This reaction is produced by lævulose, sorbose, cane sugar, and inulin, an intense colour being given within an hour or two. Dextrose, maltose, milk sugar, galactose, and the polyhydric alcohols give, if anything, only insignificant colours, and these only after long standing. The authors therefore suggested that the reaction might be employed as a means ofdistinguishing these classes of carbohydrates, the rapid production of the purple colour being indicative ofketohexoses, or of substances which produce these by hydrolysis.
By relying only on the production of the purple colour, however, a mistake might possibly arise, owing to the fact thatxylosegives a somewhat similar colour after standing for a few hours. Hence, the observations should be confirmed by isolation of the crystals of brommethylfurfural. No trace of this substance is obtained from the xylose product.
In order to identify the substance, the ether extract, after neutralisation, is allowed to evaporate to a syrup, and crystallisation promoted either by rubbing with a glass rod, or by the more certain and highly characteristic method of 'sowing' with the most minute trace of ω-brommethylfurfural, when crystals are almost instantly formed. These are recrystallised from ether, or a mixture of ether and light petroleum, and further identified by the melting-point (59.5-60.5°), and, if considered desirable, by estimation of the bromine.
It is now found, so reactive is the bromine atom in this compound, that the estimation may be accurately made by titration with silver nitrate according to Volhard's process, the crystals for this purpose being dissolved in dilute alcohol:
0.1970 gram required 10.5 c.c.N/10 AgNO3. Br = 42.63 p.ct., calculated 42.32 p.ct.
This method of applying hydrogen bromide in ethereal solution is, of course, unsuitable for investigations where a higher temperature has to be employed, or where long standing is necessary, since, under such circumstances, the ether itself is attacked. Wishing to make investigations under these conditions, the authors have tried several solvents, and, at present, find that chloroform is best suited to the purpose. In each of the following experiments, 10 grms. of thesubstance were covered with 250 c.c. of chloroform which had been saturated at 0° with dry hydrogen bromide. The mixture was contained in an accurately stoppered bottle, firmly secured with an iron clamp, and heated in a water-bath to about the boiling temperature for two hours. After standing for several hours, the mixture was treated with sodium carbonate (first anhydrous solid, and afterwards a few drops of strong solution), filtered, and the solution dried over calcium chloride. Most of the chloroform was then distilled off, and the remaining solution allowed to evaporate to a thick syrup in a weighed dish.
The product was then tested for ω-brommethylfurfural by 'sowing' with the most minute trace of the substance, as described above. It was then warmed on a water-oven, kept in a vacuum desiccator over solid paraffin, and the weight estimated. When necessary, the product was recrystallised from ether, and further identified by the tests mentioned. The following results were obtained:
Weight of crude residue.Swedish filter paper3.0crystallised at onceby 'sowing.'Ordinary cotton3.3""Mercerised cotton2.1""Straw cellulose[6]2.3""Lævulose2.2""Inulin1.3""Potato starch0.37""Cane sugar0.85""Dextrose0.33uncrystallisable.Milk sugar0.37"Glycogen0.34"Galactose0.34"
The products fromdextrose,milk sugar, andgalactoseabsolutely refused to crystallise even when extracted with ether and again evaporated, or by 'sowing,' stirring, &c.
Theglycogenproduct deposited a very small amount of crystalline matter on standing, but the quantity was too minute for examination; moreover, it refused altogether to crystallise in contact with the aldehyde. It may fairly be stated, therefore, that these last four substances give absolutely negative results as regards the formation of ω-brommethylfurfural; if any is formed, its quantity is altogether too small to be detected.
