A KANSASALCOHOLPLANT, INCLUDING STORAGE TANKS AND SHIPPINQ-ROOM'
Alcoholic Fermentation of Jerusalem Artichokes L. A. UNDERKOFLER, W. K . McPHERSON, AND ELLIS I. FULMER Iowa State College, Ames, Iowa
NTEREST in the fermentative production of ethanol has been growing rapidly because of the increased attention being given to the production of power alcohol from domestic farm crops. The first plant in the United States designed solely for this purpose began operation a year ago at Atchison, Kansas. The plant has a daily capacity of 10,000 gallons of anhydrous alcohol. Fermentation studies have been made on a number of farm crops including corn, barley, rice, oats, milo, kaffir, white potatoes, sweet potatoes, and molasses. All of the above materials have been successfully processed. The so-called Jerusalem artichoke or girasole (Helianthus tuberosus), a plant native to this country, has attracted considerable attention as a possible new farm crop. The yields of tubers are high, and they are rich in levulans which are easily hydrolyzed by mild acid treatment. This crop has therefore been suggested as a commercial source of crystalline levulose, and a semicommercial plant, capable of producing 22 pounds of the product per batch run, was in continuous operation in the Chemistry Department of the Iowa State College from 1931 to 1934 (4, 7).
I
1
The photographs illustrating this article are reproduced by aourtesy of
The Chemical Foundation of Kansaa Company.
The Jerusalem artichoke has been recognized as a possible source for the manufacture of alcohol for many years past (2, 17, ZO), and the tubers were employed a number of years ago in a few small-scale manufacturing operations in Germany and in France. More recently this crop has been under consideration in the United States as a raw material for the production of industrial alcohol. Important progress has been made in developing the best methods for harvesting, handling, storing, and processing the tubers for this purpose. Several varieties of the Jerusalem artichoke were studied with reference to yield and sugar content by Boswell et al. ( I ) . The data presented in Table I are based upon those given by these workers. The mean average yield of the twenty varieties investigated was 10.69 tons per acre; some varieties gave yields as large as 21 tons per acre under the most favorable conditions, I n Table I are listed those varieties which gave the average yield or better, together with the sugar content per ton and the pounds of sugar per acre. In the next to the last column are given the gallons of anhydrous alcohol per acre, based on expected commercial yields (90 per cent of theoretical); in the last column are given the bushels of corn per acre that would be required to give the same amount of alcohol. Little is known of the value of the dry by-product feed from the fermentation of the artichoke. Maaz (6) states that the slops from artichoke fermentations in a French distillery were fed to cattle, with results comparable to those obtained using the fermentation slops from corn, rice, or millet. Certain British investigators (3) state that the residue left after fermentation, if suitably dried, should form a good cattle cake with approximately the following composition: moisture 20.0 per cent, protein 32.3, ash 10.8, fat 3.7, crude fiber 10.0, and carbohydrates 23.2. It is anticipated that the results of experimental feeding tests on the dry by-product feed from artichoke fermentations will shortly be available. Intensive research on the breeding, cultivating, and harvesting of the tubers, a$ well as feeding experiments with both the tubers and distillery residues, will all be factors in establishing the economic status of this crop. Experiments on the use of fresh artichoke tubers for the production of alcohol were reported by Windisch (18, IO),Riidiger ( l a , I S ) , Lampe (6),Obrosov (Q), and Vadas (16). The average yields of alcohol obtained by each of these investigators, as well as by Maaz (6) in plant-scale operations, were approximately the same and corresponded to 16.8-21.8 gallons per ton of fresh tubers. Windisch obtained the highest yields by fermenting the raw mash, made by merely grinding the washed tubers with water. Treating the mash with malt or steaming either had no effect or lowered the alcohol yields. Rudiger found that it was advantageous to heat the mash for one hour at 56" to 56" C., followed by rapid cooling to fermentation temperature before yeasting. This could not be confirmed by Lampe, however. The latter worker obtained his highest yields by weakly acidifying the raw mash before fermenting it. Riidiger stated in his first report ( l a ) that acid
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Although alcoholic fermentations of pulpy mashes of the Jerusalem artichoke do not consistently give maximum yields, an aqueous extract prepared in a diffusion battery is an excellent yeast substrate. The extract can be kept from microbial decomposition by concentrating under reduced pressure to 70 per cent solids and storing under a carbon dioxide atmosphere. The carbohydrates in the sirup are stable up to 110 O C. at pH values between 4.8 and 9.0. No nutrients need be added to the extract, and preliminary acid hydrolysis of the carbohydrates is not necessary for successful fermentation. Various yeast strains give satisfactory alcohol yields (above 90 per cent conversion), and continuous cultivation of yeasts on unhydrolyzed artichoke extract increases their ability to produce high alcohol yields from this substrate.
