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successfully in the determination of other radioactive substances in small quantity for scientific purposes; b u t since it is the object of the present paper t o deal only with t h e practical methods of measuring radium itself, they do not require consideration here. T H E GAMMA-RAY METHOD OB MEASURING RADIUM
Radium itself emits a-rays only, b u t both R a B and R a C emit y-rays which present t h e most convenient means of measuring radium in quantities above 0.1mg. and of not less t h a n 0.0j per cent purity. Since R a B and R a C are products resulting from t h e decay of radium emanation, a gas, it is necessary t o confine radium preparations in a closed vessel t o prevent t h e escape of gas before t h e measurement is made. The measurement may be carried out after t h e vessel has been closed for a month or more, in which case the y-radiation will have reached a constant maximum and no time correction will be necessary; t h e y-radiation then having become directly proportional t o the quantity of radium present, as is t h e case of all standard tubes of radium salt which have been sealed for more t h a n a month. If t h e measurement is made prior t o this period, a correction must be made for the unelapsed time. This correction is readily made by reference t o t h e Kolowrat table, just as described in P a r t 111 for the emanation method.
Fro.3
I n order t h a t the accumulation of emanation shall have taken place over a definite period of time, the starting point must be rendered exact by sealing t h e radium salt in a glass tube as soon after crystallization as possible. I t is first necessary, however, t o d r y t h e salt thoroughly by raising t h e temperature for 20 min. or more t o 2 5 0 ' C. or higher. Otherwise, decomposition by the a-rays of any water remaining, even in the form of water of crystallization, would generate a dangerous gas pressure in the limited volume of t h e tube. If t h e zero period is indefinite or not known, a series of measurements must be made a t different intervals, from which t h e final maximum value can be calculated by comparisons with t h e Kolowrat table. The measurement itself consists simply of a comparison of the rates of discharge produced b y a t u b e with known radium content and t h a t of t h e unknown, each being placed successively in t h e same fixed position a t a suitable distance from the discharge chamber. Almost any type of electroscope m a y be used b y placing a lead screen, one-eighth t o one1
LOC.c i t .
1701.
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fourth inch thick, between t h e instrument a n d t h e tube containing t h e radium. A type of y-ray electroscope is shown in Fig. 3. An accuracy of about I per cent can be readily attained with ordinary precautions by t h e use of t h e simple aluminum or gold-leaf electroscope. Radium salts are bought a n d sold in t h e United States almost entirely on the certificate of t h e Bureau of Standards. The measurements are made electroscopically by the y-ray method, using standards that. have been compared with t h e International standard in Paris. Every radium laboratory should have a t least one secondary standard t h a t has been certified: by t h e Bureau of Standards. Radium emanation, which is now quite largely used therapeutically instead of radium itself, may be measured by t h e y-ray method exactly as radium, and is expressed in equivalent units, one curie being the amount of emanation i n equilibrium with onegram of radium element. It is necessary only te allow t h e emanation t o remain in a closed vessel f o r 4 hrs. t o arrive a t maximum y-radiation before making t h e measurement. I n making this measurement, one additional correction is necessary. On account of t h e short life of radium emanation (3.8j days half period) R a C lags behind in decaying by 0.8 per cent; a n d since i t is R a C , not emanation, which furnishes the principal ?-rays, this correction must be deducted from t h e y-ray indication t o give t h e true quantity of emanation. If one wishes t o know simply the y-radiation and not the actual quantity of radium emanation, this correction is not necessary. The writer is indebted t o the Denver Fire Clay Company for Figs. z a n d 3 , a n d t o the Sachs-Lawlor Company of Denver for permission t o describe Mr. Elzi's arrangement shown in Fig. I . T h e electroscopes described are made b y t h e Sachs-Lawlor Company a n d distributed b y t h e Denver Fire Clay Company. THE DISTRIBUTION OF CERTAIN CHEMICAL CONSTANTS OF WOOD OVER ITS PROXIMATE CONSTITUENTS By W. H:Dore DIVISION O F AGRICULTURAL CHEMISTRY, UNIVERSITY O F CALIflORNIA AGRICULTURAL EXPERIMENT STATION, BBRKBLEY,CAL. INTRODUCTORY
I n a previous paper,' the author has proposed a scheme for separating wood into a number of proximate groups. I n addition to t h e groups designated, certain organic radicals (such as CH3.0 and CH2.CO) a r e known t o occur in woods. Any given species is characterized by definite contents of these radicals which have accordingly become quite generally recognized as constants for t h a t particular wood. They found no place in the proposed scheme for the reason that. t h e quantitative relations between these so-called constants and t h e proximate groups were not known a n d i t appeared likely t h a t their inclusion would produce a n overlapping of constituents. The purpose of 1
THZSJOURNAL, 11 (19191, 556.
