I N D U S T R I A L A N D ENGINEERING CHEMISTRY
February, 1924
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Determination of Cellulose in Wood' Chlorination Method By G. J. Ritter and L. C. Fleck FOREST PRODUCTS LABORATORY, MADISON, WIS.
HIS study was suggested by some of the results given
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in Paper V I P of the series from this laboratory on the chemistry of wood. These results are found in Table I. They show the propor tion of lignin remaining in three species of sawdust residues after varying periods of chlorination. The samples in Paper VI1 were first extracted with a minih u m boiling solution of alcohol-benzene in a Soxhlet apparatus, thoroughly washed with warm water in an alundum crucible connected with a suction pump. Four to five samples of each species were then alternately chlorinated and extracted with sodium sulfite, with the exception of Basswood Samples 3 and 4,which were not extracted at the end of the first 15-minute chlorination. It will be noticed in this case that scarcely any lignin (0.10 per cent) was removed by the second 15-minute treatment with chlorine. The intervals in which the tanbark oak and incense cedar sawdusts were in contact with chlorine were shortened to 10 and 5 minutes to ascertain the effect on removing lignin.
This study was made in order to determine (1) the efficiency of the short chlorination periods for removing lignin from cellulose and (2) whether the cellulose prepared by the short and long chlorination periods is the same as to quantity and chemical composition.
EXPERIMENTAL
Sawdust (80-100 mesh) was extracted with minimum boiling alcohol-benzene solution for 4 hours, thoroughly washed with hot water, and sucked dry in an alundum crucible connected to a suction pump. The cellulose was then determined in each of the species in Table I1 by using the following two chlorination periods: 20, 15, 15, 10, 10, and 5 , 5, 5, 5, etc. I n the table the first series of chlorinations is indicated as the long and the second as the short periods. Any material differencein the cellulose prepared by the two methods should be found in one or more of the following constants: total cellulose, pentosans in cellulose, lignin in cellulose, cy-, 8-, and y-cellulose in cellulose. The samples prepared were PARTIALLY CHLORINATED accordingly analyzed, with the results found in Table IT.
TABLEI--PER CENT
OF LIGNININ ORIGINAL AND SAWDUST (Results based on oven-dry weight of original wood) Chlorination Period Per cent SPECIES Minutes Lignin Basswood (original) 1 0 20.70 5.16 2 15 3 15" 15 5.06 4 15., i 5.. 1 5 3.39 0 23.70 Tanbark oak (original) 1 10 5.29 2 10 5 1.78 3 10, b, 5 1.38 4 0 37.73 Incense cedar (original) 1 2 10.70 5 2.80 3 5, 5 1.00 4 5, 5, 5 5.5. 5. 5 0.75 5 Q No suldte extraction between first and second chlorinations. I
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The results on the three woods used indicate that chlorinations of 15 minutes' duration are no more effective than those of 5 minutes. With basswood 45 minutes, three 15minute periods, reduced the lignin content from 20.7 to 3.39 per cent. Twenty minutes of actual chlorination, one 10 and two 5-minute periods, reduced the lignin from 23.7 to 1.38 per cent in tanbark oak. Four 5-minute periods reduced +,helignin from 37.73 to 0.75 per cent in incense cedar. In the first wood two sulfite extractions were made; in the second, three; in the third, four. The actual chlorination period of the last two woods is less than one-half that in the first species, but the frequency of removing the "lignin chloride" is increased. 1 Presented before the Division of Cellulose Chemistry at the 66th Meeting of the American Chemical Society, Milwaukee, Wis., September 10 to 14, 1923. 2 Tms JOURNAL, 16, 1264 (1923).
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DISCUSSION OF RESULTS CELISTLOSE IN WooD-In the determination of cellulose a difference of 0.50 per cent for duplicate samples is found to be within the experimental error. In the case of eastern hemlock (heartwood) an increase of 1.41 per cent in favor of the short method is found. An increase of 0.91 per cent in favor of the short method is also found in black locust (heartwood). The difference in yields of cellulose with eastern hemlock (sapwood) and catalpa (sapwood) is approximately 0.50 per cent. This difference in cellulose content may be due to one or a combination of three causes: 1--It is possible that hydrochloric acid formed during the chlorination hydrolyzes some of the cellulose to sugar and it is dissolved during the washing process. 2-A larger percentage of the less resistant pentosans may be removed in one process than in the other. 3-A more complete removal of lignin may be accomplished in one case than in the other.
The second and third factors were investigated as shown by Table 11. PENTOSAN IN CELLULOSE-In eastern hemlock cellulose the pentosan content is slightly higher in that prepared by the short than by the long ohlorination method; in black locust and catalpa cellulose the opposite is true. The greatest difference in the pentosan content of eellulose prepared by the two methods is 1.74 per cent in the black locust. In general, the influence of pentosans on the character of the cellulose prepared by the two methods is uniform.