hydrolysis of the mash led to slightly increased yields, but the data of his second paper (IS) show a somewhat better yield for a mash which had not been so treated. Obrosov found that Jerusalem artichokes were perfectly suited to the production of alcohol, although difficulties with packing the tubers in the cookers had to be overcome. Saccharification could be effected either with or without the use of acid. Vadas recommended two methods of pulping the tubers-mechanical grinding of the raw tubers or cooking for one hour with steam a t 1.5 atmospheres. After being ground, the raw pulp was warmed to 56-60' C. for 2 hours in order to convert the polysaccharides to fructose by action of enzymes present in the tubers, then cooled to 25" C., yeasted, and fermented. If the tubers were cooked, thus destroying the enzymes, 20 per cent of them were ground raw and mixed with the cooked pulp a t 56" to 60" C. in order to convert the polysaccharides to fructose. Experiments on the production of alcohol from Jerusalem artichokes were carried out in the laboratoryand in a semitechnical plant by British investigators (3) beginning in 1919. In the laboratory trials one kilogram of fresh tubers was used in each experiment; in the semitechnical trials a ton of tubers was fermented each time. They reported that the average yield of alcohol from tubers of 16.7 per cent carbohydrate content in seven laboratory experiments corresponded to 22.2 U. S. gallons of 95 per cent alcohol per ton of fresh tubers; in three semitechnical plant experiments the average yield was 22.4 gallons. These yields represent approximately 78 per cent of the theoretical yield. Samples of two varieties of artichokes were fermented on a semitechnical scale in 1921 and gave yields corresponding to 26.6 and 28.4 gallons, respectively, of 95 per cent alcohol per ton of tubers. The mashes used in the above-mentioned tests were not hydrolyzed. Laboratory trials had shown that a preliminary acid hydrolysis, with various concentrations of either sulfuric or lactic acid, resulted in the same or lower yields of alcohol. It is well known (15) that fresh Jerusalem artichoke tubers deteriorate rapidly even when stored under carefully regulated
1161
conditions. Therefore the tubers must be suitably processed for storage in order that this crop may be adapted for continuous operation of an industrial alcohol plant. Previous workers have not reported the use of artichoke materials other than the fresh tubers in the alcoholic fermentation. The present paper deals with preliminary laboratory studies of this phase of the use of the Jerusalem artichoke for alcohol production.