The specimen ofstarchexamined was freshly prepared from potato, and purified by digestion for twenty-four hours each withN/10 KOH,N/4 HCl, and strong alcohol; it was then washed with water and allowed to dry in the air. It will be seen that this substance gave a positive result, but that the yield was extremely small, and might yet be due to impurity. Considering the importance of the behaviour of starch, for the purpose of drawing general conclusions from these observations, it was thought advisable to make further experiments with specimens which could be relied upon, and also to investigate the behaviour of dextrin. This the authors have been enabled to do upon a series of specimens specially prepared by C. O'Sullivan, and thus described by him:
1. Rice starch, specially purified by the permanganate method.2. Wheat starch " " "3. Oat starch, contains traces of oil, washed with dilute KOH and dilute HCl.4. Pea starch, first crop, washed with alkali, acid (HCl), and strong alcohol.5. Natural dextrin, D = 3.87, αD= 194.7; K = 0.95, (c2.628).6. α-Dextrin, C equation purified without fermentation, 30 precipitations with alcohol (Trans., 1879, 35, 772).
1. Rice starch, specially purified by the permanganate method.
2. Wheat starch " " "
3. Oat starch, contains traces of oil, washed with dilute KOH and dilute HCl.
4. Pea starch, first crop, washed with alkali, acid (HCl), and strong alcohol.
5. Natural dextrin, D = 3.87, αD= 194.7; K = 0.95, (c2.628).
6. α-Dextrin, C equation purified without fermentation, 30 precipitations with alcohol (Trans., 1879, 35, 772).
The examination of these specimens was conducted on a smaller scale, but under the same conditions as before,one gramof the substance being treated with 12.5 c.c. of the saturated chloroform solution and heated in sealed tubes for two hours as above. The results were as follows:
Weight of crude residue.1. Rice starch0.046crystallised at onceby 'sowing.'2. Wheat starch0.044""3. Oat starch0.049""4. Pea starch0.064""5. Natural dextrin0.088""6. α-Dextrin0.055""
The results may therefore be summarised as follows:—Treated under these particular conditions all forms of cellulose give large yields of ω-brommethylfurfural, some varieties giving as much as 33 per cent. Lævulose, inulin, and cane sugar give yields varying from 22 to 8.5 per cent.; various starches give small yields (average about 4.5 per cent.); and dextrins 5 to 8 per cent., whereas dextrose, milk sugar, and galactose give, apparently, none at all.
The yields represent the solid crystalline residue; this when purified by recrystallisation gives, probably, about three-quarters of its weight of pure crystals. (In the case of dextrose, &c., the yields represent the weight of syrup.)
These numbers, however, by no means represent the maximum yields obtainable, owing to the comparatively slight solubility of hydrogen bromide in chloroform. The process was conducted in the above manner only for the sake of uniform comparison. The ether method previously described gives much larger yields; for example, 12 grms. of inulin treated with only 60 c.c. of the saturated ether gave 2.5 grms.of substance. For the purpose of obtaining larger yields, other methods are being investigated.
The facts recorded above, taken in conjunction with those given in our previous communications, appear to point definitely to the following general conclusions. First, that the various forms ofcellulosecontain one or more groups or nuclei identical with that contained inlævulose, and that such groups constitute the main or essential part of the molecule. Secondly, that similar groupings are contained instarchesanddextrins, but that the proportion of such groupings represents a relatively small part of the whole structure.
The nature of this grouping is, according to the generally accepted constitution oflævulose, the six-carbon chain with a ketonic group:
But the results might, on the other hand, be considered indicative of the anhydride or 'lacton' grouping, which Tollens suggested for lævulose:
The latter very simply represents the formation of ω-brommethylfurfural from lævulose,[7]
giving
although by a little further 'manipulation' of the symbols the change could, of course, be represented by reference to the ketonic formula.
In this paper the authors discuss more fully the theoretical bearings of the observations of Fenton and Gostling, the two papers being simultaneously communicated. The paper is mainly devoted to a review of the antecedent evidence, chemical and physiological, and to a general summing up in favour of the view that cellulose is a polyketose (anhydride).
(p. 79)Composition of the Seed Hair of Eriodendron(Anf.)—Some interest attaches to the results of an analytical investigation which we have made of this silky floss. There is little doubt that cotton is entirely exceptional in its characteristics: both in structure and chemical composition it fails to show any adaptation to what we may regard as themore obviousfunctions of a seed hair—which certainly do not demand either structural strength or chemical resistance. The following numbers determined for the kapok differentiate it widely from the cottons:
Ash, 1.3; moisture, 9.3; alkaline hydrolysis (loss) (a) 16.7, (b) 21.8. Cellulose, by chlorination, &c., 71.1.
