Refined zircon sand is finding increasing use as a natural addition to porcelain or ceramic bodies to reduce the coefficient of expansion and increase the dielectric strength-for example, in spark plug bodies. A still newer use is in the manufacture of molds for cast steel and as an insulator in electric heating devices. Brazil is the only source of the natural zirconium oxide (brazilite or zirkite) a t present; extensive and workable deposits are found in the vicinity of Popos de Caldas. There are few commercial deposits of the unusual ores which present more interesting geologic as well as economic features than do the deposits of natural zirconium oxidein Brazil. The Caldas region is situated in the states of Minas Geraes and Stio Paulo, approximately 130 miles north of the city of Sbo Paulo. It is a mountainous plateau with a main elevation of about 3600 feet. The area is bounded on all sides by ridges rising abruptly from 600 to 1200 feet above the general level and forming a roughly elliptical enclosure about 20 miles in length. The town of Popos de Caldas is a health resort and boasts of many hot springs of reputed medicinal value. The presence of these highly mineralized waters has undoubtedly played an important part in the formation of the zirconium ore bodies. It has been estimated by Brazilian authorities that the ore reserves in this area are around 1,790,000 tons. Natural zirconium oxide appears on the market in two forms (a) in large ,compact, gray to blue-black masses carrying from 70 to 75 per cent zirconium dioxide, and (a) in the form of water-worn pebbles, known locaIly as favus, which contain from 80 to 90 per cent zirconium dioxide. The 70 to 75 per cent grade is by far the most plentiful and finds its principal use in the manufacture of ferrozirconium and as a high-grade refractory. Pure zirconium oxide melts around 4580" F., but because of impurities the natural oxide will not withstand temperatures much in excess of 3200" F. This lower melting point is to some extent offset by other important characteristics, such as high resistance to slag corrosion, low thermal conductivity, and low coefficientof expansion. To those eager for the conquest of new worlds, the less familiar elements, particularly those here treated, present a challenge with the promise of rich rewards.
Literature Cited
Protein Plastics Relation of Water Content to
Plastic Properties BROTHER, L. L. MCKINNEY
A. C. BECKEL, 0. H. AND
U. 5. Regional Soybean Industrial Products Laboratory, Urbana, 111.1
Soybean protein has been found to possess properties which permit the production of two different types of plastic material. Addition of water to soybean protein or meal leads to a product similar to casein plastic, whereas reduction of the moisture content below 5 per cent gives a zeinlike plastic. A new method for rneasuring plastic flow has been developed and applied.
HE best known and only industrially important protein plastic material up to the present time is casein plastic. The history of the development of casein plastics, as well as their properties and methods of manufacture, has already been published (3). Briefly stated, casein plastics are produced by adding water to the casein up to a total of 25 to 40 per cent, the mixture is plasticized by RECEIVED January 4, 1938. Presented as part of the Symposium on the Less heat and pressure, formed into the desired shape, and hardFamiliar Elements, the Second Annual Symposium of the Division of Physiened by soaking in dilute formaldehyde solution. cal and Inorganic Chemistry, American Chemical Society, held in Cleveland, It has been claimed that soybean (6) or other vegetable Ohio, December 27 to 29, 1937. proteins (7) can form the base for the manufacture of a number of plastics ranging from celluloidlike to rubberlike materials, but apparently none of these claims has been substantiated by a successful industrial process in this country. Olivine and Forsterite RefractoriesSoybean meal has found some application in a mixed type Correction of plastic (4, 8, Q), but it is of second8ry importance; that is, the plastic is essentially the phenol-formaldehyde condensaAn error occurs in my article, which appeared on pages 32 to 34 of the January, 1938, issue of INDUSTRIAL AND ENGINEERING tion resin type, and at most the function of the protein is that of a modifier. CHEMISTRY.Inadvertently, incorrect data were given for the The objective of the present investigation has been t o p r e chemical analysis of a typical shipment of olivine rock in the pare plastics from soybean meal and protein, and compare middle of column 1, page 33. The corrected items are as follows: them with plastics made from other protein material. To NiO 0.27% date this investigation has been confined to a study of the coo 0.038 (1) Chambers, G.H..German Patent 614,712(Oct., 1930); French Patent 741,994 (Dec., 1932); British Patent 393,449 (June, 1933); Belgian Patent 390,851 (Dec., 1932); U.S. 2,036,119 (March, 1936); Italian Patent 320,026 (Aug., 1934). (2) Clarke, F. W.,and Washington, H. S., U. S. Geol. Survey, Profesaional Paper 127 (1924).