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t h e present investigation has been t o learn t h e relations existing between t h e more important constants and proximate groups. Experiments have, therefore, been conducted t o ascertain t h e distribution of (I) furfuralyielding groups, ( 2 ) acetic-yielding groups, and (3) methoxy groups, over t h e two chief proximate groupscellulose a n d lignin. T h e three above-mentioned constants have been considerably investigated. T h e pioneer work of DeChalmotl on t h e furfural-yielding complex a n d of Benedikt and Bamberger2 on t h e methoxy groups has resulted in quantitative d a t a for t h e most important woods and fibrous products and considerable information as t o t h e relation of these d a t a t o t h e life history Qf t h e plant. Cross and Bevan3 have studied t h e production of acetic acid from t h e lignocelluloses b y various reactions of decomposition. Of these reactions, acid hydrolysis may probably be safely taken as a measure of t h e acetic-yielding groups preexistent in t h e woods, which according t o these authors are not acetyl groups, C H 3 C 0 , b u t acetic residue groups CH2.C0.4 Schorgers has recently reported values for all three of these constants for a number of American woods. T h e yields of acetic acid b y hydrolysis and methoxy groups b y t h e Zeisel method have a considerable industrial significance as measures, respectively, of t h e maximum commercial yields of acetic acid and wood alcohol obtainable b y destructive distillation. T h e fact t h a t t h e full yield of these substances is never realized industrially, due t o losses b y secondary reactions,6 detracts from the practical value of their determination. On t h e other h a n d , it affords a n incentive for t h e improvement of t h e manufacturing processes in t h e direction of a closer approach t o theoretical yields. T h e furfural yield is not a measure of valuable products in t h e wood, b u t its determination in finished products has been used t o give information as t o t h e source of raw materials used i n their manufacture. While precise information is lacking as t o t h e relation of these constants t o cellulose and lignin, certain opinions have found considerable support. The methoxy group is generally recognized as being closely connected with t h e lignin complex and t h e methoxy determination has been proposed as a measure of t h e lignin content.8 T h e furfural-yielding groups have been found t o be partly associated with t h e cellulose a n d partly with t h e lignin. W. E. Crossg has concluded from his experiments t h a t t h e groups yielding acetic acid b y hydrolysis are contained i n t h e lignin a n d absent from t h e cellulose portion of woods. T h e extent t o which a n y of these radicals remain attached t o either t h e cellulose or lignin, when lignocellulose is subjected t o reactions of decomposition, 1 2 8
4
6 6
7 8 0
A m Chem J , 16 (1894), 218, Cross and Bevan, “Cellulose,” p. 181. Monalsh , 11 (1890), 260, “Cellulose,” p 188. “Cellulose,” p 191 Cross and Bevan, “Researches THISJOURNAL, 9 (1917), 560. Palmer, I h z d , 7 (1915), 633; Tollens, J SOC Chem. I n d , 26 Renedikt and Bamberger, L o 6 Ber., 43, 1526.
