I N D U S T R I A L A N D ENGINEERING CHEMISTRY
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Progress in the Soap Industry during the Last Fifty Years’ By Martin Hill Ittner CCJLCATE & Co., JERSEY CITY,N. J.
HE soap industry, on account of its long standing, is one of the most venerable chemical industries. Although great progress has been made during the last half-century, there have not been many outstanding or revolutionary improvements in the art of soap-making. Most of the valuable improvements have resulted from the gradual development of ideas conceived long ago, thus making it extremely hard to survey the field and sort out that which is new from that which is old. If one well versed in the history of soapmaking were to go carefully through an up-to-date soap plant and examine the various processes in detail, he might look upon most of them and say that they were old. Thus it might seem that but little progress has been made. The advanced ideas of fifty years ago have now become commonplace and many of the methods then prevalent have been abandoned, while most of the equipment of that period has been relegated to the scrap heap. Although Chevreul and other chemists had furnished a good foundation for soap chemistry more than fifty years ago, the industry has only begun during comparatively recent years to avail itself thoroughly of this knowledge. Engineering progress has also been greatest during recent years. The reason for this is clear. The old-time soap factories were necessarily small. The packing industry had not yet been concentrated in our larger cities, and there was not a single large source of fats that could be drawn upon for soapmaking materials. In the olden days each meat shop saved the fatty scraps and the small soap-maker came around to collect them to produce the tallow he made into soap. Soapmaking in the hands of these small operators was a trade. The small factory didn’t dream of hiring a chemist. Few soap-makers realized that a chemist could be of any value. The soapmaker boiled his pan until he observed foam on the soap surface of a character that he had come to associate with a successful boil. He had trouble from the start of the saponification $0 the end of the boil and usually occupied a number of days in making a small batch of soap, the whole process being in the nature of a series of adjustments, until finally a n appearance was brought about that indicated to his eye a successful conclusion. Although some soapmakers had begun to use steam for heating soap pans more than fifty years ago, fire heating was still largely in vogue and those factories that used steam had not perfected the control of steam that is now to be found in the modern soap factory, where closed and open steam jets connected with high-pressure steam give the soap-boiler complete mastery of the heat in his pan. Most of the boiled soap formerly made was curd soap that was dipped off from the lye with which it was boiled down. These soaps usually contained much excess alkali and salt. In some cases the soap-maker subjected the soap to a “fitting” operation in which weak alkali was usually added. This operation was the direct forerunner of the “settled soap process,” though it was a groping in the dark that was not then understood and that was under poor control, whereas every soap chemist now understands the
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Received May 28. 1926.
balanced two-phase system, which enables him easily to separate most of the soap in a phase almost free from excess alkali and other impurities, leaving a small distinct layer or phase of diluted lye containing practically all the excess alkali and impurities along with a little dissolved soap that can be recovered and worked over. Alkali Manufacture
Great progress has been made in the manufacture of alkali. Soap-making alkalies were formerly very impure, containing different sulfur bodies and much iron and other impurities. Wood ashes were depended upon largely to furnish soap alkali, and when a soda soap was wanted successive washes of the soap with salt solutions were relied upon to displace much of the potash in the soap with the soda obtained from the salt by a chemical interchange. The Solvay process for making alkali, competing with the older LeBlanc process, was a good thing for the soapmaker, as the quality of the alkali on the market improved faster on this account than if either process had had the field to itself. With the centralization of the soap industry in larger factories many improvements and economies became common that were formerly impossible. A number of soapmakers now make their own caustic soda by causticizing sal soda solution with milk of lime, and the electrolytic process has become a successful reality for producing caustic soda direct from salt. Glycerol Recovery
Chevreul showed long ago that the fats all yielded glycerol, but the soap-maker was very slow to take advantage of this fact and up to comparatively recent years he ran his spent lyes containing the glycerol to the sewer. It was the candle-maker who first recovered glycerol from fats. The candle-maker was usually a soapmaker also, but it was easier to recover glycerol in the process of saponifying fats to fatty acids than in the process which made them into soap. Catalytic processes were developed many years ago for saponifying fats to fatty acids and glycerol, though no one thought then to call them catalytic. It was found that fat heated under pressure in the presence of water and a little acid or a little lime was saponified readily to fatty acids and glycerol. It was a comparatively easy matter to neutralize the acid or alkaline water obtained in this way which contained the glycerol. Thus, either lime or acid was largely eliminated as precipitated calcium sulfate, and after the filtered solution was evaporated down a crude containing in the neighborhood of 90 per cent glycerol was obtained, which was further purified by distillation. I n the olden days this distillation was performed over fire and the glycerol was usually contaminated with some decomposition products. It was not such a simple process to recover glycerol from soap lyes. Salt, which is used in graining out soap and washing it free from glycerol and impurities, is very soluble in the lye, even after much of the water has been evaporated off. Soda, the alkali used for saponifying in soapmaking, is very much more soluble than the lime used in candlemaking, and whereas most of the lime can be removed by
INDUSTRIAL d.VD ENGINEERING CHEMISTRY