Materials Used McGlumphy et al. (7) demonstrated that desiccation of thinly sliced Jerusalem artichoke tubers, when the process is properly carried out, causes no loss of sugar and that the dried chips keep indefinitely without change in carbohydrate content. For most of the work reported here, the dried artichoke chips prepared by McGlumphy and Eichinger and stored a t Iowa State College were employed, thus ensuring a uniform material throughout the course of the investigations. A sirup was prepared from the chips by the method of McGlumphy et al. (7). The dried artichoke chips were extracted in a n eight-cell diffusion battery with water a t approximately 80" C.; a dark brown sirup was the result, which contained about 24 per cent solids based on refractive index, or about 22 per cent reducing sugar equivalent, varying slightly with the individual extracts. Concentrations as high as 40 per cent can be obtained if desired. Tests on the chips after extraction showed less than 0.3 per cent carbohydrate remaining. An extract from the fresh tubers can as easily be obtained by processing in the same manner. The sirup spoiled quickly, however, because of abundant and rapid growth of native microorganisms and hence could not be stored. This disadvantage was overcome by evaporating the extract under reduced pressure to a concentration greater than 70 per cent total solids. The resulting eirup was rather thick but was as easily handled as molasses. After 3 months no growth by bacteria or yeast was evident in this concentrate, but considerable mold growth, principally Aspergillus niger, had appeared on the surface. The growth of molds was overcome by storing the thick concentrate under an atmosphere of carbon dioxide. I n addition to the chips and the sirup, twelve varieties of fresh artichoke tubers received from the Luling Foundation, Luling, Texas, were subjected to fermentation tests. A 50pound sample of artichoke flour, about which no information as to method of preparation was available, was also subjected to fermentation.
Analytical Procedure Conversion of the polysaccharides of the artichoke into simple sugars was brought about by the method of McGlumphy, Eichinger, et al. (4, 7), by acidifying to a pH of 1.75 with hydrochloric
JERUSALEM ARTIC H O K E TUBERS JUST TAKEN FROM STORAGE
Fermentation of Dried Artichoke Chips and Artichoke Flour Preliminary experiments showed that cooking the ground dried artichoke chips with water and fermenting directly, either with or without acid hydrolysis, did not give good results. Such fermentations "headed" badly; that is, the solid matter was carried to the surface by the gas evolution and in this way was removed from contact with the liquid. This resulted in incomplete conversion of the carbohydrates into alcohol. Hence, no further laboratory tests were made directly on the dried material. However, the sample of artichoke flour was subjected to fermentation a t the plant of the Bailor Manufacturing Company, Atchison, Kansas, employing a 100-gallon culture tank. The artichoke flour was thoroughly mixed with sufficient water to make about 90 gallons of mash which were sterilized in the tank for 30 minutes a t 15 pounds per square inch pressure. The mash was inoculated with 2 gallons of an active culture of Saccharomyces anamensis grown in molasses medium, and the fermentation was allowed to proceed to completion. The yield of alcohol obtained was 80.5 per cent of theoretical. Moreover, difficulties with heading were again experienced.
Fermentation of Fresh Artichokes
acid (or Hof 1.5 withsulfuric acid) and heating to 80" C. for one hour. $he carbohydrate content of the materials employed was determined by subjecting them t o complete acid hydrolysis and estimating the reducing sugars formed (levulose and dextrose) by the Shaffer-Hartmann method (14). Fermentations were analyzed for alcohol by distilling measured volumes of the fermented mash, collecting the distillates in volumetric flasks, and determining the specific gravity (d;:) of the distillates with a Chainomatic Westphal balance; alcohol concentrations were then read from appropriate tables. The experimental results are expressed in terms of grams of alcohol per Cc. of medium, and also in per cent of theoretical conversion of total carbohydrate t o alcohol according to the equation: CBH~ZOR +2C02 2CtHsOH
+
The data re resent the average values for duplicate fermentstions, and a% yields are corrected for the amount of alcohol introduced with the inoculum.
