November, 1932
I N D U S T R I A L A N 13 E N G I N E E R I N G C H E M I S T R Y
exposed iron, (3) controlled temperatures of distillat ion, and (4) provision in rosin manufacture of means for remclving the water-soluble portion of the gum. The first three faciors have long been known and practiced, but the fourth has hitherto received little or no attention. Possibly a fifth factor-filtration of the gum before distillation-should be added. I n the present experiment., howerer, washed strained roiins and washed unstrained rosins gave exactly the same colors upon dehydration. The removal of suspended dirt is rssential; this is necessary for considerations other than color. It seems probable, therefore, that a combination in manufacture of an efficient gum-cleaning device n-ith a steam still properly
1249
designed for washing the rosin should give the highest grades of rosin. LITERATURE CITED (1) F r o m m , 2. physiol. Chem., 33, 579-94 (1900). (2) Neubera, Ibid., 44. 114-26 (1903). (3) Semmler, “ D i e aetherisohen Oele,” Vol. 1.pp. 12-13, Veit & Co., Leipzig, 1906. (4) Veitch and S m i t h , S a v a l Stores Rev., 38, S o . 46, 18 (1929). ( 5 ) Vezes, M., Report de la laboratoir d e chimie applique a I’industrie des resines, Bordeaux, 1902-3.
RECEIVED April 7, 1932. Presented before the Division of Agricultural and Food Chemistry a t the 83rd Meeting of the American Chemical Society, New Orleans, La., March 28 to April 1, 1932.
Bagasse Cellulose D. F. ;r. LYKCHAND M. J. ~ o s s Bureau of Chemistry and Soils, 1.;. S. Department of Agriculture, Washington, D. C .
T
HE past few years have available each year a t the sugar An analytical study of the cariety of bagasse mills in continental United States witnessed a stupendous available is made to determine some commercial growth in all the cellubetween 250,000 (1-4)and 500,000 use for the by-product. The comparatively high ( I O ) tons of bagasse. Bagasse is lose industries of this country. crude-fiber content would indicate that bagasse not, however, a waste product. The raw cellulose needed by any m a y be used as a source f o r cellulose. The one of the younger cellulose inIt is used as a fuel a t the sugar mills and in the production of industries is small in comparison optimum conditions are determined f o r the prowith the pulp demanded in our sulating and building board. duction of cellulose f r o m bagasse by the soda p a p e r production. Together, method, the sulfate method, and the neutral COJIPOSITION OF BAGASSE hov-ever, these younger indussulJite method. Experiments indicate that by tries u t i l i z e a c o n s i d e r a b l e For many years bagasse has rigid control of conditions slightly higher yields amount of cellulose, and they come under the scrutiny of the require a higher grade of oellulope sugar chemists. The strenuous of cellulose cafi be obtained than those previously than that found satisfactory by competition i n t h e sugar reported. The neutral suljite digestion gives our paper manufacturers. industry has d e m a n d e d that slightly higher yield than the other methods Those manufacturers using nieach sugar mill remove from the tested. Becauc;eof the poor recovery of the cellutrated c e l l u l o s e and the procane p r a c t i c a l l y all the ecolose present in the bagasse, a study of the nitric ducers of cellulose acetate are denomically available sugar. To pendent, a t the present time, for i n s u r e this end, rigid control acid pulping process is made with this bytheir raw material on cotton linwork has t o b e m a i n t a i n e d product. Under the optimum conditions higher ters. The viscose rayon process, on the bagasse before it can be yields and better cellulose are obtained W i t h this which supplies over 80 per cent of discarded. The usual absence process. Owing to the oboious adcantages of the world’s production of rayon, of cheap fuel in cane-growing this process and the probability of cheap nitric employs, however, for the bulk of areas has also served to direct its cellulose supply, high-grade the attention of e n g i n e e r s to acid f r o m the oxidation of ammonia, there are wood pulp prepared from spruce the use of this waste as a fuel. indicated commercial possibilities of using the wood. Other cellulose processes Doubtless, t h e r e f o r e , t h e r e yearly supply of 250,000 to 500,000 tons of -for example, the production of exists a large amount of unpubbagasse as a source for a-cellulose. a b s o r b e n t c~ellulow--are each lished analytical 1%-orkon this year taking larger amounts of