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Vol. 21, No. 2
Studies in Chemical Patent Procedure I-Hall
Patents for Aluminum Production’ Lloyd Van Doren WARFIELD
&
WATSON.
247
PARK
This study in chemical p a t e n t procedure is t h e first of a series of studies which will a t t e m p t t o present various
AvE., N E W
YORK,
N. Y.
refutation, t h a t it h a s now become axiomatic. Therefore, if greater s t r e n g t h can be built i n t o our chemical patents, the foundations of our chemical industry will be more secure. One of t h e surest ways of reaching t h i s goal is t o have better chemical p a t e n t s granted, a n d a fuller knowledge of t h e procedure necessary t o t h e filing a n d prosecution of applications for letters patent o n t h e part of those engaged in chemical work will be a large factor. These studies are n o t a n a t t e m p t t o m a k e a p a t e n t a t t o r ney of t h e chemist, b u t simply t o present various phases of p a t e n t procedure so t h a t h e m a y gain t h a t fuller knowledge. T h e Hall patents for t h e production of a l u m i n u m are here t a k e n t o illustrate t h i s study. Subsequent studies will be concerned with such patents as t h e Baekeland p a t e n t for Bakelite, t h e Goodyear p a t e n t for rubber, t h e T i l g h m a n patent for decomposing fat, t h e Hyatt p a t e n t for celluloid, t h e Cheseborough patent for Vaseline.
phases of t h e procedure necessary t o t h e granting of United States letters patent. T h e background for these studies will be various p a t e n t s which are looked upon as basic or outstanding. Most of those considered will be chemical patents, b u t patents in other fields which are deemed t o be of interest t o t h e chemist will also be treated. T h e object is t o give t h e chemist a better understanding of t h e procedure involved in t h e granting of patents, so t h a t when h e considers that h e h a s m a d e a n invention h e will be able t o assist t h e attorney in a way which will result in the drafting of a stronger specification a n d claims, t o t h e end t h a t stronger chemical patents m a y be granted. This, in t u r n , will eventuate i n t h e placing of t h e chemical industry u p o n a firmer foundation. It has often been said that t h e p a t e n t system is t h e foundation of o u r remarkable industrial progress a n d development. In fact, the s t a t e m e n t h a s been so frequently made, a n d without
. . . . . ... HE aluminum industry of today had its real inception in and was founded upon the work of Charles M. Hall a t Oberlin College, Oberlin, Ohio, in reducing aluminum electrolytically from a cryolite bath. This process was protected by patents and upon these patents as a foundation the industry developed to its present magnitude. At the time that Hall’s invention was made, in 1886, the production of aluminum amounted to only 6000 pounds per year and cost $12 a pound, this being a marked decrease in cost over that prevailing in 1855, when i t was $90 a pound. The reduction in cost over this period was due largely to the work of Henri St. Claire Deville. The earlier work of Deville utilized aluminum chloride and reduced it by means of sodium, which was a modification of the work of Oersted and Wohler, who prepared aluminum in 1825 and 1827, and obtained it by reducing aluminum chloride with potassium and its amalgam. Later improvements made by Deville included the use of cryolite as a flux. This use was later urged in a contention that the principal patent granted on the Hall process was invalid. It may properly be said that the aluminum industry of the United States, which today is producing about 160 million pounds of aluminum, is only one of many great industries which are founded upon and have been fostered and brought to a rich development because of the protection given by our patent system. This applies quite as particularly to the chemical industry as it does to the mechanical or electrical industries, and perhaps more so, inasmuch as in the chemical industry the substances, processes, and reactions are of an intangible nature, whereas in the mechanical and electrical industries they are tangible. The dependence of the chemical industry upon patent psotection was shown to our disadvantage by the condition of the chemical industry prior to, during, and immediately following the World War. The domination of the chemical markets of the world by the great chemical industries in Germany was founded upon the protection which they had
T
1
Received July 23, 1928.
