated phenols has generated further pressure to abandon the use of the latter. Forintek Canada Corp. has done extensive laboratory and field testing of fungicides for the lumber industry. Most of the field experiments were four-month studies (1) although one dealt with a two year evaluation of preservative retention and protection (2). In June 1981, under contract to Agriculture Canada, we began a field test of five new fungicidal formulations, comparing them with sodium tetra- and pentachlorpheates (NaTCP).
A J Cserjesi, A Byrne, E L Johnson


An evaluation of the potential of ion mobility spectrometry for detection of organic wood preservative components in solutions and treated wood
1994 - IRG/WP 94-20038
For the disposal of wood waste under ecological sound conditions information about its hazardous potential is required. Until now, no highly sensitive rapid analytical methods are available for the detection of wood preservatives under industrial process conditions. Preliminary experiments showed that Ion Mobility Spectrometry (IMS) could be a promising method for rapid detection of organic preservatives in waste wood. A number of organic wood preservatives (i.e. Al-HDO, Quat, Armoblen, Azaconzole, HCH, Creosote, DCFN, Furmecylox, MBT, Methyl-parathion, PCP, Permethrin, K-o-PP, TBTO, TCMTB and Tebuconazole) was studied. Both solutions and treated wood samples were analyzed with IMS. IMS-spectra are generated by analyzing the ionized volatile compounds of the samples. The time each ion needs to proceed to a detector is specific and can be characterized by a comparable Ko value, the so-called reduced mobility constant. A 'fingerprint' of the wood and the chemicals is obtained. IMS was able to distinguish between most of the preservatives. However, in wood, some of the chemicals could not be determined. So far the results are provisional and further investigation is needed.
A Voss, J N R Ruddick, W J Homan, H Militz, H Willeitner


Leaching of active components from preservative-treated timber - Ongoing research: Status after approx. 4 months’ out-door exposure
2003 - IRG/WP 03-20276
The Danish Technological Institute is together with manufacturers of active ingredients and formulators of wood preservatives running a project aiming at finding realistic leaching rates from preservative treated wood in hazard class 3 (above ground). The project is focussed on developing a field trial method for investigating leaching. According to BPD hazard assessment has to be carried out for biocide products and a part of that includes possible environmental impact of preservative treated wood. Leaching of active ingredients from treated wood has to be measured and assessed. Several organisations (CEN, OECD and others) are in progress of developing laboratory leaching test methods. In order to give more realistic data for leaching of active ingredients it is important to study natural exposure. According to recent publications (IRG/WP 01-50171), it appears to be a significant difference between natural leaching and laboratory leaching methods and a relative comparison is, therefore, needed. Data from close to practice applications are important in order to support products in the BPD. Furthermore, the results are needed to provide benchmarking data to allow other laboratory or accelerated leaching data to be put into perspective. The results from the project are intended to serve as part of the basic documentation for leaching of active ingredients in hazard class 3. Panels are exposed outdoors under natural conditions at the field trial at Danish Technological Institute and the leachate is collected and monitored by chemical analysis of the active ingredients. The project is ongoing and the paper presents results from approximately 6 months of exposure. The study includes commercially available organic and in-organic fungicides using 4 different application methods: pressure-, vacuum-, flow-coat- and supercritical treated wood. Different test set-ups are investigated and the results obtained from outdoor exposure will be compared with a laboratory test method (CEN/OECD). Furthermore, the laboratory method suggested by CEN/OECD is evaluated and suggestions for improvement are stated.
N Morsing


Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 5: Effect of wood species and preservative composition on the leaching during storage
1975 - IRG/WP 354
Conversion reactions during storage of CCA treated wood take place even at and below the fiber saturation point as long as ion transport is possible. Increase in drying temperature increases the final pH of the treated wood and the leachability of Cu and decreases slightly the leachability of Cr, while the leachability of As is not affected. This temperature effect is considered to be of no technical importance, but may be of importance when preparing material for biological testing. The length of the wet fixation period before the drying does not influence the results. The presence of alkali sulfates in some preservatives affects the pH of the unleached wood but not the leachability of the active elements. The natural pH of the wood determines to a considerable extent the final pH and the leachability. A correlation was established between the leachability of Cu and As versus the final pH in wood. When treated with 2-2.5% preservative solutions some wood species: Douglas fir, Ponderosa pine and to a lesser degree Southern yellow pine, showed unexpectedly high As leachability, while on doubling the concentration normal leachability data were obtained. The study included three commercial CCA preservatives: Boliden K33, Celcure AP and Tanalith C, and one experimental variety of Celcure AP without sodium sulfate.
S-E Dahlgren


Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 6: The length of the primary precipitation period
1975 - IRG/WP 359
The end of the primary precipitation fixation period of CCA preservatives coincides with the first peak in pH versus time. This offers a simple way of estimating the duration of the period. The duration is determined by a number of factors and their interactions, the most important of which are: wood species (anatomy, natural pH, accessibility of reducing agents), preservative type, preservative concentration and temperature. For interpretation of experimental data the effect of these factors is discussed in the light of the chemistry and the mechanism of fixation of CCA preservatives. For a proper handling of the treated timber, knowledge of the duration in actual working conditions is essential.
S-E Dahlgren


Next Page