on Cellulose,” 3, 103. Schorger, I h z d , 9 (1917), 556. (1907), 987, cz1
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must necessarily depend very much upon t h e n a t u r e a n d intensity of these reactions. T h e experiments herein described were conducted t o ascertain t h e distribution of t h e constants under certain specified conditions, namely, those of t h e analytical determinations of cellulose and lignin. T h e results may therefore be t a k e n t o indicate whether t h e constants are t o be regarded as groupings attached t o and subordinate t o these chief proximate groups, or as possessing an independent existence a n d themselves entitled t o rank a s proximate groups. EXPERIMENTAL
T h e experiments were confined t o redwood (Sequoia sempervirens). A quantity of sawdust was obtained b y making a number of cross-sectional cuts through a redwood slab. T h e mixture of coarse and fine sawdust was sifted through a so-mesh screen a n d t h e selected fine material used for t h e various determinations. T h e samples were analyzed in t h e air-dry condition with a moisture content of 11.62per cent. P R E P A R A T I O N OF E X T R A C T E D wooD-Portions of 2 g. were weighed into alundum thimbles and extracted in a Soxhlet apparatus for 6 hrs. with benzene, t h e n for a further 6 hrs. with g j per cent alcohol. T h e substance was t h e n transferred t o Gooch crucibles, containing as a filtering medium disks of mercerized cotton cloth, and washed with distilled water. Material so prepared is regarded as purified lignocellulose free from extractives. PREPARATION OF CELLULOSE-TWO grams of t h e wood, extracted as above, were subjected t o t h e altern a t e action of chlorine and hot 3 per cent sodium sulfite solution in accordance with t h e procedure of Sieber and Walter.1 T h e moistened material was placed in a Gooch crucible and t h e gas drawn through it b y suction for 4 periods of 2 0 , ~ j I,j , and I O min. After each chlorination t h e residue was treated with half saturated sulfurous acid, washed with hot water, digested in 3 per cent sodium sulfite solution for 45 min., filtered off, and washed thoroughly with hot water. After t h e final treatment t h e residue was dried for 16 hrs. a t 100‘ C. PREPARATION OF LIGNIN-TWO grams of t h e wood were extracted as before, partly dried a t 60’ C. a n d placed in a 7 j o cc. Erlenmeyer flask. 2 0 cc. of 7 2 per cent sulfuric acid were added and t h e flask rotated so as t o bring all parts of t h e sawdust i n contact with t h e acid. I t was then allowed t o s t a n d 3.5 hrs. Fifty cc. of cold water were added, followed b y j o o cc. of h o t water, t h e mixture filtered on a Gooch crucible containing a cloth filtering disk, washed and dried for 16 hrs. a t 100’ C. ANALYTICAL METHODS FOR D E T E R M I S I N G THE
CONSTANTS
GRouPs-These were determined by distillation of t h e material with 1 2 per c e n t hydrochloric acid (sp. gr. 1.06)and precipitation of t h e furfural in t h e distillate with phloroglucine, according t o t h e method described b y Schorger for pentosans.2 No correction was made for methyl furfural, t h e t o t a l precipitate being calculated t o furfural. FURFURAL-YIELDING
1 2
Pagzer-Fahr., 11, 1179, Chem. A b s , 8 (1914), 1202. THISJOURNAL, 9 (1917), 558.