acquired in foreign countries through patents. A realization of this condition arose immediately following the war, and in order to strengthen the chemical industry The Chemical Foundation was created and purchased from the Alien Property Custodian several thousand alien-owned chemical patents, many of which they have licensed non-exclusively to beneficially American-owned chemical plants. Apatent is B contract between the inventor and the Government, representing the people. I n accordance with the terms of this contract, the inventor is granted a monopoly of his invention for a period of seventeen years, for which he in turn makes a full, clear and concise disclosure of the invention, so that a t the end of the monopoly period the public may be able to practice and avail itself understandingly of the benefits of the invention. Development of Hall Process
The manner in which Mr. Hall developed his process for winning aluminum from alumina, utilizing a bath of fused cryolite as the electrolyte, may best be told in his own words:* My &st knowledge of chemistry was gained as a schoolboy at Oberlin, Ohio, from reading a book on chemistry which my father studied in college in the forties. I still have the book, published in 1841. It is minus the cover and the title-page, so I do not know the author. I t may be interesting now to see what this book, published seventy years ago, says about aluminum: “The metal may be obtained by heating chloride of aluminum with potassium in a covered platinum or porcelain crucible and dissolving out the salt with water. As thus prepared i t is a gray powder similar to platinum, but when rubbed in a mortar exhibits distinctly metallic luster. It fuses a t a higher temperature than cast iron and in this state is a conductor of electricity, but a non-conductor when cold.” Later I read about Deville’s work in France, and found the statement that every clay bank was a mine of aluminum, and that the metal was as costly as silver. I soon after began to think of processes for making aluminum cheaply. I remember my first experiment was to try to reduce aluminum from clay by means of carbon at a high temperature. I made a mixture of clay with carbon and ignited it in a mixture of charcoal with 2
J. IND.ENG.CHEX.,5, 146 (1911).
February, 1929
INDUSTRIAL AND ENGINEERING CHEMISTRY
chlorate of potassium. It is needless to say that no aluminum was produced, I thought of cheapening the chloride of aluminum thus used as the basis for aluminum manufacture, and tried to make it by heating chloride of calcium and chloride of magnesium with clay, following the analogy by which iron chloride is produced when common salt is thrown into a porcelain kiln. A little later I worked with pure alumina and tried to find some catalytic agent which would make it possible to reduce alumina with carbon a t a high temperature. I tried mixtures of alumina and carbon with barium salts, with cryolite, and with carbonate of soda, hoping to get a double reaction by which the final result would be aluminum. I remember buying some metallic sodium and trying t o reduce cryolite but obtained very poor results. I made some aluminum sulfide but found it very unpromising as a source of aluminum then, as it has been ever since. On a later occasion I tried to electrolyze a solution of aluminum salt in water, but found nothing but a deposit of hydroxide on the negative electrode. I did not give a great deal of time to these experiments, as I was then a student in college and was working on three or four other attempted inventions. I had studied something of thermochemistry, and gradyally the idea formed itself in my mind that if I could get a solution of alumina in something which contained no water, and in a solvent which was chemically more stable than the alumina, this would probably give a bath from which aluminum could be obtained by electrolysis. In February, 1886, I began to experiment on this plan. The first thing in which I tried to dissolve alumina for electrolysis was fluorspar, but I found that its fusing point was too high. I next made some magnesium fluoride, but found this also t o have a rather high fusing point. I then took some cryolite, and found that it melted easily and in the molten condition dissolved alumina in large proportions. I rigged up a little electric battery-mostly borrowed from my professor of chemistry, Professor Jewett, of Oberlin College, where I had graduated the previous summer. I melted some cryolite in a clay crucible and dissolved alumina in it, and passed an electric current through the molten mass for about two hours. When I poured out the melted mass I found no aluminum. It then occurred to me that the operation might be interfered with by impurities, principally silica, dissolved from the clay crucible. I next made a carbon crucible, enclosed it in a clay crucible, and repeated the experiment with better success. After passing the current for about two hours, I poured out the material and found a number of small globules of aluminum. I was then quite sure that I had discovered the process that I was after. I undertook to broaden and improve the method, and found that I could use, instead of cryolite, other double fluorides, particularly a double fluoride of potassium and aluminum. The most important change, however, which I made a t this time, was in the material used as an anode. I wanted to get rid of the burning up of the carbon anodes. I tried a platinum anode and found that it seemed to work all right, but it was too expensive. I discovered that if I used a fusible bath of a potassium double fluoride with a sodium double fluoride, I could use a copper anode, which immediately became coated with a thin film of copper oxide and acted like a permanent platinum anode. This was not a step in advance as I had hoped, because more or less copper got into the reduced aluminum, and the use of a copper anode led me to use very fusible baths, which on the whole did not work as well as the less fusible baths. It is probable that this change delayed a successful result for a year or two. When worked on a small scale, this process, with any of the baths I have mentioned and with either copper or carbon anodes, is not apparently promising. The ampere efficiency is low, sometimes zero, and the bath, whether composed of sodium or potassium salt, becomes fdled with a black substance which accumulates and renders the process very difficult. I presume that my friend, Dr. Heroult * * * who invented the process independently in France about the same time, encountered the same difficulties. I n spite of the difficulties mentioned, however, I had great faith in the theoretical possibilities of the process, and believed that the practical obstacles could be overcome, so I stuck to it from the start.
