GAL4CTAN IN WESTERN EARCH WOOD 
 
 May 1950 
 
 No. R1771 
 
 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE 
 
 FOREST SERVICE 
 FOREST PRODUCTS LABORATORY 
 Madison 5, Wisconsin 
 
 In Cooperation with the University of Wisconsin 
 
 
 ^-WV, . 
 
 n i 
 
 - 
 
GALACTAN IN WESTERN LARCH WOOD^ 
 
 By 
 
 R. L. MITCHELL, Chemist 
 and 
 
 GEO. J. RITTER, Chemist 
 
 2 
 Forest Products Laboratory, - Forest Service 
 
 U. S. Department of Agriculture 
 
 Abstract 
 
 A quantitative determination was made "by the U. S. Forest Products 
 Laboratory of the galactan in western larch woods and sawmill reff.se. This 
 work was done to obtain data useful to those contemplating commercial ven- 
 tures designed to produce and market various materials made of galactan. 
 
 Galactan in the lateral roots of virgin trees ranged from approximately 
 11 to 23 percent, based on the weight of the oven-dry wood. The galactan 
 content of slabwood from virgin-growth butt logs was found to be about 14 
 percent; from the middle logs, k.2 to 10 percent; and from the top logs, 
 about 5 percent. Butt logs from fire-killed virgin trees contained approxi- 
 mately 9 "Uj 16 percent of galactan; the middle logs, 6.6 to 12.1 percent; 
 and the top logs, 6.6 to 7.8 percent. Butt logs of stand thinnings contained 
 from 3.8 to 5*3 percent of galactan; the middle logs, 2.1 to 3»5 percent; 
 and the top logs, 2.2 to 3.1 percent. 
 
 Introduction 
 
 Western larch differs from most other species of wood in that it con- 
 tains appreciable quantities of galactan in the form of a hot-water-soluble 
 polymer of arabinose and galactose (j£, 2) » This form of galactan has a 
 re-occurring building unit which consists of one molecule of arabinose and 
 
 —This work was done in cooperation with the Forest Utilization Service unit 
 of the Northern Rocky Mountain Forest and Range Experiment Station, 
 Missoula, Mont. 
 
 2 
 
 —Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 
 
 ■^Underlined numbers in parentheses refer to Literature Cited at end of this 
 reuort. 
 
 Rept. Ho. R1771 -1- Agriculture-Madison 
 
si:: molecules of galactose (5, 6, 2) • It is thus an arabogalactan poller 
 rather than galactan, as commonly designated. Borgin (l) found that galac- 
 tan from western larch consists of two components having molecular weights 
 of 100,000 and 16,000, respectively. 
 
 The arabogalactan, on hydrolysis with acid, can "be converted to 
 arabinose and galactose. In turn, the arabinose portion can, under more 
 drastic conditions, "be changed "by means of acid to furfural. The galactose 
 portion is oxidizable "by means of nitric acid to mucic acid, which is insol- 
 uble in water or aqueous solutions of nitric acid. This is the basis for 
 the quantitative determination of galactose in the material commonly desig- 
 nated galactan. 
 
 Mucic acid finds uses in the manufacture of intermediate organic 
 chemical products; among them are baking powder, effervescent salts, arti- 
 ficial yeast, an accelerator of yeast growth, a component of esters and 
 salts for pharmaceuticals, in disinfectants, in acidulants, an ingredient 
 of soft drinks, a component in electroplating baths, and mordants for dyeing 
 textiles. Most of these uses require no large tonnages of mucic acid. 
 Accordingly, new uses would have to be developed before large-scale produc- 
 tion of mucic acid would be economically feasible. 
 