by- p r o d u c t , Considering the high-grade wood pulp. The fear that the northern foIests may large number of varieties of cane,the many different locaiities some day be insufficient t o supply these increasingly cnormous from which it is harvested, and the nature of the material, amounts of cellulose, together Tvith the fact that thehe forests there is exhibited good agreement in the published analytical are yearly receding from the cellulose markets with increasingly results. higher freight charges. have directed considerable attention to From the results in Table I it is safe to assume that the the possibility of increasing the range of raw materids avail- cellulose content of moisture-free bagasse will average oneable for these important industries. half its weight. Air-dried bagasse has been reported to Many of our crop wastes naturally suggest themselves as contain 8.3 per cent of moisture by Kumagawa and Shimopossible sources of crude cellulose. To merit attention, mura ( I S ) , 10.8 per cent moisture by the Imperial Institute however, the crop waste must be arailable in large volume at Laboratory ( I ) , 10.3water hy S’alenzuela and West (sa),and, low cost. One important item of expense that i. usually on the samples available, has been found by this laboratory encountered is the cost of collection. This cost, if high, may to range from 9.9 to 12.5 per cent. preclude further serious consideration of the material. -2 RAWMATERIAL waste product already collected in the marketing of some main product is, therefore, desired. One product that meets When all the sugar has been extracted from the cane, the theqe requirements is bagasse. There are collected and green bagasse, containing 45 to 55 per cent water, is dis-
.
INDUSTRIAL AND ENGINEERING
1250
Vol. 24, No.11
CHEMISTRY
TABLEI. ANALYSISO F MOISTCRE-FREE BAGASSE PENTOSAN %
SOURCB
ASH
Prinsen-Geerligs (88) 22.0 Remington et al. (84) Connon (4) Shimomura (la) 27.4 Valenzuela and West (88) 22.8-28.1 Browne 3) 28.51 Bull. of fmp. Inst. (I) This laboratory 21.L23.5 a Pectin is included with lignin in this determination. b Checked by M a x Phillips in his lignin investigations.
... ...
ACTIVE ALKALI
-CHEMICALS-NaOH %
.... ....
16 20 25 30 35
RATIO
%
.... .... *.
FATA N D WAX
%
CELLULOSE
%
...
... 27.i6;
2.0 1.5 5.6 2.6 3.6-5.8 2.01 1.2 4.3-6.0
charged from the sugar mill. Up to ten years ago this was an economic waste, used only as a fuel at the sugar mills (14). Today, however, any new manufacturing process utilizing bagasse would have to compete with the structural insulation industry for its raw material. Likewise, such a new industry would encounter many of the difficulties which the manufacturers of structural insulation had to solve, such as the storing and the preservation of this fibrous material. Within 90 days (the grinding period in our sugar industry) a plant would have to receive and store its year’s supply of raw material. I n a warm moist atmosphere the traces of sugar remaining in the material quickly start to ferment, with the aid of wild yeasts which are always present. There are patented processes for preserving this raw material from fermentation and destruction by vermin (14,18,1Q,I I ) . To the sugar mill operators bagasse represents not only a constant supply of available fuel, but also under certain conditions an extra source of income. Owing to the usual scarcity of fuel in cane-growing areas, the sale of this material necessitates some arrangement whereby another fuel can be substituted. The structural insulation industry purchases its bagasse by contract whereby fuel oil or gas is supplied the sugar mills. The value of the bagasse is, therefore, affected by the local price of other fuels. I n some localities-for example, Egypt-the cost of other fuel is so high that it is not profitable to purchase the bagasse for insulation board. In this country, the price agreed upon fluctuates with the cost of fuel oil or gas in that locality during the grinding season (14). On the basis of different conditions of moisture content and boiler efficiency the fuel value of bagasse has been calculated by several investigators for the logical price range of fuel oil (2,6,16,IQ). This value ranges from $0.75 to $3.00 a ton. Naturally, there is little published information upon the selling price of bagasse. Little (16),basing his calculation on conditions prevailing in 1912, assumed a selling price of $1.20 a ton for green bagasse, while in 1926 Redgrave (23) stated that in the tropics bagasse could be dried and baled for about TABLE11.
