INDUSTRIAL A N D ENGINEERING CHEMISTRY
1166
V d . 15, No. 11
Partial Hydrolysis of W h i t e Spruce Cellulose' By E. C. Sherrard and G. W.Blanco FOREST PRODUCTS LABORATORY, MADISON, Wrs.
URING the investigation of the hydrolysis of spruce cellulose, attention was directed to the presence of considerable quantities of easily hydrolyzable material contained in cellulose prepared by the Cross and Bevan method. That this material is not present as such but is produced by mild hydrolysis is indicated by the fact that, although after isolation it is extremely soluble in water, it can be removed from the cellulose only upon prolonged boiling with water. It has been obtained in the form of a white powder by concentrating the water extract to a thick sirup and precipitating with ethyl alcohol. This powder has a relatively small reducing value and gives no test for mannose. After hydrolysis with dilute acids, however, the reducing value is increased to about five times that of the original and a sharp test for mannose is obtained. Pentoses are also present in considerable quantity. This solid material has been partially purified by dissolving in water and fractionally precipitating with alcohol. The product so obtained is so extremely soluble in water that when exposed to the air the particles or crystals coalesce and finally liquefy. Some doubt exists a t this time as to the nature of the material, since on two occasions well-formed, needle-like crystals were present when examined .under a low power microscope in the presence of the mother liquor. While under examination these needles would absorb water and completely dissolve. Subsequent attempts to purify further by repeated reprecipitations resulted in obtaining the material in an extremely fine powder. Upon long standing, needles again appeared but they constituted only about one-half of the total powder, the remainder consisting of the fine transparent particles noted above. The fine material showed the same tendency to dissolve when exposed to air or moisture. The presence of this water-soluble material in the cellu-
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1 Presented before the Division of Cellulose Chemistry at the 66th Meeting of the American Chemical Society, Milwaukee, Wis., September
lose was at first ascribed to a mild hydrolysis by residual acetic acid during drying. As a consequence, a new quantity of cellulose was prepared and hydrolyzed immediately after the final chlorination both before and after drying. A second portion was treated with acetic acid in the usual way and then hydrolyzed before and after drying. A third sample had the acetic acid removed by washing with dilute ammonium hydroxide and drying. The results of these experiments are given in Table I. It will be noticed that drying has the most pronounced effect in increasing the watersoluble material as indicated by the loss in weight of the cellulose. Treatment with acetic acid without subsequent drying decreases the water-soluble, but after drying an increase is obtained. The removal of acetic acid by ammonia decreases the yield quite markedly. The reducing values given in terms of dextrose agree quite well with the quantity of cellulose lost upon hydrolysis, except that after acetic acid treatment the reducing value of the water-soluble material is increased. Successive refluxing indicated that not all the material is removed until after the third 4-hour treatment with boiling water. The ratio of reducing values of the water-soluble material before and after hydrolysis varies from 1: 2 to 1: 5, and indicates that partial hydrolysis occurred during extraction or that the material is not homogeneous. The ratio of mannose to total reducing material is fairly constant in Experiments 1 and 5, but Experiment 2 indicates that hydrolysis is more complete after drying, while 6B indicates additional hydrolysis by the combined action of acetic acid and heat. Two samples of the water-soluble material were prepared in the form of a white powder and were subjected to an examination, the results of which are given in Table 11. The reducing values are given in terms of dextrose. Sample 1 was prepared in the usual way, while Sample 2 was washed with about 20 liters of boiling water to make sure that no water-soluble material remained in the cellulose.