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precipitation as calcic sulfate, the soda salts cannot he removed from soap lyes by this means. The recovery of glycerol from soap lyes was therefore a more difficult process than the method a t first employed in the candle industry for glycerol recovery, and the necessity for a more elaborate and expensive equipment long delayed all attempts to recover glycerol from soap lyes, which were therefore thrown away. Chemists and engineers have been very busy during the last thirty or forty years in perfecting the extraction of glycerol from soap lyes, and they have accomplished the task so well that the success of soap-making often depends on the recovery of the glycerol. The general process used is to neutralize the glycerol lye already freed from most of its alkali and to filter i t with some coagulant. It is then evaporated down until most of the salt present crystallizes out, after which the crude glycerol so obtained is distilled in vacuo with high-pressure steam. A number of successful types of apparatus have been devised for distilling glycerol, but the best all utilize vacuum, steamheating, and steam jets. I n some the latent heat of the distillate is utilized to supply heat to another stage of the process. Glycerol made in this way is free from the objectionable impurities that were always present when fire distillation was used and especially when vacuum was not employed. Cold-Process Soaps
The cold process of making soap was formerly used by most small soap-makers, and much toilet soap was made in this way. The melted fat, which was necessarily of fairly good quality in the beginning, as the process involved no purifying action, was mixed with a calculated equivalent of strong lye. This formed an emulsion due to partial saponification, which held the fat and oil in intimate contact so that the saponification proceeded spontaneously on standing. These soaps always contained some free alkali or unsaponified fat, usually both, as well as impurities originally present in the fat, and the glycerol formed in the process. They had a good appearance, but were objectionable from most other standpoints. This process has now been displaced in nearly all large soap factories making toilet soaps by boiling processes that insure complete saponification, purification of the soap, freedom from excess alkali, and recovery of glycerol. Saponificat on
I n reading over old books on soap-making one is impressed with the difficulty that was encountered in trying to effect complete saponification. A small batch of soap was boiled for days with many changes of lye of varying strength. I n a large modern factory saponification has been made so simple that it is no longer a matter of grave concern. A hundred thousand pounds of fat, or more, can be saponified with ease about as fast as the materials can be pumped into the soap pan through 4-inch pipes. It is only necessary that a n excess of uncombined alkali be present ;it all times, that the concentration of the alkali not be allowed to become great enough to cause the soap formed to be insoluble in the lye in the pan, and that the contents of the pan be kept in constant agitation by means of steam so as to effect thorough mixing. If these precautions are observed the mass will remain thin and there will be no troublesome swelling, as excess he:tt will pass off in steam. Shaping
Toilet soaps were formerly made into salable shapes by cutting cakes from large blocks of soap that had been chilled in molds. Such soap necessarily contained much water,
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and the cakes dried and twisted and in time presented an unsightly appearance. Methods gradually came into use whereby soap was cut up and dried and then pounded into usable shapes. This drying was formerly accomplished by cutting into chips the soap containing 30 per cent or more of water, spreading the chips on trays, and letting them dry in the air or in dry rooms, then mixing the dried chips with perfume and pounding them into shapes for sale. An up-to-date soap factory now takes the pure, practically neutral soap from tanks, where i t is kept melted, and runs the soap over large, hollow steel rolls through which cold water circulates. The soap is thus chilled to a thin film, and this film is cut into ribbons which run on wire belts through a heated drying chamber in which a large volume of dry air is circulated. I n this way a continuous supply of pure, dry soap is produced, This is fed to mixers in which perfume is added to increase the attractiveness of the product. It then passes between massive rolls, which work it over and over until it becomes homogeneous. After this i t is subjected to great pressure and is forced to flow through a nozzle as a smooth, continuous bar, which is cut into uniform lengths and pressed into cakes. Most of this work, including the subsequent wrapping, is automatically accomplished by machinery. Toilet and laundry soaps are now better than soap-makers were able to make fifty years ago. No country makes soap any better than it is made in the United States. This is particularly true of shaving soap. American shaving soaps set the standard of excellence in every country and there is one American brand of shaving stick that can be found in practically every town of any size in the world. Floating soaps for the bath have come into very general use in America. They have become popular both because they have met a need and because they have been well made. Manufacture and Treatment of Raw Material
Some of the greatest developments in the soap industry have been made in the manufacture and treatment of the raw materials. Mention has already been made of improvements in alkali manufacture. Oil seeds from all parts of the world have been studied, and some of them have been utilized for the production of enormous quantities of valuable fats and oils. Hundreds of thousands of tons of fats and fatty oils are now produced annually from this source where little or none was produced before. Large quantities of these fats and oils after proper refining are made into soap. Some of thein if used alone as obtained would make soap too soft to suit the general public. Candle-makers and soap-makers have always looked for some means to harden soft fatty acids. This would seem to necessitate a method for saturating with hydrogen some of the double bonds in soft fat or fatty acid molecules. During the last twenty-five years successful methods have been developed for adding hydrogen gas to fatty oils by catalytic means in order to give harder fats, which in turn yield harder soaps. I n this way the amount of material suitable for soapmaking has been greatly extended. The early soap-maker used to put all kinds of crude, impure fats into his soap pan, depending largely upon the destructive action of boiling caustic soda to effect some purification. His product was often so poor that much also depended on the leniency of the consumer. This has all changed now in the large modern soap factories. I n the first place, the fats and oils are produced with greater care with competent chemical supervision and are commonly free from objectionable impurities. Where necessary, subsequent treatment is given for further purification.
