Creative Chemistry Part 7

In the chapter on explosives I explained how cellulose treated with nitric acid in the presence of sulfuric acid was nitrated. The cellulose molecule having three hydroxyl (--OH) groups, can take up one, two or three nitrate groups (--ONO_{2}). The higher nitrates are known as guncotton and form the basis of modern dynamite and smokeless powder.

The lower nitrates, known as pyroxylin, are less explosive, although still very inflammable. All these nitrates are, like the original cellulose, insoluble in water, but unlike the original cellulose, soluble in a mixture of ether and alcohol. The solution is called collodion and is now in common use to spread a new skin over a wound.

The great war might be traced back to n.o.bel's cut finger. Alfred n.o.bel was a Swedish chemist--and a pacifist. One day while working in the laboratory he cut his finger, as chemists are apt to do, and, again as chemists are apt to do, he dissolved some guncotton in ether-alcohol and swabbed it on the wound. At this point, however, his conduct diverges from the ordinary, for instead of standing idle, impatiently waving his hand in the air to dry the film as most people, including chemists, are apt to do, he put his mind on it and it occurred to him that this sticky stuff, slowly hardening to an elastic ma.s.s, might be just the thing he was hunting as an absorbent and solidifier of nitroglycerin. So instead of throwing away the extra collodion that he had made he mixed it with nitroglycerin and found that it set to a jelly. The "blasting gelatin"

thus discovered proved to be so insensitive to shock that it could be safely transported or fired from a cannon. This was the first of the high explosives that have been the chief factor in modern warfare.

But on the whole, collodion has healed more wounds than it has caused besides being of infinite service to mankind otherwise. It has made modern photography possible, for the film we use in the camera and moving picture projector consists of a gelatin coating on a pyroxylin backing. If collodion is forced through fine gla.s.s tubes instead of through a slit, it comes out a thread instead of a film. If the collodion jet is run into a vat of cold water the ether and alcohol dissolve; if it is run into a chamber of warm air they evaporate. The thread of nitrated cellulose may be rendered less inflammable by taking out the nitrate groups by treatment with ammonium or calcium sulfide.

This restores the original cellulose, but now it is an endless thread of any desired thickness, whereas the native fiber was in size and length adapted to the needs of the cottonseed instead of the needs of man. The old motto, "If you want a thing done the way you want it you must do it yourself," explains why the chemist has been called in to supplement the work of nature in catering to human wants.

Instead of nitric acid we may use strong acetic acid to dissolve the cotton. The resulting cellulose acetates are less inflammable than the nitrates, but they are more brittle and more expensive. Motion picture films made from them can be used in any hall without the necessity of imprisoning the operator in a fire-proof box where if anything happens he can burn up all by himself without disturbing the audience. The cellulose acetates are being used for auto goggles and gas masks as well as for windows in leather curtains and transparent coverings for index cards. A new use that has lately become important is the varnis.h.i.+ng of aeroplane wings, as it does not readily absorb water or catch fire and makes the cloth taut and air-tight. Aeroplane wings can be made of cellulose acetate sheets as transparent as those of a dragon-fly and not easy to see against the sky.

The nitrates, sulfates and acetates are the salts or esters of the respective acids, but recently true ethers or oxides of cellulose have been prepared that may prove still better since they contain no acid radicle and are neutral and stable.

These are in brief the chief processes for making what is commonly but quite improperly called "artificial silk." They are not the same substance as silkworm silk and ought not to be--though they sometimes are--sold as such. They are none of them as strong as the silk fiber when wet, although if I should venture to say which of the various makes weakens the most on wetting I should get myself into trouble. I will only say that if you have a grudge against some fisherman give him a fly line of artificial silk, 'most any kind.

The nitrate process was discovered by Count Hilaire de Chardonnet while he was at the Polytechnic School of Paris, and he devoted his life and his fortune trying to perfect it. Samples of the artificial silk were exhibited at the Paris Exposition in 1889 and two years later he started a factory at Basancon. In 1892, Cross and Bevan, English chemists, discovered the viscose or xanthate process, and later the acetate process. But although all four of these processes were invented in France and England, Germany reaped most benefit from the new industry, which was bringing into that country $6,000,000 a year before the war. The largest producer in the world was the Vereinigte Glanzstoff-Fabriken of Elberfeld, which was paying annual dividends of 34 per cent. in 1914.

