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INDUSTRIAL AND E-VGINEERING CHEMISTRY
applied on printing plates, including electrotypes for long editions-e. g., of cartons, labels, and wrappers, and intaglio plates for printing paper currency. It is safe to predict that in the printing industry alone there are a large number of plants which might to advantage install chromium plating, though their total consumption of chromium (as chromic acid) would not be large. Other uses resting especially upon the hardness of chromium include its application to dies, gages, gears, shafts, and other steel parts which are now usually casehardened. The extensive adoption of chromium plating on these or other articles of very irregular shapes will depend upon improving its “throwing power,” which is usually rery poor in the present type of baths. Blthough the reflecting power of chromium is only about 65 per cent as compared with 90 per cent for silver, its resistance to tarnish makes it especially suitable for outdoor reflectors, such as in headlights and flood lights, for which its use will no doubt soon become commercial. I n connection with the more general application of chromium plating, it is necessary to recall that chromium does not protect exposed iron against corrosion. I n order, therefore, for chromium to exert a protective action superior to a nickel coating, it is necessary that the chromium plating be more nearly impervious than the nickel plating. Whether this can be accomplished practically remains to be seen. From present indications, however, i t seems safe to predict that chromium plating will be used largely as a supplement to nickel plating, to increase the resistance to tarnish and abrasion, rather than as a substitute for nickel plating. Thus i t is sigdicant that one motor firm that has adopted chromium plating for radiator shells and other parts is applying the’ chromium over a substantial coat of nickel.
Electroforming In electroforming we include electrotyping, a well-established industry, and the production of tubes and sheets, which latter process is still in its infancy. I n electrotyping, which like electroplating has in past years been conducted largely on an empirical basis, there has been recently a new interest in applications of science. From present indications this interest is more likely to manifest itself in the standardization of existing processes than in the development of radically
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new procedures. There is good reason to believe, however, that by careful study it might well be possible to bring about marked improvements in this industry, which has not changed greatly in recent years. The manufacture of sheets and tubes by electrodeposition has always been a fascinating dream of the inventor. Its attraction lies in the fact that it is apparently simple to make by electrodeposition very complicated shapes, and, unlike rolling or drawing processes, it is cheaper to make article5 with thin walls than thick ones. I n spite of these apparent advantages electroforming has been, a t least until recently, a will-of-the-wisp that has attracted large investments and yielded few returns. During the past few years copper sheets and iron tubes have been successfully made on a commercial scale in this country, but it is still too early to tell whether these processes will survive competition. The chief obstacles to success are the difficulty of producing impervious deposits and of getting uniform distribution of metal of suitable structure and physical properties. While there is no reason to believe that such obstacles are insuperable, it is a t least safe to say that they will never be overcome except by careful research, involving the application of all germane principles, and by scrupulous control of operating conditions, such as freedom of the solutions from suspended matter and other impurities. In short, the successful electroforming of sheets and tubes will be a scientific and not an empirical process. Conclusion
I n making the foregoing suggestions and predictions, it is fully realized that industrial success in any project depends jointly upon sound scientific principles, sound engineering, and sound economics. In emphasizing the importance of scientific research in this field, I hare in no way intended to belittle the significance of the other two essentials, either of which may in a given problem be the determining factor for success. The importance of engineering and economics is often more obvious, especially to executives, than is the need for basic scientific studies. As chemists it is therefore our right and duty to emphasize the scientific aspects, and thus help to build a sound and broad foundation for the future of the electrochemical industries.