LIGXIN
%
... 0.87
22.3 16.6-18.3 16.23
2.5512.6 0.79
16.4-is.7 b
2.3512.7
% 56 47.1 54.82 51 48.7-51 50.37 57.4 53.7-57
$5.00 (21)a ton. Recent estimates, however, obtained from commercial sources on the price of air-dry baled bagasse are considerably higher than this figure. BAQASSEPULP The availability each year of large amounts of bagasse with its known low-fuel value has induced many to search for a more profitable use for this by-product. The comparatively high cellulose content has suggested the conversion of the bagasse into paper pulp. The literature contains numerous reports of investigations on the pulping of this raw material. The reported results do not agree, and the number of patents issued on innovations in the pulping of bagasse indicates some difficulty in the production of good bagasse pulp. Arthur D. Little, Inc., produced for the United Fruit Company a great variety of good paper a t the former’s experimental mill from Cuban bagasse. I n the report on the work, however, the four commercial attempts a t producing paper pulp from bagasse are listed as unsuccessful.1 Most of the reported pulping work on bagasse was carried out with the soda method. Some few investigators used the sulfate method, but, since there existed no report on the neutral sulfite (Keebra) method and no comparable results obtained with these different pulping processes with the same species of bagasse, it was decided to make such a comparative study.
EXPERIMEKTAL PROCEDURE The actual production of bagasse pulp on a small scale was investigated by this laboratory. Conditions and equipment prevented a thorough investigation of the application, t o bagasse, of the acid sulfite and Pomilio’s chlorine pulping methods. Investigations, however, were carried out to as11900, E. H. Cunningham Company, Sugarland, Tex., poor grade of paper. 1903, United Railways Trading Company, brittle paper. 1915,United Fruit Company, Preston, Cuba, poor wrapping paper. 1917, Sugar Cane By-products Company of Louiaiana, practically no production.
PRODCCTION OF C E L L U L O S E FROM B.4GASsE (Results obtained with various cooks)
TIME Hours
PRESSCRE Lb./sq. in. ( K g . / s q . cm.)
TYPESOF PCLP
YIELDS
%
SODA M E T H O D
3:1-5:1 3:1-5: 1 3: 1-5: 1 3:l-5:l 3: 1-5:1
3-6 3-6 3-6 3-6 3-6
75-150 75-150 75-150 75-150 75-150
55-48 55-43 49-33 46-30 42-26
(5.3-10.5) (5.3-10.6) (5.3-10.5) (5.3-10.5) (5.3-10.5)
SULFATE METHOD
NaOH Parts 10
NazS Parts 3 3
10 2 2 2
3 1 1 1
i.. n
NaiCOi Parts 1 1 1
.. .. ..
20 15 10 15 20 25
3:1-5:1 3:1-5: 1 3:1-5: 1 3:1-5: 1 3:l-5:l 3:1-5: 1
3-6 3-6 3-6
3-6 3-6 3-6
Unbleachable to good pulp Unbleachable 40 good pulp No effect t o fair pulp Difficultlv bleachable to -eood DUID. B1IeTchabIe to good pulp BIleachable to poor pulp
47-37 51-41 56-45 45-33 43-31 42-27
Burnt t o poor pulp Unbleachable t o good pulp Difficultly bleachable to good pulp
00-46 48-35 44-35
NEUTRAL SULFITE OR K E E B R A METHOD
NazSOs
.. .. ..