Considerable difficulty was experienced in operating on a small scale, and this process, quite contrary to that which is usually the case: was attended by fewer difficulties when operated on a large scale. When operating on a small scale, the baths clogged and were spoiled, which caused Mr. Hall much trouble for more than three years. When he came to the Pittsburgh Reduction Company-now the Aluminum Company of America-in the summer of 1888, he started to
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build larger cells, and after a few weeks in determining the dimensions of the cells, they were put into operation and then the difficulties which he had previously experienced disappeared “as if by magic.” As has been the experience of many an inventor with a meritorious invention, Mr. Hall had great difficulty in securing financial backing, and from February, 1886, a t which time he successfully reduced aluminum from alumina until the summer of 1888, he met with disappointment after disappointment. It was then that he was able to interest the gentlemen of the Mellon Bank of Pittsburgh, who formed the Pittsburgh Reduction Company and put the invention into commercial practice. Application for Patent
Mr. Hall realized the importance of his invention and presented his data to a patent attorney for the preparation of the necessary papers for filing an application in the United States Patent Office. Such papers consist, f i s t , of a petition in which the inventor sets forth that he has made an invention and requests the Commissioner of Patents to grant him a patent thereon. The petition part of the papers usually carries also a power of attorney. It might be said here that it is not necessary for an inventor to have an attorney for the drafting of his specification and claims and for the prosecution before the Patent Office. However, inasmuch this work requires a full knowledge of patent law and patent procedure, it is considered highly desirable that an inventor have a properly qualified attorney to prepare his application and prosecute it rather than attempt to do so himself. This is advocated by the Patent Office, which maintains a register of qualified patent attorneys, but does not make any recommendation. The second part of the application consists of the specification in which the invention is described in accordance with the statutes in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it appertains to make and use the same, and he shall set forth the best mode in which he contemplates applying the invention so as to distinguish it from other inventions. He must particularly point out and distinctly claim the part, improvement, or combination which he claims as his invention or discovery. The specification with the appended claims is the most important part of the application papers, and too much care cannot be taken in its preparation. The usual form of presentation is to give first the art to which the invention relates, the objects which the invention accomplishes, and a general statement as to the procedure or practice of the invention; then a more detailed statement as to how the invention may be practiced; and this followed by one or more examples giving specific applications of the manner in which the invention may be carried out. There may then follow a statement as to the benefits, exclusive of laudatory remarks which the carrying out of the invention brings about, and closing the part of the specification immediately preceding the claims with a statement as to the scope of the invention and any particular meaning as to terms and phrases as used by the inventor, and perhaps somewhat outside of the usual meaning. The courts have frequently held that an inventor or applicant may define his own terms. The claims follow, and these are the most important part of the specification, because it is in these that the inventor’s protection resides. They should be of sufficient scope to cover fully all that is shown in the specification and its proper equivalents. Unless they do so cover the showing of the specification, the invention is not adequately covered and a competitor may thus be able to evade the claims quite easily. The proper drafting of claims is an art, and perhaps i t
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might be said, a science in itself. The courts have repeatedly set forth the importance of having the specification and claims well prepared. For example, in Topliff v. Topliff (145 U. S. 171): The specification and claims of a patent, particularly if the invention be at all complicated, constitute one of the most difficult of legal instruments to draw with accuracy, and in view of the fact that valuable inventions are often placed in the hands of inexperienced persons to prepare such specifications and claims, it is no matter of surprise that the latter frequently fail to describe with requisite certainty the exact invention of the patentee, and err either in claiming that which the patentee had not in fact invented, or in omitting some element which was a valuable or essential part of his actual invention.