The Future Trend of Cellulose Chemistry By Gustavus J. Esselen, Jr. SKISNER, SHERDlAS
8r ESSELEX, INC.,
EVERAL years ago, before the method of x-ray crystal analysis had been discovered, a small group of chemists was discussing informally what might be the next great step forward in the science of chemistry. -4younger member of the group expressed the thought that perhaps the simple formula NaCl or Cas04 might not tell the whole story and that the next great advance might be some sort of constitutional formula for our simple inorganic salts. Since this \vas an entirely revolutionary idea so far as inorganic chemistry was concerned, it was rather frowned on by the older members of the group. Yet in a few years the discovery of the new research tool showed that our young friend’s idea was almost prophetic. It must, therefore, be recognized that similar new and revolutionary developments, which may suddenly change the trend of progress, may arise at any time. Such discoveries may make or break any prophecy, yet such speculation is not entirely futile and may be justified
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on the ground that it does no harm and may even be a stimulus in pointing out needs and thereby stimulating research. K e can at least consider what the tendency appears to be and whether this is what we would like to have it. I n the last analysis the trend of progress in any branch of science is going to be governed largely, if not entirely, by the demand. The word “demand” is used here neither in the economic sense nor in the sense of a need of industry, but rather to denote the securing of information necessary for further progress, be it in pure science or in industry. Of course, i t will be remarked that this is obvious in industrial research, but is it not also true in the field of pure science? Many researches are undertaken for the prime purpose of securing data required for the solution of other problems, and in almost all researches many points arise which in themselves would be interesting t o investigate further but which must be put aside in concentrating on those phases of the problem
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most important for the advance of science in general. This is what is meant by the general trend being governed by the demand. Now the demand, in turn, is dependent upon our power of imagination to conceive what we would like to have or could use profitably if we had it, and again it is not intended to limit the thought to the monetary profit of industry but to include the scientific profit of advancing knowledge. Even if “necessity is the mother of inventionlJJimagination is the mother of progress. Advances in Cellulose Chemistry Probably the two recent advances of most significance to cellulose chemistry have been the recognition of the colloidal character of cellulose and its compounds, and the results of x-ray studies which have shown thst even with this colloidal character there is a definite crystal structure. Of almost equal importance have been the profitable speculations as to the constitution of the cellulose molecule, which have resulted in structural formulas which give a far more satisfactory picture of the molecular configuration of cellulose than ever before. Recent researches have even given us a basis for estimating the molecular weight of cellulose and its esters. Undoubtedly, we have a right to expect even greater advances along these lines in the near future, particularly in view of the widespread interest in the subject not only in this country but also in Canada and several European lands. I n connection with the crystal structure of cellulose it has been observed that the crystallites in a natural fiber have a definite orientation and regular arrangement, whereas in rayon (artificial silk) there is no definite orientation. Doubtless we shall soon know the underlying causes of this orientation in the natural fibers and perhaps even be able to produce it in the artificial. Then we will know whether there is any marked relationship between this and strength, and whether resistance to water and aqueous alkalies is in any way connected with it-all of which should be of considerable interest not only scientifically but also to the rayon industry. I n view of the great strides on the structural side of cellulose chemistry, it may seem almost a paradox to say that probably no one has yet prepared a sample of really pure cellulose, absolutely free from degradation products or impurities of any sort. The fundamental need for such a pure material to serve as the basis of research is thoroughly appreciated by workers in this field, and much thought has been given and still is being given t o the matter. Although decided progress has been made, we can reasonably anticipate that here, too, the near future will unfold much of real value. With a pure standard cellulose to work with, it should then be possible to straighten out the very unsatisfactory state of the analytical side of cellulose chemistry. Practically all of our so-called methods of analysis are little more than empirical tests, in which the behavior of the sample under examination is observed, and perhaps measured, under certain arbitrary conditions. The results are defined in terms of the conditions of the test and do not necessarily represent any true chemical property of the sample. Furthermore, for the most part the arbitrary conditions used are not easy to duplicate by different laboratories and in some cases even by different workers in the same laboratory. I n some of our analytical methods, also, it has recently been pointed out that conditions are such that there is really a race between the reaction which measures the property in which we are interested and a second reaction which is neutralizing that property so that it is no longer reactive. An illustration of this situation is the behavior of cellulose when treated with solutions of sodium hydroxide. By definition alpha-cellulose is the material which is not affected by 17.5 per cent aqueous sodium hydroxide when immersed
