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dried blood, even-where the soil was 50 per cent coarse sand, i t seems evident t h a t the loss of nitrate nitrogen must have been Iess t h a n the loss of organic nitrogen, though we have been accustomed t o think t h a t the reverse is true in soils containing considerable sand. The average percentage of nitrogen recovered in the crops from the nitrate cylinders is greater t h a n the average from t h e blood cylinders in 8 out of the I O series. With 7 0 per cent sand, the recovery from blood is slightly in excess of the recovery from the nitrate, and with I O O per cent sand, the average stands, nitrate 31.8 per cent and blood 39. I per cent. The percentage of nitrogen recovery is well maintained for both nitrate and blood in soil mixtures containing as high as 70 per cent sand. Indeed, where t h e nitrate was used, the recoveries are higher with 3 0 , 40, 50, and 7 0 per cent sand t h a n with I O and 2 0 per cent sand. Where blood was used, the highest average recovery was with 80 per cent sand and t h e next highest with 3 0 per cent sand. The average recovery for all nitrate cyIinders is 8. 7 per cent higher t h a n the average for all blood cylinders. FIELD EXPERIMENTS-NITRATE
OF SODA A N D NITRATE
OF LIME COMPARED WITH DRIED BLOOD, FISH, A N D TANKAGE
In a study of so important a problem, i t did not seem wise t o rely entirely on cylinder experiments for data, and therefore, in 1908, 40 one-twentieth acre field plots were laid out for use in a detailed study of t h e relative availability of a number of nitrogenous materials. Since calcium nitrate was claiming attention a s a fertilizer a t this time, i t was included among the other materials. T h e figures reported herewith in Table I11 are t h e averages of I O yrs. results from the sodium and calcium nitrate plots on t h e one hand, and the dried blood, fish, and tankage (organic nitrogen) plots on the other. TABLE 111-AVERAGE YIELD
OF DRY MATTER A N D PER CENT NITROGEN RECOVERED-FIELD EXPERIMENTS 1908-1917 Averaee Per Cent . . ...-.Lbs ~... Dry Matter Nitrogen Per Acre Recovered First Second First Second 5 yrs. 5 yrs. 5 yrs. 5 yrs. TREATMENT 38.2 31.8 3432 Nitratenitrogen nolime 4191 3462 51.0 28,8 4467 Nitrate nitrogen’with lime.. 3821 2856 27.3 25.4 Organic nitrogen, no lime.. , 3063 28.5 24.9 3734 Organic nitrogen with lime..
........ .... .. .. ..... ... ... .......
A 5-yr. rotation has been followed, the crops being for the first 5-yr. period, one year of corn, 2 yrs. of oats, one year of wheat and one year of timothy. For the second 5-yr. period the rotation was slightly changed so t h a t there was only one year of oats and 2 yrs. of timothy. A careful record has been kept of the total dry matter produced and of the amount of nitrogen applied as fertilizers, and of the amount removed by the crops. It will be noted t h a t the nitrate plots gave the largest yield of dry matter and the highest recovery in both periods. If a n average is taken of the yields of dry matter from the limed and unlimed nitrate plots and the limed and unlimed organic fertilizer plots, i t is found t h a t the difference is close t o 500 Ibs. annually in favor of the nitrate plots for each of t h e two 5-yr.
