This article deals with the possible recovery and utilization of chemical products from t h r e e webtern pines. The newer methods of wood analysis, which were developed on other woods, are applicable to these important commercial woods. The extractives are not an integral part of the lumber, and since the pines are rich in this wood fraction, they offer an opportunity for economic recovery. This article is confined chiefly to the dhemical characterization of the wood itself.- - T h e p h o t o g r a p h shows a sawmill with the pond full of large sugar pine logs.
ARTHUR B. ANDERSON Western Pine Association Research Laboratory, Portland, Orrg.
0 DEVELOP means for effectively utilizing potential chemical products from commercially important western pines, the proximate chemical composition of these American woods has been determined. The species included in the present study consist of ponderosa ( P i n u s ponderosa), Idaho white (Pinus monticola), and sugar (Pinus lambertiana) pines. The western pines are not used for chemical purposes or processes as are the southern pines, for example, which are utilized in the production of naval stores and in the manufacture of paper. Some thirty years ago studies were made on the possible use of the oleoresin from the western pines as a source of naval stores (8, I S ) , but no commercial developments resulted. The western pine forests occur beyond the Great Plains, extending from Canada south to Mexico and west to the Sierra Nevada in California and the eastern slopes of the Cascade Mountains in Oregon and Washington. Ponderosa pine is the principal tree in this region; it grows in each of twelve states and is found in greatest total volume. Idaho white pine grows mostly in northern Idaho, eastern Washington, and western Montana; sugar pine occurs in the Sierra of central California and northward into southern Oregon. The latter tree is the largest of all the pines, occasional specimens measuring as much as 12 feet in diameter and 250 feet in height. The estimated production for 1942 of lumber from the western pine region amounted to 6,052,000,000board feet or 34.5% of the total softwood lumber produced by the three softwood regions-western pines, West Coast (Douglas fir), and the South (southern pines). Almost two decades have passed since comprehensive chemical analyses of western pines (4,6,9) have been made, and since that time many methods have been revised and new ones introduced. The most notable is the recent procedure for determining total carbohydrate fraction in extracted wood (holocellulose) by Kurth and Ritter (8) and a later revision by Van Beckum and Ritter ( I C ) . Some of these revised and newer methods were selected to determine the major entities present in these coniferous woods. The authenticity of the wood samples in all cases has been verified by microscopic identification. When it was difficult to distinguish the sapwood from the heartwood, the benzidine color reaction (7) for identifying the sapwood and heartwood was used.
T
The collection date, age, diameter, and thickness of sapwood and heartwood, and samples of each of the woods analyzed are on file a t this laboratory for reference. The results reported here are not meant to represent the average analysis of the various species investigated, but rather the proximate analysis of the species a t the particular locality from which the samples were obtained. All wood samples were taken from 4-fOOt bolts of each tree a t a point approximately 20 feet above the ground. Immediately after removal from the tree, these bolts were shipped to the laboratory, and analysis was started shortly after arrival. This precautionary measure was taken to avoid any discrepancies that might occur due to wood-staining organisms, such as blue stain. Six-inch disks were cut through the center of the 4-foot bolt, and the sapwood and heartwood were separated. Massed pitch areas, knots, and other blemished areas present in the disk were removed and discarded before the samples were ground. The segregated wood was chipped and reduced to sawdust in a Wiley mill. The material which passed a 60-mesh but remained on an 80-mesh sieve was retained for analysis. The ground samples were kept in sealed glass jars. The ash content, solubility in water, and ether and alcoholbenzene extracts were determined by standard procedures (3). Pentosan content was determined by the phloroglucide method ( 1 ) ; the quantitative estimation of lignin was determined by the 72% sulfuric acid procedure as modified by Ritter, Seborg, and Mitchell ( I d ) . The cellulose content was estimated by the Cross and Bevan method as revised by Ritter and Mitchell (11). The amount of holocellulose was determined by the method proposed by Van Beckumand Ritter (14). The results and summative analyses are presented in Table 1. SUMMATIVE ANALYSIS
The holocellulose determination assumes importance not only because it represents the total carbohydrate fraction of extracted wood, but it permits the wood analyst, for the first time, to present a summation of the analytical test values to total 100% of the wood; it is no longer necessary to calculate the last component by difference. Thus the ash represents the total mineral content 662
INDUSTRIAL AND ENGINEERING CHEMISTRY
July, 1944
Pine Species Ponderosa Sapwood Heartwood Idaho white Sapwood Heartwood Sugar Sapwood Heartwood
*
TABLE I. ANALYSESOF
WESmRN PINES, I N P E R
Ash, a
-0lubility Cold water
Alcoholbaneene, b
0.3 0.2
CENT
OF
OVEN-DRY (105”
663
c.) SAMPLES Hot-Water
Hot water
Ether
1.0 3.3
4.3 6.2
4.8 5.0
0.2 0.2
2.8 2.7
4.1 4.5
0.2 0.2
1.7 8.4
3.1 10.3
Sol.
