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INDUSTRIAL A N D ENGINEERING CHEMISTRY
a large part of the entertainment. Both the production and projection of motion pictures are dependent on our modern electric illuminants. Altogether, we owe a great deal of our
Vol. 18, KO.9
progress to the improvements in electrical illumination during the past fifty years. It is constantly contributing to our prosperity, progress, safety, comfort, and happiness.
Fifty Years’ Progress in Aluminum’ By Junius David Edwards ALUMINUM COMPANYOF AMERICA, NEWKENSINGTON, PA.
I
N LOOKIKG back fifty years to the date of the founding
of the AXERICANCHE~V~ICAL SOCIETY,we are struck by the fact that, practically speaking, the aluminum industry did not then exist; it has reached its present state of development within the lifetime of the SOCIETY. I n contradistinction to the other common metals, aluminum can only be produced by methods involving chemical and electrochemical discoveries and technic, and these are the reasons why it remained totally unknown to the human race until the early part of the last century. While its progress has been rapid in many ways, it nevertheless has made but a beginning, and the future is one of great promise. Aluminum is the only common metal whose ores require an extensive and exhaustive chemical refining treatment to produce a chemically pure compound before its reduction to metal. Every other material consumed in its reduction must also be of the highest purity. The production of aluminum is particularly dependent, therefore, on chemical manufacturing and control processes. Men of an earlier age could and did produce iron, copper, gold, silver, lead, and tin by rule-of-thumb processes, but only the development of modern science makes possible the production of aluminum. Preparation First made by the Danish chemist and physicist, Oersted, in 1825, its early history was one of purely chemical development. The names of Wohler and Deville are closely associated with the production of aluminum by the reduction of aluminum fluoride and cryolite with metallic sodium. I n an effort to cheapen the production of aluminum, Castner discovered and developed his process for the production of sodium. Although the price of aluminum fell to about seven dollars a pound, this did not prove to be the solution of the problem. It remained for Charles M. Hall, an American chemist just out of college, to discover, early in 1886, the electrolytic process of reduction which marked the birth of an industry. The story of Hall’s persistent and successful fearch for a practical method of producing aluminum has already been told. I n France, and at almost the same time, P. V. Heroult discovered substantially the same process as did Hall. The United States Patent Office, however, awarded priority of invention to Hall. The preparation of a pure oxide of aluminum from the naturally occurring crude hydrate, bauxite, was worked out by Bayer. I n spite of the great variety of processes which have been studied and proposed by inventors in every land, substantially all of the aluminum oxide consumed by the industry is still prepared from bauxite by a chemical process involving the production of sodium aluminate (either by digesting bauxite with caustic soda or fusing it with soda ash) and its decomposition (by hydrolysis or precipitation with carbon dioxide) to form the pure hydrate, which is converted to the oxide by calcination. The numerous processes for extracting the oxide from clay, usually by digestion with acids, followed by purification and de1 Received May 27, 1926.