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periods. The average nitrogen recovery of all the nitrate plots for the I O yrs. is 37.4 per cent as compared with 2 6 . 5 per cent for the organic fertilizer plots. The reason for the greater effectiveness of nitrate nitrogen t h a n organic nitrogen is not entirely clear but the residual crop which is grown every year in cylinder experiments (Series B) seems t o throw .some light on this question. This crop gets practically no benefit from the nitrate-the first crop having utilized practically all t h a t was not lost in some way-whereas i t is benefited slightly by the dried blood. I n other words, t h e organic nitrogen does have a slight residual effect, whereas the nitrate has practically no residual effect. However. the initial effect of the nitrate so much exceeds the initial effect of the organic nitrogen t h a t the total recovery is distinctly in favor of the nitrate. It would appear, therefore, t h a t the nitrate is especially beneficial t o the plant in the early stages of its growth a t a time when the organic material has not yet become fully effective, and having t h u s obtained a good start, the plant grows rapidly a n d utilizes the nitrogen t o such good advantage t h a t the loss is really less than from a material t h a t is not so readily soluble. Furthermore, the good start which t h e nitrate gives the plant enables i t t o utilize the soil moisture and mineral plant food t o better advantage t h a n the plant which is slower in getting started. The writer wishes t o give due credit t o the late Dr. E. B. Voorhees, and t o Dr. Jacob G. Lipman for their part in planning, inaugurating, and conducting for some time the experiments here described. THE DETERMINATION OF CELLULOSE IN WOODS By W. H. Dore DIVISION O P AGRICUI.TURALCHEMISTRY, UNIVERSITY OF CALIPORNIA AGRICULTURAL EXPERIMENT STATION, BERKELEY, CAI.. Received July 19, 1919
I n a previous paper1 t h e author proposed a tentative scheme for the proximate analysis of woods, t h e object of which was t o account for practically all of the constituents present. It was then shown t h a t the process was fairly successful with the coniferous woods but not with t h e hardwoods. It was recommended t h a t t h e dried sample be extracted successively with benzene and alcohol, then digested successively with water and one per cent sodium hydroxide solution and the amounts of material removed by each of these reagents recorded a s analytical data. It was assumed t h a t the resulting residue represented a purified lignocellulose suitable for both the cellulose and lignin determination. T h e hydrolytic treatments with water and the dilute alkali were considered as resulting in the removal of the less resistant lignins and cellulose corresponding approximately t o t h e LLproto”a n d “hemi” bodies of K6nig’s classification,2 leaving t h e “ortho” forms, of true cellulose and lignin, practically unattacked. The former paper offered data based upon separations made by this alkaline treatment, with a full 1Tx1s JOURNAL, 11 (1919), 556. 2.Nahr. Genussm., 28 (1914). 177.
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realization of t h e arbitrary character and doubtful propriety of t h e procedure. It was believed, however, t h a t some form of hydrolysis was necessary t o secure a cellulose free from hemicelluloses. The various suggested processes were carefully considered. While there was a lack of comparative data as t o results by these methods, theoretical considerations seemed t o indicate moderate alkaline hydrolysis as least objectionable and i t was accordingly tentatively adopted. Results of investigations of the effects of acid and alkaline hydrolysis upon wood cellulose, here presented, indicate a revision of some of the methods and opinions of the earlier paper. The original method of Cross a n d Bevan for the determination of cellulose’ directed t h a t the material should be treated with a one per cent sodium hydroxide solution previous t o chlorination and t h a t sodium hydroxide should be added t o t h e sulfite solution used in dissolving the chlorinated product. The addition of alkali previous t o chlorination was practiced, partly because i t was considered essential t o t h e removal of hemicelluloses t h a t would otherwise contaminate the final product and partly t o assist in removing the lignin a n d opening up the tissues for attack by the chlorine. A critical study of this and other cellulose processes published by Renker2 in 1910 showed t h a t the use of alkali either before or after chlorination is not essential t o obtaining a residue free from lignin, b u t t h a t if t h e alkali is used a lower percentage residue is obtained. He accordingly concluded t h a t the cellulose is attacked by alkaline treatment and modified the process t o