The raw materials, as may be seen, are cheap and abundant, merely cellulose, salt, sulfur, carbon, air and water. Any kind of cellulose can be used, cotton waste, rags, paper, or even wood pulp. The processes are various, the names of the products are numerous and the uses are innumerable. Even the most inattentive must have noticed the widespread employment of these new forms of cellulose. We can buy from a street barrow for fifteen cents near-silk neckties that look as well as those sold for seventy-five. As for wear--well, they all of them wear till after we get tired of wearing them. Paper "vulcanized" by being run through a 30 per cent. solution of zinc chloride and subjected to hydraulic pressure comes out hard and h.o.r.n.y and may be used for trunks and suit cases. Viscose tubes for sausage containers are more sanitary and appetizing than the customary casings. Viscose replaces ramie or cotton in the Welsbach gas mantles. Viscose film, transparent and a thousandth of an inch thick (cellophane), serves for candy wrappers.

Cellulose acetate cylinders spun out of larger orifices than silk are trying--not very successfully as yet--to compete with hog's bristles and horsehair. Stir powdered metals into the cellulose solution and you have the Bayko yarn. Bayko (from the manufacturers, Farbenfabriken vorm.

Friedr. Bayer and Company) is one of those telescoped names like Socony, Nylic, Fominco, Alco, Ropeco, Ripans, Penn-Yan, Anzac, Dagor, Dora and Cadets, which will be the despair of future philologers.

[Ill.u.s.tration: A PAPER MILL IN ACTION

This photograph was taken in the barking room of the big pulp mill of the Great Northern Paper Company at Millinocket, Maine]

[Ill.u.s.tration: CELLULOSE FROM WOOD PULP

This is now made into a large variety of useful articles of which a few examples are here pictured]

Soluble cellulose may enable us in time to dispense with the weaver as well as the silkworm. It may by one operation give us fabrics instead of threads. A machine has been invented for manufacturing net and lace, the liquid material being poured on one side of a roller and the fabric being reeled off on the other side. The process seems capable of indefinite extension and application to various sorts of woven, knit and reticulated goods. The raw material is cotton waste and the finished fabric is a good subst.i.tute for silk. As in the process of making artificial silk the cellulose is dissolved in a cupro-ammoniacal solution, but instead of being forced out through minute openings to form threads, as in that process, the paste is allowed to flow upon a revolving cylinder which is engraved with the pattern of the desired textile. A sc.r.a.per removes the excess and the turning of the cylinder brings the paste in the engraved lines down into a bath which solidifies it.

Tulle or net is now what is chiefly being turned out, but the engraved design may be as elaborate and artistic as desired, and various materials can be used. Since the threads wherever they cross are united, the fabric is naturally stronger than the ordinary. It is all of a piece and not composed of parts. In short, we seem to be on the eve of a revolution in textiles that is the same as that taking place in building materials. Our concrete structures, however great, are all one stone.

They are not built up out of blocks, but cast as a whole.

Lace has always been the aristocrat among textiles. It has maintained its exclusiveness. .h.i.therto by being based upon hand labor. In no other way could one get so much painful, patient toil put into such a light and portable form. A filmy thing twined about a neck or dropping from a wrist represented years of work by poor peasant girls or pallid, unpaid nuns. A visit to a lace factory, even to the public rooms where the wornout women were not to be seen, is enough to make one resolve never to purchase any such thing made by hand again. But our good resolutions do not last long and in time we forget the strained eyes and bowed backs, or, what is worse, value our bit of lace all the more because it means that some poor woman has put her life and health into it, netting and weaving, purling and knotting, twining and twisting, throwing and drawing, thread by thread, day after day, until her eyes can no longer see and her fingers have become stiffened.

But man is not naturally cruel. He does not really enjoy being a slave driver, either of human or animal slaves, although he can be hardened to it with shocking ease if there seems no other way of getting what he wants. So he usually welcomes that Great Liberator, the Machine. He prefers to drive the tireless engine than to whip the straining horses.

He had rather see the farmer riding at ease in a mowing machine than bending his back over a scythe.

The Machine is not only the Great Liberator, it is the Great Leveler also. It is the most powerful of the forces for democracy. An aristocracy can hardly be maintained except by distinction in dress, and distinction in dress can only be maintained by sumptuary laws or costliness. Sumptuary laws are unconst.i.tutional in this country, hence the stress laid upon costliness. But machinery tends to bring styles and fabrics within the reach of all. The shopgirl is almost as well dressed on the street as her rich customer. The man who buys ready-made clothing is only a few weeks behind the vanguard of the fas.h.i.+on. There is often no difference perceptible to the ordinary eye between cheap and high-priced clothing once the price tag is off. Jewels as a portable form of concentrated costliness have been in favor from the earliest ages, but now they are losing their fact.i.tious value through the advance of invention. Rubies of unprecedented size, not imitation, but genuine rubies, can now be manufactured at reasonable rates. And now we may hope that lace may soon be within the reach of all, not merely lace of the established forms, but new and more varied and intricate and beautiful designs, such as the imagination has been able to conceive, but the hand cannot execute.