composition of the salts, seem to be inherently unable to compete with the Bayer process except under very exceptional conditions. The electric furnace processes for refining bauxite have not been a commercial factor up to this time, but seem to have important possibilities of future development. The preparation of purified alumina is in itself an immense chemical industry. The estimated production of 300 million pounds of aluminum in 1925 required the preparation of more than 600 million pounds of purified alumina. One works alone in the United States produces over 400 million pounds of alumina annually with a n average impurity content of only about 0.5 per cent, of which less than 0.1 per cent (silica and iron oxide) is reduced and appears in the metal. The early years of the aluminum industry were largely occupied in solving the technical and engineering problems incident to establishing the electrolytic process on a commercial scale. To the versatile genius of Charles M. Hall, aided by the enthusiastic support of his associate, Alfred E. Hunt, is due much of the credit for this development. Many inventions, some patented but most of them not, were Hall’s contribution to the art. His faith in the future of aluminum was such that he confidently urged continued expansion, even though no immediate market for the metal was in sight. I n recognition of his achievements Hall was presented with the Perkin Medal by the Society of Chemical Industry in conjunction with the AMERICANCHEMICAL SOCIETY and the American Electrochemical Society in 1911. When hydroelectric power became available in quantity a t Niagara Falls, the aluminum industry of this country moved there. However, with the constantly increasing demand for power, in and around our large cities, the center of production has moved to lower cost water-power cites. The latest of these developments is the establishment of new works on the Saguenay River, Province of Quebec, Canada, where there is a potential 800,000 horsepower waiting to produce aluminum. Uses
Having learned how to make aluminum, there still remained the formidable problem df finding a stable market. For many years practically every use of aluminum was a new use. The producer was frequently forced into a manufacturing business in order to prove that aluminum could be satisfactorily employed for this purpose or that. Fabricating methods had to be devised or adapted, and the industry still finds it has countless problems to solve in the melting, casting, rolling, drawing, spinning, extruding, forging, ,pressing, machining, welding, soldering, and finishing of aluminum and its alloys. The aluminum cooking utensil formed one of the first and best known outlets for aluminum. Singularly, one of the latest uses has been its extensive employment in electric household devices, such as the vacuum cleaner and washing machine. Through the vision and inventive ability of William Hoopes the practicality of aluminum conductors for electric power
traiismissioii was ~lemoiistrated. Over lj0,oOO nriles aluminum coirductor are now in service and this sllhstanti~l total is rapidly being increased. Weiglxt for weiglit, aluniinuin lias twice the conductivity of copper. An aluminum conductor of given capacity has a greater surface and eonsequeiitly lower corona loss than a similar copper conductor. Its lighter weight permits further economies in tlie eoirstruction and rriiiriber of supporting towers required for a power line. Aleminum found an early aud extensive use in the automobile. Now that its usefulness has .. -~ bccn dernonstrat~edin tire modern and u w e l forms of transportation, aircraft and the motor bus, t,he railroads are goiiig back to fundanrcnt,als to see diether alumiiium will not also solve many of their problems. Along still another line mention may be made of t h e e n t r a n c e of aluminum-bronze po~~-dcr irrto the paint field.
querioliiug is to form a solid solution of certitiri of the elements, notably copper, in aluminum. Moreover, the atomic mobility is still sufficient., even at 20" C., to permit the excess dissolved material held in the quenched solution to precipitate in the form of submicroscopic particles. This highly dispersed precipitate is responsible for the marked increase in strength and hardness of the alloy after aging. The t,beory of Merica and his co-workers stimulated further rcsearcll in tlie ficld of heattreated allovs and it has proved a fertile one iniced. Archer and Jeffries4discovered that the hinary aluminum-copper alloys which aft.er q u e n c h i n g do not age-harden substantially at room temperature may be made to do so by heating at temperat,ures of about 100" to 175" C . A t the National Physical Laboratory in England it was discovered that aluminum alloys containing magnesium and silicon, hut without copper, ageAlloys h a r d e n a t room temperature after queaching from about .WOO" C.3 CerAt the beginning of the twmtietll tain of the alumiiiuin alloys containing wutury the field of tlie possible emmagnesium and silicon but without ploymcnt of aluminum had been surcoppor are inore plastic and worknble rcyed in a broad way. Its uses for tlrnn Duralumin and by quenching structural purposes were limited hy and then aging at an elevated temtlic physirill propcrt.ies available in tlic perature their strength and hardness known wrought alloys which had n are increased much more tluin hy tcnsile strength of about 30,000 to room temperature aging.