INDUSTRIAL A N D ENGINEERING CHEMISTRY
1264
Vol. 15, N o . 12
Chemistry of Wood' VII-Relation
between Methoxyl and Lignin in Wood By G. J. Ritter
FOREST PRODUCTS LABORATORY, MADISON,Wrs.
EXPERIMENTAL WORK T Is a well-known fact The isolated lignins from the two classes of woods differ in chemthat softwoods Yield ical composition. A larger per cent of the total methoxyl is reless methanol thanhardMETHOXYL AND LIGNIN couered in softwood lignin than in hardwobd lignin. woods when Subjected to Approximately 62 per cent of the total methoxyl in white oak and CONTENT O F DIFFERENT destructive d i s t i l l a t i o n . yellow pine sawdust was recovered as methanol by treating the WooDs-These determinaThe difference in Yields of wood with dilute alkali under pressure. The methanol obtained tions were made in the by the dilute alkali and pressure treatment is equicalent in amount same manner as given in m&hanol is even greater to the methoxyl found in the crude volatile products of the destructive the preceding paper of this than would be expected when compared with the distillation of wood. series on the chemistry of It is indicated that the actual period of chlorination can be rewood.4 Theresultsaregiven difference in the methoxY1 content of the two classes in Columns 1and 2, Table I. duced approximately one-ha[f in isolating cellulose. of%woods. Softwoods, in METHOXYLCONTENT OF general, contain about 85 1S 0 L A T E D LI G XI N-The per cent as much methoxyl as hardwoods, although some methoxy content of the lignin, isolated by the method desoftwoods contain more than some hardwoods. In destruc- scribe'd in the preceding papers of this series, was determined tive distillation the methanol yield from softwoods is ap- by the Zeisel method. The results are recorded in Column proximately one-half that obtained from hardwoods. 4, Table I. A comparison of Columns 3 and 4 shows that This difference in behavior suggests that there is a differ- the theoretical and isolated lignins of softwoods are more ence in the linkage of the methoxyl group in the two classes nearly identical in chemical composition than the correof woods. A difference in the linkage of the methoxyl group sponding lignins of hardwoods. By subtracting the figures is further suggested when the ratio of the methoxyl to the in Column 4 from the corresponding numbers in Column lignin content in the different woods is compared. For in- 3, the methoxyl not recovered in the lignin is obtained. A stance, tan oak2has a methoxyl content3 of 5.74 per cent and comparison of the corresponding values in Columns 3 and 5 a lignin content of 24.85 per cent. Yellow cedar has a meth- indicates that from 10 to 21 per cent of the methoxyl in oxy1 content of 5.25 per cent and a lignin content of 31.32 softwoods and from 21 to 38 per cent of the methoxyl in per cent. The ratio of the methoxyl to the lignin in the for- hardwoods are not recovered in the isolated lignin. mer wood is 23.1 per cent; in the latter wood it is 16.7 per I n order to show a different relationship between some of cent. If, as is generally believed, the methoxyl is wholly the constants given in Table I, the significant Columns 2 associated with the lignin, then the chemical composition of 4, and 5 are all calculated on the dry weight of the wood the two lignins differs. If the methoxyl is only partially and arranged in Table 11. I n Column 3, Table 11, is found associated with the lignin, the two cases cited above indicate the methoxyl which is not recovered in the isolated lignins. a different methoxyl linkage. Here again it is shown that the methoxyl not recovered in the I n order to obtain more detailed information on the manner isolated lignin is considerably less in the softwoods than in the in which the methoxyl is combined in the wood and on the re- hardwoods. This experimental fact, however, does not
I
TABLE I-RELATION O F METHOXYI, AND LIGNININ WOODS
SPECIKS
Per cent Lignin in Wood
Per cent CHsO in Wood
'
Per cent CHsO X 100 Per cent Lignin (3) 16.64 18.40 16.16 17.84 22.06 24.53 24.69 25.45 25.34 .
Western yellow pine Western white pine Incense cedar Mesquite Tan oak Eucalyptus Yellow poplar (sapwood) Yellow poplar (heartwood) Pignut hickory (heartwood)
lation between the methoxyl and the lignin, the following experimental studies were carried out: (1) methoxyl and the lignin content of various species; (2) methoxyl content of the isolated lignin of several species; (3) methoxyl liberated as methanol when different species are repeatedly treated with dilute alkali under pressure; (4) methoxyl and lignin content of the residues when different species are chlorinated for varying periods of time. 1 Presented before the Division of Cellulose Chemistry at the 65th Meeting of the American Chemical Society, New Haven, Conn., April 2 to 7, 1923. a Same species as tanbark oak in Paper V of this series. a THIS JOURNAL, 14, 1 x 0 {i922).