Ash, 1.3; moisture, 9.3; alkaline hydrolysis (loss) (a) 16.7, (b) 21.8. Cellulose, by chlorination, &c., 71.1.
In reacting with chloride it shows the presence of unsaturated groups, similar to the lignone of the woods. This wasconfirmed by a well-marked reaction with ferric ferricyanide with increase of weight due to the fixation of the blue cyanide.
But the most characteristic feature is the high yield of furfural on boiling with condensing acids. The following numbers were determined:
Total furfural from original fibre14.84In residue from alkali hydrolysis11.5In cellulose isolated by Cl method10.4
Treated with sulphuric acids of concentration, (a) 92.1 grs. H2SO4per 100 c.c., (b) 105.8 grs. per 100 c.c., the fibres dissolve, and diluted immediately after complete solution it was resolved into
(a)(b)Reprecipitated fraction68.743.7Soluble fraction yielding furfural13.214.3
By these observations it is established that the furfuroids are of the cellulose type and behave very much as the furfuroids of the cereal celluloses.
This group of seed hairs invites exhaustive investigation. The furfuroid constituents are easily isolated, and as they constitute at least one-third of the fibre substance it is especially from this point of view that they invite study.
(a) A typical oxycellulose prepared from cotton cellulose by the action of HClO3(HCl + KClO3) in dilute solution at 100° for one hour gave the following numbers:
CHOElementary composition43.556.0350.42OxycelluloseOriginal celluloseAnalysis by Lange's methodSoluble in KOH (at 180°)87.612.0Insoluble in KOH (at 180°)12.488.0OxycelluloseOriginal celluloseHeat of combustion4124-41334190-4224Heat evolved in contact with 50 times wt. normal KOH per 100 grms.1.3 cal.0.74 cal.OxycelluloseCelluloseAbsorption of colouring matters at 100° per 100 grms.Saffranine0.70.0Methylene blue0.60.2
(b)Yield of furfural from cellulose, oxy- and hydro-cellulose.—From the hydrocelluloses variously prepared the author obtains 0.8 p.ct. furfural; from bleached cotton 1.8 p.ct.; and from the oxycelluloses variously prepared 2.0-3.5 p.ct. The 'furfuroid' is relatively more soluble in alkaline solutions (KOH) in the cold. The insoluble residue is a normal cellulose.
(c)Nitrates of cellulose, oxy- and hydro-cellulose.—Treated with the usual acid mixture (H2SO43 p., HNO31 p.) under conditions for maximum action, the resulting esters showed uniformly a fixation of11.0 NO2groups per unit mol. of C24. The oxycellulose nitrate was treated directly with dilute solution of potassium hydrate in the cold. From the products of decomposition the author obtained the osazone of hydroxypyruvic acid [Will, Ber. 24, 400].
(d)Osazones of the oxycelluloses.—Oxycelluloses prepared by various methods are found to fix varying proportions of phenylhydrazine (residue), viz. from 3.4-8.5 p.ct. of the cellulose derivative reacting, corresponding with, i.e. calculated from, the nitrogen determined in the products (0.87-2.2 p.ct.). The reaction is assumed to be that of osazone formation.
The author has also established a relation between the phenylhydrazine fixed and the furfural which the substance yields on boiling with condensing acids. This is illustrated by the subjoined series of numbers:
Fixed p.ct.formed p.ct.Cotton (bleached)1.731.60Oxycellulose(HClO3)7.942.09"(HClO)3.371.79"(CrO3) (1)7.033.00"(CrO3) (2)7.713.09"(CrO3) (3)8.483.50
(e)Constitution of cellulose and oxycellulose.—The results of these investigations are generalised as regards cellulose (C_6) by the constitutional formula
The oxycelluloses contain the characteristic group
in union with varying proportions of residual cellulose.