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in it for thirty minutes at room temperature. Yet it does not take a cellulose expert to recognize that the character and extent of agitation and the degree of subdivision of the sample will have a real effect on the result, to mention only two of a number of conditions which obviously have a bearing. If we finally obtain a sample of pure cellulose, will it show by this test 100 per cent alpha-cellulose or will we have to change our empirical definition? Also, do small amounts of socalled soda-soluble impurities exert any catalytic influence on t h e action of caustic soda solutions on cellulose? One thing we do know-that if the amount of alkali-soluble is determined in a given sample of cellulosic material by boiling it for three hours in a 7.14 per cent solution of sodium hydroxide (or 10 per cent potassium hydroxide), and the residue, presumably free from alkali-soluble material, is then subjected to the same analytical conditions, a further percentage of alkali-soluble material is indicated, and so on for at least six times and probably until the sample is entirely decomposed. Furthermore, there is no definite relationship between the results obtained in this way and the alphacellulose content mentioned above which also depends upon the action of a caustic soda solution, though of different concentration and under different conditions. This does not mean that the behavior of a given sample of cellulose under the particvlar conditions of this analytical procedure is not a valuable index to certain of its properties. It is; yet it is obvious that much progress can be expected in the way of correlating, if possible, the results of these two sodium hydroxide treatments, and at any rate in giving us a dependable scientific method for determining the percentage of true, nondegraded cellulose. Another analytical method which will undoubtedly be much improved before long is that which seems to measure, among other things, the degree of aggregation of the cellulose micelle or, perhaps strictly speaking, the average degree of aggregation. The method involves dispersing the sample in a cuprammonium solution and measuring the viscosity of the resulting solution. To indicate, however, the difficulty of obtaining results which will be comparable among different workers, i t is only necessary to point out that there is no general agreement as t o the composition of the cuprammonium solution or the amount of cellulose to be dissolved in it, and, what is more, the viscosity of the resulting solutions depends, among other things, on the time and character of the agitation during the solution of the cellulose and on the age of the solution before testing. Yet the degree of aggregation of the cellulose micelle is so important a property that the development in the near future of some satisfactory method for measuring it seems almost a certainty. We know pretty well how to vary the viscosity of cellulose and its compounds, and this is done every day in industry; yet the fundamental chemical or physico-chemical change in the cellulose aggregate on which this variation in viscosity depends is not known. Recent work has reasonably established that the fundamental cellulose from different vegetable sources is chemically the same individual. We shall hope to learn a little later more about the relationship between the cellulose and the accompanying pentosans, lignin, etc., which obviously will pave the way for advances in our methods of separating the cellulose for industrial purposes. Sources of Cellulose Products From the point of view of the practical applications of cellulose, one of the outstanding problems of the future seems to be the source from which shall come the raw material t o furnish the ever increasing amounts of cellulose which are being called for. A recent survey of Chemical Abstracts disclosed that during the years 1924 and 1925
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October, 1926
thirty-nine articles were published giving experimental data on methods for producing cellulose from fifty-nine different woods and fibers, practically none of which are being utilized in a commercial way today. At the same time strenuous efforts are being made to produce from wood a cellulose that is the equivalent of cotton cellulose, particularly for such purposes as nitration and viscose productions. I n this case the advances recently made have been so marked that the goal is actually in sight, and i t seems safe to count on such a product in the near future. Somewhat more speculative is another possible source of cellulose, practically unlimited in extent, but to which very little attention has been paid. I n nature, cellulose is synthesized from carbon dioxide and water, and a t least the preliminary steps have been taken toward showing t h a t we may some day be able t o duplicate this in the laboratory. It is not intended to hold out hope that this is a likelihood in the immediate future, but when we remember the strides that have been made in the fixation of atmospheric nitrogen, one of the most inert of materials, is it unreasonable to believe that we may some day fix carbon dioxide in the form of cellulose and do it in a few days, or perhaps even hours, as compared with the years required by nature? There would be the further advantage that the cellulose would be free from admixture with foreign material, from which it is now necessary to free it by rather cumbersome methods. I n connection with the supply of cellulose for industrial purposes, there is a n interesting development taking place quietly which seems to hold considerable significance for the future, and that is the trend toward the South. The southern states of this country have the advantage in this regard, that the rate of growth of wood, even for lumber purposes, is so comparatively rapid that with proper operating and logging conditions a twenty-fire year crop cycle can be maintained, thus assuring a regular supply. Already much kraft paper is being made from southern wood and there is a prospect that new methods will permit the utilization of these woods for other papers as well. Pulp and Paper