I
Per cent CHsO not Per cent Recovered in Isolated CHaO in Isolated Lignin Lignin (Column 3 Column 4) (4) (5) 13.13 3.51 15.10 3.30 14.51 1.66 14.05 3.79 16.99 5.07 15.01 9.52 17.00 7.69 20.22 5.23 18.43 6.91
-
justify the conclusion that the methoxyl not recovered in the isolated lignin is associated with some chemical constituent other than lignin, for it may be removed as a cleavage product in the process of isolating the lignin. These results on hardwoods and hardwood lignins confirm those of DoreJ6 which are discussed by Ritter and Fleck.@ I n the case of softwood (redwood),' however, Dore was able to recover the total methoxyl of the wood in the isolated lignin. I n the isolation of the redwood lignin the material was not boiled 'THIS JOURNAL, 16, 1055 (1923). Ibid., la, 986 (1920). 6 I b i d . , 14, 1050 (1922). 7 Ibzd., 12, 475 (1920). 6
INDUSTRIAL A N D ENGINEERING CHEMISTRY
December, 1923
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ate 3.87 per cent methanol from white oak and 2.93 per cent methanol from western yellow pine. I n the experiment the two woods yield the same percentages of total methoxyl -namely, 63 per cent-but the composition of the residues differs; the hardwood residue by analysis (Zeisel) contains the remaining methoxyl, whereas the softwood residue contains none. This again suggests a different methoxyl linkage in the two classes. It is of interest to compare the yields of methanol obtained in this study with the percentage of methoxyl liberated as TABLE 11-RELATION OF TOTALMETHOXYL TO METHOXYL IN ISOLATED methanol in the crude volatile products by destructive disLIGNIN (Figures in Dercentaaes based on weiaht - of oriainal wood) tillation. In a paper by Hawley and Aiyarg are found the . CHsO not Redata given in Table V. The ratio of the methoxyl obtained CH30 in covered in CHaO Isolated Isolated in the volatile products to the total methoxyl in the three in Wood Lianin Lianin SPECIES cases cited is approximately 62 per cent, the same as obtained Western yellow pine 4.45 3151 0: 94 Western white pine 4.47 3.66 0.81 in the volatile products by the alkali hydrolytic treatment Incense cedar 6.09 5.46 0.63 Mesquite 5.49 4.30 1.19 of two woods. This suggests that the methanol recovered Tan oak 5.70 4.19 1.51 in this study comes from the same methoxyl groups found in Eucalyptus 6.56 4.01 2.55 Yellow poplar (sapwood) 5.89 4.05 1.84 the crude volatile products in destructive distillation. Yellow poplar (heartwood) 6.03 4.79 1.22
after diluting the sulfuric acid with hot water, whereas the lignin analyzed in this paper was boiled after diluting with water to aid coagulation of the material. I n this latter case some methoxyl may have been hydrolyzed from lignin, and thus account for the results obtained. It is of interest to note that with the exception of eucalyptus the values in Column 3, Table 11, agree closely with the yields of methanol obtained by destructively distilling the woods belonging to the corresponding classes.
Pignut hickory (heartwood)
5.79
4.21
1.58
LIGNINAND METHOXYL COXTENT OF SAWDUST RESIDUES
MXTHOXYL LIBERATED AS METHAKOL WHEN SAWDUSTAFTER VARYING Is TREATED WITH DILUTEALKALI UNDER PRESSURE-A 500-gram sample of sawdust which passed through a 40mesh sieve was treated with 1500 cc. of 7 per cent sodium hydroxide solution. The mixture was placed in a large autoclave, which was heated in a nitrate bath. The temperature was raised gradually until an increase in pressure ranging from 115 to 120 pounds was noted. This pressure was maintained for 3 hours, after which it was released gradually and the distillate condensed. The distillate was treated in the regular standard method used a t the Forest Products Laboratory for determining methanol in pyroligneous acid.8 The residue in the autoclave was again thoroughly mixed with 600 cc. of water and the heating repeated at a still higher pressure. The residue was thus retreated, as shown by the table, until no methanol appeared in the distillate. The final residue was washed with hot water until neutral, dried, weighed, and analyzed for methoxyl. White oak and western yellow pine sawdusts were treated as outlined above. The results are recorded in Tables I11 and IV. The data show that repeated treatments of the sawdust with dilute alkali under increasing pressures gradually liber8