omit it. The d a t a offered by various authors, while not strictly comparable, indicate t h a t t h e highest results for cellulose are obtained by the Renker method in which neither acid nor alkaline preliminary treatment is used. Renker’s findings were confirmed by Schorger,3 of the United States Forest Products Laboratory, who used the Renker modified method in his investigations of American woods. Schorger found t h a t when digestion in one per cent sodium hydroxide was practiced there was a considerable decrease in t h e percentage of cellulose in the hardwoods. T h e difference was less marked in t h e conifers. Johnsen and Hovey4 have proposed a process of acid hydrolysis, using a mixture of acetic acid and glycerin previous t o chlorination, claiming t h a t this produces a purer cellulose, and t h a t the lower figures resulting represent a closer approach t o the true cellulose value t h a n Schorger’s results by the Renker method. They obtained results which were consistently lower by 2 t o 4 per cent t h a n those obtained when no hydrolytic treatment was used. It is obvious t h a t the three methods proposed, i. e . , no preliminary hydrolysis, alkaline hydrolysis with one per cent sodium hydroxide, and acid hydrolysis “Cellulose,” 2nd Ed., p 95. “Bestimmungsmethoden der Cellulose.” 8 THIS JOURNAL, 9 (1917), 556 and 561. 4Paper 1231, 21 (1918), 36, also J . Soc 132-73
with acetic acid and glycerin, are not comparable upon the basis of cellulose yield alone. A smaller yield may indicate a purer cellulose and accordingly a more accurate determination, or i t may indicate a partial destruction of the cellulose itself and a less accurate result. It is necessary t o determine the purity of the products in order t o compare the merits of the processes. The d a t a on this point are somewhat meager. It appears t h a t with suitable mechanical preparation of t h e material all of these processes are capable of yielding material free from lignin. The residue b y Renker’s method gives a considerable yield of furfural on distillation with hydrochloric acid and for t h a t reason the method has been criticized as yielding a n impure cellulose. The claims of Johnsen and Hovey for the superiority of their process are based partly upon the reduced furfural yield of the residue. It is t o be noted in this connection t h a t the process of alkaline hydrolysis has had for one of its objects the removal of xylan, or wood gum, a furfural-yielding substance. The available data indicate t h a t the residues by all of these cellulose processes contain some furfural-yielding material resistant t o the hydrolytic treatments employed. Cross and Bevanl have maintained t h a t this highly resistant furfural-yielding material is not a pentosan but an oxycellulose and a normal constituent of celluloses derived from lignified tissues. These views have been disputed by Konig2 but have been accepted by most cellulose investigators. From the above discussion i t is clear t h a t we are much in need of a standard of purity and a more exact definition of cellulose. As applied t o the cellulose of woods, the term has been commonly accepted as a group designation, signifying a residue remaining after successive alternate treatments with chlorine and dilute sodium sulfite solution until free from lignin derivatives. T h e amount and character of the residue necessarily varies considerably with t h e treatment i t has undergone preliminary t o chlorination. Cellulose derived from cotton is a homogeneous substance with such definite chemical properties t h a t i t is quite generally accepted as a chemical entity. It is much more precisely described as “norma1 cellulose” and is characterized by t h e absence of free carbonyl, methoxy, or furfural-yielding groups. It has been quantitatively hydrolyzed t o dextrose and has accordingly been described as a “polydextrose anhydride.”3 Cellulose residues derived from woods show no such homogeneity. Cross and Bevan4 have shown t h a t the celluloses derived from lignified tissues are mixtures of a cellulose similar t o or identical with the normal cellulose of cotton. and other celluloses of less stability which are distinguished from normal cellulose by a feebler resistance t o reagents a n d b y the presence of methoxy and furfural-yielding groups.
1
‘’Cellulose,’’ 2nd ed pp. 82, 101. “Bestimmung der Zellulose in Holzarten und Gespinnstfasern ” a “Researches on Cellulose,” 111, p 42. 4 ‘‘Cellulose,” 2nd Ed., p. 93
I
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Chem. I n d . , 37 (1918),