TABLE 11-COMPARISONOF CELLULOSS PREPARED BY SHORT AND LONGCALORINATION PERIODS SPECIES Eastern hemlock
(sapwood)
(heartwood) Black locwt (heartwood) Catalpa (heartwood)
(Percentages based on oven-dry weight of materials) Method of Chlorination Periods Cellulose in Pentosans in Lignin in Wood Cellulose Cellulose Chlorination Minutes 54.23 6.98 1.50 foFig; 54.76 6.15 1.30 54.18 7.04 1.60 30,5;f,'3,:0, 52.77 6.10 1.50 5 5 5 3 52.82 23.02 1.27 zb,i5;15,io 51.91 24.76 1.32 55.33 21.68 0.95 %~j~:?5,10 65.78 22.90 1.15
{ SLhOonrgt { SLhOonrgt { E% { EE
F5flo
a-Cellulose in Cellulose 49.7 45.3 46.3 48.1 71.3 45.0 73.7 71.4
@-Cellulose r-Cellulose in Cellulose in Cellulose 31.7 18.6 83.8 20.9 23.8 29.9 22.6 29.3 18.7 10.0 32.0 23.0 7.6 24.7 17.8 10.7
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
LIGNININ CmLTJLosE-The lignin content of the cellulose prepared by the two methods agrees within the experimental error. This is to be expected, for in either case the chlorination was carried on until the sodium sulfite solution used for extracting the chlorinated product showed no discoloration. cy-, p-, AND Y - ~ E L L U L O S EIN CELLuLosE-The only marked difference between the effect of the two methods on cycellulose is shown in black locust. P-Cellulose is considerably lower in black locust and catalpa cellulose prepared by the short chlorination method. From the limited amount of data available it appears that short-chlorinated cellulose is more stable than that prepared by the long method. A comparison of the results obtained from the short and long chlorination methods indicates that the reaction between chlorine and lignin is fairly rapid. The substance “lignin chloride,” soluble in sodium sulfite, must be removed from the surface of the wood particles. The “lignin chloride’’ seems impermeable to chlorine, for prolonged contact of the gas with the chlorinated sawdust has little effect in further removing lignin. This statement is based on the data of (1) the last samples of basswood, tanbark oak, and incense cedar
Vol. 16, No. 2
(Table I), in which two, three, and four sulfite extractions were made, respectively, and (2) the cellulose prepared by the short and long methods (Table 11) in which the number of extractions are equal. Prolonged chlorination does, however, break down the a-cellulose. CONCLUSION In preparing pulp for paper commercially, it is found that from 40 to 45 per cent of the wood is utilized. Approximately 60 per cent should be utilized, for that amount of cellulose can be isolated from the wood by the chlorination method. Thus, 25 per cent of the paper-making material is lost in commercial operations. It is this lost cellulosic material that the progressive paper manufacturer is striving to recover by modifying his pulping process. There are two objections to the chlorination method-the number of steps involved and the cost of the chlorine. If the amount of chlorine can be reduced in a commercial operation in the same proportion as reported in this paper, one of the objections against introducing the chlorination process for preparing pulp commercially will have been overcome.
The Solubility of Sulfur in Rubber’ By W. J. Kelly and K.B. Ayers GOODYEAR TIRS & RUBBERCo.,AKRON, OHIO
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N THE discussions of ratios of the concentrations The question as to whether or not rubber adsorbs sulfur has been the theories of vulcanin the two phases are condiscussed quite extensively in the literature. I n the following work stants, the system obeys ization which have been it is proved by a study of the distribution of sulfur between rubber and Henry’s law and the sulfur published in the past sevanother phase that the system obeys Henry’s law and hence the sulfur is dissolved by the rubber. eral years, many references is dissolved in and not adsorbed by the rubber. Figures are given are made to the fact that Thus by plotting the correshowing the solubility at diflerent temperatures and degrees of vulsponding values of the conthe first step in the process canization. The bearing of this on theories of vulcanization is incentrations a straight line mas either the solution of dicated and the possibility of using the laws of chemical kinetics to passing through the origin sulfur in or its adsorption study the reaction between sulfur and rubber is pointed out. would be obtained. Even if by the rubber. No definite the sulfur were dissolved in Tv-ork t o show which of these processes actually took place was done until Skellon2 pub- the rubber it would be possible to have a curved line passing lished his experiments on the migration of sulfur in rubber. through the origin if the molecular weight of the sulfur in the As a result of this work Skellon concluded that the rubber rubber were different from that in the other phase. Assumdissolved the sulfur and hence did not adsorb it. Venable ing for the moment that in the liquid phase sulfur were present and Green3 also m’ade some similar experiments, but went as SSand in the rubber as Sd, we should have the reaction further and determined the maximum amount of sulfur which expressed by the equation the rubber would take up under certain conditions. Both sa e 2% these methods had one thing in common. The sulfur was taking place a t the interface, and instead of expressing allowed to diffuse into the rubber-in Skellon’s work from another piece of rubber containing a large excess of sulfur, Henry’s law as Cl = K and in Venable and Green’s experiments from the elementary (1) sulfur itself. Both authorities conclude from their work we should have to write that the rubber dissolves the sulfur. The conditions of the experiments do not permit the definite conclusions that the sulfur is not adsorbed, becausein both cases the sulfur might have diffused through the vapor phase and been adsorbed by the rubber. The best way to and the result would be a curve of the second degree. I n this determine whether sulfur is dissolved or adsorbed by the case it would be difficult to distinguish between solubility rubber is to study the distribution of the sulfur between and adsorption without resorting t o other means, as the Tubber and a known solvent for the sulfur in which the rubber adsorption isotherm is expressed by the equation is insoluble. In this way if an equilibrium exists between (3) t h e two phases it can be approached from both sides. If the 1 Presented before the Division of Rubber Chemistry at the 65th Meetwhich, if n = 2 or 0.5, gives exactly the same curve as Equai n g of the American Chemical Society, N e w Haven, Conn., April 2 to 7. tion 2. 1922. For the experiments to be described in this paper n-butyl 2 I n d i a Rubber J . , 46, 251 (1913). alcohol was chosen as the liquid, and it was found that when THISJOURNAL, 14, 319 (1922).
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