Total
99,718
These corrections are published because the proportion of nickel and cobalt in rocks is a matter of scientific interest. V. M. GOLDSCHMIDT 436
T
1 A coaperative organization participated in by the Bureaus of Chemistry and Soils and of Plant Industry of the United States Department of Agriculture, and the Experiment Stations of the North Central States of Illinois. Indiana, Iowa, Kansas, Miohigan, Minnesota, Misaouri. Nebrasks, North Dakota, Ohio, South Dakota, and Wisconsin.
from Soybean Products
ONE OF
THE
RESEARCH LABORATORIES OF THE UNITEDSTATES REQIONAL SOYBEAN INDUSTRIAL PRODUCTS LABORATORY
did not spontaneously fracture on drying but were quite hygroscopic. When placed in 4 per cent formaldehyde solution, the concentration most favorable for hardening casein, they swelled excessively. However, they hardened fairly satisfactorily in 40 per cent formaldehyde. Commercial soybean protein was found to mix with water to produce a mixture more nearly similar to casein than to soybean meal, but it plasticized excessively with heat and pressure. The presence of aluminum sulfate improves this condition somewhat, but considerable study and experimentation will be necessary in order to produce a satisfactory plastic from commercial soybean protein by this method. As with the meal, the plastic produced is quite dark in color, brittle, and hygroscopic; it holds its shape well, does not fracture spontaneously on drying, and is almost transparent. These results demonstrated the feasibility of developing a plastic material similar to casein plastics from soybean meal or soybean commercial protein, although serious obstacles (chiefly the dark color and the tendency toward greater hygroscopicity) remained to be overcome. It was realized, however, that promotion of the large-scale use of soybean meal in the plastics field was contingent upon the development of a material not merely similar to casein plastics, but of a new and different type, as free as possible from the disadvantages that handicap the casein product. Themost serious of these disadvantages have been the long expensive process of manufacture and the hygroscopicity of the finished product, both of which are direct consequences of the use of water as a pla7ticizer in the manufacturing process. I n the course of expenments in this laboratory, it had been found that, in contrast to previous published and known procedures with protein materials, the soybean protein possessed flow properties a t reduced moisture content. It was considered advisable t o investigate this property of soybean meal and protein, for if it should be possible to plasticize the anhydrous material with
effect of water content on plastic properties. Other possible plasticizers, as well as reactants and hardening agents, will be the subject of subsequent study.
Materials The soybean meal used in this investigation was prepared in this laboratory from Illini beans grown during 1936 in the St. Joseph, Ill., area. The beans were cracked and flaked on rolls and extracted with hexane in a modified Sando extractor (6) for about 16 hours. The excess solvent was then removed by air drying at room temperature. Analysis showed 0.35 per cent residual oil, 9.28 per cent moisture, and 7.79 per cent nitrogen (crude protein = 7.79 X 6.25 = 48.69 per cent). Part of the meal was reduced to a flour in a Wiley mill; the remainder was used without further treatment. For comparative purposes various other protein materials were obtained from commercial sources. They included commercial soybean protein,2 expeller soybean flour, zein, linseed meal, cottonseed meal, rennet casein, and lactic acid casein. Preliminary Investigations Preliminary studies showed that it was practically impossible to work the soybean meal by exactly the same process as is employed regularly in the manufacture of casein plastics. The addition of water produced a sticky gummy mass which is very difficult t o handle. However, a solution containing 10 per cent aluminum sulfate, based on the weight of the meal, restrained the dispersing action of the water and made possible a mixture somewhat similar to casein and water. This mixture plasticized readily with heat and pressure, and molded well. The resulting plastic was dark reddish brown in color and translucent. Molded pieces held their shape well and * Sold aa Alpha soybean protein. The sample used had the designation "AP 267."
431
INDUSTRIAL AND ENGINEERING CHEMISTRY
438
0
2
4 6 PERCENTAGE
8
MOISTURE
IO
I2
FIGURHI 1. PLASTICFLOW OF PROTEIN MATERIALS
a nonvolatile water-repelling agent, then both disadvantages inherent in casein plastics would be obviated in the case of the product from soybeans. Therefore soybean meals of varying water content were examined with respect to the property of plastic flow under conditions of constant temperature and pressure.