U. S. D e p f . Agr., Bull. 29, 5.
PERIODS O F CHLORINATION-In this study duplicate sawdust samples of known lignin and methoxyl content were extracted with a minimum boiling alcoholbenzene solution. The residues were then chlorinated for varying periods of time, and the lignin chloride formed was extracted with sodium sulfite. These residues were thoroughly washed with hot water, dried, and weighed. These final residues were then analyzed for lignin and methoxyl to determine the relation between the ratios of lignin removed to total lignin and methoxyl removed to total methoxyl. In Table VI, Columns 4 and 5, respectively, are found the percentages of total lignin and methoxyl in the residues after the various chlorinations. In the case of basswood the corresponding ratios in the two columns agree fairly well. With incense cedar the first corresponding ratios are a t variance, the remaining three agree very favorably. The same data for tan oak show no agreement in the 10-minute chlorinated residue. The agreement is better in 15 and 20minute chlorinated residues. If the proportions of the total methoxyl and lignin were the same in the individual residues obtained by varying periods of chlorination, then the conclusion that all the methoxy1 i s associated with the lignin and that all i s combined a
THISJOURNAL, 14, 1066 (1922).
TABLE 111-PERCENTAGE OF METHOXYL RECOVERED AS METHANOL FROM SAWDUST TREATED WITH NaOH SOL,UTION
UNDER PRESSURE (Methoxyl content of original wood = 6.12 per cent = 6.31 per cent methanol. Moisture content of original wood = 7.00 per cent) Dry Weight Pressure 7 Per cent Per cent of for 3 NaOH Water Methanol Methanol on Per cent Sample Hours Added Added Obtained Dry Weight of Methoxyl SPECIES Treatment G. Lbs. cc. cc. G. Wood Content White oak 1 465 105 t o 11.5 1500 9.86 2.12 600 1.54 115 t o 120 0.33 600 2.52 160 t o 180 0.54 Residue from above 600 2.24 160 t o 180 0.48 600 1.87 180 to 200 0.40 600 0.00 180 to 200 0.00 Total alcohol in distillate 18.03 3.87 Final residue 280 3.65 Methoxyl retained in residue calculated a s methanol 10.55 2.26 Total methoxyl accounted for as methanol in distillate and residue 6.13
TABLE IV-PERCENTAGE
OF METHOXYL RECOVERED A S METHANOL FROM WESTERN YELLOW PINE SAWDUST TREATED WITH N a O H SOLUTION UNDER PRESSURE
(Methoxyl content of original wood = 4.55 per cent = 4.70 per cent methanol. Moisture content of original wood = 7.50 per cent) Dry Weight Pressure 7 Per cent Per cent of for 3 NaOH Water Methanol Methanol on D r y Weight of Sample Hours Added Added Obtained SPECIES Treatment G. Lbs. cc. cc G. Wood Western yellow pine 1 416 110 t o 120 1500 6.11 1.47 600 2.49 140 t o 160 0.60 600 2.51 160 t o 180 0.60 Residue from above 0.26 180 t o 200 600 1.08 600 0.00 180 to 200 0.00 Total alcohol in distillate 12.19 2.93 Final residue 221 (Zeisel) no methoxyl Total methoxyl accounted for as methanol in’distillate and residue 2.93
{!