Dissolving nitrocellulose in ether and alcohol we get the collodion varnish that we are all familiar with since we have used it on our cut fingers. Spread it on cloth instead of your skin and it makes a very good leather subst.i.tute. As we all know to our cost the number of animals to be skinned has not increased so rapidly in recent years as the number of feet to be shod. After having gone barefoot for a million years or so the majority of mankind have decided to wear shoes and this change in fas.h.i.+on comes at a time, roughly speaking, when pasture land is getting scarce. Also there are books to be bound and other new things to be done for which leather is needed. The war has intensified the stringency; so has feminine fas.h.i.+on. The conventions require that the shoe-tops extend nearly to skirt-bottom and this means that an inch or so must be added to the shoe-top every year. Consequent to this rise in leather we have to pay as much for one shoe as we used to pay for a pair.

Here, then, is a chance for Necessity to exercise her maternal function.

And she has responded n.o.bly. A progeny of new substances have been brought forth and, what is most encouraging to see, they are no longer trying to worm their way into favor as surrept.i.tious surrogates under the names of "leatheret," "leatherine," "leatheroid" and "leather-this-or-that" but come out boldly under names of their own coinage and declare themselves not an imitation, not even a subst.i.tute, but "better than leather." This policy has had the curious result of compelling the cowhide men to take full pages in the magazines to call attention to the forgotten virtues of good old-fas.h.i.+oned sole-leather!

There are now upon the market synthetic shoes that a vegetarian could wear with a clear conscience. The soles are made of some rubber composition; the uppers of cellulose fabric (canvas) coated with a cellulose solution such as I have described.

Each firm keeps its own process for such substance a dead secret, but without prying into these we can learn enough to satisfy our legitimate curiosity. The first of the artificial fabrics was the old-fas.h.i.+oned and still indispensable oil-cloth, that is canvas painted or printed with linseed oil carrying the desired pigments. Linseed oil belongs to the cla.s.s of compounds that the chemist calls "unsaturated" and the psychologist would call "unsatisfied." They take up oxygen from the air and become solid, hence are called the "drying oils," although this does not mean that they lose water, for they have not any to lose.

Later, ground cork was mixed with the linseed oil and then it went by its Latin name, "linoleum."

The next step was to cut loose altogether from the natural oils and use for the varnish a solution of some of the cellulose esters, usually the nitrate (pyroxylin or guncotton), more rarely the acetate. As a solvent the ether-alcohol mixture forming collodion was, as we have seen, the first to be employed, but now various other solvents are in use, among them castor oil, methyl alcohol, acetone, and the acetates of amyl or ethyl. Some of these will be recognized as belonging to the fruit essences that we considered in Chapter V, and doubtless most of us have perceived an odor as of over-ripe pears, bananas or apples mysteriously emanating from a newly lacquered radiator. With powdered bronze, imitation gold, aluminum or something of the kind a metallic finish can be put on any surface.

Canvas coated or impregnated with such soluble cellulose gives us new flexible and durable fabrics that have other advantages over leather besides being cheaper and more abundant. Without such material for curtains and cus.h.i.+ons the automobile business would have been sorely hampered. It promises to provide us with a book binding that will not crumble to powder in the course of twenty years. Linen collars may be water-proofed and possibly Dame Fas.h.i.+on--being a fickle lady--may some day relent and let us wear such sanitary and economical neckwear. For shoes, purses, belts and the like the cellulose varnish or veneer is usually colored and stamped to resemble the grain of any kind of leather desired, even snake or alligator.

If instead of dissolving the cellulose nitrate and spreading it on fabric we combine it with camphor we get celluloid, a plastic solid capable of innumerable applications. But that is another story and must be reserved for the next chapter.

But before leaving the subject of cellulose proper I must refer back again to its chief source, wood. We inherited from the Indians a well-wooded continent. But the pioneer carried an ax on his shoulder and began using it immediately. For three hundred years the trees have been cut down faster than they could grow, first to clear the land, next for fuel, then for lumber and lastly for paper. Consequently we are within sight of a shortage of wood as we are of coal and oil. But the coal and oil are irrecoverable while the wood may be regrown, though it would require another three hundred years and more to grow some of the trees we have cut down. For fuel a pound of coal is about equal to two pounds of wood, and a pound of gasoline to three pounds of wood in heating value, so there would be a great loss in efficiency and economy if the world had to go back to a wood basis. But when that time shall come, as, of course, it must come some time, the wood will doubtless not be burned in its natural state but will be converted into hydrogen and carbon monoxide in a gas producer or will be distilled in closed ovens giving charcoal and gas and saving the by-products, the tar and acid liquors.

As it is now the lumberman wastes two-thirds of every tree he cuts down.

The rest is left in the forest as stump and tops or thrown out at the mill as sawdust and slabs. The slabs and other sc.r.a.ps may be used as fuel or worked up into small wood articles like laths and clothes-pins.