To separate the hemicelluloses, celluloses, and the constituents of lignin without essential change, the substance, after being freed from fat, is extracted with dilute hydrochloric acid and ammonia, and the residue frequently agitated for a day or two with 5-6 p.ct. caustic soda solution. It is then diluted, the extract poured off, neutralised with hydrochloric acid, treated with sufficient alcohol, and the hemicellulose filtered, dried, and weighed. The residue from the soda extract is washed on a filter with hot water, and extracted with Schweizer's reagent.
When the final residue (lignin) is subjected to prolonged extraction with boiling dilute ammonia (a suitable apparatus is described, with sketch) until the ammonia is no longer coloured, a residue is obtained which mostly dissolves in Schweizer's reagent, and on repeating the process the residue is found to consist largely of mineral matter. The dissolved cellulose-like substances often contain considerable amounts of pentosanes.
According to the nature of the substance, the extraction with ammonia may take weeks, or months, or even longer; the ammonia extracts of hard woods (as lignum vitæ) and of cork are dark brown, and give an odour of vanilla when evaporated down. The residues, which are insoluble in water, but redissolve in ammonia, have the properties of humic acids. Other vegetable substances, when extracted, yielded, besides humic acids, a compound, C6H7O2, soluble in alcohol and chloroform, but insoluble in water, ether, and benzene; preparations from different sources melted between 200° and 210°.
FOOTNOTES:[4]The original paper is reproduced with slight alterations.[5]This purple colour would appear to be due to a highly dissociable compound of ω-brommethylfurfural with hydrogen bromide. The aldehyde gives yellow or colourless solutions in various solvents, which are turned purple by a sufficient excess of hydrogen bromide. Dilution, or addition of water, at once discharges the colour.[6]Other forms of cellulose were also examined—for example, pinewood cellulose—and the substances separated from solution as thiocarbonate (powder and film). All of these gave good yields of ω-brommethylfurfural.[7]The change is empirically represented asC6H12O6+ HBr - 4H2O = C6H5O2Br.
[4]The original paper is reproduced with slight alterations.
[4]The original paper is reproduced with slight alterations.
[5]This purple colour would appear to be due to a highly dissociable compound of ω-brommethylfurfural with hydrogen bromide. The aldehyde gives yellow or colourless solutions in various solvents, which are turned purple by a sufficient excess of hydrogen bromide. Dilution, or addition of water, at once discharges the colour.
[5]This purple colour would appear to be due to a highly dissociable compound of ω-brommethylfurfural with hydrogen bromide. The aldehyde gives yellow or colourless solutions in various solvents, which are turned purple by a sufficient excess of hydrogen bromide. Dilution, or addition of water, at once discharges the colour.
[6]Other forms of cellulose were also examined—for example, pinewood cellulose—and the substances separated from solution as thiocarbonate (powder and film). All of these gave good yields of ω-brommethylfurfural.
[6]Other forms of cellulose were also examined—for example, pinewood cellulose—and the substances separated from solution as thiocarbonate (powder and film). All of these gave good yields of ω-brommethylfurfural.
[7]The change is empirically represented asC6H12O6+ HBr - 4H2O = C6H5O2Br.
[7]The change is empirically represented asC6H12O6+ HBr - 4H2O = C6H5O2Br.
In a preliminary discussion the author critically compares the results of various of the methods in practice for the isolation and estimation of cellulose. The method of F. Schulze [digestion with dil. HNO3with KClO3—14 days, and afterwards treating the product with ammonia, &c.] is stated to be the 'best known' (presumably the most widely practised); W. Hoffmeister's modification of the above, in which the nitric acid is replaced by hydrochloric acid (10 p.ct. HCl) is next noted as reducing the time of digestion from 14 days to 1-2 days, and giving in many cases higher yields of cellulose. The methods of treating with the halogens, viz. bromine water (H. Müller), chlorine gas (Cross and Bevan), and chlorine water, are dismissed with a bare mention, apparently on the basis of the conclusions of Suringar and Tollens (q.v.). The method of Lange, the basis of which is a 'fusion' with alkaline hydrates at 180°, and the modified method of Gabriel, in which the 'fusion' with alkali takes place in presence of glycerin, are favourably mentioned.