Yeasts and Media
Since previous investigators have rather extensively studied the fermentation of fresh artichoke tubers, no attempt was made to exhaust the possibilities of the fermentation of this material. However, fermentation tests on the fresh tubers were carried out in duplicate in 500-cc. Erlenmeyer flasks with each of twelve artichoke varieties. Each flask contained 100 grams of finely ground tuber. Two methods of treatment before were For One series lZ5 Of water were added $0 each flask before cooking in the autoclave for 30 minutes a t 15 pounds steam pressure. For the other series, 75 cc. of water and 25 cc. of 1 N sulfuric acid were added to each flask before heating for hours at 8oo the flasks were cooled and 21 cc. of 1 sodium hydroxide were added to each to bring the pH to 5.5. All the flasks of both series were cooled to 30" C., and the contents were inoculated with 30 cc. of an active culture of Saccharomyces anamenS i S @own in molasses medium. These fermentations headed badly, and frequent shaking r a s necessary in order to keep the solid matter down in the liquid in attempts to secure complete fermentation. After 4 days analyses for alcohol were made, and the results are given in Table II. Because of the heading, the fermentations, as shown by the analyses, were incomplete in most cases and the results quite erratic, varying from 49 to 99 per cent of the theoretical yield. However, the data show no significant differences among the varieties as to alcohol yields, and, in
c.;
The yeasts used in the fermentation experiments were pure culture strains of Saccharomyces anamensis, Saccharomyces cereoisiae, and Xchizosaccharomyces pombe. The cultures were carried and maintained in active condition by transfer at 48-hour intervals into fresh stock medium. Three stock media were used: beer wort (meVARIETIES OF JERUSALEM TABLE I. YIELDDATAFOR SEVERAL dium A), unhydrolyzed artichoke extract (medium ARTICHOKE B), and hydrolyzed artichoke extract (medium C). The artichoke extracts contained carbohydrate Corn --Yield per Acre-Av. Equivaequivalent to 16 per cent reducing sugar, and the Cor- WashingAv. Total Sugar Aloohol leht pH was adjusted to 5.5. The stock media were variety or Urbana, "allis ton Per Per sterilized for 20 minutes at 15 pounds per square Accession NO. Ill. Wash: D. d. Mean ton acre e& ? e::] inch (1 kg. per sq. om.) steam pressure. MultipliTons Ton8 Tons Tons Lb. Lb. Gal. Bu. cation of-the yeasts was rapid and fermentation 238.0 91.2 7.90 10.92 313.8 3426 6.43 18.42 Blano Ameliore was vi orous in each of these media. 275.7 106.6 8.48 11.14 356.4 3969 19.96 4.98 Chicago 13.22 316.4 289.7 4170 111.0 21.51 8.88 For fermentation studies the experimental media 9.28 26,944 97.7 256.0 6.32 io.90 336.8 3670 6.36 20.00 26,984 were always adjusted to a pH of 5.4-5.5, using so267.7 102 ; 6 9.55 12.10 318.4 3863 8.11 18.62 27,007 dium hydroxide or hydrochloric acid solutions. They 283.1 108.5 11.08 368.0 4076 8.80 8.81 16.52 27,079 306.1 117.3 were inoculated by adding a measured amount of 7.67 18.08 11.13 12.29 358.6 4407 27,095 379.7 146.6 10.95 20.78 11.40 14.38 380.2 5467 27,574 active yeast culture in stock medium to ertch ex250.8 96.1 7.53 11.75 307.2 3610 19.08 7.74 28,098 uerimental flask with a sterile -uiuet - and were inkubated at 30' C . for 4 days.