Ext. Summative,
Pentosan
Lignin, c
Cellulose
Holocellulose, d
7.2
5.1
10.5 10.4
22.8 22.9
59.9 58.1
69.9 66.3
2.8 3.3
100.9 99.9
3.4 3.6
3.4 5.7
9.2 9.5
25.6 25.4
59.0 57.7
68.5 66.0
2.5 2.8
100.2 100.1
3.1 4.5
3.8 12.0
10.4 9.5
26.8 24.8
58.7 54.1
68.5 62.5
1.5 1.1
100.8 100.6
of wood. The extractives are those substances in wood which are not a n integral part of the cellular structure and which can be removed from the wood by such solvents as water, ether, alcoholbenzene, and other nonreactive solvents. The extractives may include such substances as certain of the soluble carbohydrates, tannin, phlobaphenes, natural pigments, fats, fatty acids, resin acids, sterols, waxes, and hydrocarbons. The hot-water-soluble material was determined on wood which’ had been previously extracted with alcohol-benzene, since some of the extractives removed by alcohol-benzene are likewise removed when the wood is extracted with hot water. The remaining integral part of the structural elements of wood consists of the noncarbohydrate fraction, known as lignin; the carbohydrate fraction is designated as holocellulose. The summation of the proximate groups ash, extractives, lignin, and holocellulose should equal 100%. These results, as summed up in Table I, equal 100 (+O.Q)%. I n most cases, the sum of pentosan plus cellulose is greater than the percentage of holocellulose reported here, since the pentosan is not completely removed from the cellulose. RELATION OF SAPWOOD AND HEARTWOOD CONSTITUENTS
While i t is always hazardous to present definite conclusions regarding the chemical analysis of wood because of the many factors which affect composition, certain generalizations appear to be evident. Results on the species examined (Table I ) may be briefly summaTized as follows: ASH. The ash contents of both heartwood and sapwood are so close that no general distinction can be made. EXTRACTIVES.The water and organic-soluble extractives in the heartwood are greater than in the sapwood. This confirms the generalization made b y Ritter and Fleck (IO). Thenecessity of removing the massed pitch and knot areas from the wood prior to determining the proximate analysis should be pointed out, for some of the massed pitch areas examined contained as high as 60% or more extractives, while the knots varied from 30 to 45% extract. PENTOSAN AND LIGNIN. I n general, there are no marked differences between the pentosan yield from the heartwood and sapwood of each species examined. This is also true of lignin content. CELLULOSE.I n each case the sapwood contains more cellulose than the heartwood. This is likewise confirmed by Ritter and Fleck (IO). HOLOCELLULOSE. Since no marked differences occur in the pentosan content of heartwood and sapwood and the amount of cellulose is higher in the sapwood than in the heartwood, as anticipated, the holocellulose content is also higher in the sapwood than in the heartwood. DIFFERENCES BETWEEN SOME SOFT- AND HARDWOODS
Freeman and Peterson (6) determined the proximate analysis of some American hardwoods, which include large-toothed aspen, beech, sugar maple, fire cherry, paper birch, and yellow birch. With the exception of pentosan and holocellulose determinations, these investigators applied the same methods used here. The discrepancies in results due to differences in methods of determining pentosan and holocellulose are small enough to allow some generalization to be made:
in Residue from b , e
Total of
a , b, c ,
d, e
ASH. The heartwood of softwoods contain less ash than that of hardwoods. No marked differences exist between the ash content of the sapwoods of the two classes of wood. EXTRACTIVES. The amount of extractives present in the sapwood and heartwood of the softwoods runs higher than those from the hardwoods. PENTOSANS. The quantity of pentosans in the softwoods runs decidedly Ipss than the amount found in the hardwoods, the ratio being roughly 10 to 24. LIGNIN. The lignin content of softwoods runs higher than that in the hardwoods. CELLULOSE.No generalization can be drawn. HOLOCELLULOSE. The total carbohydrate fraction in softwoods runs less than t h a t in hardwoods. The most marked differences between the softwoods and hardwoods are in the pentosan content, a conclusion which has been brought out before. Thus, as a possible raw material for the production of furfural, for instance, the hardwoods are by far a richer source for the production of this chemical. APPLICATION O F RESULTS
The western pines contain relatively large quantities of extractives, and these substances do not appear to play a n important role in the ultimate value or use of the finished wood products. As a result, the problem of the possible removal and recovery of these extractives from wood presented itself; preliminary investigations have shown that it is possible to remove all or a portion of the extractives from lumber. This extractive removal process may not only result in ways to obtain a further improvement in the lumber offered by manuficturers but may also add a commercial volume of extractive products heretofore not available from these woods. Both phases are under investigation by this laboratory. ACJCNOWLEDGMENT
The author is indebted to J. F. Bunnett for preparing the samples and carrying out some of the preliminary determinations, and to Albert Hermann for comments and suggestions. LITERATURE CITED Assoo. of Official Agr. Chem., Methods of Analysis, p . 361 (1940). Betts, U. 5. Forest Service, BuEI. 116 (1912).
Bray et al., U. S. Forest Products Lab., Mimeograph R19 (Rev., Sept., 1939). Dore, J. IND.ENO.CRBM.,11, 556 (1919). Freeman and Peterson, IND. ENO.CHEM.,ANAL.ED., 13,803-6 (1941).
Hawley and Wise, “Chemistry of Wood”, p. 176, A.C.S. Monograph Series, New York, Chemical Catalog Co., 1926. Koch and Krieg, Chem.-Ztg., 15, 140-1 (1938). Kurth and Ritter, J. Am. Chem. SOC.,56, 2720 (1934). Ritter and Fleck, J. IND.ENQ.CKBM.,14, 1050 (1922) ; 18,608 (1926).
Ibid., 15,1055 (1923). Ritter and Mitchell, U. S. Forest Products Lab., Mimeograph R1028 (April, 1934). Ritter, Seborg, and Mitchell, IND.ENO.CHEM.,ANAL. ED., 4, 202 (1932).
Schorger, U. S. Forest Service, BUZZ. 119 (1913). Van Beckum and Ritter, Paper Trade J., 18, 127-30 (1937).