% 20
40 50
*.
4:3-2: 1 2:l-4:l 5:2-5: 1
3-6 3-6 3-6
75-125 (5.3-8.8) 75-125 (5.3-8.8) 50-125 (3.5-8.8)
November, 1932
INDUSTRIAL A N D ENGINEERING
CHEMISTRY
1251
obtained u n d e r the certain the best conbest conditions. Sod i t i o n s as to time, STEAM dium s u l f i t e , howtemperature, percentever, is not a very age of chemicals, and effective pulping ratio of solutions in agent, even a t high relation to the charge pressures, in concenmith the soda method, t r a t i o n s lower than t h e sulfate method, 20 per cent. The low and the neutral suldensity of the bagasse, fite orKeebramethod. on the o t h e r h a n d , The size of the apdemands a large WATER paratus a v a i l a b l e AiR volume of liquor to limited the “cook” to p r e v e n t the charge 2 or 3 kg. of raw mafrom burning. terial. These two conditions I n Table I1 t h e r e WATER AlR n e c e s s i t a t e the use are shown the miniof large amounts of mum and maximum s o d i u m s u l f i t e to variances of the coneffectively pulp this centration of chemimaterial. cals, solution, time, Mechanical separaand pressure w h i c h tion of the pith from were used in all exthe fiber, which has periments. For exbeen recommended ample, in the experiby many investiments with the soda gators, should be method in the group m o r e profitably inof runs in which the corporated i n t o t h e a m o u n t of s o d i u m neutral sulfite method hydroxide added was t h a n into the other equal to 25 per cent methods, because of of the raw material, the concentrated forty-eight cooks were BLEACHER BLEACHER liquor demanded. made. First, t h e S e v e r a l batches of ratio of the solution bagasse were beaten to t h e c h a r g e was in both a wet and a v a r i e d from 3 : 1 to dry state, and sifted 4 : l and then 5:l. to remove the pith: Sext, the time factor the resulting fiber was was v a r i e d f r o m 3 CELLULOSE PULP STORAGE pulped according to to 6 hours, h o l d i n g t h e three processes. t h e o t h e r condiALPHA CELLULOSE ALPHA CELLULOSE The amount of chemitions constant; and DRYING MACHINE c a l s necessary per finally the p r e s s u r e unit weight of pulp rew a s v a r i e d b y 25 TEXTATIVE FLOWD 1 l i G R . 4 ~FOR a-CELLULOSE MANUFACTURE FROM BAGASSE c o v e r e d was l e s s . pounds (1.8 kg.) per (Prepared in cSperation with Godchaux Sugars, Inc.) The yields per unit run from 75 to 150 weight of o r i g i n a l p o u n d s per square inch (5.3 t o 10.5 kg. per sq. cm.) Owing to the low density of bagasse were, however, considerably less in all cases. These liagasse, the variation in the ratio of liquor to charge is limited. results agree with those in the Little report (16), those of the To prevent the charge from burning, an amount of liquor Imperial Institute ( I ) , and those reported by Kumagawa and about three times the weight of the bagasse must be added. Shimomura (13). The latter investigators analyzed the pith The yields of unbleached pulp obtained from this group of collected in the mechanical separation of pith from the fiber forty-eight experiments ranged from 49 to 33 per cent, and and found that the pith contained as high as 36 to 41 per cent the quality of the pulp obtained varied from unbleaohable to pentosan-free cellulose. All the pulp designated as bleachable good soft pulp. With an amount of soda equal to 25 per cent was found to have a bleach consumption of not over 20 per of the charge, a liquor ratio of 5:1, and a 6-hour cook a t 125 cent of its dry weight, with a loss in weight of less than 10 pounds per square inch (8.8 kg. per sq. cm.) pressure with per cent of the dry pulp. The bleached pulp is soft, has an the variety of bagasse available, a yield of 34 to 35 per cent of ash content of about 0.5 per cent, and, according to Schorger’s good bleachable pulp can be obtained. These were the a-cellulose determination (27), averages 75 to 78 per cent optimum conditions as determined by the different groups of a-cellulose This cellulose is composed of fibers of varying soda cooks represented in Table 11. With two parts of length and thickness. The long fibers were about 5.0 mm. sodium hydroxide to one of sodium monosulfide, an active al- in length, which compares favorably with wood fiber, but the kali percentage of 25 per cent, and a liquor ratio of 5:1, a short fibers measured just a little more than 0.5 mm., with an 6-hour sulfate cook a t 100 pounds per square inch (7 kg. per average length of 1.9 mm. The authors found the maximum cm.) pressure gave a yield 1 to 1.5 per cent higher than the diameter of the fiber to be 0.050 mm., and the minimum best average yield of good pulp obtained with the soda proc- 0.016 mm., with an average diameter of 0.026 mm., thus ess. With the Keebra or sodium sulfite method, yields of agreeing with the determinations reported by the Imperial 37.5 per cent of good, easily bleachable pulp can be readily Institute (1). Although it was found that, by selecting the