These methods were applied to a range of widely different raw materials to determine, by critical examination of the products, both as regards yield and composition, what title these latter have to be regarded as 'pure cellulose.'
This portion of the investigation is an extension of that of Suringar and Tollens, these latter confining themselves tocelluloses of the 'normal' groups, i.e. textile and paper-making celluloses. The present communication is a study of the tissue and cell-wall constituents of the following types:—
1. Green plants of false oat grass (Arrhenatherium, E.).2. Green plants of lucerne (Medicago sativa).3. Leaves of the ash (Fraxinus).4. Leaves of the walnut (Juglans).5. Roots of the purple melic grass (Molinia cærulea).6. Roots of dandelion (Taraxacum officinale).7. Roots of comfrey.8. Coffee berries.9. Wheat bran.
These raw materials were treated for the quantitative estimation of cellulose by the method of Lange (b), Hoffmeister (c), and Schulze (d), and the numbers obtained are referred for comparison to the corresponding yields of 'crude fibre' (Rohfaser) by the standard method (a).
As a first result the author dismisses Lange's method as hopeless: the results in successive determinations on the same materials showing variations up to 60 p.ct. The results bycanddare satisfactorily concordant: the yields of cellulose are higher than of 'crude fibre.' This is obviously due to the conservation of 'hemicellulose' products, which are hydrolysed and dissolved in the treatments for 'crude fibre' estimation. A modified method was next investigated, in which the process of digestion with acid chloroxy- compounds (candd) was preceded by a treatment with boiling dilute acid. The yields of cellulose by this method (e) are more uniform, and show less divergence from the numbers for 'crude fibre.'
The author's numerical results are given in a series of tables which include determinations of proteids and ash constituents, and the corresponding deductions from the crudeweight in calculating to 'pure cellulose.' The subjoined extract will illustrate these main lines of investigation.
Raw MaterialCrude FibrePure CelluloseWeende Method.(a)Hoffmeister Method.(c)Hoffmeister, modified by Author.(e)Oat grass30.3534.931.5Lucerne25.2528.720.5Leaves of ash13.0515.413.8Roots of melic21.6029.121.4Coffee beans18.3035.123.3Bran8.219.39.3
The final conclusion drawn from these results is that the method of Hoffmeister yields a product containing variable proportions of hemicelluloses. These are eliminated by boiling with a dilute acid (1.25 p.ct. H2SO4), which treatment may be carried out on the raw material—i.e.before exposure to the acid chlorate, or on the crude cellulose as ordinarily isolated.
Determination of Tissue-constituents.—By the regulated action of certain solvents applied in succession, it appears that such constituents of the plant-complex can be removed as have no organic connection with the cellular skeleton: the residue from such treatments, conversely, fairly represents the true tissue-constituents. The author employs the method of digestion with cold dilute alkaline solutions (0.15 to 0.5 p.ct. NaOH), followed by exhaustive washing with cold and hot water, afterwards with cold and hot alcohol, and finally with ether.
The residue is dried and weighed as crude product. When necessary, the proportions of ash and proteid constituents are determined and deducted from the 'crudeproduct' which, thus corrected, may be taken as representing the 'carbohydrate' tissue constituents.
Determination of Hemicelluloses.—By the process of boiling with dilute acids (1.25 p.ct. H2SO4) the hemicelluloses are attacked—i.e. hydrolysed and dissolved. The action of the acid though selective is, of course, not exclusively confined to these colloidal carbohydrates. The proteid and mineral constituents are attacked more or less, and the celluloses themselves are not entirely resistant to the action. The loss due to the latter may be neglected, but in calculating the hemicellulose constants from the gross loss the proteids and mineral constituents require to be taken into account in the usual way.
(p. 88) The separation of the cellulose-like carbohydrates of sunflower husks is described.