10 t o 14, 1923. TABLEI-EXPERIMENTSON THE REPLUXING OF WHITESPRUCE CROSSAND BEVANCELLULOSE WITH WATER FOR 4 HOURS EXAMINATION OF WATER EXTRACT Before Hydrolysis with 4.5y0 HnSOa 7-After Hydrolysis with:4.5% HBO4Total ReReducinc Total Celducine Reducing MateriaT Mannose Cellulose culose ExReducing Materiil Material in Per Mannose Per cent Per cent of Total Extracted tracted Per cent in Per cent Per cent Per cent in Per cent cent of of Reduc- of Cellu- Total Cel- of OrigiReducPer cent Per cent of Reduc- of Cellu- of Totall Condiing Malose Re- Cellulose ing Malose Re- lulose Re- nal Celing Maof Origi- of Origition of terial moved moved nal nai terial moved Removed lulose tirial TREATMENT Expt. Cellulose F'irst refluxing with 1 Wet water. Before ace5.00 .35.84 13.95 1.00 7.17 1.17 23.40 tic acid treatment. 13.95 Refluxin of residue 3 Dry 3.13 41.07 37.70 21.57 0.62 8.14 7.51 from &pt. I . . 7.62 Refluxing of residue 4 Dry 22.85 1.28 from Expt. 3.. First refluxipg with 2 Dry water. Before acetic 8.21 37.64 21.80 21.80 3.01 13.80 13.80 3.80 46.16 acid treatment.. Refluxin of residue 5 Dry 4.51 77.00 46.00 5.87 27.61 15.50 1.25 from 2xpt. 2.. 1.28 21.80 28.00 First refluxing after 6A Wet 6.60 97.25 6.80 2.13 6.80 3.15 46.32 32.30 acetir acid treatment Cellulose after acetic 7 Dry acid treatment washed with 1 pe; cent NHiOH and re8.33 2.30 56.37 4.08 4.08 0.34 8.33 tluxed with water.. First refluxing after 6B Dry acetic acid treat7.49 46.12 4.97 66.30 16.24 3.96 24.38 ment. ............. 16.24 3.25 20.96 0.93 17.58 2i:io Residue from Expt. 6 B 4.72 9 Dry 52: ii Trace 1.15 74:07 ... 1.54 6.62 Residue from Expt. 7 10 Dry 70.83 3.28 45.87 1.00 1i:oo 29:03 7.15 13.95 Residue from Expt. 6A 11 Dry Hydrolysis of cellulose 12 Dry residue from Expt. 14.88(HC1) 68.51 60.03 21.72 42.68 3.20 9 with 5% HCI..
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November, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
TABLE II--REFLUXING OF
CROSS AND BEV.4N CELLULOSE-W
PRECIPITATED MATERIAL Sample 1 nETERMINATION Per cent Cellulose removed. , . . .... . 16.56 Precipitated material. , . . . . . . . . . . , . 12.57 Reducing material before hydrolysis.. . . , . . . , 15.96 Reducing material after hydrolysis, 4.5y0 HzS04 70.73 Mannose in per cent of sample.. , . 33.37 Mannose in per cent of total reducing material. 47.18 Pentose in per cent of sample., . 19.30 Pentose in per cent of total reducing material. 27.28 TlON OF
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ATER
1167
EXAMTNA-chloroform, acetone, methanol, and benzene.
Sample 2 Per cent 11.00
12.03
57.21 11.20 27.00 47.00 21.58 37.70
The yield of 12 per cent water-soluble material corresponds approximately with the loss in the preparation of a-cellulose and is a trifle less than the loss in cellulose. The material upon ignition leaves no ash, is insoluble in alcohol,
The melting point is not definite but the material begins to darken a t 220’ C.; a t 235’ C. it turns dark and begins to decompose. It shows no reaction with phenylhydrazine. The quantity of pentose contained corresponds to 37.4 per cent of the pentose present in the original cellulose. The mannose content of the powder corresponds to 42.8 per cent of that contained in the original cellulose. No attempt js made a t this time to ascribe a definite chemical constitution to this material. Were it not for its apparently crystalline form, it might well be considered a mannan. Further investigation of this material is now under way.