It is hard t o predict what may ultimately result from the many studies continually being made, not only of the old, established pulping processes, but of new ways of preparing pulp from wood. The application of the methods of physical chemistry t o these researches should ultimately result in operating economies in the mill, and new pulping methods give promise of spreading pulp production to materials and localities which have not hitherto been available. New and special uses are continually being developed for paper, but for the most part these are of relatively limited significance. The next development which will greatly extend the usefulness of paper will be a method for increasing its resistance to heat. Rayon
The outstanding technical development in cellulose chemistry in the recent past has been the rayon industry. Progress here has been so rapid on t h e production side that it is almost staggering; yet one feels t h a t the scientific side has not kept pace with production developments. For example, why is it necessary t o take five or six days for the preparation of viscose suitable for rayon manufacture? Surely research will find a way t o shorten this period materially. Although the rayon of today is distinctly stronger than former products, considerable improvement in this direction also can confidently be expected, probably in the not distant future. Then there is the problem of overcoming the loss of strength when wet, on which many minds are working and for which there will doubtless be a satisfactory
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solution, as well as for numerous other lesser questions which serve to keep the life of the rayon chemist interesting. Photographic Films
Another large industry dependent upon cellulose chemistry is that of photographic films. Here cellulose nitrate has long reigned supreme as the basic film material, but recently, owing to its relative noninflammability, cellulose acetate has been finding greater and greater usage. The chief bar to wider adoption of this valuable material is that of price. but recent work by one of the largest producers of acetate in this country has resulted in the development of methods of handling the acetylation reaction in such a way as to recover a large part of the acetyl values remaining in the reaction mixture, which were formerly lost. This has been a big step in advance. A cheap way of producing acetic anhydride or a method for making cellulose acetate direct from acetic acid would help still more. Even without these, however, the noninflammable film is in wide use and it is probably only a question of time before it outstrips its pyroxylin rival. It is too early to say whether the ultimate noninflammable film will have cellulose acetate as its base or whether the base will be some form of cellulose ether, compounds which have been prominent in the patent literature in recent years. So far there has been little, if any, commercial application of the cellulose ethers, but the number of patents granted in connection with them during the last few years indicate that, in some quarters a t least, much is expected of them. Other Cellulose Products
Many other new compounds and derivatives of cellulose, such as those with aniline, guanidine, quaternary ammonium bases, thiourea, etc., are continually being discovered and many are being patented, but whether they are to be guideposts indicating the trend of cellulose chemistry or merely markers on the way depends largely on whether or not they meet a need, either actual or potential. I n the cellulose plastics industry the crying need has long been for methods of reducing inflammability. Various more or less helpful expedients have from time to time been put forward, of which the use of certain organic phosphates has perhaps been the most important; but even these have their drawbacks which prevent universal adoption. It is of interest to note, however, that a noninflammable combination with cellulose nitrate as its base, has recentlyappearedon the market in sheet form. This is a line along which continued progress may well be anticipated. Advances will probably also come in increased permanency on exposure to light, and longer retention of flexibility where this property is desirable. The modern pyroxylin lacquer industry is another of the recent outstanding achievements of cellulose chemistry which seems to have a great future before it. It is another of those instances where practice is ahead of theory. We know how to modify the viscosity of cellulose nitrate in such a way as to give us the relatively high concentrations which make modern lacquers possible, but we are not sure as to just what constitute the changes in the cellulose aggregate on which these variations in viscosity depend. When we do, there would seem to be a reasonable likelihood of being able to produce still lower viscosities and a t the same time retain the properties of a smooth, tough, wear-resisting film. Cotton Textile Industry
While no claim for completeness can be made for so brief a paper covering so wide a field of activity, nevertheless one omission would be noticeable were no reference made to it, and that is the cotton textile industry, one of the largest cellulose-using industries. Although this, of all the cellu-
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lose industries, is more largely dependent upon mechanical operations, it nevertheless deals with a complex chemical material and a wider recognition of this fact in the industry might well result in notable advances. This is the more true since rayon has been finding its way into cotton textiles in increasing amounts. For example, every cotton man knows how the strength of cotton varies with the moisture content, yet the reason for this is not fully understood. It would be very helpful to have a thorough knowledge of the relationship between t h e physical properties of cotton and the character of the soil on which it was raised. Such a study might lead to ways of controlling certain desirable properties and possibly even of varying them a t will, and might perhaps also throw light o n the perplexing problem of “neps.” The work might well be extended to include a study of the effect of chemical properties on the various physical characteristics on which depends the successful use of cotton fiber in the various textile operations. It is recognized that certain natural impurities in fibers seem to have an effect on these properties and the study of these impurities and their effects might well yield valuable results.