Methods and Results Soybean meal, with the normal moisture content of 9.28 per cent in this case, plasticized quite satisfactorily when subjected to 100" C. and a pressure of 5000 pounds per square inch (351.5 kg. per sq. cm.) for 5 minutes. The moisture content was reduced by a number of different methods, and the meal samples were pressed under the conditions stated above. AI1 exhibited flow until the moisture content was about 1 per cent. As the moisture content was lowered below about 5 per cent, the resulting plastic underwent a marked alteration in appearance. The color became lighter, the transparency increased, and the product assumed a hard, vitreous, and somewhat resinlike appearance. The moisture in the meal was reduced by heating in drying ovens a t atmospheric and reduced pressures, by placing the meal over solid caustic soda in a desiccator a t room temperature, and by treating it with absolute ethanol or acetone. Independent of the method used for dehydration, meal with a moisture content of about 5 per cent or less gave what appeared to be a different type of plastic when pressed. In order to determine the effect of heat treatment on the plastic properties of the protein, a sample of soybean meal was dried a t 100" C. and atmospheric pressure for 2.5 hours. A portion pressed at 100" C. and 5000 pounds per square inch for 5 minutes showed little flow. The remainder was divided into two parts; one was sealed in an airtight flask and the other was left exposed to the air. At the end of 5 days the latter had a moisture content of 7.69 per cent; when introduced into the press as previously described, it flowed perfectly. Under the same conditions the former flowed to the same extent as did the sampIe in the check test. It is evident that the lack of flow in the cases of the check and protected
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sample was due to extremely low'moisture content rather than to any change in the properties of the protein caused by the heat treatment. The validity of this conclusion was further substantiated by the observation that prior treatment of the meal with absolute ethanol or acetone led to the same type of dehydrated plastic. The following experiment may be considered typical of the method used and the result of the effect of an organic solvent dehydration treatment : After treatment with absolute alcohol, the meal was evacuated at 70" C. in a flask, and the vapors removed were condensed by a mixture of solid carbon dioxide and acetone. Assuming the complete removal and condensation of both alcohol and water, the original moisture in the meal may be calculated from the loss in weight of the sample and percentage of alcohol in the condensate, as determined by specific gravity. Thus a treated sample of 33.121 grams lost 10.5436 grams of condensate with a density (di55) of 0.81468. The percentage of water in the original sample was therefore (1.0733/23.6507) or 4.54 per cent, and the resulting plastic, as expected, was of the dehydrated type. Other protein materials, such as zein, linseed meal, cottonseed meal, rennet casein, and lactic acid casein, were superficially studied in the same way for comparison. They gave somewhat analogous results; that is, they all flowed more or less readily a t reduced moisture content, but only in the case of soybean meal and protein was there any marked evidence of the formation of a differenttype of plastic.
Method for Measuring Plastic Flow Measurement of the flow characteristics of a plastic material presents many difficulties which have been discussed frequently in the literature ( I , 2 ) . I n general, the complete description of these characteristics requires the measurement of the time rate of deformation under several different values of shearing stress. It may reasonably be assumed, however, that the more important characteristics of a material designed to be used in die molding may be approximated by a single measurement made under a condition of stress similar to that which would be used in actual molding. A given protein material, for example, will have a different fluidity-pressure relation for every different moisture content. The curves representing this relation will form a "family" whose variation from one another is dependent upon the moisture content only. Therefore a measurement a t constant pressure, temperature, and time will give a comparison of the apparent fluidities a t the various moisture contents. The type of deformation chosen for measurement in the present work was the compression and radial flow of a molded disk under constant load. Temperature and load were chosen a t such values as to correspond approximately to molding conditions for materials of this type. The dimensions of the test disk were accurately measured before the test and again after the lapse of a constant length of time sufficient to give easily measurable deformation of practically all the samples. Although an effort was made to keep the initial dimensions of the test pieces the same, only the diameter was actually constant at slightly over 1 inch (2.54f cm.); the thickness varied between 0.10 and 0.28 inch (0.254 and 0.711 cm.) with an average of about 0.20 inch (0.508 cm.). Since the diameter of a sample disk after deformation is difficult to measure with accuracy, the proportional change in thickness of the sample was chosen as the simplest and most precisely measurable index of the deformation. Then by definition : (ht - hZ)/F*l = coefficient of plastic flow where h~ = initial thickness of disk h?:= final thickness of disk
INDUSTRIAL AND ENGINEERING CHEMISTRY
APRIL, 1938
The coefficient is obviously not a constant for any given material, but it will vary with the length of time the sample is under load, as well as with the load and temperature. There is undoubtedly also some effect of the initial thickness of the disk (a thick disk will flow somewhat more easily than a thin one), but several check experiments indicated that this effect is minor. The test disks were molded in the same closed-type die under constant conditions from carefully controlled material. The total moisture was determined as the loss in weight on heating for 2 hours in an oven a t 130" C. and atmospheric pressure. The samples containing various known percentages of moisture were prepared by heating in the oven at 130" C. for periods varying from 5 minutes to 2 hours. The samples were about 5.5 grams each. TABLE I. ANALYSES OF PROTEIN MATERIALS Material
Normal ,Moisture
% Regular solvent-extd. soybean meal Soybean commercial protein Soybean expeller flour Zein Rennet casein a Per cent N X 6.25.
