October, 1924
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1019
Examination of Photosynthetic Sugars by the Methylation Method'
HE sirup originally supplied by Professor Baly2 was a viscous, amber-colored liquid which reduced Fehling's solution readily. Mineral salts were present in considerable amount, and the sirup also contained a variable quantity of water. I n appearance and general properties the material resembled the sirups obtained by condensing formaldehyde or trioxymethylene by means of dilute alkali, but preliminary examination revealed the following irregular properties:
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1-When heated, particularly with a trace of acid, rapid discoloration set in between 80' and 100' C. 2-The action of Fehling's solution corresponded to the presence of about 25 per cent of sugar (calculated as glucose), but this value diminished when the sirup was heated with acid under conditions that would hydrolyze a glucoside or polysaccharide. Part of the reducing power was therefore contributed by compounds other than sugars. A further deduction is that anhydrosugars and polysaccharides of the type CeHloOs were absent. 3-No condensation with methanol took place in the presence of 0.5 per cent of hydrogen chloride a t 15' C., showing that ketoses were absent. In this respect the sirup differed sharply from a-acrose. 4-Alkyloxy compounds were present and thus the original material gave an apparent methoxy content, varying from 9 t o 12 per cent. No doubt, this was because the formaldehyde employed had apparently reacted in part as a methylating agent. This view was confirmed by the observation that the alkyloxy content was not diminished by heating with alkali and that on heating under highly diminished pressure a small quantity of distillate was obtained which undoubtedly contained methoxy compounds.
This observation introduced serious complications into attempts to ascertain the analytical composition of Baly's sirup. The same irregular properties were discernible in further specimens of the photosynthetic sirup which had been subject t o repeated purification by precipitation from alcoholic solution by the addition of chloroform. The examination of this material, however, has provided evidence that compounds possessing the properties of hexose sugars are present to the extent of approximately 9.3 per cent.
ESTIMATION OF TOTAL CARBOHYDRATE CONTENT It was desirable to ascertain not only the total material but also the corresponding to the reducing hexoses (CBH~ZOS), amount, if any, of anhydro hexoses (CJ3100b) present either as such or in the form of polymerized aggregates. Four-gram samples of the sirup were heated a t 80" C., first in a vacuum of 3 mm. and subsequently under 0.2 mm., until the weight was constant. The apparent methoxyl content of the residual sirup had then diminished to 6.8 per cent methoxyl, and the reducing power had increased to a value corresponding with the presence of 32 per cent of reducing sugar, calculated as glucose. The dried sirup was dissolved in methanol containing 0.25 per cent of hydrogen chloride and heated a t 100" C. for 50 hours. The solution darkened at once, but this discoloration was not increased by continued heating. Coloring matter was removed by treatment with charcoal, and on working up the product in the usual manner a pale, light red sirup remained. After drying until constant Abstract of paper presented before Section B (Chemistry) at the meeting of the British Association for the Advancement of Science, Saskatoon, Saskatchewan, August 22, 1924. 3 See preceding article. 1
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a t 80" C. and 10 mm. pressure, an thereafter at 80" C. and 0.2 mm. pressure, it was ascertai ed that (a) the methoxyl content had increased from 6.8 to 12.0 per cent, and ( b ) the reducing power had decreased {rom 32 to 5.5 per cent. The increase in methoxyl content due to glucoside formation is thus 5.2 per cent, whereas an increase of 16 per cent is required if the sirup examined is egtirely CsH120eor CaHl0O6. I n other words, the amount of glucoside formed corresponds with the condensation of 32.5 per cent of glucose, whereas the titration results indicate that ably 26.5 per cent of sugar took part in the condensation. I n other words, according to the change in reducing power, t h methoxyl content should have increased to the extent of 4 2 per cent, whereas 5.2 per cent was actually obtained. The increase in the methoxyl content is thus approximately consistent with the diminution in deducing power, and consequently two important conclusions are reached:
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1-Polysaccharides or anhydro su ars are absent. 2-The amount of aldose sugar ca not exceed265 per cent.
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EVIDENCE OF MET
YLATION
The purified dried sirup was subj cted to one methylation with methyl sulfate under conditi ns that would convert the reducing component into the corresponding methyl glucoside. The total sirup soluble in chloroform amounted to one-third of the weight of sirup aken, and this was subjected to the silver oxide reaction and the product soluble in ether was then distilled in a vacuu . One hundred grams of sirup gaI t 20 grams of distillate. CH30 = 49.0 per cent. After two more methylations by the silver oxide method and recti cation of the product, distillates were obtained as follows:
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Temqerature Fraction I Fraction I1 Fraction I11
100-110 c' 110-130 130
Pressure Mm.Hg
0.23
~
0.2
+
0.2
Weight Grams
9
2.5 1.5
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I n addition, a small first fraction 2 grams) was collected which agreed in properties with met yl a-hydroxypropionate and possessed the same characteristic smell. EXAMINATION OF FRACTION I- raction I was a colorless, mobile liquid, freely soluble in or anic solvents; the solubility in water was not complete, a turbid solution being obtained which showed that compo nds other than methylated glucosides were present. Th behavior towards Fehling's solution was correct for a glucoside except that the cuprous oxide had a tendency to re ain colloidal, and these properties, together with the fact t a t the refractive index was 1.4561 instead of 1.4464, showed that further purification Was necessary. The main fraction was accordin ly redistilled twice, the middle fraction being retained in eac case.
3
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Second fractionation gave 4.8 grams, b iling point 90' to 98' C., a t 0.14 mm. pressure, nD = 1.453 Third fractionation gave 1.3 grams, nD 1.4509.