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ACETIC-YIELDING GROUPS-The material was hydro- T h e U-tubes were placed i n a beaker of water arranged lyzed by hehting for 3 hrs. under a water-cooled reflux t o be heated by a Bunsen burner. F r o m t h e second condenser with IOO cc. of 2.j per cent sulfuric acid. U-tube, a delivery tube r a n t o t h e absorption a p p a r a t u s T h e mixture was quickly filtered into a 7 5 0 cc. flask t o which consisted of a n Erlenmeyer flask a n d a Fresenius avoid t h e introduction of carbon dioxide and washed nitrogen bulb. T h e general arrangement a n d dimenwith COz-free water t o a t o t a l volume of about zoo cc. sions of t h e apparatus are shown i n t h e accompanying T h e acetic acid i n t h e solution was then distilled off figure. T h e paraffin a n d water baths and t h e carbon and determined by means of t h e following apparatus: dioxide generator are omitted. T h e 750 cc. flask was placed in a paraffin b a t h a n d 7closed by a rubber stopper containing a glass stopcocked funnel t u b e a n d a delivery tube. T h e funnel t u b e served t o introduce COz-free water during t h e I distillation and was protected by a soda lime t u b e attached t o its open end b y means of a rubber stopper. I T h e delivery t u b e bent downward and terminated in a vertical condenser. This in t u r n was connected by a rubber stopper t o a suction filter flask which served as a receiver for t h e distillate. I s Suction was applied t o t h e receiver and t h e paraffin G b a t h raised t o a n d maintained a t 85’ C. Higher temperatures were avoided as tending t o t h e formation of formic acid from t h e hexose carbohydrates present. When most of t h e liquid h a d distilled over from t h e flask, I O O cc. of COa-free water were introduced and distilled over, after which t h e procedure was repeated I with a second I O O cc. T h e total distillate was t h e n removed and titrated with standard sodium hydroxide I solution using phenolphthalein as indicator. The results, representing “total volatile acids,” were I expressed as acetic acid. I -I-, T o obtain t h e actual acetic acid i t was necessary t o correct for t h e formic acid invariably present. A few cc. of silver nitrate solution were added t o t h e solution after titration a n d t h e mixture left upon t h e s t e a m b a t h for several hours. T h e silver formate was thereby decomposed, yielding a n amount of metallic silver corresponding t o t h e formic acid present. T h e precipitated silver was filtered off, washed, dissolved i n dilute nitric acid, precipitated as silver chloride, filtered off, washed, ignited, a n d weighed. F r o m t h e weight of silver chloride so obtained t h e amount of I n t h e first a n d second absorption flasks were placed acetic acid equivalent t o t h e formic acid was calculated b y multiplying by t h e conversion factor 0.4. This 35 a n d 1 5 cc., respectively, of freshly filtered alcoholic result, deducted from t h e total acidity as found above, silver n i t r a t e solution. ( T h e solution was prepared b y dissolving I O g. of solid silver nitrate in 2 5 cc. of water gave t h e actual acetic acid present. M E T H O X Y GRoups-Methoxy groups were deter- a n d adding 2 2 5 cc. of 95 per cent alcohol.) 0.3 g. of mined by t h e Zeisel meth0d.l T h e apparatus a n d material was placed i n t h e decomposition flask a n d procedure here described have been found t o give 1 5 cc. of hydriodic acid (1.70sp. gr.) were added. T h e mixture was heated t o 130’ C. on a paraffin b a t h a n d consistent results. T h e decomposition flask was a small distillation t h e temperature maintained at 130’to 140’ C., while a flask (of about 130 cc. capacity) having its side t u b e slow stream of carbon dioxide was passed through t h e T h e beaker of water surrounding t h e connected with a carbon dioxide generator. I n t h e apparatus mouth of t h e flask was placed a perforated cork carry- U-tubes was kept at a temperature of 50’ t o 60’ C. ing a delivery tube. This delivery t u b e r a n vertically throughout t h e process. T h e operation was continued for jo cm. and so acted t o some extent as a reflux con- until t h e precipitated silver iodide i n t h e absorption denser a n d fractionating column. I t then made two apparatus settled o u t , leaving a clear supernatant right-angled bends and, descending, was connected a t liquid, indicating t h e completion of t h e reaction. T h e apparatus was t h e n disconnected a n d t h e conits lower extremity with two U-tubes in series. T h e first of these contained distilled water and a few milli- t e n t s of t h e absorption flasks rinsed into a 600 CC. grams of phosphorus, t h e second distilled water only. beaker. Water sufficient t o make about joo CC. was added a n d t h e whole evaporated on t h e steam b a t h 1 Monatsh., 6 (1885), 989; Meyer-Tingle, “Determination of Radicals t o a volume of 1 5 0 t o zoo cc. in order t o expel t h e in Carbon Compounds,” John Wiley & Sons, Inc., p. 38.