,
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OCTOBER, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
1163
grams of reducingsugars per 100 cc.; the pH a t this dilution was 5.4. The acidity of four portions was adjusted to a series of different p H values by adding hydrochloric acid to Fermentation of Artichoke Sirup three of the portions, and the solutions were held a t 80” C. far one hour. The amounts of reducing sugars present in The difficulty with heading experienced in the fermentaeach solution following this treatment are shown in Table tion of the dried artichoke chips and the fresh tubers led to IV. After cooling, the pH was adjusted to 5.4 in each case the conclusion that fermentation of pulpy artichoke mashes by addition of sodium hydroxide, and fermentations were carwas not very practical. Preliminary fermentation tests had ried out with 200 cc. of medium in each 500-c~.Erlenmeyer shown that the aqueous extract from the dried chips furnished flask. The media were inoculated with 10 cc. of the indian excellent substrate for yeasts. Attention was therefore cated culture. The data for these fermentations are also concentrated on this material. given in Table IV. The results show that complete hydrolysis did not improve TESTSWITH DIFFERENT VARIETIES the yields of alcohol, a t least with Saccharomyces cereuisiae TABLE11. FERMENTATION OF FRESH ARTICHOKE TUBERS and Schizosaccharomyces pombe. The maximum yield obtained with the former yeast (99 per cent of theoretical) was Yieldsecured in the medium which had been heated a t a pH of 4.1. With the latter culture there was practically no difference in the yields from the media heated a t pH values of 4.1 and 5.4 19.0 Acid at 80° C. 7.44 USDA 27,574 76.8 (99.0 and 99.1 per cent of theoretical, respectively). At 6.04 Steam-cooked 62.0 least partial hydrolysis was necessary for the most successful 6.64 Acid at 80’ C. 18.2 56-7082, Milsmers Seedling 60.6 6.42 Steam-cooked 68.3 fermentation using Saccharomyces anamensis; the maximum Acid at SO0 C. 7.13 21.2 65.6 K-7 French, Mammouth white 5.30 48.9 Steam-cooked yield of 95.3 per cent of theoretical was obtained with the 12.7 Acid at 80’ C. 6.06 78.1 C, Oreg. medium most completely hydrolyzed. It is likewise obvious 4.46 Steam-cooked 68.9 Acid at SOo C. 7.72 99.4 15.2 USDA 26,984 from the data that the cultures acclimated by continuous Steam-cooked 5.54 71.4 21.1 transfer in unhydrolyzed artichoke extract produced higher Acid at 80’ C. 6.88 63.8 H4N, 31,642 Steam-cooked 6.72 62.3 alcohol yields. This is particularly evident with the unhydro6.47 16.1 Acid at SOo C. 78.7 B, Iowa 59.4 Steam-cooked 4.88 lyzed and less completely hydrolyzed media. Acid at 80’ C. 6.53 18.9 67.6 F-2. 26,723
general, yields were slightly better in the acid-hydrolyzed mashes.
Nebr. Black Land
19.3
E-1, Dunning
18.6
G-3, Chicago
14.4
Nebr. Sandy Land
19.1
Steam-cooked Acid at 80° C. Steam-cooked Acid at 80” C. Steam-cooked Acid at 80° C. Steam-cooked Acid at SO0 C. Steam-cooked
5.60 7.46 6.47 7.70 6.47 7.17 6.04 8.50 6.79
68.0 76.8 65.7 82.2 68.2 97.4 82.1 87.1 69.6
Discussion of Results The data presented above show conclusively that the Jerusalem artichoke offers excellent possibilities as a raw material for the production of industrial alcohol. When fresh tubers or dried material are made up into a mash directly and fermented, “heading” causes such difficulty that there is considerable doubt as to whether the artichokes can be successfully fermented to produce maximum yields in this manner. However, the aqueous extract produced from the artichokes by diffusion provides an excellent medium for alcoholic fermentation, and the extraction of either the fresh tubers or
Levulose is not stable at elevated temperatures, decomposition being especially rapid above 80” C. Mathews and Jackson (8) carried out extensive investigations on the stability of this sugar. It was desirable, however, to determine the stability of the carbohydrates in the artichoke extract a t higher temperatures, since the most convenient method of storing the material, as stated above, was found to be evaporation to a thick concentrate. The temperatures to which the TABLE111. INFLEENCE OF TEMPERATURE AND PH ON STABILITY sirup can be subjected during evaporation, without loss of OF CARBOHYDRATES IN THE EXTRACT FROM ARTICHOKE CHIPS carbohydrate content, were investigated. Portions of an exCarbohydrate as % of Reducing Sugar, after PH heating 1 Hr. at: tract a t various pH values, representing increasing acidities, 900 c. 1000 c. 1100 c . were prepared by the addition of hydrochloric acid. These 9.0 24.36 24.30 24.30 solutions were heated for one hour a t the temperatures indi8.2 24.40 24.40 24.30 24,45 24.40 24.35 7.0 cated in Table 111. After cooling, the solutions were hydro24.40 24.40 24.40 5.6 lyzed, neutralized, and analyzed for reducing sugars. The 24.35 24.30 24.36 4.8 2 4 . 