9,28 8.27 7.58 7.35 7.77
Oil Content
Crude Protein5
%
% 48.69 8S,30 49,30 92.00 82,50
0.35 0.12 7.45 0.16 0.11
439
When the moisture content of the soybean expeller meal was above 7 per cent, it was found extremely difficult to mold the test disk a t 142" C. and 24 tons pressure since the mass became very mushy in the die and shot out through the loosefitting sides. This was probably due to the formation of an emulsion, since the oil content was rather high. A study of the data and curves indicated that, with the exception of expeller meal which is probably plasticized by oil, zein is the least dependent upon moisture for plasticization and flow, casein is the most dependent, and the other soybean products are intermediate. For the zein protein under the conditions of the experiment there is definite flow a t zero per cent moisture and little increase in plasticity as water content is increased until the latter reaches 2 to 2.5 per cent, and plasticity probably approaches the limit at little above the normal moisture content of most protein materials. Zein does not form the water-plasticized type of plastic material as do casein and soybean meal a t higher moisture content. On the other hand, casein shows greater dependence upon water for flow. From the data and curve no flow under the conditions of the experiment would be expected with less than about 4.5 per cent moisture content. Theoretically no plastic of the zein type should be expected, and in this study none was produced. It is interesting to note the sharp break in the soybean commercial protein curve a t 2.5 to 3.0 per cent moisture, when it appeared from the slope that the point of no flow would be above 2.0 per cent moisture. It is probable from the soybean curves that plastic flow will be possible down to nearly 1 per cent moisture, and again this is in accord with actual experience in this study. If the chemically combined water of this material is presumed to be of the order of about 1 per cent, it is evidently possible that soybean protein can flow, as in the case of zein, without the aid of any free water. Casein, the only animal protein studied, shows marked differences in plastic behavior from the other proteins. Amplification of this work to include other animal and vegetable proteins to determine the extent of these differences would be of value, but it is not intended a t present to continue this line of work. The zein-type plastic produced from soybean meals and protein of less than about 5 per cent moisture content is of no great commercial value in itself. Although it comes finished from the die and does not shrink or warp excessively, as in the case of the casein-type plastics, it is very hygroscopic and inclined to be rather brittle. Its importance lies in the
The samples were introduced into the cold die, the plunger previously heated to 142' C. was inserted, and the die was held a t 142" C. and 24 short tons (21,772 kg.) pressure in a hydraulic press between steam-heated platens. The die was then cooled under pressure by circulating cold water through the platens, the disk.was removed, and the thickness a t the center was accurately measured with a micrometer. The disks measured about 0.197 X 1.063 inches (5 X 27mm.). The measured disk was placed in a larger die (in this case about 2.24 inches or 57 mm. in diameter) which had been preheated to 142°C.; with the temperature maintained a t 142"C., the disk was held under a constant hydraulic pressure of 2000 pounds (907.2 kg.) for exactly 5 minutes. The die was then cooled as before, but this time for exactly 7 