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alcohol. A few drops of nitric acid were added, t h e solution again diluted t o about 5 0 0 cc. and allowed t o stand on t h e steam b a t h for about one-half hour for t h e silver iodide t o settle. T h e precipitate was then collected. i n a t a r e d asbestos Gooch crucible, washed, dr'ied at 130' C. for 2 hrs., and weighed. CH3.0 was calculated from t h e weight of silver iodide by multiplying b y t h e factor 0 . 1 3 2 . By t h e above methods t h e furfural yield, acetic yield on hydrolysis, and methoxy yield were determined upon t h e raw wood, extracted wood, cellulose, and lignin. T h e results are shown i n t h e table. DISTRIBUTION OF GROUPINGS IN REDWOOD Expressed in Percentages of Air-Dried Wood (1 1.62 Per cent Moisture) Total Volatile Formic Actual Acids by Acid Acetic Furfural Hydfoly- Expressed Acid by Methoxy Yield sis as Acetic Difference Group R a w Wood... . . . . . . . 5.73 0.94 0.16 0.78 5.46 5.95
1.03
0.16
5.65
0.75 1.03
0.09 0.06
2.69
0.75 0.66
0.21 0.10
0.23
0.09 0.09
hVERAGE.. .... 5.84 Extracted Wood. . . . . 5 . 7 7
.....
AVERAGE. 5.7 1 Cellulose.. .......... 2 . 3 6 AVERAGE., .... 2.52 Lignin.. . . . . . . . . . . . . 0 . 2 4 AVERAGE.. . . . . 0.24
0.87 0.83 0.66 0.97 0.82 0.54 0.56 0.55 0.09 0.09 0.09
5.74 5.60 5.33 5.35 5.34 0.35
0:3i 5.49 5.78 5.63
Determinations were also made of t h e furfural yield of the filtrates and washings from t h e cellulose determination. T h e combined solutions from four determinations or 8 g. of wood were evaporated t o somewhat less t h a n 5 0 0 cc., placed in a j o o CC. volumetric flask, and diluted t o t h e mark. 1.2 j cc. aliquots corresponding t o 2 g. of original wood were placed i n t h e distilling flasks a n d mixed with 3 0 cc. of concentrated hydrochloric acid. T h e determination was t h e n carried out as usual. Three determinations gave 2 . 3 0 , 2 . 0 8 , and 2 . 0 8 per cent of furfural in t h e chlorination liquors, t h e results being referred t o t h e weight of air-dried wood. Determinations of t h e methoxy group were made upon portions of lignin t h a t had been hydrolyzed by boiling with 2 . 5 per cent sulfuric acid for 3 hrs. after being separated b y t h e usual treatment with 7 2 per cent sulfuric acid. T h e methoxy content based on t h e original wood was 4 . 0 8 and 3 . 8 8 per cent. There is accordingly a n average loss of 1.65 per cent of methoxy during t h e hydrolysis. Separate experiments have shown t h a t t h e weight of lignin after t h e treatment is about 2 per cent less t h a n when prepared in t h e usual manner. From t h e above results i t is evident t h a t t h e loss in weight of lignin is due chiefly t o t h e splitting off of t h e methoxy group. DISCUSSION
T h e foregoing results indicate t h a t none of t h e three radicals investigated is t o be regarded as existing entirely independent of t h e proximate constituents cellulose and lignin. Apparently they are so related t o these substances t h a t , when lignocellulose is attacked b y hydrolytic reactions, they tend t o remain a t least partially joined t o t h e cellulose or t h e lignin or t o both. No method is known whereby lignocellulose may be separated so as t o yield both cellulose and lignin unchanged, b u t in every case one of t h e m is obtained as a residue while t h e other is converted into alteration products a n d removed. It is therefore unsafe t o draw
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t h e conclusion t h a t radicals found with either cellulose or lignin, or both, exist similarly associated with t h e m in t h e original lignocellulose complex. The radical is rather t o be regarded as occupying a n intermediate position between these chief proximate constituents, and remaining with t h e residue according t o t h e extent t h a t i t resists t h e treatment employed. T h e same portion t h a t remains with t h e cellulose under t h e conditions of one t y p e of decomposition may remain with t h e lignin under another set of conditions. A comparison of t h e d a t a for raw and extracted wood shows t h a t none of t h e three constants examined is materially affected b y treatment with non-hydrolyzing solvents. About half of t h e furfural-yielding complex remains in t h e cellulose residue. Most of t h e remaining portion is found in t h e chlorination liquors. As was pointed out in a previous paper1 this last portion is probably due t o xylan or other true pentosan existing as such in t h e wood, while t h e non-hydrolyzable furfuralyielding material contained in t h e cellulose is probably oxycellulose. T h e amount of furfural-yielding material remaining with t h e lignin is almost negligible. T h e amount of acetic acid present in redwood is small and its determination is rendered uncertain by t h e presence of formic acid either preexisting or produced b y t h e action of t h e hydrolyzing acid upon hexoses. N o