2 0 2 4 . 3 0 3 . 7 24.00 results (Table 111) show that the carbohydrates in the extract 24.10 24.05 23,80 2.8 2 3 . 6 0 19.05 1 . 8 23.95 are stable a t temperatures as high as 110’ C. a t pH values between 4.8 and 9.0. It is of interest to note that acid tolerance decreased with inTABLE IV. EFFECT OF HEATINU AT VARIOUS PH VALUES, AND OF DIFFERENT crease in temperature, which is no doubt due CULTURES ON ALCOHOL YIELDSFROM ARTICHOKE SIRUP to increased formation of levulose a t higher acidiYeast ties. Inocu-Ethyl Alcohol Yield lum Saccharomyces Saccharomyces Schizosaccharomyces Unhydrolyzed artichoke sirup was successfully Crown anamensas cerevasaae pombe PH Reducing on , employed as one of the stock media for carrying during Sugars Me- G./100 G./lOO % of C./lOO % ’ of % of yeast cultures and gave vigorous fermentations. Heating G./lOO do. diumQ cc. theory cc. theory .cc. theory This led to an experiment to determine whether 1.8 12.35 A 6.13 94.8 6.16 95.3 5.95 92.0 B 6.16 95.3 6.16 95.3 6.06 93.8 hydrolysis is necessary to secure maximum yields 2.6 6.72 A 6.08 94.0 6.09 94.1 6.13 94.8 of alcohol, and also whether continuous cultivaB 6.13 94.8 6.16 95.3 6.16 95.3 4.1 2.10 A 6.06 93.8 5.99 92.6 6.08 94.0 tion of the yeasts on the artichoke medium imB 6.13 94.8 6.40 99.0 6.40 99.0 proved them for use in fermenting this substrate. 6.4 0.09 A 5.62 87.0 6.82 90.1 6.10 94.4 B 5.78 89.4 92.6 6.41 99.1 The concentrated sirup was diluted so that on 6.99 complete hydrolysis the medium contained, by a A = beer wort: B = unhydrolysed artichoke extract. analysis, the carbohydrate equivalent of 12.65
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7
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INDUSTRIAL AND ENGINEERING CHEMISTRY
the desiccated chips presents no serious problems. The types of diffusion batteries used in the beet sugar industry should be adaptable to handling artichokes, although drawbacks are cited by Proffitt and co-workers (IO,11).. Since fresh artichoke tubers cannot be stored readily, in order for year-round operation of an alcohol plant using artichokes to be possible, it will be necessary for the newly dug tubers, which may be harvested in the fall or spring, to be processed promptly. A part of them can be extracted and the sirup fermented directly, but by far the larger part of the tubers must be processed for storage. One method would be to concentrate the diffusion extract to a thick sirup and store it under a carbon dioxide atmosphere. Adequate supplies of this gas would be available a t any alcohol plant. Tripleor quadruple-effect evaporators would be suitable for the evaporation. The temperatures met in the evaporator would not cause decomposition of the carbohydrates of the extract, according to the experimental findings reported here. Another method of processing for storage is desiccation of the sliced tubers. The experimental results show that fermentation of the artichoke sirup presents no difficulties. The sirup needs only to be properly diluted, sterilized, cooled, and inoculated with suitable yeast culture. Carbohydrate concentrations equivalent to those commonly used in industrial plant practice for other raw materials give approximately complete conversion. No nutrients need be added, and preliminary hydrolysis of the levulans is not required for successful fermentation. The three yeasts used gave satisfactory alcohol yields (above 90 per cent conversion), although results were a little better with the culture of Schizosaccharomyces pombe, especially in fermentations of the unhydrolyzed medium. Strains of Saccharomyces cerevisiae are most commonly employed in industrial alcohol plants, and it is possible that some other strain of
VOL. 29, NO. 10
species will give better results than the one which happened to be selected for these studies. Continuous cultivation of the yeasts on artichoke medium increases their ability to produce high alcohol yields from this substrate.