In order to ascertain the effect of dilute ammonia on the cellulose substances of lignin, a dried 5 p.ct. caustic soda extract was extracted successively with 1, 2, 3, and 4 p.ct. sodium hydroxide solution. Five grams of the 2 p.ct. extract were then subjected to the action of ammonia vapour; the cellulose did not completely dissolve in six weeks. Cellulose insoluble in caustic soda (32 grms.) was next extracted with ammonia, in a similar manner, for 10 days, dried, and weighed. 30.46 grms. remained, which, when treated with 5 p.ct. aqueous caustic soda, yielded 0.96 grm. (3 per cent.) of hemicellulose.
When cellulose is dissolved in Schweizer's solution, theresidue is, by repeated extraction with aqueous sodium hydroxide, completely converted into the soluble form. On evaporating the ammonia from the Schweizer's extract, at the ordinary temperature and on a water-bath respectively, different amounts of cellulose are obtained; more hemicellulose is obtained, by caustic soda, from the heated solution than from that which was not heated. In this operation the pentosanes are more influenced than the hexosanes; pentosanes are not always readily dissolved by caustic soda, and hexosanes are frequently more or less readily dissolved. Both occur in lignin, and are then undoubtedly indigestible. These points have to be considered in judging the digestibility of these carbohydrates.
A comparison of analyses of clover, at different periods, in the first and second years of growth, shows that both cellulose (Schweizer's extract) and lignin increase in both constituents. In the second year the lignin alone increased to the end; the cellulose decreased at the end of June. In the first year it seemed an absolutely as well as relatively greater amount of cellulose, and lignin was produced in the second year; this, however, requires confirmation. The amount of pentosanes in the Schweizer extract was relatively greater in the second than in the first year, but decreased in the lignin more in the second year than in the first: this result is also given with reserve.
(p. 84) Straw cellulose is resolved by two methods of acid hydrolysis into a soluble furfural-yielding fraction, and an insolublefraction closely resembling the normal cellulose. (a) The cellulose is dissolved in sulphuric acids of concentration, H2SO4.2H2O, H2SO4.3H2O. As soon as solution is complete, the acid is diluted. A precipitate of cellulose hydrate (60-70 p.ct.) is obtained, and the filtered solution contains 90-95 p.ct. of the furfuroids of the original cellulose. The process is difficult to control, however, in mass, and to obtain the latter in larger quantity the cellulose (b) is digested with six times its weight of 1 p.ct. H2SO4at 3 atm. pressure, the products of the action being (1) a disintegrated cellulose retaining only a small fraction (1/12) of the furfural-yielding groups, and (2) a slightly coloured solution of the hydrolised furfuroids. An investigation of the latter gave the following results: By oxidation with nitric acid no saccharic acid was obtained; showing the absence of dextrose. The numbers for cupric reduction were in excess of those obtained with the hexoses. The yield of ozazone was high, viz. 30 to 40 p.ct. of the weight of the carbohydrate in solution. On fractionating, the melting-points of the fractions were found to lie between 146° and 153°. Ultimate analysis gave numbers for C, H, and N identical with those of a pentosazone. The product of hydrolysis appears, therefore, to be xylose or a closely related derivative.
All attempts to obtain a crystallisation of xylose from the solution neutralised (BaCO3), filtered, and evaporated, failed. The reaction with phloroglucol and HCl, moreover, was not the characteristic red of the pentoses, but a deep violet. The product was then isolated as a dry residue by evaporating further and drying at 105°. Elementary analysis gave the numbers C 44.2, 44.5, and H 6.7, 6.3. Determinations of furfural gave 39.5 to 42.5 p.ct. On treating the original solution with hydrogen peroxide, and warming, oxidation set in, with evolution ofCO2. This was estimated (by absorption), giving numbers for CO2, 19.5, 20.5, 20.1 p.ct. of the substance.
The sum of these quantitative data is inconsistent with a pentose or pentosane formula; it is more satisfactorily expressed by the empirical formula
which represents a pentose monoformal. Attempts to synthesise a compound of this formula have been so far without success.
