I N D U S T R I A L A N D ENGI NEERING CHEMISTRY
November, 1923
rials mentioned above were distilled with steam from both 12 and 20 per cent hydrochloric acid. The heat was adjusted so that temperatures of 103’ to 104’ C. were maintained in the 12 per cent distillation, while temperatures of 107’ to 108’ C . were held in the 20 per cent distillations. Within the limits of experimental error, theoretical results were in all caseB obtained from the pentoses used, regardless of the concentration of acid. This is shown in Table 111. The pentosan materials gave constant yields, indicating that no loss of furfural had occurred. (Table IV) Furthermore, the rate of distillation did not affect the yield, as shown by the marked differences in volumes of distillates obtained. Evidently, even a slow current of steam is sufficient to sweep out the furfural as fast as it is formed from the pentoses. DISTILLATIONS B Y STEAM FROM TABLE IV-PENTOSAN DETERMINATIONS. 12 AND 20 PERCENT HC1 SOLUTIONS
Per cent Acid 12
20
Weight of Sample Grams 0.5018 0.5033 0,5053 0.5016 0.5004 0.5053 0.5047 0.5036
Volume of 0.1 N KBrOa Distillate cc. Cc. Gum Arabic 820 24.50 24.25 1160 24.65 725 925 24.40 640 24.25 685 24.50 940 24.50 900 24.50
Pentosan Found (Factor = 0.006605) Gram
Pentosan Per cent
0.1618 0.1602 0.1628 0.1611 0.1602 0.1618 0.1618 0.1618 AVERAGE
32.2 31.8 32.2 32.1 32.0 32.0 32.1 32.1 32.1
Sawdust
0.1535 15.3 0.1535 15.3 0.1542 15.3 0.1552 900 15.4 615 0.3064 15.3 0.3054 710 15.3 20 0,3071 625 15.3 0.3071 15.3“ 2,0032 600 575 0.1519 1.0026 15.1’ 12 870 0.1535 15.P 1.0077 0.1535 15.3“ 530 1.0018 AVERAGE 1 5 . 3 a These distillations were carried out accordinc according t o Heuser’s method hydroxide p e rcent ~ c i -sodium-hydroxide nsodium t (1921) the samples being macerated with 4 ~per before’distilled with acid. N o increased yield of pentosan was obtained. Heuser’s determinations always ran 4 per cent higher b y this treatment. Hence the foregoing data further substantiate the claim that theoretical yields of furfural are obtained from pentosans by the proposed distillation procedure. 12
1.0020 1.0017 1.0056 1.0064 2.0020
935 875
1000
23.25 23.25 23.35 23.50 46.40 46.25 46.50 46.50 23.00 23.25 23.25
A comparison of the pentose results in Tables I1 and 111 indicates that the reason low results are obtained by the official method is that some of the furfural is destroyed by long contact with strong acid. Moreover, this destructive effect can be entirely eliminated by carrying a slow current of steam through the hydrolysate, thereby removing the furfural as fast as it is produced. Hence the following method for the quantitative production of furfural from pentose materials is proposed.
PROPOSED METHODFOR DISTILLATION OF PENTOSESPlace a weighed (0.20 to 5.0 grams depending upon the pentose or pentosan content) sample of the material, and 200 cc. of 12 per cent hydrochloric acid (specific gravity, 1.06) in a 750-cc. distilling flask fitted up for steam distillation. Conduct a slow current of steam into the mixture and as soon as the mixture reaches the boiling temperature heat the distilling flask with a low flame so that the boiling temperature remains between 103’ to 105” C. as measured by a thermometer inserted in the vapor in the neck of the distilling flask. 13y observing this precaution the addition of fresh acid will rarely be required. About one-half of the original volume of liquid should remain in the flask a t the end of the distillation. Continue distillation until a drop of the distillate no longer gives a red coloration with aniline test paper on being allowed to stand 3 to 5 minutes. By following this procedure theoretical yields of furfural have been obtained from all the pure pentose materials which have bechn tested. Representative data are found in Table V.
TABLE v-PENTOSE Weight of Sample Gram
1169
DISTILLATIONS B Y THE PROPOSED METHOD
0 . 1 N KBrOa
.
0.2000 0.2005 0.2015 0.2021 0.2030 0.2025 0.2037 0.2040
cc Arabinose 26.50 26.50 26.75 26.85 27.00 27.00 27.25 27.25
0.3020 0.3035 0.3010 0.3027 0.3040 0,3070 0.3082 0.3044
40.00 40.30 40.00 40.30 40.45 41.00 41.20 40.60
pactor = Grams Pentose Cc. 0 . 1 N KBrOz 0.00755 0.00755 0.00753 0,00752 0,00752 0.00780 0.00747 0.00748 AVERAGE 0.007515
Xylose 0.00755 0.00753 0.00752 0,00761 0.00754 0.00749 0.00749 0.00752 AVERAGE 0.007519 TOTAL AVERAGE0.007517 0.007806 THEORETICAL
CONCLUSIONS The data presented seem to warrant the following conclusions : 1-Distillations of pentose materials, carried out according to the method of the Association of Official Agricultural Chemists, take place from hydrochloric acid of 18 to 20 per cent concentration, instead of from 12 per cent acid as usually stated. 2-Hydrochloric acid of this concentration has a considerable destructive effect on furfural, and is no doubt partly responsible for the low yields of furfural that are obtained from all pentoses when the official method is used. 3-The passage of a slow current of steam through the distillation mixture is sufficient to carry the furfural off as rapidly as it is formed, thereby avoiding the destruction of furfural by long contact with strong acid. M o t i o n Pictures t o Show C o t t o n D u s t i n g M e t h o d Two thousand feet of “movie film” were recently made by the motion picture office of the Department of Agriculture, showing the method of spreading calcium arsenate dust over fields of cotton by airplane for control of the boll weevil. The pictures were taken a t Tallulah, La., where the experiments in cotton dusting by airplane are being conducted under the direction of B. R. Coad, in charge of the Delta Laboratory there. Results obtained by this method of spreading the poison have been sufficiently satisfactory to give promise of the use of airplanes on a commercial scale in fighting the boll weevil, and the film was made largely for the purpose of creating an interest in further development of detail and to show the progress alrtady made. I t will be shown first before officials of the Department of Agriculture and of the War Department, which is cooperating in the tests by supplying the air machinery and personnel. The best results to be obtained in spreading the poison in this manner are to, be had by early morning flights when the air is still and there are no air pockets to make flying more dangerous. Three days were taken to complete the making of this negative and ten flights of from 10 to 30 minutes each were made. The planes used were two De Havilaiid bombers which have a speed of from 90 to 100 miles an hour.
M c B a i n Tells Boston Chemists a b o u t S o a p A number of chemists of the Northeastern Section met James W. McBain of the University of Bristol, England, a t luncheon on Monday, October 15. With J. F. Norris of the Massachusetts Institute of Technology as toastmaster, greetings were tendered the guests by A. B. Lamb of Harvard, H. P. Talbot of the Massachusetts Institute of Technology, L. C. Newel1 of Boston University, and L. C. Pratt of the Merrimac Chemical Company. I n the evening Professor McBain addressed the regular monthly meeting of the Northeastern Section on “A Study of Soap Solutions and Its Bearing on Colloid Chemistry.” Supported by many fine microphotographs, the speaker argued convincingly that a soap gel has a filamentary or “brush-heap’’ structure.