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Greases that are not pure enough to be made directly into soap are subjected to some kind of aqueous aaponification, usually with a small amount of sulfonic acid saponifier, which gives glycerol solution and crude fatty acids. These can be made white and pure by distillation in vacuo with smerheated steam. Consumption, etc.
%Xause of the recovery of glycerol as a by-product, soap is now sold much cheaper than would have been possible
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by old methods, and because of its superior qualities both for household and toilet purposes it gives greater satisfaction in use than ever before. The consumption of soap has thus grown to be enormous, more than anyone can conceive. People once experiencing the many advantages derived from its use cannot Dossiblv do without it. There is no more accurate measure of {he enlightenment of a race than a gage of the amount of soap used by it. The use of soap is bound t o continue as civilization advances,
The Portland Cement Industry’ By Richard K. Meade 10 WEST CHASE ST., BALTIMORE, MD.
HE American Portland cement industry and the AMERICAN CHEMICAL SOCIETYjust missed being twinsthe first plant for the manufacture of this important building material being the Coplay Cement Company, established in 1875, by David Saylor, at Coplay, Pa. This concern is still a n active producer, but has, of course, grown to many times its original size. The site of this works is in the famous Lehigh cement district, which produces about one-third the cement made in the United States. Other works were established about the same time in other parts of the country. Most of these failed. They were all, including Saylor’s plant, quite small, manufacturing only a few thousand barrels of cement a year by primitive methods of European origin. Today the production of cement in the United States averages about half a million barrels per day. The advances in the art of cement-making during the intervening fifty years have therefore been most notable. While the quality of the product has been steadily improving, the greatest advance in the industry has been largely mechanical and along the line of efficient quantity production. At the same time, the chemist has been an important factor in this development. With the introduction of large units and the handling and proportioning of such immense quantities of raw material, many chemical problems were encountered and solved, while the constant demand for uniform material of high quality requires that the industry now employ a large number of well-trained and experienced chemists. Many of the cement-makers of the last fifty years have themselves been chemists. This is notably true in Europe; while in this country the destinies of some of our large cement works have been in the hands of chemists-at least so far as the management of the plant is concerned.
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Beginning of the Industry
The invention of Portland cement is generally credited to one Joseph Aspdin, a bricklayer of Leeds, England, who took out a patent in 1824 on “an improvement in the modes of producing artificial stone,” the specifications of which describe essentially the production of Portland cement. To his product he gave this latter name because when hardened it resembled stone from the famous quarries of Portland, England. The establishment of the American industry occurred chronologically about midway in the present life of the industry as a whole. The methods employed a t the first works in this country did not differ materially from those employed in Europe a t that time, or indeed, for that matter, 1
Received June 4, 1926.
from the early process employed by Aspdin. Naturally, the materials were somewhat different from those used i n Europe, but the steps in the process and the machinery employed were essentially the same. By Saylor’s time the value of chemical control of the process had been recognized, and all the early successful American mills had 8, chemist and a laboratory where the raw materials were properly proportioned and the product was subjected to a few simple tests. Saylor selected as his chemist John W. Eckert, a graduate of Lehigh University, and his scientific knowledge undoubtedly had much to do with the placing of the product from the Coplay works on a sound footing with architects and engineers. Theory of Cement Manufacture
Portland cement is made by combining a calcareous material, such as limestone, marl, or chalk containing lime, with an argillaceous one, such as clay or shale containing silica and alumina. These raw materials are intimately mixed by finely grinding the two together and this fine powder is then burned until it just begins to fuse or vitrify. The resulting powder, called “clinker,” after cooling is mixed with about 2 per cent of gypsum and ground so fine that a t least 78 per cent of it will pass a test sieve having 200 meshes to the inch. If the cement is to be satisfactory, the raw materials must be of proper composition a t the beginning and the proportioning must be carefully done. So far as chemical composition is concerned, it is doubtful if the intervening years between 1876 and 1926 have seen much change in the ideas as to standards set. It has generally been recognized that cements high in lime, provided they are sound, are stronger and more regular in setting properties than those low in lime. I n order to manufacture a sound cement from materials high in lime, however, it is necessary to grind the raw materials very finely. The more efficient machinery now used for pulverizing allows much finer grinding than was possible in 1876, and consequently the tendency of late years has been to produce Portland cement higher in lime, and so better, than was done fifty years ago. The strength of the concrete made from cement is largely influenced by the fineness of the cement. Owing to the improved machinery, cements are ground much finer now than they were in 1876, with the result that they are much stronger. The present output of any cement mill is much more uniform than it was in 1876, on account of improved methods of handling, storing, and blending the raw materials, the clinker, and the cement itself. I n 1876 the theory of the composition of Portland cement