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A partial measure of the industrial importance of a wood cellulose is the amount of normal cellulose present. I n manufacturing wood pulp by the sulfite and soda processes all except the normal form is largely destroyed. Celluloses derived from woods have found but little application in the nitrocellulose and other cellulose ester industries, chiefly because the presence of other celluloses t h a n the normal results in byproducts of low stability and diminished yields of main product, These points have been recently covered in a paper by Baker.' I n experimental research, a t least, a statement of the analysis of woods and other fibrous products might well include not only t h e total amount of cellulose obtained by chlorination, but also the amount of nopmal cellulose contained in this residue. In the present investigation the determination of the normal cellulose in the residues is used t o indicate the extent t o which the cellulose has been attacked by the preliminary hydrolysis, A diminished yield of normal cellulose indicates t h a t the treatment has been too severe and has attacked the most resistant member of the series. As a means of determining the normal cellulose, the mercerization test of Cross and Bevan2 is available. I t depends upon the fact t h a t normal cellulose unites with sodium hydroxide of mercerizing strength t o form alkali cellulose and is regenerated without loss of weight upon diluting and washing out the lye. AS the other celluloses are dissolved by this treatment, the residue may be dried and weighed as normal or a-cellulose. The sodium hydroxide solution upon neutralization with acetic acid yields part of the dissolved cellulose as a precipitate, while a third portion of the cellulose remains permanently in solution. These celluloses are designated as /3- and y-cellulose, respectively, and signify progressively less resistant forms of cellulose. EXPERIMENTAL
Fine redwood sawdust was obtained by sifting somewhat coarse sawdust through a jo-mesh sieve. The sample was sawed from slabs and accordingly consisted chiefly of sapwood. There was no attempt t o make the sample representative of the species as the data were wanted for comparative purposes only. For the same reason the data have not been calculated t o a dry basis but refer t o material with an average moisture content of 11.62 per cent. EXTRACTION-POrtiOllS of 2 g. each were weighed into alundum thimbles, placed in a Soxhlet apparatus, and extracted with benzene for 6 hrs., then with 95 per cent alcohol for 6 hrs. The residues were experimented upon with the three different treatments here described. (I) Rertker Modification of Cross alzd Bevan's MethodHydrolytic treatment was entirely omitted. The material was transferred t o Gooch crucibles provided with filtering disks of mercerized cotton cloth and washed with hot water. material ( 2 ) Original Cross and Bevan Method-The 1 2
P a p e r 1231, 21 (1918), 78. "Researches on Cellulose," 111, p. 22.
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was similarly washed, and transferred t o Erlenmeyer flasks provided with reflux condensers. I O O cc. of a one per cent sodium hydroxide solution were added and the material digested for a n hour a t boiling temperature. A t the end of t h a t time i t was filtered through Gooch crucibles, washed with hot water, dilute acetic acid, and finally with hot water again. (3) Johnsen and Hovey Method-The material was placed in Erlenmeyer flasks provided with ground-in reflux condensers. To each flask were added 75 cc. of a mixture of glacial acetic acid and glycerin (sp. gr. I . 26) in the ratio of their molecular weights (60 : 92). The mixture was placed in a paraffin bath and heated for 4 hrs. a t 1 3 5 O C. A t the end of t h a t period t h e contents of t h e flasks were filtered and washed first with strong acetic acid, then dilute acid, and finally with hot water. The washing with acetic acid of diminishing concentration was intended t o prevent reprecipitation within the residue upon dilution. The lack of agreement in the results, as shown in t h e table below, may be due t o this reprecipitation. N o quantitative significance should be attached t o the loss of weight by this treatment. Experimental data, showing the loss of material in each treatment, are given in Table I. TABLEI-LOSS OF WSIGHT BY VARIOUS HYDROLYTIC PROCESSES Loss on drying ...................................... 11.62 0.30 Loss on extraction with benzene Loss on extraction with alcohol. ... . . . . . . . . . . . . . . 3.88
-
Material removed b y above pro
...
. . .. . . . . . . .
. .. .
15.80 --
Residue by difference. ... . . . . . . .. . . 84.20 Residue after washing with water: 4 determinations varying from 84.13 to 84.60 show that no measurable loss of material occurs by this process. Residue after digestion in one per cent sodium hydroxide. 4 determinations varying from 76.40 to 7 7 . 7 1 , average 76.87 Loss in weight by this proce . 7.33 Residue after treating with n: 3 determinations varying fr ge.. 76.76 ., 7.44 Loss in weight by this process..
...
. .. . .