@Archer and 10,OOO pounds per square inch, with Jeffries also discovered how to lieata limited duct.ility. About thia time treat, aluminum alloy castings to pro:mi epoch-making discovery was mail(: cluc:e coirimercially valuable results. by Alfred Wilm,2 wlieri hc found tlmt As a result of these inventions and aluminum alloys of a particular contheir intensive development by the inp o s i t i o n were susceptible to 'Rent dustry new horizons have been opened treatment of a novel character. Alfor aluminum. most at a stroke the a t t a i n a b l e s t r c n g t l i of aluminum alloys was -4s an interesting comment, up to Charles M. Hnll 11863-19141 ~. doubled. With aluminurn alloys ha,This ptioto is from the scuipfuie hy about 1020 silicon had been generally 0 . Morriti, a Pitfsburgh ~ u l p i o r .and i s ing the st,rengtli of mild steel aiid considered an undesirable element in cart from aluminum-siiieon anoY It is *,ow in t h e Carnegie hIvarum oi Piitslrurgh. ndequate ductility, it is little wonder aluminum. Now that its . nromr . use if metallurgists i n d u l g e d i n s o m e and possibilit,iesare better undcrstood, roseate dreams. i t has quickly taken its place as one of Without more than an empirical knowledge of the meehan- thc important alloying elements. Aladar Pacz' directed the ism of his heat process, Wilrn developed one of the best at,tcnt,ion of aluminum metallurgists to the aluminum(if the "sbrong" aluminurn alloys now available. Yet it silicon alloys by his invention of a process of modifying tlre remained for workers a t our o m National Bureau of Stand- alloy structure hy treatment of the molten alloy with sodium ards to offer a satisfactory explanation of the heat treatment fluoride. This "modification" process is an interesting process. Wilm's alloy, which he called "Duralumin," and novel example of "colloidal metallurgy." Two or three contaius as its essential ingredients about 4 per ceut. copper, lrundredths of a ncr cent of metiLllic sodium introduced into 0.5 per cent magnesium, and the silicon and iron present the molten alloy before castiug increases its tensile strength as impurity in the ingot aluminum, together with about by 50 per cent and the ductility by several hundred per 0.6 per cent added manganese. When the wrought alloy Aside from this development, which has not yet found exis heated to ahout 500" C. and quenchcd therefrom, it is tensive use, silicon was found to have valuable alloying in a metastable condition. On stauding at room iemperaturc properties from the staidpoint of facilitating casting procit begins to harden almost immediately; after four days the esses; its use has almost revolutionized aluminum die-casting. hardening or aging is practically complete. The tensile Although a practical process of refining impure aluminum strengt.h, which may have been, for example, about 45,WO has long been desired, it is only ivithm the last five years pounds per square inch shortly after quenching, has increased that i t lias become an actuality. William Hoops, in coto about 60,000 pounds per square inch on standing a t room operation with the research staff of the Aluminum Company temperature. 4 U. S. Patent 1,472,738 (applied for December 20, 1921); Tranr. Merica, Waltenberg, and Scott,Z by an ingenious chain . .win. M ~ LEW., . 71, 828 (1925). of reasoning based on their own experimental work, advanced ~ minst. Henroii and Gayier, J. I n # Mctoli, 18, 321 (1021). tlie theory that the result of heating the alloy previous to 6 Archer and Jeffries, U. S. retent 1,472,739 (applied for December f
9
German Patents 170,085 (October 20, 1903) and 244.534 (March 20,
1909). 3
20, 1921J. 7 U. S. Patent l,3S7,9W (appliedforFebruary 13, 1920). 6
Bur. Slondovds, Bull. 16, 271 (1919); Trans. Am. Inst. Mia. Met.
E w . , 64, 41 (1Y20).
Edwards and Archer, Chcm. Met. Eng., 81, 504 (1924); Edwsrds, U. S. Patent 1,410,461 (applied for November 27.
Yrary, and Churchill, 1s201.
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IiVD USTRIAL A N D ENGINEERISG CHEMISTRY
of A m e r i ~ a ,devised ~ and put into successful operation a refining process similar in principle to an early proposal of his own and a later patent of Anson G. Betts.Io I n this process a heavy liquid anode of aluminum-copper-silicon alloy and a cathode layer of liquid aluminum are separated by a layer of fused electrolyte of intermediate density. The three molten layers are thus superimposed on each other in the order of their densities. Current passing from the lower anode layer selectively dissolves pure aluminum and deposits it on the upper cathode layer. For the first time since the inception of the industry, aluminum of a purity as high as 99.98 per cent has become available. It is too early to predict the uses this high-purity metal will have in the industry; it has, however, been invaluable in the scientific study of the properties of aluminum and its alloys. The modern development of alloys is particularly 9 Hoopes, U. S. Patent 673,364 (applied for September 1, 1900); Hoopes, Frary, Edwards, Horstield, U. S. Patents 1,534,315,1,534,317, 1,534,318, 1,534,319, 1,534,320, 1,534,321,1,534,322(all applied for December 21, 1922). See also Frary, Trans. Am. Electrochem. Soc., 41, 276 (1925). $ 0 U. S. Patent 795,886 (applied for April 1, 1905).