and also in Westinghouse Electric & Mfg. Company v. Metropolitan Electric Mfg. Company (290 Fed. 664) : What any patentee. has invented is theoretically what he discloses, and the disclosure is the specification. A claim is a definition of that which has been described in the specification. * * * Theoretically the * * * “man skilled in the art” knows how to do what the inventor did when he has perused the disclosure. Whether one infringes a patent primarily depends, to be sure, upon consideration of the claims; but no man would know how to practice the invention by reading the claims * * * A claim not supported by the specification is a bad claim * * * A disclosure which tells how to do a thing not claimed is a misfortune for the patentee. Granting of Patent
Mr. Hall, having prepared, with the assistance of a patent attorney, the specification and claims, filed the same in the United States Patent Office on July 9, 1886, and was granted a patent thereon on April 2, 1889, bearing No. 400,766 and entitled “Process of Reducing Aluminium by Electrolysis.” This patent, as originally filed, contained broad claims and specific claims, both to the use of a fused bath composed of the fluorides of aluminum and sodium, and to a fused bath composed of the fluorides of aluminum and potassium. The Patent Office examiner required division between the claims to a bath composed of the fluorides of aluminum and sodium, and claims to a bath composed of the fluorides of aluminum and potassium. Accordingly, the claims for the bath containing the fluorides of aluminum and potassium were divided out and a divisional application filed on February 2, 1887, carrying these claims. A patent is granted for a single invention. Therefore, when it is the opinion of the Patent Office that more than one invention is claimed with a given specification, and in a single application, it will require that all claims ‘other than those to a single invention be removed from this certain application. The inventor may be of the opinion that the claims are all for a single unitary invention and will present an argument to the patent examiner setting forth his views and the reasons therefor. If the examiner retains his original belief, he will repeat the requirement for division and then the inventor must either accede and remove those claims, filing them, if he desires, in a divisional application, or take an appeal. If he takes an appeal and the judgment is adverse, he has no other avenue open but to remove the claims and file them in a divisional application. On the other hand, of course, if the judgment is favorable, the claims in controversy remain in a single application and are granted in a single patent. A divisional application sets forth generally the same subject matter as that in the original application from which it was divided out, and claims particularly a species of the original invention. For priority purposes it carries the date of the original application. The patent which was granted on the Hall divisional application is dated April 2,. 1889, and bears No. 400,664. I n addition to the two patents hereinbefore mentioned, there were granted on the same date three other patents
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pertaining to Hall’s process for the manufacture of aluminum. These patents are numbered 400,665, 400,666, and 400,667, each of which will be briefly mentioned later. The principal patent in this situation, and the one which may be termed the “basic” patent, is No. 400,766. I n this patent Hall described the practice of his invention as follows: In the practice of my invention I prepare a bath for the solution of the alumina fusing together in a suitable crucible, A, the fluoride of aluminium and the fluoride of a metal more electropositive than aluminium-as, for example, the fluoride of sodium potassium, &.-these salts being preferably mingled together in the proportions of eighty-four parts of sodium fluoride, and one hundred and sixty-nine parts of aluminium fluoride, represented by the formula Na2AlzFs. A convenient method of forming the bath consists in adding to the mineral cryolite * 3 8 / 4 2 ~ of its weight of aluminium fluoride. The object of thus adding aluminium fluoride is to secure in the bath the proper relative proportions of the fluorides of aluminium and sodium. To this fused bath is added alumina or the oxide of aluminium in sufficient quantities, and the alumina being dissolved by the fused bath an electric current is passed through the solution, by means of suitable electrodes, C and D, connected with a dynamo-electric machine or other suitable source of electricity and immersed in the solution. By the action of the electric current, which preferably has an electromotive force of about four to six volts, oxygen is released at the positive electode C, and aluminium is reduced at the negative electrode D, which, on account of the affinity of aluminium for other metals, is formed of carbon when it is desired to produce pure aluminium. The positive electrode may be formed of carbon, copper, platinum, or other suitable material. When formed of carbon the electrode C is gradually consumed, and must therefore be renewed from time to time; but when formed of copper an oxide coating is formed over the surface of the electrode. This coating serves to protect the electrode from further destruction by the action of the oxygen, but does not interfere materially with the conducting qualities of the electrode.