 Virgin-growth western larch heartwood appears reddish brown in color 
 on the cross-sectional surface of the stump and butt log. If the galactan 
 content is high, the reddish-brown color is tinged with blue. On exposure 
 of the cut to summer heat and sunlight, the galactan accumulates in the 
 form of a white powder on the surface of the stump and the cross-sectional 
 face of the butt log. High concentrations of galactan are generally associ- 
 ated with ring shake and rot in the butt log of western larch ( 2) • The 
 presence of these two defects led to the practice of loggers to place the 
 top cut for the long butt sufficiently high up the tree so as to eliminate 
 physical indications of the shake and rot. In recent years, loggers have 
 developed uses for the less intense ring-shake stock and, as a result, the 
 discarded butts are becoming shorter and less frequent. 
 
 Previously the U. S. Forest Products Laboratory showed that a limited 
 number of samples of wood from the butt log of virgin-growth western larch 
 had an average of 17.9 percent of galactan, and samples of wood from the 
 top log of the tree had an average of 5*9 percent of galactan. In contrast, 
 samples of wood from the butt log of second-growth western larch had an 
 average of only 5»6 percent galactan. 
 
 The object of the present work was to determine the percentage of 
 galactan in western larch wood discarded during log-harvesting and lumber- 
 cutting operations in Montana, Idaho, and Washington as a source of infor- 
 mation for anyone who might consider exploring the feasibility of utilizing 
 the material. 
 
 Rept. Ho. R1771 
 
 __?_ 
 
Hood Types Tested 
 
 Samples of western larch wood that were analyzed consisted of (a) 
 roots; (b) cross sections from the butt, middle, and top parts of fire- 
 killed trees; and (c) cross sections from the "butt, middle, and top part of 
 trees removed in thinning operations, and (d) samples of slabwood from dif- 
 ferent heights of the trees. The wood samples were collected and shipped 
 to the Forest Products Laboratory in December 1948 by the Forest Utilization 
 Service of the Northern Rocky Mountain Forest and Range Experiment Station, 
 Missoula, Mont. 
 
 The root samples were collected along a highway constructed In 1948, 
 north of Seeley Lake on the Lolo National Forest. Thoy were from one of 
 the largest virgin larch stands in the Northern Region. Many of the trees 
 in this stand ranged from 300 to 400 years in age. The sampling; was con- 
 fined to lateral roots as it was impossible to remove the main roots of the 
 stumps. Three root samples which differed in surface appearance as grayish, 
 bark-covered, and black, respectively were analyzed. 
 
 The slabwood samples were obtained at a sawmill near the place at 
 which the root specimens were collected and represented the same typo of 
 virgin western larch as the roots. The test samples analyzed v/ero cut from 
 the slabs at 0, 6, 16, 32, and 64 feet above the stump of the tree. 
 
 Samples of fire-killed virgin-growth trees were collected on the 
 Colvillo National Forest in northeastern Washington. They were taken from 
 an estimated area of 250,000 acres, which was burned over in 1929 • The 
 fire-killed trees were still in a relatively good state of preservation, as 
 shown by visual examination of the samples, and constitute a major utiliza- 
 tion project of the region. Samples from three trees designated, as Nos. 3» 
 4, and 6 were analyzed. 
 
 Samples from thinning operations were taken from second-growth stands 
 of western larch 60 to 80 years of age on the Cabinet National Forest near 
 IToxon, Mont. This area is located on the eastern fringe of the western white 
 pine stands and is considered one of the best western larch cites in the 
 region. It is representative of the type of stand on which thinning would 
 be advantageous. The average diameter of the trees was approximately 6 inches 
 at breast height and their height was approximately 70 feet. Samples from 
 three trees designated Nos. 1, 9, and 13 were analyzed. 
 
 The wood samples were reduced to sawdust and the coarse particles 
 eliminated by means of a 20-mesh screen. 
 
 Rept. No. R1771 -3- 
 
Methods and Results of Tests 
 
 G-alactan in the wood was quantitatively determined by Schorger' s 
 method (.2) • It involves treating a given \\reight of air-dry unextracted wood 
 sawdust of known moisture content with boiling 3 percent nitric acid, filter- 
 ing, washing the residue with boiling water, adding the washings to the 
 original acid filtrate, concentrating the filtrate, oxidizing the galactose 
 in the concentrated filtrate to mucic acid by means of 25 percent nitric 
 acid, concentrating the mixture, adding a known weight of mucic acid to 
 start crystallization of the mucic acid in the filtrate, and allowing to 
 stand 48 hours. The mucic acid was filtered off, washed, dried and weighed. 
 A correction was made for the mucic acid added and the remainder was multi- 
 plied by the factor 1.2 for conversion to galactan. 
 