T h e Estimation of Pentoses and Pentosans’” I-The
Formation and Distillation of Furfural By Norville C. Pervier and Ross A. Gortner
. UNIVERSITY O F MINNESOTA,MINNEAPOLIS, MI“. structiveby effect on furfural, a HAT the wide distriFollowing a reoiew of preoious work on the formation of jurfural, shown Fraps (1901), k)ution of the pentoPart I is a study of the factors influencing the production of furfural ~ ~(1go5), l M~~~~ l ~and ~~ ~ 1 sans in nature, as from pure arabinose, pure zylose, gum arabic, and pine sawdust. lens (1907), and van Haarst A method for distilling pentoses from acid solution by steam is deand Olivier (1914), and also pointed out by Tollens in upon pentose as argued by 1891, may be of considerscribed, in which theoretical yields of furfural are discussed. Unger and Jager (1903), and able significance in plant Part II, which will appear in a subsequent issue, describes se~eral praps (1915). ~ l araban ~ ~ , economy, is indicated by new oolumetric methods for the determination of furfural in aqueous and fucosan, as well as the corresponding sugars, prosolution, and includes a bibliography on pentoses and pentosans. the work of Spoehr, Hooker, duce furfural very slowly so and Rosa. These subthat the yield from them is stances also constitute a lower than that from others large portion of the nitrogen-free extract of many animal of the group due to the destructive action of the acid, as has been feeds and have been the subject of numerous experiments in shown by the above-mentioned writers and by Kunz (1916). The yields of furfural usually obtained are recorded in Table 1. animal metabolism. (McCollum and Brannon, Swartz.) The TABLE I-YIELDS OF FURFURAL OBTAINED FROM PENTOSE SUGARS BY DE.pentosan determination has also been used as a basis for deTILLATION WITH ACIDS termining the degree of milling of flours (Gerum). It is ap- Pentose Recovery Yield of Furfural Per cent Per cent OBSERVER. parent, then, that a convenient and accurate method for Arabinose estimating these substances is very necessary. Because of 75.00 48.00 74.32 47.56 the serious shortcomings inherent in the official method for 74.54 to 82.35 47.7 to 52.7 73.44 ‘determining pentosans, the present work was undertaken. 47.00
T
HISTORICAL FORMATION OF PuRFvRAL-Dobereiner (1832) first obtained furfural by the distillation of sugar with pyrolusite and sulfuric acid. Stenhouse (1840) later showed the pyrolusite to be unnecessary, while Volckel (1853) found that furfural was a decomposition product of many carbohydrate materials. Stenhouse (1850) was the first to prepare furfural on any appreciable scale. He distilled wheat bran with strong sulfuric acid. The use of a strong solution of zinc chloride in the distillation procedure was proposed by Babo (1853). Stone and Tollens (1888) and Wheeler and Tollens (1889) used sulfuric acid oE various concentrations. Phosphoric acid was tried by Mann, Kruger, and Tollens (1896). Glacial acetic acid was used by Testoni (1917). It was early recognized, however, that the use of 12 per cent hydrochloric acid gave better yields of furfural, in a shorter time, with more accurate duplication of results, and with less “humin” formation, than when any other acid was used [Allen and Tollens (1890), Gunther and Tollens (1890), de Chalmot and Tollens (1891), Councler (1892), Stone (1897), Hauers and Tollens (1903), Jolles (1905), Ling and Nanji (1921)]. Moreover, even acid of 12 per cent concentration has an appreciable de1 Presented before the Division of Biological Chemistry at the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. Received April 10,1923. @ Published with the approval of the director as Paper hTo. 382,Journal Series Minnesota Agricultural Experiment Station. Condensed from a thesis submitted by Norville C. Pervier t o the Graduate School of the University of Minnesota in partial fulfilment of the requirements for the degree of doctor of philosophy.
100
98.7 to 100.8 89.85 90.00 87.5t092.2 97.5 to 100.3
64.00 64.00 Xylose 57.50 57.60 56 t o 59 64.00
Unger and Ja er (1903) Browne (19127 DeChalmot andTollens (1891) Jolles. (1906)
Substances other than pentose may also yield furfural on distillation with acid. Glucuronic acid is one of these, and Tollens (1909) has determined it by a method identical with that for pentoses. However, glucuronic acid is rarely encountered. It has also been claimed that oxycellulose produces furfural, This statement appears to be based on the early work of Cross, Bevan, and Beadle (1894), Vignon (1899), and Faber and Tollens (1899), which was done before the production of hydroxymethylfurfural from hexose materials was established. Moreover, much of the furfural said to be produced from cellulose may really have its origin in true pentosans (hemi- and ortho-pentosans) contained in the cellulose. [Konig and Rump (1914), Schwalbe (1918), Heuser and Haug (1918), Schwalbe and Becker (1920).] Other interfering substances have been mentioned, but little is known concerning their composition and distribution. Bray and Staid1 (1922) claim to have worked out a correction to lessen the error due to these substances, but have not published it. TESTSFOR FURFURAL-For determining when distillation is complete, aniline acetate has usually been used. This is prepared by adding glacial acetic acid to a mixture of equal parts of colorless aniline and water until the mixture suddenly clears. It has been frequently observed, however, that acetic acid often gives a positive test, due to the presence in it of furfural, as was shown by V. Meyer (1878). To avoid the difficulty, the use of