The bath or solvent is rendered more fusible by substituting lithium fluoride for a portion of the sodium. For example, for one-fourth of the sodium fluoride an equivalent amount of lithium fluoride based on molecular weights may be used. Thus, 26 parts of lithium fluoride may displace 42 parts of sodium fluoride, and the bath composition would then contain 26 parts of lithium fluoride for every 126 parts of sodium fluoride and 338 parts of aluminum fluoride. The patent has three claims, which are as follows: 1. As an improvement in the art of manufacturing aluminium, the herein-described process, which consists in dissolving alumina in a fused bath composed of the fluorides of aluminium and a metal more electropositive than aluminium, and then passing an electric current through the fused mass, substantially as set forth. 2. As an improvement in the art of manufacturing aluminium, the herein-described process, which consists in dissolving alumina in a fused bath composed of the fluorides of aluminium and sodium, and then passing an electric current, by means of a carbonaceous anode, through the fused mass, substantially as set forth. 3. As an improvement in the art of manufacturing aluminium, the herein-described process, which consists in dissolving alumina in a fused bath composed of the fluorides of aluminium, sodium, and lithium, and then passing an electric current, by means of a carbonaceous anode, through the fused mass, substantially as set forth.
The divisional patent, No. 400,664, differs from its original, No. 400,766, by using a bath having the fluorides of aluminum and potassium, instead of the fluorides of aluminum and sodium. There are two claims to this patent which are similar to claims 2 and 3 of the original patent, only potassium is used in place of sodium. These claims are more specific than claim 1 of the original patent, which may be said to be the dominating claim in the situation. The other three patents are in the nature of improvement patents. No. 400,665 is for the use of a bath consisting of a combination of aluminum fluoride and an alkali-earth metal fluoride, specifically calcium fluoride. The object of this improvement was to overcome the formation of a black or
February, 1929
IlVD USTRIAL AiVD ENGINEERING CHEMISTRY
dark substance in the bath which interfered with the electrolytic action and increased the resistance. Because of this it had previously been found necessary t o change the bath a t frequent intervals. No. 400,666 is also designed to obviate the formation of this black or dark substance which necessitated comparatively frequent renewal of the bath, and consists in preparing the bath by using a combination of the fluorides of aluminum, calcium, and sodium, to which there may be added also some calcium chloride. No. 400,667 pertains t o a continuous method of operation in which the bath is composed of the fluorides of aluminum and a fluoride of an alkaline-earth metal which may include some sodium fluoride and also some calcium chloride. The claims contain the added feature of continuously adding a fresh supply of alumina t o the bath and removing the aluminum. Infringement Proceedings
The invention of Hall was of such outstanding importance that infringement was practiced, and that by the Cowles Ellectric Smelting & Aluminum Company was complained of by the Pittsburgh Reduction Company. This cause was heard in the Circuit Court, Northern District of Ohio, Eastern Division, and the decision was handed down January 20, 1893, by then Circuit Judge William Howard Taft, now Chief Justice of the United States Supreme Court. The claims sued upon were claims 1 and 2 of patent No. 400,766, and much art was set up by the Cowles Company in its defense that the Hall claims were invalid. That upon which they relied principally was the work of Deville. The art and the defendant’s arguments against the validity are treated very fully in the Court’s opinion, in which the nonapplicability of one after the other of the citations is pointed out. The claims were held t o be valid and infringed and in summing up the Court speaks of Hall’s invention as follows (55 Fed. 318): Hall’s process is a new discovery. It is a decided step forward in the art of making aluminum. Since it has been put into practical use the price of aluminum has been reduced from $6 to $8 a pound to 65 cents. This is a revolution in the art, and has had the effect of extending the uses of aluminum in many directions, not possible when its price was high. An effort has been made to show that this reduction in the price is due to the improvements in the application of electricity to the manufacture of aluminurn. That the new inventions in the line of producing electric currents of great volume and intensity have contributed to render the Hall process an economical one is true, but without the Hall process the manufacture of pure aluminum must have continued to be a purely chemical one. The Cowles brothers made aluminum alloys by the use of electrical furnaces which they have brought to a high state of perfection, doubtless, and that had an effect to reduce the price of aluminum alloys, and perhaps indirectly affected the price of pure aluminum. The fact was that the price of pure aluminum was so high that its uses were few, and the market for it was small. When Hall’s process, however, came into the field of commercial manufacture, pure aluminum was largely substituted for aluminum alloys, and, if alloys are now desired for particular purposes, they are generally made from pure aluminum. Hall was a pioneer, and is entitled to the advantages which that fact gives him in the patent law.