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V$. 15, No. 12
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
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in the same manner would be justified. This conclusion is substantiated in the case of basswood and incense cedar, but not in the case of tan oak. In Table VI it will be noted that the chlorination periods were shortened in going from basswood to incense cedar. I n basswood the 30 and 45-minute samples were not extracted with sodium sulfite after the first 15-minute chlorination, although they were stirred a t 5-minute intervals. Columns 1 and 2, Table V, show very little lignin and methoxyl removed by the second 1Bminute chlorination. The tan oak TABLE V-DISTRIBUTION OF METHOXYL IN PRODUCTS OF WOOD
DISTILLATION (Figures in percentages of dry weight of wood distilled) Hard Maple White Oak Incense 6 . 0 9 Per 5 . 1 2 Per Cedar 5 . 9 Per cent-CHaO cent-CHaO cent-CHaO PRODUCTS Blank Blank Blank Pyroligneous acid 1.62 1.16 0.97 Dissolved tar 0.34 0.22 0.10 Settled tar 0.52 0.46 1.04 Gas (calculated as CHd 1.31 1.34 1.60 Total methoxyl recovered in volatile aroducts 3.79 3.18 3.71 Volatile C H ~ O 62 62 63 Total - CHsO
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and incense cedar show how more frequent alternation of chlorination and sodium sulfite extraction may reduce the actual chlorination period in isolating cellulose. This has been studied more fully end will appear in a separate paper. TABLE VI-RELATION O F METHOXYL TO 1,IGNIN (Figures are percentages calculated on dry weight of wood) Residual Residual CHsO X 100 Lignin X 100 CHsO X 100 Lignin CHaO Lignin Total Lignin Total CHaO Basswood Original wood 15-minute chlorination 30-minute chlorinationa 45-minure chlorination
20.7
6.02 5.16 1.23 5.06 1.01 3.39 0.78
24.2 23.8 20.0 23.0
Tan oak 5.31 Original wood 23.7 IO-minute chlorination 5 . 2 9 2 . 3 4 15-minute chlorination 1 . 7 8 0 . 3 3 20-minute chlorination 1 . 3 8 0 . 1 7
22.4 44.2 18.5 12.3 Incense cedar 16.3 Original wood 37.73 6 . 1 4 1.10 10.3 5-minute chlorination 1 0 . 7 0.43 15.4 10-minute chlorination 2 . 8 16.0 15-minute chlorination 1 . 0 0 . 1 6 12.8 20-minute chlorination 0 . 7 5 0 . 0 9 6 o N o t extracted with sodium sulfite.
...
24.9 24.4 16.3
...
22.3 7.5 5.8
...
28.3 7.4 2.6 1.9
...
24.5 20.1 15.5
...
44.0 6.2 3.2 1+:9
7.0 2.6 1.6
Charles Proteus Steinmetz
vv
HEN
Charles Proteus Steinmetz died on October 26, 1923, science lost one of its unique figures. Born a t Breslau, Germany, April 9, 1865, Dr. Steinmetz studied mathematics, physics, and kindred subjects at the University of Breslau, and it is curious to note that so great a mathematician in his younger years experienced much difficulty in learning the multiplication table. While a t the university he espoused the cause of socialism, fell under the ban of the German Government, and was forced to leave the university and to flee the country. He continued his studies in Switzeriand and was persuaded by an American student a t the Polytechnic a t Zurich to accompany him to America. He narrowly escaped rejection at the hands of the immigration officials, but within two weeks after admission was devoting his talents to the improvement of the electric street cars at Yonkers. In 1893 he joined the staff of the General Electric Company, and there found the congenial environment and support necessary for a genius like his to accomplish most for the benefit of mankind. Freed from financial worries, with the resources of a great corporation in cooperation with him, and provided with facilities for the furtherance of research, he was able to overcome one after another many of the obstacles in the way of electrical progress. His investigation in the field of magnetism, which led to formulating and determining the laws governing the losses in iron subjected to varying magnetic induction, was one of his first great pieces of work. It made possible the improvement of electrical machinery with the reduction in the weight and the cost. He abolished the mystery an$ obscurity
surrounding alternating current apparatus and did much to teacb engineers how to design machines with as much ease and certainty as those employing the familiar direct current. Of late years; when alternating current power transmission lines carrying large amounts of energy spread over the country, he turned his talents to the study of the problem of protecting such lines from lightning. His study of the phenomena produced by lightning effects led him to prcduce his famous lightning generator which has been so much discussed in the public press. Dr. Steinmetz’s practical inventions literally cover the entire field of electrical applications, and of the two hundred or more patents in his name perhaps most important are the induction regulator, the method of phase transformation as from two phases to three phases, and the metallic electrode arc lamp. He was a prolific inventor, a skilled mathematician, a trained engineer, and an inspiring teacher, not only possessing marvelous insight into scientific phenomena, but a wonderful ability to explain in simple language the most difficultand abstruse problems. He was the author of many original scientific papers and books, was an ardent believer in the value of education, and was always willing to share his great gifts with any who sought his counsel. He was a patient, sympathetic, and cheerful man, with a fine appreciation of nature, and one who constantly made friends with children. He was an earnest, simple man, who devoted his mind and talents to the service of his fellow-men to an extraordinary degree. His life was a successful one for he accomplished that for which he worked, and lived as pleased him.