general conclusions can therefore be drawn in regard t o its distribution but it appears t o be associated chiefly with t h e cellulose constituent. With t h e lignin there is very little. T h e combined amount found with t h e lignin and cellulose is slightly less t h a n t h e total amount i n t h e wood, indicating t h a t p a r t of t h e acetic-yielding groups separates independently. I n view of t h e small quantities involved t h e results are not conclusive. I n t h e case of redwood, and probably also i n t h e case of other coniferous woods, which yield only small amounts of acetic acid on hydrolysis, i t would appear t h a t acetic acid should not be considered as a n independent proximate group b u t as a radical already largely accounted for in t h e cellulose a n d lignin residues. This conclusion probably does not apply t o hardwoods, where t h e acetic yield is much higher. T h e methoxy groups are found quantitatively in t h e lignin constituent, directly confirming t h e frequent assertion t h a t methoxy is a purely lignin characteristic. This occurs only when lignin is separated b y t h e method described and subsequent hydrolysis avoided. If this is not done there is considerable splitting off of t h e methoxy groups. These facts have an important bearing upon t h e proximate analysis of wood. A summative analysis of a wood may be made b y drying, extracting with benzene and alcohol, and determining t h e cellulose a n d lignin i n t h e manner previously described. I t appears from t h e foregoing results t h a t , when this is done, t h e cellulose and lignin constituents account for all of t h e methoxy group, nearly all of t h e acetic-yielding groups, a n d about half of t h e furfural-yielding groups. Except for t h e furfural due t o hydrolyzable pentosans found 1
Dore, THIS JOURNAL, 12 (1920). 264.
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in t h e chlorination washings, these constants are not t o be regarded as proximate constituents but rather as radicals connected with t h e constituents cellulose and lignin. With t h e exception noted, these constants may be ignored in t h e summative analysis of coniferous woods. SUMMARY
I-A study is made of t h e distribution of t h e groups contained i n redwood which yield furfural, acetic acid, and methoxy, with t h e object of learning their relation t o t h e constituents cellulose and lignin. 11-About half of t h e furfural-yielding groups are associated with t h e cellulose, b u t only a small amount with t h e lignin. T h e portion present as true pentosan is hydrolyzed and removed during chlorination. 111-The acetic-yielding groups are partly associated with t h e cellulose, much less so with t h e lignin. A small amount appears t o be detached from either. T h e results are not conclusive in view of t h e small amount present i n redwood a n d t h e analytical difficulties. I n t h e case of coniferous woods acetic acid probably need not be considered as a proximate group. IV-The methoxy groups are wholly associated with t h e lignin. They may be partially split off from it b y acid hydrolysis. V-In t h e summative analysis of coniferous woods, all of t h e acetic-yielding and methoxy groups a n d part of t h e furfural-yielding groups may be disregarded as already accounted for in t h e cellulose and lignin. T h e furfural-yielding substances contained in t h e chlorination washings and representing hydrolyzed pentosans should be estimated. THE PROXIMATE ANALYSIS OF CONIFEROUS WOODS By W. H. Dore DIVISIONOB AGRICULTURALCHEMISTRY, U N I V E R S I T Y OF CALIFORNIA AGRICULTURAL EXPERIMENT STATION, BERKELEY,CAL Received November 18, 1919 INTRODUCTORY
A method has been recently proposed b y t h e author for t h e summative proximate analysis of woods.l.* Later investigations have shown t h e advisability of certain modifications of t h e original scheme which are considered in detail in this paper. T h e proposed system for t h e analysis of wood effected a separation of t h e wood substance into t h e fol!owing fractions: loss on drying, benzene extract, alcohol extract, water-soluble, soluble in one per cent sodium hydroxide, cellulose, and lignin. Full information as t o t h e composition of these fractions was lacking, b u t it was believed t h a t t h e wood constituents were separated into logical groups based upon chemical similarity and economic value. T h e scheme was found t o account for nearly all of t h e material of coniferous woods i n t h a t t h e sum of all constituents varied from 96 t o 97 per cent for the three conifers examined. With t h e hardwoods t h e method was unsuccessful, as I O t o 1 7 per cent of t h e constituents remained unaccounted for. T h e available d a t a seem t o indicate t h a t t h e chemistry of t h e hardwoods is an entirely separate problem. The woods of t h e broad-leaved trees have accordingly been omitted
* Numbers refer to Reference, page 479.