1252
INDUSTRIAL AND ENGINEERING CHEMISTRY
optimum conditions as determined by the experiments reported in Table 11, and rigidly controlling these conditions, good bagasse cellulose could be obtained in yields slightly above those previously reported, it was felt that larger percentages of the cellulose present in the bagasse should be recovered. KITRICACID PULPISGPROCESS General statements are encountered in the literature that better cellulose and larger yields are obtained with fractional digestion and with a combination of the well-known pulping methods. It was therefore decided to direct some work to the application of some one of the newer pulping methods to this cellulose material. The reported success from Germany of the nitric acid pulping process with beech wood, straw, reeds, and similar cellulose material led to a study of this method. The use of nitric acid as a pulping agent dates from the Barr6 and Blonde1 patent in 1861 ( I b ) . Fine pieces of wood were soaked in 36" B6. nitric acid in the cold for 24 to 30 hours. The solution was then diluted with a large volume of water, and heat applied. The pulp was finally treated with alkali. Young in 1884 (33) suggested weaker acid with heat, as did Cross and Bevan (5). I n 1891 Lipschutz (15) introduced sulfuric acid into the nitric acid, while in 1907 Schwalbe (28) used nitric oxide gas. Muller (20) in 1918 patented the use of the diluted waste nitric and sulfuric acids obtained from nitrations. With the advent of cheap nitric acid in Germany there appeared evidence of considerable activity in the adaptation of this pulping method to Germany's cheap beech wood (11, 26). The I. G. Farbenindustrie fit.-Ges. holds a patent (8) for the treatment of the cellulose material with the vapors of nitric acid, and another patent (9) incorporating a pretreatment with steam to remove any resin present; Krais (12) has a German patent for the introduction of a stream of air into the hot material to convert any nitric oxide formed into nitrogen peroxide for re-use in this process. TABLE111. AIR-DRYMATERIAL
H20
cellulose and lower yields. A volume of acid that would cover the charge was necessary. A low volume could be maintained by keeping the charge pressed down in the acid with weights. (These weights should be such that the acid will not react with them.) From this group of experiments it was found that, if bagasse was steeped for 3 hours in a 5 per cent nitric acid solution a t room temperature, the resulting cellulose was of a good quality and the yields higher. The amount of the acid solution necessary in these experiments was equal to about five times that of the air-dry charge. Seventy per cent of this acid was recovered by draining. The only two variables in the next step were time and temperatures. It was found convenient to surround the receptacle containing the charge with boiling water. The temperature of the charge remained about 80" C. Heating for one hour was found sufficient. Then the charge had to receive a thorough washing. This washing was continued until the wash waters were colorless. If the material was then subjected to boiling in a 2 per cent sodium hydroxide solution for 30 to 45 minutes, a soft, easily bleachable pulp was obtained in good yields. In the best runs these yields of pulp averaged more than 4 per cent higher than those obtained under the optimum conditions with the Keebra method. The pulp is very easily bleached with a low consumption of chlorine and with a loss in weight equal to only a little more than 5 per cent of its dry weight. The bleached pulp had an average ash content of 0.4 per cent, some batches having less than 0.3 per cent ash. The a-cellulose determination showed this pulp to contain from 86.1 to 92.5 per cent a-cellulose. The soda-soluble, or nitrator's test (17), however, showed from 16 to 31 per cent of this cellulose to be soluble in hot dilute alkali, although the phloroglucinolpentosan determination ( l a ) showed the cellulose to contain from 9.43 to 11.00 per cent pentosans. It has also been the experience of most analysts that the phloroglucinolpentosan determinations run high. An explanation of this high soda-soluble content advanced by this