minutes. The disk was removed, and the thickness a t the center was again measured accurately with a micrometer. For detailed comparison with the regularly solvent-extracted soybean meal, plastic flow coefficientswere determined by the foregoing method for soybean commercial protein, soybean expeller flour, zein, and rennet casein. Analyses TABLE11. PLASTIC FLOWMEASUREMENTS OF PROTEIN MATERIALS of these products for normal moisture, CoeffiCoeffi. protein, and oil content are given in cient of cient of Moisture Initial Final Plastic Moisture Initial Final Plastio Table I. Content Thickness Thickness Flow Content Thickness Thickness Flow The zein and rennet casein were % Inch (mm.) Inch (mm.1 yo Inch ( m m . ) Inch (mm.) selected from the group studied superSoybean Expeller Meal Soybean Extracted Meal ficially because they appear to represent 2.14 0.127 (3.226) 0.107(2.718) 0.157 2.02 0.238 (6.045) 0.223 (5.664) 0.063 3.44 0.138 (3.505) 0.077 (1.956) 0.442 2.61 0.237 (6.020) 0,199 (5.055) 0.160 the two extremes of plastic flow in this 4.22 0.103 (2.616) 0.063 (1.600) 0.388 3.00 0.223 (5.664) 0.160 (4.064) 0.283 group; the former showed unusual readi7.49 0.188 (4.775) 0 . 0 5 8 (1 ,473) 0.691 4.09 0.240 16.096) 0.133 (3.378) 0.446 5.27 0.236 (5.994) 0.126 (3.200) 0.466 ness to flow a t reduced moisture content, Z€:in 5.77 0.229 (5,817) 0,098 (2.489) 0.572 6.74 0,231(5.867) 0.089 (2.261) 0.615 and the latter showed the most reluc0.00 0.139 (3.531) 0.137 (3.480) 0.014 7.82 0.222 (5.639) 0.083 (2.108) 0.626 tance. The results obtained are given 0.67 0.140 (3.556) 0.138 (3.505) 0.014 10.94 0.283 (6.426) 0.079 (2.007) 0 . e87 2.57 0.130 (3.302) 0.110 (2,794) 0.154 10.94 0.262 ( e .655) 0.077(1.956) 0.706 in Table 11and in Figure 1. 5.34 0.141 (3.581) 0 071 (1.803) 0.496 9.48 0.159 (4.039) 0,039(0,991) 0.754-k" At a little above normal moisture Commercial Sciybean Protein content, zein flowed so readily that it Rennet Casein 2.11 0.208 (5,283) 0.199 ( 5 . 0 5 5 ) 0.043 2.71 0.189 (4.801) 0.178 (4.521) 0.058 completely filled the large testing die 4.92 0.199 (5.055) 0.192 (4.877) 0.035 4.11 0.166 (4.216) 0.114(2.896) 0.313 5 . 0 2 0.278(7.061) 0.257(6.528) 0.076 and flowed up the sides as well. The 4 37 0.209 (5.309) 0.125 (3.175) 0.402 5.79 0.142(3.607) 0.116 (2.947) 0.183 6.61 0.187 (4.750) O.OSS(2.235) 0,529 maximum flow measurable in the die 6.38 0,151(3.835) O.lll(2.819) 0.265 9.65 0.224 (5,690) 0.075 (1,905) 0,665 6.56 0.171 (4.343) 0.124 (3.150) 0.276 used would be represented by the coef7.98 0.151 (3.835) 0.097 (2.464) 0.358 7.98 0.132 (3.353) 0.086(2.184) 0.348 ficient 0.754. The true value for the a Flow t o o great to be measured by this method zein would be greater than 0.754, as is with the equipment used. indicated on the curve by the dotted line.
'
INDUSTRIAL AND ENGINEERING CHEMISTRY
440
new field of possibilities it opens for the development of a new line of moldable resinous plastics (IO). Since the material is thermoplastic and not dependent upon water for plasticization, it should be possible to work into it water-resistant plasticizers or reactants which would increase its thermoplasticity at the same time and render it reasonably impervious to water. Up to the present it has not been possible to do this in the field of protein plastics because water was considered essential for plasticization. Obviously it is difficult, if not impossible, to render the plastic water resistant if it already contains considerable water. There may be a number of means of effecting this result, the most promising and practical of which will be investigated.