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concerned with the effects of very small amounts of alloying elements. The use of high-purity aluminum permits the study of such effects without the confusing presence of the appreciable amounts of iron and silicon always existing in aluminum made by the Hall process. Conclusion
I n the United States and Canada a production of about 40,000 pounds of aluminum per year, in 1890, has grown to over 200,000,000 pounds today. As statistics, these figures are imposing, but no more so than would be the complete story of the technical development of the aluminum industry. This brief review has touched upon only a few of the more interesting and outstanding technical and commercial milestones of progress, but mention must be made of the indispensable efforts of the technical staffs of the producers, which have brought these and other inventions to commercial fruition. With the tools of research made available by modern physics and chemistry, it is not too much to expect that the next fifty years will be equally impressive.
The Role of Chemistry in the Manufacture of Silk' By Walter M. Scott CKENEYBROTHERS, SOUTH MANCHESTER, CONN.
H E introduction of the technically trained chemist into the textile industry, and particularly into the silk branch of this industry, is a comparatively recent event. Fifty years ago no article could have been written on this subject and, in fact, no one would have attempted to write such an article, because chemistry was not even thought of in connection with silk. Ten years ago the chemist had progressed far enough so that he was in a position a t least to write an apology, defending his entrance into the silk industry chiefly from the standpoint of the number of problems waiting to be solved, and prophesying great things for the future. At the present time, although it cannot be truthfully said that we have arrived a t a complete understanding of all the processes of silk manufacture-still we can, with a reasonable amount of pride in our profession, assert that the application of the principles of chemistry has pointed the way to the solution of a number of these problems. At the very beginning the chemist had to possess more than the usual amount of temerity, which is generally ascribed to him, to expect to make any impression on an industry that had been in continuous operation since the dawn of history. We have authentic evidence that in the early ages the cultivation of the silk worm and the manufacture of silken fabrics were placed under the direct supervision of kings and emperors, and they were even dignified by occupying a space in the writings of the famous Chinese philosopher, Confucius, who lived about 500 B. C. Ever since the beginning of time the processes involved in the manufacture of silk have been jealously guarded. I n the early days in China the cultivation of silk was made part of a religious ceremonial and there was a penalty of death for anyone who divulged the secrets of the art to unauthorized persons. During the Middle Ages in Europe there were developed very powerful guilds of silk workers, to
which a man was admitted only after many years of apprenticeship. Even fifty years ago the idea of handing down the secrets of the trade from father to son still persisted, particularly among silk dyers and finishers. These people were naturally opposed to having their formulas and processes analyzed and interpreted by an outsider, and equally so to making any radical changes in the methods that they had been using for many years. Fortunately, an outside influence came to the aid of the chemist. The gradual development of synthetic dyestuffs during the past fifty years necessitated radical changes in dyeing procedure and paved the way for the scientifically trained man to work out new methods of application to fit the new types of coloring matters. Finally, the readjustments brought about by the World War, including the threatened famine of dyestuffs in the early years of the war and the gradual substitution of American types for the corresponding German ones, left the chemist more firmly entrenched than ever. Naturally, the persons most interested in the advent of the chemist in the silk industry were the silk manufacturers themselves. They felt, and rightly so, that it was up to the chemist to show that his knowledge could be applied to their problems so as either to improve the quality of their goods or to decrease the cost of their production. The fact that more and more chemists are finding a place in this industry is a good indication of the value placed upon them at the present time by all progressive manufacturers. However, in order to give an intelligent idea of the contacts that have been established between chemistry and silk, we will now take up in detail the various processes that are involved in the transformation from fiber to fabric.
Presented in part before a joint meeting of the American Section of the Societ6 de Chimie Industrielle and the Society of Chemical Industry and the New York Section of the American Chemical Society and the American Electrochemical Society, New York, N. Y., May 21, 1926.
be termed the career of Before starting upon what let us pause for a moment to consider the constitution the of the raw material. The pure silk fiber, which is called
T
Raw Materials