The defendant petitioned for a rehearing. One of the grounds presented as the basis for this rehearing was that new evidence had been found which could not have been brought before the Court by due diligence a t the original hearing. The motion for the rehearing was heard by Judge Taft, and was denied in an opinion handed down November 9, 1894. An appeal was taken by the Cowles Electric Smelting & Aluminum Company from the decision handed down by the District Court. Later, about 1900, the Electric Smelting & Aluminum
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Company sued the Pittsburgh Reduction Company for infringement, particularly of the Bradley patent No. 468,148 by its operations under the Hall patent No. 400,766, for reduction of aluminum ores. The Bradley process consists essentially in passing an electric current through a mass of ore, such current being sufficiently strong to fuse the ore and to effect its continuous decomposition. It was held by the Circuit Court, Western District of New York, on October 22, 1901, that the operations under the Hall patent did not infringe the Bradley patent, and the bill was dismissed. From this decision an appeal was taken and in a decision handed down by the Circuit Court of Appeals for the Second Circuit, October 20, 1903, the decision of the lower court was reversed, and it was held that the operations under the Hall patent infringed the broad claims in the Bradley patent. It was pointed out in this decision, however, that it was impossible to compete commercially with the Pittsburgh Reduction Company without using Hall’s improvement and also that the cryolite and alumina electrolyte could not be used so long as the decision sustaining the validity of the Hall patent was undisturbed. The validity of the Hall patent was not further questioned, and it is an excellent example of a patent which was the foundation upon which a great industry was built and which has withstood the test through the courts. Attention might be directed to numerous instances where industries have been developed from or founded upon the protection which has been granted through patents, but to consider these a t this time would make the present paper entirely too voluminous. Various of these instances will be mentioned and presented in subsequent papers. H&oult’s Invention
It may be of interest to point out that a t about practically the same time that Hall made his invention in this country, the same invention was made entirely independently by Paul L. V. HBroult in France. Hbroult was granted a patent by the French Government on April 23, 1886. He filed an application for patent in the United States Patent Office on May 22, 1886. Hall’s application was not filed until July 9, 1886. The patent examiner adjudged the subject matter of the claims t o be the same, and hence set up an interference, which is a proceeding before the Patent Office solely for the purpose of determining who the prior inventor is when conflict arises, as was the case here between Hall and HBroult. Evidence was taken by the parties, as is usual, and Hall established that he had made his invention and put it into operation February 23, 1886. This evidence was adjudged to prove beyond any reasonable doubt that the Hall process had been put into successful operation a t that time, and thereupon the Patent Office decided the prior right in Hall’s favor. The patent was granted to Hall. The success of Hall in establishing his date of invention indicates very clearly the importance of a careful keeping of the laboratory notebook. Much might be said as to the proper notation of laboratory results, but suffice it to ’say a t this time that the results of all experiments should be placed in the notebook with care and attention t o sufficient detail t o establish a complete operative procedure. The date of such notation should be placed upon the sheet, and the sheet signed by the experimenter. When it is felt that a result of unusual importance has been obtained, not only should the notebook sheet be signed by the experimenter, but i t should be read and witnessed by one or two others, who will place their signatures upon the sheet. The record should be complete from the date when the idea first came to mind until the work is completed or, in other words, successfully reduced to practice. There should be a show-
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ing of continuity and logical development throughout, so that any charge of lack of diligence might be readily overthrown. It is likely that such data will never be needed, but if it is needed to establish priority in an interference proceeding such as that between Hall and HCroult, or to establish a date of invention earlier than the filing date of a patent application in litigation, it becomes of the utmost value and may be that evidence, either by itself or in corroboration of oral testimony, which constitutes the difference between success and failure. The mere fact that HBroult’s patent in France was granted before Hall’s fling date did not constitute a bar, because an
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inventor’s right to a patent is not debarred by the reason that the invention was previously patented in a foreign country, provided that it has not been in use in the United States more than two years before the inventor’s filing date, and provided his date of invention antedates the date of the foreign patent, as did Hall’s inasmuch as the H6roult patent was granted April 23, 1886, and Hall’s invention date was proved to be February 23, 1886. As HBroult did not obtain a patent here, so Hall did not obtain a patent in France, and by mutual agreement the operations under the Hall process were confined to this country and operations under the HCroult process were confined to France and Europe.