hJALYSIS OF
BAQASSE CELLULOSE
(Nitric acid process) PENTOSANE
% .9.9-12.5 4.0- 7 . 0 3.9- 6 . 8 4.0- 6 . 5
4.3 -6.0 Bagasse 0.29-0.95 Unbleached pulp 0.25-0.45 Bleached pulp 0.12-0.28 Treated bleached pulp 0 Corrected to dry basis. b This determination is run only on oven-dried cellulose. c Calculated a8 bone-dry cellulose from bone-dry bagasse.
Published reports on the general method advise that the cellulose material be cut up into small strips 1 to 2 mm. in thickness. It is opened up then by impregnating with dilute nitric acid. This is done by covering the charge with a 15 to 20 per cent solution of nitric acid and allowing it to steep for 2 to 3 hours a t temperatures ranging from room temperature to 50" C. The excess acid is poured off, and the moist charge is heated for about one hour a t 79-100" C. The exact time of this step is determined by taking out a sample of the material and treating it, after washing, with boiling dilute sodium carbonate solution. The material should completely disintegrate into soft pulp in the hot carbonate solution. When the charge reaches this condition, it is thoroughly washed and boiled in dilute sodium hydroxide (7,SO). After preliminary runs of this method had indicated satisfactory results with bagasse, each step was investigated to determine the optimum conditions. I n the first step the time, temperatures, strength, and volume of nitric acid necessary were studied. The concentrations of 15 and 20 per cent nitric acid were found too high. In the same way, any heating of the charge in this first step resulted in poor
Vol. 24, No. 11
% 19.4 -21.3 10.55-12.95 9.43-11.00 2.41- 3 . 1 1
a-CELLULOBEa
sODA-sOLCBLEb
%
%
....... .......
86.1-93.5 93 .O-97.4
....... . . , . . ..
16.0-31,O 5,3-11.5
YIELDSC
KO. ..
42-46 38-40 32-33
laboratory is that fine cellulose fibers are dissolved by hot dilute sodium hydroxide (17 ) . This high soda-soluble content of the pulp can be lowered by treating with a 9 per cent sodium hydroxide solution a t 100' C. Careful and thorough washing is then necessary to remove all traces of sodium hydroxide to keep the ash low. The recovered sodium hydroxide solution is used in making up the 2 per cent solution required in the third step of the process. By this treatment the soda-soluble content of the pulp was lowered to 5.3-11.5 per cent (average 8.4 per cent). The bagasse cellulose obtained by this treatment, if washed well, has an ash content less than 0.3 per cent (average 0.2 per cent) and an a-cellulose content of 93.0 to 97.4 per cent (average 95+ per cent). There are two commercial high-grade wood pulps which find use in the viscose rayon process. The older brand has an ash content of about 0.4 per cent, a-cellulose content of 86 to 89 per cent, and a soda-soluble content of about 15 per cent; it is quoted a t $88.00 a ton. The newer product (25) sells on the following specifications: copper number below 2.5, ash under 0.4 per cent, soda solubility under 12 per cent,
css on a coininerais1 scale. For cxample, in the first step by pressing or centrifuging, some method must he devised t o remove from the large batches of the moist bagasse all the nihric acid except just that amount necessary in the pulping process. Another difficulty will be, no douht, t.o maintain all parts of a hatch of several tons of this moist material at ahout 80" C. for oiie hour. The recovered nitric acid soloLions vi11 also offer the difficulty that, although a i d a b l e for effectire repeated use, at, some time some of these recovered acid solutions will have t o be purified or discarded. These problems, however, are outside tlie scope of this work and should lie solved on a manufacturing scale by organizations wishing t o develop tlic process on a commercial basis.