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This refractionated material behaved as a glucoside and gave CHIO = 54.5 per cent instead of the calculated value 62 per cent required for a fully methylated glucoside. This result may be explained by the presence of glucosides of al-
1020
INDUSTRIAL A N D ENGINEERING CHEMIXTRY
doses lower than hexoses, or by contamination with alkyloxy esters. The molecular weight, determined by the freezing point method in benzene, was 232 instead of 250. HYDROLYSIS TO GIVE A METHYLATED HEXOSE This was conducted as usual by means of 8 per cent hydrochloric acid a t the boiling point. The solution turned yellow and then pale red (an indication that pentoses were present). After filtering from a little resin which had formed, the solution was neutralized and extracted with chloroform. An amber-colored sirup was obtained which boiled at 105’ C. and 0.10 mm. pressure. As will be seen from the table, the general properties were those of an alkylated hexose: Methylated sirup %D
CHaO
C
H
Tetramethyl hexose
1.4592 51.44 51. OS 8.73
In calculating yields the most favorable assumption is that the total methoxyl content of distilled material can
Vol. 16, KO. 10
be attributed to the presence of tetramethyl methylhexoside and that all fractions had the same composition as the analytical sample. One hundred grams of original sirup (CH30 = 6.8 per cent) have 13 grams distilled methylated glucoside with CHBO = 54.5 per cent. The maximum amount of hexoside present was therefore 10.0 per cent. As the general experience is to obtain a-yield of methylated sugar equal to the weight of the parent compound, this figure is equivalent to the presence of 9.3 per cent of sugar in the original sirup. NATUREOF EXTRANEOUS PRODUCTS The bulk of the photosynthetical sirup, a t least to the extent of 80 per cent, consists of nonsugar compounds which contain hydroxyl groups. On methylation this material gives an amber sirup, which is nonvolatile and easily resinified on heating, either alone or with acids, suggesting polyhydroxy phenols. As stated, hydroxy acids or their lactides also constitute a considerable proportion of the reaction product.
Lignite, a Future Fuel?’ By 0.P.Hood BUREAUO B MINES,WASHIKGTON, D. C .
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HE processing of lignite still awaits commercial development. Each essay in that direction comes a little nearer something stable, but a business has not as yet arrived. The investigations of the Bureau of Mines under the Federal Act of February 25, 1919, have shown “commercial practicability” in certain directions, but there are no going concerns that afford illustration. Briefly, the situation seems to be that the right combination of men, money, and method has not yet been found. A goodly number of?menare anxious to venture into the field with the other fellow’s money. They usually want something exclusive, such as a patent on apparatus, or process or binder for which great claims can be made, and upon which a stoclrselling scheme can be based. There is too often the suspicion that money is to be made for somebody out of stock distribution, rather than out of the service a business can render t o the community. Many of these men are without much knowledge, except of the ways of the world. Since it is an ,engineering problem not yet standardized, such equipment is inadequate, and failure is likely to follow. Most of these efforts, fortunately, do not get very far, but they do attract attention periodically to the matter, and the great Northwest is again saved through its immense fuel resources. This sort of atmosphere has surrounded the problem for a long time and those who have a firm belief in the possibility of a really useful development of lignite have been hoping that more substantial interests would risk their own money and get somewhere. It is not likely that Government money can establish such a business. Neither the Canadian effort costing over a million, nor our own costing fifty thousand dollars, resulted in establishing a continuing operating plant on a busiiiess basis, although both had visions of doing this, and both, contributed to the technical situation. The use of Government funds is so surrounded by limitations fatal to the development of a new business that the best that could be done would be to cooperate with forces less restricted. I n a new venture such cooperation requires something more than selfinterest, so that the field of possible cooperators is greatIy limited. There are few technically equipped a t the present time in this kind of work. Under the act of February 25, 1919, efforts were made to 1
Received August 21, 1924.
cooperate with parties who would conduct the business end of the matter while the technical end was developed and directed under the Government fund. The right men were not found. There were very many opportunities to spend the money, but under impossible conditions or conditions that were manifestly not good business. The greatest technical need was a means of carbonizing lignite with ti Iow capital outlay and smaller labor charge. This need was successfully met, and is available to any one interested. A small plant was operated through a season in order to assure a knowledge of costs of production, so that the cost of producing lignite char briquets is pretty well established. The market situation was studied, and the genera1 concIusion reached that there was a market for a fuel competing with anthracite in the lignite area. The market for by-products at this time, and in the lignite area, is sufficiently doubtful to make it unwise to make the capital investment necessary to recover them. The plant most likely to succeed will be one of greatest simpIicity, of low initial cost, producing only Iignite char briquets, and competing with anthracite coal. Such a plant is available to any one, without patented devices. A report covering some years of work is prepared but not yet published. The Canadian plant at Bienfait was an effort of the Dominion Government, Manitoba, and Saskatchewan. There was difficulty with the process, and before the difficuIties could all be remedied the substitution of Alberta coal for anthracite so changed the situation that the interest wouId no longer hold the three parties together. The plant is now the property of Saskatchewan, and awaits the next move. This plant was composed of three main elements: a drying process, a carbonizing process, and a briquetting element. The separate drying process was not economical, the carbanizhg qocess lacked development, and the briquetting end was not trled for lack of product. The device developed by the United States Bureau of Mines was finally used for carboniaing the Iknite, with success, and was favorably reported. The Canadian investigators reached the same conclusion as our own Bureau of Mines with regard to the present recovery of by-products. A most valuable report has bmn issued by the Canadian Lignite Board, in which they have h d the mmage to tell of their troubles as well as their successes. This board has now been dissolved.