 Analytical data for the root and slabwood samples are recorded in 
 table 1. Yields of galactan from the root samples Nos. 1, 2, and 3 were 
 23.0, 10,7, and 16.9 percent, respectively. Yields of galactan from the 
 slabwood at feet height were 14. 1 percent and gradually decreased to 4.7 
 percent at 64 feet above the stump. Being slabwood, the samples contained 
 considerable sapwood which has less galactan than heartwood. The concen- 
 tration of the galactan decreased with height above the stump and confirmed 
 the results of previous analysis of virgin western larch wood. 
 
 Galactan yields of the butts of the three fire-killed trees were 
 13»5> 15»7» a nd 9*2 percent, respectively, as shown in table 2; those of the 
 samples taken from the middle of the corresponding trees were 9»3» 12.1, 
 and 6.6 percent; and those from the top of the corresponding trees v/ere 
 7,8, 7»1» and 6.6 percent. 
 
 Galactan yields from the butts of the three thinning trees ranged 
 from 3.8 to 5*8 percent; those from the middle ranged from 2.1 to 3 .5; and 
 those from the top ranged from 2.2 to 3.1 percent. 
 
 Radial distribution of the galactan in a tree was also determined. 
 To dp this cross sections v/ere cut from the butt, middle, and top of the 
 fire-killed western larch tree No. 3 for the analytical work. Sectors 
 removed from the cross sections were divided, parallel to the boundary 
 between the annual growth rings, into outside and inside parts. The radial 
 dimensions of the two parts are shown in table 3 in connection with the 
 analytical data. Galactan content was 1$ .1, 10.0, and 9.5 percent in the 
 outside part of the sectors from the butt, middle, and top, respectively; 
 it was 8.3, 6.0, and S*5 percent in the inside part of the corresponding 
 sectors. 
 
 Obviously, the roots, the slabwood from the lower 6 feet of the butt 
 log, and the butt logs of virgin western larch trees are rich in galactan. 
 The stumpwood, which is located between the roots and butt log, presumably 
 also contains galactan in yields ranging from about 10 to 23 percent. On 
 the other hand, trees removed by thinning operations are a poor source for 
 galactan. Killing of the trees by forest fire appears to have had little 
 if any effect en the galactan content of the wood. 
 
 Rept. Ho. R1771 -4- 
 
Table 1. — Percentage of galactan in western larch root 
 sections and slabwoo&i 
 
 Typo 
 
 : Uumber 
 
 : Galactan 
 
 : : Type 
 
 : Height 
 
 Galactan 
 
 of 
 
 : of 
 
 
 :: of : 
 
 of sample 
 
 
 material 
 
 : sample 
 
 
 , : material 
 
 : in tree 
 
 
 
 ! 1 : 
 
 ! Percent 
 
 : : Slabwood 
 
 Feet 
 i 
 
 : Percent 
 
 Root 
 
 23.0 
 
 14.1 
 
 sections 
 
 
 
 
 
 
 
 2 : 
 
 10.7 
 
 
 6 : 
 
 10.1 
 
 
 3 ! 
 
 16.9 
 
 
 1 16 
 
 - 32 
 
 64 
 
 4.2 
 
 6.6 
 
 4.7 
 
 ""Based on weight of oven-dry wood. 
 
 Table 2. — Percentage of galactan in fire-killed western larch and 
 thinnings from second-growth ! 
 