Summary Water-plasticized material analogous to casein plastics from soybean meal or protein can be prepared, but modified procedure would be necessary and it is questionable whether as good a product would result. Reduction below about 5 per cent of the moisture content of soybean meal or protein gives a base material from which a
VOL. 30, NO. 4
different type of plastic material results. Its properties more closely resemble those of zein than those of casein. Using this dehydrated protein base, it should be possible to develop resinouslike plastics that would come finished from the die and have greater water resistance than would be possible with water-plasticized material.
Literature Cited (1) Bingham, E. C., J . Phys. Chem., 29,1201-4(1925).
(2) Bingham, E. C., and Lowe, B., Colloid Symposium Annual, 7 , 205-12 (1930). (3) Brother, G.H.,in E. Sutermeister’s “Casein and Its Industrial Applications,” A. C. S. Monograph Series, Chap. 6, New York, Chemical Catalog Co., 1927. (4) Chase, Herbert, Brit. Plastics. 7, 518-21 (1936). (5) Sando, C. E., IND. ENG.CHEM.,16, 1125 (1924). (6) Satow, Sadakichi, U. S. Patents 1,245,975-6, 1,245,979-80 (Nov. 6, 1917). (7) Ibid., 1,245,978, 1,245,983-4(Nov. 6,1917). ( 8 ) Sturken, Oswalt, Ibid., 2,063,850(Sept. 8. 1936). (9) Taylor, R.L., Chem. & Met. Eng., 43,172-6 (1936). 29, 673-4 (1937). (10) Walsh, J. F.,IND. ENG.CHEM.,
RECEIVED Deoember 17, 1937.
STRUCTURE IN ASPHALTS Indicated by SolventTreated Surfaces are usually conA SPHALTS sidered to bemotected lyophobe.sols (3) made u p of
R. N. TRAXLERI AND C. E. COOMBSZ The Barber Company, Inc., Barber, N. J.
soft, rather f l u i d m a t e r i a l as the medium, and harder carbon compounds of higher molecular weight as the dispersed lyophobe portion. The soft medium or continuous phase is usually known as petrolenes or malthenes, the dispersed materials are called asphaltenes. Since they may best be compared with resins, the protective colloids, which are regarded as unsaturated
A study of flow characteristics indicates that asphalts possess varying degrees of internal structure, depending upon the source of material, method of processing, and temperature at which the rheological test is made. Asphalts which show distinct anomalous flow characteristics as manifested by a high rate of age hardening, marked elastic properties, etc. , give surface designs when treated with partial solvents such as ethyl ether and 86” Be. naphtha; with asphalts that are essentially viscous, no designs are obtained. Consequently, the presence of a surface pattern may be an indication of the presence of structure in an asphalt.
h y d r o c a r b o n s with a high sulfur or oxygen content, are frequently k n o w n a s a s p h a l t i c resins. Kalichevsky and Fulton ( 2 ) reviewed briefly the work done chiefly in Russia on the chemical composition of asphalts. Methods are described for separating the asphaltenes, asphaltic resins, asphaltous acids, and oily constituents. Traxler (6) found that dialysis of pyridine solutions of asphalt results in the sepsration of a soft diffusate from a harder dialyzate, with the properties of each fraction depending on the source of the asphalt and the method used in processing it. Rheological investigations ( I , 6) on various kinds of asphalt indicated that many of them possess the anomalous flow characteristics commonly associated with the colloidal state, and that the type of flow possessed by an asphalt depends on (a) the source, (b) the method and degree of processing, (c) the temperature of the asphalt, (d) the rate of shear a t which the flow test is conducted, and (e) the age of the sample. The phenomenon of age hardening of asphalt is, during its early stages, a reversible process and has been ascribed (7, 8) to the gradual development of a structure within the material. This structure, a portion of which is thixotropic in nature, causes an increase in consistency and is frequently accompanied by the appearance or exaggeration of nonNewtonian or anomalous flow characteristics. A visual confirmation of the existence of structure within those asphalts whose rheological properties point to such a condition would be of value. This paper presents the results of preliminary experiments made to obtain such visual evidence. The only previous work of this kind that has come to the attention of the authors was that of Schwarz (4) who Present address, The Texas Company, Port Neohes, Texas. Present address, Cellophane Semi-Works, E. I. du Pont de Nemours & Co., Ino., Buffalo, N. Y . 1
2