Literature Cited (1) Boswell, V.R., Steinbauer, C. E., Babb, M. F., Burlison, W. L., Alderman, W. H., and Schoth, H. A.. U. S. Dept. Agr., Tech. Bull. 514 (1936). (2) Brachvogel, J. K.,“Industrial Alcohol,” New York, Munn and Go., 1907. (3) Dept. Sci. Ind. Research, Gr. Brit., “Power Alcohol from Tuber and Root Crops in Great Britain,” London, H. M. Stationery Office, 1925. (4) Eichinger, J. W., MoGlumphy, J. H., Buchanan, J. H., and Hixon, R. M., IND. ENQ.CFXEM., 24,41 (1932). (5) Lampe, B., Z. Spiritusind., 55,121 (1932). ( 6 ) Maaz, B., Zbid., 39,359(1916). (7) McGlumphy, J. H.,Eichinger, J. W., Hixon, R. M., and Buchanan, J. H., IND.ENO.CHEM.,23,1202 (1931). (8) Mathews, J. A., and Jackson, R. F., Bur. Standards S.Research, 11, 619 (1933). (9) Obrosov, N.,Brodil’naya Prom., 10,No.2,27 (1933); Chimie & industrie, 31, 1191 (1933). (10) Proffitt, M.J., IND. ENQ,CHEM.,27, 1266 (1935). (11) Proffitt, M.J., Bogan, J. A., and Jackson, R. F., J . Research Natl. Bur. Standards, 17,615 (1936). (12) Rfidiger, M., 2. Spiritusind., 43,203(1920). (13) Ibid., 44,222 (1921). (14) Shaffer, P. A., and Hartmann, A. F., J . B i d . Chem., 45, 365 (1921). (15) Traub, H.P.,Thor, C. J., Willaman, J. J., and Oliver, R., Plant Physiol., 4, 123 (1929). (16) Vadas, R., Chem.-Ztg., 58,249 (1934). (17) Wiley, H.W.,and Sawyer, H. E . , U. S. Dept. Agr., Farmera’ Bull. 429 (1911). (18) Windisch, K., 2. Spiritusind., 39,314 (1916). (19) Ibid., 43,292,300(1920). (20) Windisoh, K., and Jetter, W., Ibid., 30,541,552 (1907). RECEIVED June 1, 1937.
admiurn-Indium Alloy System
T
HE scarcity and resultant high price of the rare metal indium have made difficult any systematic study of its alloys. Consequently an investigation in this field not only fills a gap in the knowledge of binary alloy systems but is of primary importance as a basis for further theoretical and even industrial considerations. Because the a i n D -i n d i u m diagram’ was worked out in this same laboratory, the cadm i u m - i n d i u m system was chosen as the next logical step, in view of the close r e l a t i o n between zinc and cadmium. The metals used were el e c t r ol y t i c cadmium a n d i n d i u m of purity g r e a t e r t h a n 99.9 per cent, both obtained from the Great Falls Reduction Department of the Anaconda Copper Min-
CURTIS L. WILSON AND OSWALD J. WICK Montana School of Mines, Butte, Mont.
ing Company. Alloys were melted in a carbon crucible and were protected from oxidation by a cover of mineral oil. Transformation points were determined with a simple differPOINTS FROM THERMAL ANALYSIS ‘-STRUCTURE SHOWS EUTECTIC HOMOGENEOUS
e-
320.91300
A - STRUCTURE
A
1
ENQ.
Wilson and Peretti, IND. CHEM.,
as,
204 (1938).
FIG. I. DIFFERENTIAL
THERMOCOUPLE
20
40 60 75 80 PERCENT INDIUM BY WEIGHT
A
100