(p. 84) Owing to the presence of 'furfuroids' in large proportion as constituents of the tissues of the stems of cereals, these plants afford convenient material for studying the problem of the constitution of the tissue-furfuroids, as well as their relationship to the normal celluloses. The growing barley plant was investigated at successive periods of growth. Yield of furfural was estimated on the whole plant and on the residue from a treatment with alkaline and acid solvents in the cold such as to remove all cell contents. This residue is described as 'permanent tissue.' The observations were carried out through two growing seasons—1894-5—which were very different in character, the former being rainy with low temperature, the latter being abnormal in the opposite direction, i.e. minimum rainfall and maximum sunshine. The barley selected for observation was that of two experimental plots of the Royal Agricultural Society's farm, one (No. 1) remaining permanently unmanured, and showing minimum yield, the other (No. 6) receiving such fertilising treatment as to give maximum yields.
The numerical results are given in the annexed tables:
DateAge of CropPlotDry WeightFurfural p.ct. of dry weight(a)Permanent tissue p.ct. dry weightFurfural from permanent tissueP.ct. of tissueP.ct. of entire plantRatioa:cMay 76 weeks119.47.053.412.76.81.03 : 1614.77.055.910.35.71.23 : 1June 410 weeks117.67.752.911.66.11.26 : 1613.58.158.513.47.81.04 : 1July 1015 weeks142.09.065.79.86.41.40 : 1632.910.665.712.58.21.30 : 1Cut Aug. 2121 weeks164.011.970.014.510.11.18 : 1664.613.470.515.010.61.26 : 1Carried Aug. 3122 weeks184.012.775.016.512.41.02 : 1686.412.478.415.111.81.05 : 1BARLEY CROP, WOBURN, 1895.May 157 weeks120.66.653.910.25.51.20 : 1617.85.856.79.65.41.07 : 1June 1812 weeks134.68.038.214.75.61.42 : 1633.47.644.515.06.71.14 : 1July 1616 weeks152.812.155.616.39.11.33 : 1654.410.646.219.18.81.20 : 1Aug. 1620 weeks166.89.249.117.08.31.10 : 1665.09.849.819.19.41.04 : 1Sept. 322 weeks184.310.445.717.68.01.31 : 1686.310.245.317.37.81.30 : 1
The variations exhibited by these numbers are significant. It is clear, on the other hand, that the assimilation of the furfuroids does not vary in any important way with variations in conditions of atmosphere and soil nutrition. They are essentiallytissue-constituents, and only at the flowering period is there any accumulation of these compounds in the alkali-soluble form. It has been previously shown (ibid.27, 1061) that the proportion of furfuroids in the straw-celluloses of the paper-maker differs but little from that of the original straws. For the isolation of the celluloses the straws are treated by a severe process of alkaline hydrolysis, to which, therefore, the furfuroid groups offer equal resistance with the normal hexose groups with which they are associated in the complex.
The furfuroids of the cereal straws are therefore not pentosanes. They are original products of assimilation, and not subject to secondary changes after elaboration such as to alter either their constitution or their relationship to the normal hexose groups of the tissue-complex.
These are a series of investigations mainly devoted to establishing the identity of the furfural-yielding group which is a characteristic constituent.
This 'furfuroid' while equally resistant to alkalis as the normal cellulose group with which it is associated, is selectivelyhydrolysed by acids. Thus straw cellulose dissolves in sulphuric acids of concentration H2SO4.2H2O - H2SO4.3H2O, and on diluting the normal cellulose is precipitated as a hydrate, and the furfuroid remains in solution. But this sharp separation is difficult to control in mass. By heating with a very dilute acid (1 p.ct. H2SO4) the conditions are more easily controlled, the most satisfactory results being obtained with 15 mins. heating at 3 atm. pressure.
(1) Operating in this way upon brewers' grains the furfuroid was obtainable as the chief constituent of a solution for which the following experimental numbers were determined:—Total dissolved solids, 28.0 p.ct. of original 'grains'; furfural, 39.5 p.ct. of total dissolved solids, as compared with 12.5 p.ct. of total original grains; cupric reduction (calc. to total solids), 110 (dextrose = 100) osazone; yield in 3 p.ct. solution, 35 p.ct. of weight of total solids.