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from consideration in this investigation and t h e conclusions are applicable t o t h e conifers only. DEFECTS I N P R O P O S E D SCHEME ( I ) ITS F A I L U R E TO G I V E C O R R E C T R E S U L T S F O R C E L L U -
was noted in t h e original p a e e r l t h a t when digestion in one per cent sodium hydroxide was used less cellulose and lignin were obtained t h a n when this treatment was omitted. I n a subsequent paper2 it was shown t h a t t h e diminished yield of cellulose was due t o partial destruction of true cellulose instead of to greater purity of t h e product. Accordingly t h e results for cellulose are incorrect. No direct d a t a are available for lignin, b u t i t has been shown in t h e preceding paper t h a t lignin readily loses a portion of its methoxy groups when it undergoes acid hydrolysis. Possibly t h e s a m e effect is produced b y alkalies. ( 2 ) T H E V A G U E S I G N I F I C A N C E O F T H E WATER-SOLUBLE A N D ALKALI-SOLUBLE FRACTIONS-In t h e absence Of detailed studies of t h e substances contained in these portions, it was believed t h a t t h e y consisted of substances corresponding approximately t o Konig’s “proto” a n d “hemi” forms of cellulose and lignins3 It is apparent from subsequent studies,2 however, t h a t they contain also degradation or hydrolytic products of t r u e cellulose and true lignin. T h e numerical expression of these fractions has therefore no value as a n analytical statement of wood constituents. L O S E A N D LrGNIN-It
(3)
THE F A I L U R E T O EXPRESS THE HEMICELLULOSES-
Schorger’s studies of mannan4 and galactan6 have shown t h a t these carbohydrates a r e Eound in all conifers, sometimes in considerable quantity. Xylan is well known as a constituent of woods. It is therefore evident t h a t a complete analysis of a wood should t a k e these hemicelluloses into consideration. I n t h e proposed scheme t h e water- and alkali-soluble portions only partially accounted for these bodies together with other substances. (4) O R G A N I C RADICALS-The original scheme took no account of organic radicals present-the so-called “wood constants.” T h e preceding paper has shown t h a t , with t h e exception of t h e furfural-yielding substapces soluble in t h e chlorination washings, these radicals may be disregarded as proximate constituents of coniferous woods.6 T h e original scheme is defective, however, in t h a t i t ignores this soluble furfural-yielding substance. T h e remedies for t h e above defects are quite evident. T h e cellulose and lignin determinations should b e made reliable b y omission of t h e alkaline hydrolysis. T h e water- and alkali-soluble fractions would disappear, leaving the hemicelluloses entirely unaccounted for. It would then be necessary t o give t h e hemicelluloses a separate place in t h e scheme, and methods would be required for their estimation either collectively or individually. T h e soluble furfural-yielding substance (probably t h e pentosan, xylan) would be included in t h e hemicelluloses. T h e present investigation is an a t t e m p t t o revise t h e original scheme in accordance with t h e above suggestions. Methods have been applied for t h e determination of t h e hemicelluloses. The revised procedure has then been checked by making these and