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Mercerization is an example of what the treatment of cotton as a chemical material has done for the textile industry, and it is not inconceivable that further application of this same point of view might produce even more valuable results. Perhaps the one development which would bring the textile chemist to realize this more quickly than any other would be the appearance of an inexpensive, strong synthetic fiber, and this is by no means beyond the range of possibility. Conclusion
Regardless of whether the future shows that the trends which have been noted above develop as anticipated or whether some now unforeseen discovery changes the course of cellulose chemistry into quite other channels, one fact at least should persist. The recognition of cellulose in its various forms as a chemical raw material has resulted in great advances both in industry and in science during the past fifty years. The continued study of cellulose from this standpoint and the application of the results of these studies to industry should combine to maintain cellulose, not only as the most common chemical raw material from the vegetable kingdom, but also. in the aggregate, the most valuable one.
Future Trends in Soil Conservation1 By Jacob G. Lipman &?EW JERSEYAORICULTURAL EXPERIMENT STATION, NEWBRUNSWICK, N. J.
OOD-EXPORTING as well as food-importing countries compete with one another in the world’s markets. It is a competition of soils, of climates, of farmers, and of selling organizations. No small part is assigned in this competition to soil-fertility factors, including soil deterioration and soil maintenance and improvement. The advantage possessed by land of virgin fertility is a transitory one, but while it lasts, and as long as there are reserve areas to be brought under the plow, it often goes hard with the tillers of older soils. At best there is but a small margin of profit in the growing of staple crops such as wheat, oats, and cotton. It is easy to change profit into loss when untoward seasonal conditions, or attacks by insects and fungi, seriously reduce the yield. It is no less easy to reach low levels of production and to encounter years of adversity when the plant-food capital of the soil begins to shrink, when physical soil deterioration takes place, when the biological machinery of the soil no longer functions a t its best. After all, we cannot regard the soil resources of our country, or those of any other country, as a matter of purely local concern. Food surpluses are in effect soil surpluses, and food surpluses will flow in the direction of a partial food vacuum. The meaning of this comes clearly to us as we think of seed time and harvest in the far-flung regions of the northern and southern hemispheres, of the desperate efforts in many countries to wrest a maximum yield of human and animal food from the soil. Is there not ample reason, then, for our asking the chemist and biologist to tell us something about our soil resources and their bearing on our present and potential supply of food?
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Our Soil Resources
The authors of the excellent essay on “The Utilization of Our Lands for Crops, Pasture and Forests”2 note with much justice that: 1 Paper No. 299 of the Journal Series, New Jersey Agricultural Ex periment Station, Department of Soil Chemistry and Bacteriology 2 Yearbook, U. S. Dept. Agr., 1929, p. 415.
The dominant characteristic of American economic life has been abundance of land resources. The assumption of this abundance has colored our habits of thought and become the essential foundation for our economic policy, both individual and public. This national tradition was iirst seriously challenged by the conservation movement, which caused our people to pause and consider whether our amazing population growth and two centuries of exploitation of natural resources might have altered the outlook.
Since this was written the post-war adjustments have gone somewhat farther. It has become more evident that our present methods of land and soil utilization are to be held accountable, in part a t least, for the economic depression in some of our agricultural regions. 4 s a basis for our consideration of the soil resources of the United States, we should note that the continental land area of the country is equivalent, in round figures, to 1,903,000,000 acres. The census returns of 1919 show that this area was used as follows: Crop harvested Humid grassland and pasture Farmland not in harvested crops pasture or forest Forest, including cut-ovez and burnt-over land pastured Semi-arid and arid pasture Forest, including cut-over and burnt-over land not pastured L-rhan, desert, marsh, roads, and railroad TOTAL
Acres 385,000,000 23 1,000,000 115,000,000 237,000,000 587,000,000 248,000,000 122,000,000 1,903,000,000
The present or future value of the different areas for agricultural uses must be determined primarily by climatic conditions. East of the one hundredth meridian the annual precipitation ranges from 20 to 60 inches. The corresponding amounts in the Great Plains area are 12 to 20 inches, while in portions of the Rocky Mountain Plateau states it is usually less than 10 inches. I n some localities in the Gulf states the annual precipitation is from 55 to 60 inches, while portions of the Pacific Coast states receive as much as 80 to 120 inches. Furthermore, it is not alone the total amount of precipitation, but also its seasonal distribution,