The figures are in all cases the average of several determinations and are expressed in percentages of t h e air-dry sawdust (I 1.62 per cent moisture). CHLORINATION-The residues from all these processes, without any intermediate drying, were submitted t o chlorination by the method of Sieber and Walter1 (also used by Johnsen and Hovey),2 which was found t o be convenient and reliable. A comparison of this method with t h e vacuum chlorination method recently proposed by the present a ~ t h o r , ~ showed t h a t the Sieber and Walter method yields a product as nearly free from lignin and oxycellulose as the former method and is simpler t o manipulate. The Sieber and Walter method is without doubt the most convenient process thus far devised and will probably be eventually adopted as the standard cellulose method. The apparatus used is shown in the accompanying cut. The material was contained in a Gooch crucible supported over a suction filtration flask in the 1 2 8
Papier-Fabr , 11, 1179-82; Chem. A b s . , 8 (1914), 1202. Loc cit. THISJOURNAL, 11 (1919), 556
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T H E JOI’RLVAL O F I i V D C S T R I . 4 L
usual manner. Around the filtration tube was fitted a n inverted rubber stopper by means o! which the crucible was capped with a glass adapter for the introduction of t h e chlorine. The smaller connecting t u b e of t h e adapter was attached t o a chlorine apparatus and a moderately rapid stream of washed chlorine was drawn through t h e material for 20 min. b y means of a suction pump. The crucible was then removed and dilute sulfurous acid added t o t h e residue, after which i t was washed with hot water. The crucible and its contents were placed in a 50 cc. beaker, sufficient 3 per cent sodium hydroxide solution added t o almost cover t h e material, and the whole heated on the steam b a t h for three-quarters of an hour. The crucible was then removed from the solution and placed on a suction filter. Sulfite solution was poured through and the residue well washed with hot water.
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26 7
cc. of cold I 7 . j per cent sodium hydroxide solution added and the whole allowed t o stand for half a n hour. It was then diluted with 50 cc. of cold water, filtered off on t h e original Gooch crucible and washed with about one liter of cold water, several times with dilute acetic acid and finally with sufficient cold water t o remove all of t h e acid. I t was then dried for 16 hrs. a t 100’ and weighed as a-cellulose. Below are given the yields of total cellulose and acellulose obtained after the three different preliminary treatments. TABLE11- COMPARISON OB METHODS OF PRELIMINARY HYDROLYSIS AS APPLIEDTO WOODS Results in percentages of air-dry wood (1 1.62 per cent moisture) Ratio a-Cellulose TOTAL CELLULOSE CELLULOSE Total Individual Individual Av. Av Cellulose ( I ) Renker’s modifica- 47.93 36.04 tion of Cross and 48.46 36.02 Bevan’s method. 48.97 36.71 No hydrolysis 48.77 36.84 48.91 48.27 48.24
( 2 ) Original Cross and 45.86 Bevan method. 1 46.28 hr with 1 per 45.85 cent sodium hy- 45.07 droxide at boiling 45.64 temperature 46.29 (3) Johnsen and Hovey 44.04 method. 4 hrs. 44.11 with acetic acid and 44.37 glycerin at 135’ C. 44.49
37.09 36.76 36.99
36.64
0.75
45.83
35.38 35.49 35.25 35.03 35.76 35.55
35.41
0.77
44.25
34.60 34.73 34.70 34.53
34.64
0.78
48.51
,
D E T E R M I N A T I O N OF FURFURAL-DeterminatiOnS were made of the furfural yield of the total and a-cellulose residues by the various processes. This was done b y the usual method of distilling t h e material with 1 2 per cent hydrochloric acid and precipitating t h e distillate with phloroglucin solution. The method as applied t o woods is described in detail by Schorger.’ KO distinction between furfural and methyl furfural was made.
TABLE111-FURFURAL YIELD OF PRODUCTS In percentages of air-dried material ( 1 1.62 per cent moisture) FROM TOTAL CELLULOSE PROM ~-CBLLULOSE Individual Av. Individual Av. ( 1 ) Renker’s process. N o 2.66 0.52 hydrolysis 2.36
....
2.69 2.38
T h e chlorination and sulfite treatments were then repeated 3 times, t h e periods of exposure t o the gas being 15, 15, and I O min., respectively. After final sulfite digestion t h e material was washed thoroughly with hot water, dried for 16 hrs. a t 100’ C. and weighed as “total cellulose.” The crucibles were weighed in weighing bottles having tightly ground glass stoppers. DETERMINATIOiV O F N O R M A L CELLuLosE-The f f - Or normal cellulose in t h e total cellulose residues b y t h e three processes was determined b y t h e Cross and Bevan mercerization test.l The dry material was transferred as completely as possible t o a beaker, 50 1
“Paper Making,” 1916 Ed., p. 97.