What the X-Ray Tells Us of the Structure of Cellulose’ E. A. Hauser2 MRTALLGSSBLLSCHAFT A. G., FRANKFURT A/M, GERMANY
This paper is based on the recent publications of Meyer ana‘ Mark, Trillat on cellulose, and analogous work on rubber and other elastic colloids undertaken by the author.
A
NY determination of the structure of cellulose must
be based on those facts in celluloseresearch which seem to be sufficiently established. For example, cellulose can be split approximately 60 per cent into cellobiose under conditions where it seems impossible that it is built up from glucose as an intermediate product. The constitution of cellobiose, however, is known. The identity period of the crystallized phase in cellulose in the direction of the fiber axis is 10.3 A., whereas the other two edges of the “imaginary” elementary unit have been calculated to be 7.9 and 8.7 A., respectively, this allows four C6H100b groups per unit cell. Until recently these facts could not be correlated, and before proceeding further it seemed necessary to try to find some way of accomplishing this. If we link two glucose residues to form one cellobiose and measure the distance between the two oxygen ends, we obtain 10.3 A. This calculation is admittedly based on the
ol - - - - - I
CH
to what we said in regard to the identity period in cellulose, we assume that the cellobiose groupings are oriented in the direction of the fiber axis. As the x-ray diagrams make it highly improbable that more than four CsHloOa groups will join to form one complex associated with a unit cell, we further assume that the cellobiose is linked up from qnit cell to unit cell in the direction of the fiber axis by glucosidic oxygen bonds. However, this necessitates the formation of a digonal helix axis, similar to molecular chains caused by association only and not by chemical bonds. The resulting model of the cellulose structure permits an interpretation in both the rhombic and monoclinic systems and explains the chemical and physical properties of cellulose very satisfactorily. 8 . 6 4
H
o------
f
CH 1
f E Figure 1
h AH H /\H HO-C C-CHzOH
I
Cellulose Linkage
0
m
f
M
LH
H\ HO-C
A
C-CHzOH
H Cellobiose
assumption that one C-C bond corresponds to 1.5 A. as in the case of diamond and the C-0 bond to 1.2 A,, this being somewhat larger than in carbon dioxide (1.10 A.) Referring 1 Received August 17,1928. Presented before the Division of Cellulose Chemistry at the 76th Meeting of the American Chemical Society, SwampScott. Mass., September 10 to 14, 1928. Non-resident associate professor of colloid chemistry, Massachusetts Institute of Technology.
*
Meyer and Mark have recently undertaken, in a masterly piece of work, to discuss all possible geometric crystallographic configurations of the unit cell and have come to the conclusion that the monoclinic configuration Ci is most satisfactory as this can readily explain the following important factors. The grouping in space can be correlated with the axial ratio a:c = 1 :1, and with the most important intensity effects in the cellulose diagram. If we consider the spatial arrangement of the primary valence chains, we find that such an arrangement as is indicated in the accompanying diagram (Figure 1) accords well with the known facts. Here the shaded rectangles represent cross sections of the CeH1006 rings, the angle beta, between the b-axis and the plane of a and c, having been selected nearly equal to 90 degrees. If we arrange the chains so that the planes of the rings 1 and 2 are parallel to the (001) plane, the axial ratio a:c will be 1:l. The most im-