 —Based on weight of oven-dry wood, 
 Kept. No. R1771 
 
 Typo : 
 
 Number of 
 
 .Galactan: 
 
 ; Type : 
 
 ITumber of: 
 
 Galactan 
 
 of 
 
 : tree and 
 
 
 : of : 
 
 tree and* 
 
 
 material 
 
 : location 
 iof sample 
 
 
 : material : 
 
 location 
 of sample 
 
 
 
 ! 3 
 
 Percent: 
 
 : Thinnings 
 
 1 
 
 . Percent 
 
 Fire-killed 
 
 
 
 trees . • . 
 
 : Butt 
 
 13.5 : 
 
 : from 
 
 ! Butt 
 
 : 5-5 
 
 
 : Middle 
 
 : 9.3 : 
 
 : second- 
 
 ! Middle 
 
 : 2.1 
 
 
 ! Top 
 
 . 7.8 : 
 
 : growth : 
 : stand 
 
 Top 
 
 2.2 
 
 
 i 4 : 
 
 
 
 9 
 
 
 
 ! Butt : 
 
 15.7 : 
 
 
 Butt 
 
 : 3.8 
 
 
 . Middle 
 
 . 12.1 : 
 
 
 Middle 
 
 : 2.3 
 
 
 : Top 
 
 7.1 : 
 
 
 : Top : 
 
 2.5 
 
 
 : 6 : 
 
 
 
 : 13 
 
 
 
 i Butt : 
 
 9.2 : 
 
 
 Butt 
 
 5.8 
 
 
 ! Middle : 
 
 : 6.6 : 
 
 
 Middle 
 
 3.5 
 
 
 Top ! 
 
 6.6 : 
 
 
 Top 
 
 3.1 
 
On the "basis of present information, the maximum yield of mucic acid 
 derivable from western larch would "be roughly 83 percent of the galactan 
 values reported. 
 
 Literature Cited 
 
 (1) Borgin, G. L. 
 
 19^-9- Molecular properties of water-soluble polysaccharides from 
 western larch. Jour. Am. Chem. Soc, Vol. 71* No* 6. 
 
 (2) Johnson, R. P. A., and Bradner, M. I. 
 
 1932. Properties of western larch and their relation to uses of 
 the wood. U. S. Dept. Agr. Tech. Bull. No. 285, 93 P?»t 
 illus. 
 
 (3) Schorger, A. W. 
 
 1926. Chemistry of cellulose and wood. New York, 538 pp. 
 
 (4) , and Smith, D. P. 
 
 19l6. The galactan of Larix occidentalis . Ind. Eng. Chem., Vol. 8, 
 No. 6. 
 
 (5) White, E. V. 
 
 19^1. The constitution of arabo-galactan. I. The components and 
 
 position of linkage. Jour. Am. Chem. Soc, Vol. 63, "0. 11. 
 
 (6) 
 
 
 19^-2. The constitution of arabo-galactan. IV. The structure of 
 
 the repeating unit. Jour. Am. Chem. Soc, Vol. 6H-, ITo. 12, 
 
 (7) Wise, L. E. , and Peterson, P. C. 
 
 1930. The chemistry of wood. II. Water-soluble polysaccharides 
 of western larch wood. Ind. Eng. Chem., Vol. 22, ITo. km 
 
 Rept. No. R1771 -5- 
 
Table 3* — Percentage of galactan acc o rding to radia l 
 
 location in sections of fire-killed western 
 larch! 
 
 Section 
 
 of 
 
 tree 
 
 Location 
 • sample^ 
 
 : Radial 
 : dimension 
 of sample 
 
 : Galactan 
 
 Butt 
 
 Outside 
 Inside 
 
 Outside 
 
 Inside 
 
 Outside 
 Inside 
 
 : Inches 
 
 5 
 k 
 
 ! 3 
 5 
 
 2 
 
 3 
 
 : Percent 
 : 15,1 
 
 
 8.3 
 
 : 10.0 
 : 6.0 
 
 9.5 
 5.5 
 
 
 —Based on weight of oven-dry wood. 
 
 2 
 
 —Each section was wedge-shaped and divided into inner 
 
 and outer samples with respect to radial direction, 
 
 Kept. No. R1771 
 
JNIVERSITY OF FLORIDA 
 
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