(2) C r o s s and Bevan’s 2.67 process. Alkaline 2.63 hydrolysis ( 3 ) Johnsen a n d Hovey’s 2.18 process Acid hy- 2.20 drolysis
0.48 2.52
0.51
0.50
2.65
0.31 0.24
0.27
2.19
0.25 0.27
0.26
HYDROLYSIS OF COTTOP-In order t o determine whether t h e destructive effect of hydrolytic agents &pon cellulose is peculiar t o cellulose derived from woods, experiments were made with cotton. The material used was a piece of cotton sheeting which had been repeatedly laundered and might therefore be considered a residue consisting of highiy resistant cellulose, mostly of t h e normal type. I t was snipped into small pieces, portions weighed out and sub1
THISJOURNAL, 9 (1917), 556.
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sistant carbohydrates with equal vigor. It appears, therefore, t h a t t h e use of preliminary hydrolytic treatments is inadmissible in an accurate cellulose process. Renker’s method is t o be regarded as t h e TABLEIV-COMPARISON OF METHODS OF PRELIMINARY HYDROLYSISmost suitable process since i t gives a product as pure AS APPLIED TO COTTON as the others and in maximum yield. In percentages of air-dried material (4.65 per cent moisture) Ratio The experiments with cotton show t h a t celluloses a-Cellulose : Total aTotal of this type are equally susceptible t o hydrolytic TREATMENT Cellulose Cellulose Cellulose action. The behavior of wood celluloses under the 85.32 0.95 A. No hydrolysis.. ................. 89.90 B. 1 per cent sodium hydroxide action of hydrolytic agents is therefore not t o be 1 hr. boiling.. ................. 85.33 82.16 0.96 C. Acetic acid and glycerin ascribed t o any peculiarities of constitution or t o the 4 hrs. at 135’C ............... 85.91 80.63 0.94 fact t h a t i t is derived from lignified material. ApparD. 40 per cent acetic acid 81.28 0.95 4 hrs. boiling. ................. 85.52 ently celluloses from any source are readily attacked E. 20 per cent acetic acid 81.68 0.94 4 hrs. boiling., ................ 86.44 by weak acid or alkaline solutions a t boiling temperatures but are unaffected by similar reagents in the cold. DETERMINATION OF T E M P E R A T U R E EFFECT-TO deThe furfural yield of normal cellulose is in every termine whether weak acid and alkaline solutions exerted any appreciable effect in t h e cold, samples of case insignificant. The total celluloses give furfural sawdust were extracted with benzene and alcohol yields t h a t do not differ materially from each other as before, allowed t o stand in such solutions for 5 and it may be concluded t h a t the hydrolytic processes days, then filtered, washed, dried and weighed, chlor- do not remove any appreciable amount of the furfural-yielding complexes from the product. Uninated as usual, and again dried and weighed. treated wood yields 5 . 8 4 per cent of furfural (average of TABLEV-EFFECT OF COLD DILUTE ACID AND ALKALI UPON W O O D two determinations). About half of the furfural-yieldResults in percentages of air-dried material (1 1.62 per cent moisture) Residue after Total ing substances, therefore, disappear during chlorinaTREATMENT Treatment Cellulose tion. The misshg portion is probably all t o be found 5 days in cold 1 per cent sodium hydroxide. ...... 81.37 48.45 5 days in cold’ 5 per cent sodium hydroxide. ...... 8 0 . 5 0 47.65 in the chlorination filtrates and washings and no doubt 5 days in cold ’ 1 per cent hydrochloric acid. ....... 83.11 48.08 5 days in cold: 5 per cent hydrochloric acid. ....... 8 2 . 5 4 48.89 represents t h a t present as xylan or wood gum. The A comparison of Table V with Table TI shows t h a t furfural still remaining in t h e residue and resistant t h e magnitude and t h e variation of the cellulose t o hydrolysis probably originates not in pentosans values in these last tests is practically identical with but in oxycellulose. The total cellulose residue obtained b y the Renker those in tests where all treatment is omitted. We may therefore conclude t h a t these reagents are wholly process was tested for mannan and galactan with negative results. The original wood (redwood), howwithout effect in the cold. An attempt was made t o obtain some information ever, has been found by t h e author t o contain 2 . 