C0NcLnsIo.v bltliough it was determined that by rigid control of ronditions slightly liigher yields of bagasse cellulose could he obtained with the sulfate and tho Keebra or neutral sulfite method than those reported, it was felt that larger pereentages of the cellulose present in the bagasse should be recovered. A study of tiie nitric acid pulping method and its application to this crop by-product showed that larger yields and better pulp could be obtained. This pulp coiitained airout 10 per cent more a-cellulose than did the bagasse pulp olitained by any of the other methods. Although tlie sodasoluble content was high, it could easily be lowered to betw?eri 5.3 and 11.0 per cent. With the exoeption of purified eottoii linters, tlie cellulose obtained by this method compares w r y favorably with any cellulose tested in this lahoratory. CIiil>~a comparatively small amount of the nitric acid used is lost,. The nitric acid recovered can he reused in succeeding runs. Certain advantages of this method-the larger yields of higher-grade cellulose arid thp availability of cheap nitric acid from the oxidation of ammonia-indicate cornmercial possibilities.
ACKNOWlrEDGXENT Aciiuowledgment is here made to J. A. I h i e for carrying out the large number of digestions, and to J. D. Reid for the analytical work on the recovered acid solutions. LITERATURE CITED (11 Anon. Bull. I m p . Znst., 27, 1-9 (1929). (la) Assoc. Oflicinl Agr. Chem. Oflioial and Tentative Methods oi Analysis, p. 284 (1931).
( l b ) Barr&, E. 11.. and Ulondcl, C. M . J., British Patent 391 (Feb. 16, 18611. (2) Brand, C. J., Bur. 1'lant Iiid., U. S.Degt. Agr., Ciic. 82, 14-15
~~"--,.
11411,
Browne, C. A. La. E m t . Sta., Bull. 91, 3 (1907); I.d m Chem. Soe.. 26, 1221 (19041. Connon, G. W.,Proc. IIIlwiiiian Suoor Planlers' Asroc.. 48. 353-65 (1928): Cross, C. F..Bntish Pntent 409 (Jan. 8, 18941. Deer*. N., intern. sugar J . , 16,378-82 ( 1 ~ 1 4 1 . Iieimsn, C., Petorsen, I.. Bayerl. A,. and Siefried, IT.. Canadian Patcnt 284,975 (Nov. 20, 1908). I. G. Farbenindustrie Ikt.-Gea., British Patent 274.892 (KoY. 24, 19271. Ihid., British Patent 276.025 (No".24, 19271. Knight, H. G.. U. 8. Dept. Agr., Ofiicid Record. p. 2 (Nov. ?I, 1928). Krais, P., German Patents 391.713 (Deo. 12. 1922); 395,191 (May 6, 1923): 395,192 (Aug.26, 1923). Krsis, I'.. German Patent 468,712 (April 26. 19351. Kumagaws. H.. and Shimomurn, K.. Z. anvew. Chem.. 36,414-18 (1923). Lsthrop, E. C., 1x0 EN*.