4 8 as t o the composition of the less resistant portion of per cent of mannan and 0.47 per cent of galactan. the cellulose residue. Several portions of total cellu- The hemicelluloses therefore disappear during chlorinalose prepared by t h e Renker method were submitted tion. T h e filtrates and washings incidental t o the t o mercerization, thy solutions containing the other chlorination operations contain considerable amounts celluloses were neutralized, and the precipitated 6- of reducing sugars which are no doubt the hydrolyzed celluloses, after standing on the steam bath for some products of t h e hemicelluloses. It is therefore evihours t o coagulate, were filtered off on gooches, dent t h a t the chlorination process itself involves washed, dried and weighed. The filtrates were hydro- sufficient hydrolysis t o remove the hemicelluloses lyzed by adding hydrochloric acid and boiling under and t h a t no additional hydrolytic treatment is necesa reflux condenser for 3 hrs., and the reducing sary. sugar determined by Allihn’s method. The results Hagglundl has shown t h a t sulfite waste liquor conwere variable and unsatisfactory. It is well known tains xylose, mannose, galactose, and levulose, but no t h a t on heating with dilute acids the hexose carbo- dextrose. On the other hand, when wood was hydrohydrates decompose more or less t o levulinic and lyzed with dilute sulfuric acid (0.5 per cent) he obformic acids. It is believed t h a t much of the less tained dextrose, in solution as well. The researches stable cellulose material was lost through this reac- of Ost and Wilkening2 have shown t h a t normal cotton tion and through conversion into furfural. cellulose may be practically quantitatively hydrolyzed t o dextrose, and presumably the same is true of DISCUSSION the a-cellulose of woods. Since the P-cellulose of It is obvious t h a t all methods involving hydrolysis woods is largely hydrolyzed by the sulfite process8 result in a reduced yield of both total and a-cellulose. and since the sulfite liquor contains no dextrose, i t is The ratios of the substances are practically identical evident t h a t the P-cellulose does not hydrolyze t o in the various processes, indicating t h a t they are dedextrose. Possibly P-cellulose is the source of t h e stroyed in. t h e same proportion. This shows t h a t levulose found in sulfite liquor. There seems t o be the hydrolytic processes do not accomplish the purno direct experimental evidence on this point. pose for which they were designed; t h a t is, instead 1 Biockem. Z.,70 (1915), 416. of exercising a selective action and producing a purer 3 Chcm.-Ztg., 84 (1910), 461. cellulose, the reagents apparently attack all of the re8 Cross & Bevan. “Cellulose,” 2nd Ed., p. 98. mitted t o various treatments, after which i t was chlorinated in the usual way, the residues treated by the mercerization process and the a-cellulose determined.
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1920
T H E J O U R N A L O F I N D U S T R I A L AiVD E N G I N E E R I N G C H E M I S T R Y
A t present there prevails a rather uncertain conception of the significance of the term “cellulose” as applied t o material derived from woods. I n general, i t may be understood t o mean a product prepared by processes of sufficient intensity t o remove all extractives (resins, dyes, etc.), incrusting substances (lignin), and hemicelluloses (condensed carbohydrates of pentose, mannose, and galactose basis) and limited in their action t o those bodies. The chlorination process as applied t o wood material, treated with non-hydrolyzing solvents only, fulfills these requirements. The definition of cellulose as a residue remaining after alternating treatments with chlorine and sodium sulfite solution may be accepted if we add the limitation t h a t t h e process be preceded with non-hydrolyzing treatments only. The residue so obtained should be free of lignin and hemicellulose, including pentosans, mannans, and galactans. I t may contain CY-, p - , and y-cellulcses corresponding t o t h e definitions of these bodies implied by the conditions of t h e mercerization test, also furfuralyielding complexes, b u t should be free from easily hydrolyzable pentosans. SUMMARY
I-A comparison is made of three proposed methods of treating woods and other lignified materials previous t o chlorination in the cellulose determination. These methods consist of ( I ) absence of hydrolysis, ( 2 ) alkaline hydrolysis, and (3) acid hydrolysis, restricted in each case t o the degree of intensity considered necessary for avoiding attack upon the cellulose proper. 11-The d a t a show t h a t all processes involving preliminary hydrolysis result in diminished yield of acellulose as well as total cellulose, and are therefore unacceptable as accurate cellulose processes. 111-The ratios of a-cellulose t o total cellulose are practically the same whether or not preliminary hydrolysis is used. This shows t h a t the highest type of cellulose is as strongly attacked during hydrolysis as the lower types. IV---During the treatments incidental t o chlorination the hemicelluloses are hydrolyzed and dissolved in t h e filtrates and washings. Preliminary treatment with the object of removing the hemicelluloses is therefore superfluous. V-A considerable proportion of t h e furfural-yiel ding complex (probably oxycellulose) remains in t h e residue practically unaffected by any of the hydrolytic treatments employed. The rest of the furfuralyielding material (probably xylan) is readily hydrolyzed and dissolved during chlorination. VI--The significance of t h e term “cellulose” as applied t o wood products is discussed. A RAPID ACCURATE METHOD FOR THE ANALYSIS OF AN IRON ORE By Ernest Little and Willard L. Hult RUTGERSCOLLEGE, NEWBRUNSWICK, N. J. Received September 22, 1919
The relative merits of the dichromate and permanganate methods for the analysis of an iron ore are too well known t o warrant any lengthy discussion of
269
them here. It is advisable, however, t o recall those particular points which have a special bearing on this article. ARGUMEXTS
FOR
A N D AGAINST
PERMANGANATE
AS
A
STANDARD OXIDIZING AGENT
The permanganate method is generalty used to-day, due t o the fact t h a t permanganate acts as its own indicator and gives a n easily obtainable end-point. Many possible errors, however, must be guarded against. The instability of the reagent makes necessary quite frequent restandardization. The solution should be kept in colored bottles and out of the light as much as possible. The introduction of organic matter, even dust, causes a reduction t o manganese dioxide. Treadwell, after giving data showing t h a t , the permanency of potassium permanganate is greatly increased by heating the solution, or allowing i t to age for z wks., and then filtering through asbestos, concludes by saying,‘ “For very accurate work, however, i t is advisable to restandardize the solution frequently.” Another troublesome feature is the reducing action of the chloride ion on the permanganate ion, necessitating the use of the rather unsatisfactory preventive solution with its possibly useless components.2 Fuming sulfuric acid may, of course, be substituted, but this operation, even in the hands of an experienced analyst, is liable t o introduce a percentage of error which is almost prohibitive in quantitative work. DISCUSSION
OF T H E U S E O F POTASSIUM DICHROMATE
AS A STANDARD OXIDIZING AGENT
The dichromate solution, on the other hand, is a permanent standard, little affected by traces of organic matter. The dichromate ion is, moreover, not reduced by t h e chloride ion, thus making the use of preventive solution, or its unsatisfactory substitutes, unnecessary. The necessity of using ferricyanide as a n outside indicator with dichromate, however, causes most analysts t o prefer the permanganate titration. Speaking of the use of dichromate as a standard oxidizing agent, Foulk says:3 “A solution of potassium dichromate, through a strong oxidizing agent, is perfectly stable under ordinary laboratory conditions. I t is unaffected by light, is not acted upon rapidly by organic matter, and does not act on dilute hydrochloric acid. The salt (KzCrz07) is easily obtained pure, and, if recrystallized and dried, is one of the best standard substances t o be used in determining the exact strength of oxidizing and reducing solutions.” He adds further: “The chief objection t o be made t o standard solutions of potassium dichromate is the fact t h a t no convenient indicator has yet been found for it.” The writers realized, therefore, t h a t if the dichromate method could be used with an accurate indicator in t h e solution, i t would be by f a r the preferable method. Little and Fenner have shown in their “Modified Dichromate Method for the Analysis of G I y ~ e r i n , ” ~ 1
Treadwell and Hall, “Analytical Chemistry,” p. 561. C h e w SOC.,32 (1910), 539. “Quantitative Analysis,” p. 167. J . A m , Lealher Chem. Assoc., June 1917.
* Hough, J . Am. 3
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