The sawdust is burned or left to rot. But it is possible, although it may not be profitable, to save all this waste.

In a former chapter I showed the advantages of the introduction of by-product c.o.ke-ovens. The same principle applies to wood as to coal. If a cord of wood (128 cubic feet) is subjected to a process of destructive distillation it yields about 50 bushels of charcoal, 11,500 cubic feet of gas, 25 gallons of tar, 10 gallons of crude wood alcohol and 200 pounds of crude acetate of lime. Resinous woods such as pine and fir distilled with steam give turpentine and rosin. The acetate of lime gives acetic acid and acetone. The wood (methyl) alcohol is almost as useful as grain (ethyl) alcohol in arts and industry and has the advantage of killing off those who drink it promptly instead of slowly.

The chemist is an economical soul. He is never content until he has converted every kind of waste product into some kind of profitable by-product. He now has his glittering eye fixed upon the mountains of sawdust that pile up about the lumber mills. He also has a notion that he can beat lumber for some purposes.

VII

SYNTHETIC PLASTICS

In the last chapter I told how Alfred n.o.bel cut his finger and, daubing it over with collodion, was led to the discovery of high explosive, dynamite. I remarked that the first part of this process--the hurting and the healing of the finger--might happen to anybody but not everybody would be led to discovery thereby. That is true enough, but we must not think that the Swedish chemist was the only observant man in the world.

About this same time a young man in Albany, named John Wesley Hyatt, got a sore finger and resorted to the same remedy and was led to as great a discovery. His father was a blacksmith and his education was confined to what he could get at the seminary of Eddytown, New York, before he was sixteen. At that age he set out for the West to make his fortune. He made it, but after a long, hard struggle. His trade of typesetter gave him a living in Illinois, New York or wherever he wanted to go, but he was not content with his wages or his hours. However, he did not strike to reduce his hours or increase his wages. On the contrary, he increased his working time and used it to increase his income. He spent his nights and Sundays in making billiard b.a.l.l.s, not at all the sort of thing you would expect of a young man of his Christian name. But working with billiard b.a.l.l.s is more profitable than playing with them--though that is not the sort of thing you would expect a man of my surname to say.

Hyatt had seen in the papers an offer of a prize of $10,000 for the discovery of a satisfactory subst.i.tute for ivory in the making of billiard b.a.l.l.s and he set out to get that prize. I don't know whether he ever got it or not, but I have in my hand a newly published circular announcing that Mr. Hyatt has now perfected a process for making billiard b.a.l.l.s "better than ivory." Meantime he has turned out several hundred other inventions, many of them much more useful and profitable, but I imagine that he takes less satisfaction in any of them than he does in having solved the problem that he undertook fifty years ago.

The reason for the prize was that the game on the billiard table was getting more popular and the game in the African jungle was getting scarcer, especially elephants having tusks more than 2-7/16 inches in diameter. The raising of elephants is not an industry that promises as quick returns as raising chickens or Belgian hares. To make a ball having exactly the weight, color and resiliency to which billiard players have become accustomed seemed an impossibility. Hyatt tried compressed wood, but while he did not succeed in making billiard b.a.l.l.s he did build up a profitable business in stamped checkers and dominoes.

Setting type in the way they did it in the sixties was hard on the hands. And if the skin got worn thin or broken the dirty lead type were liable to infect the fingers. One day in 1863 Hyatt, finding his fingers were getting raw, went to the cupboard where was kept the "liquid cuticle" used by the printers. But when he got there he found it was bare, for the vial had tipped over--you know how easily they tip over--and the collodion had run out and solidified on the shelf.

Possibly Hyatt was annoyed, but if so he did not waste time raging around the office to find out who tipped over that bottle. Instead he pulled off from the wood a bit of the dried film as big as his thumb nail and examined it with that "'satiable curtiosity," as Kipling calls it, which is characteristic of the born inventor. He found it tough and elastic and it occurred to him that it might be worth $10,000. It turned out to be worth many times that.

Collodion, as I have explained in previous chapters, is a solution in ether and alcohol of guncotton (otherwise known as pyroxylin or nitrocellulose), which is made by the action of nitric acid on cotton.

Hyatt tried mixing the collodion with ivory powder, also using it to cover b.a.l.l.s of the necessary weight and solidity, but they did not work very well and besides were explosive. A Colorado saloon keeper wrote in to complain that one of the billiard players had touched a ball with a lighted cigar, which set it off and every man in the room had drawn his gun.

The trouble with the dissolved guncotton was that it could not be molded. It did not swell up and set; it merely dried up and shrunk. When the solvent evaporated it left a wrinkled, shriveled, h.o.r.n.y film, satisfactory to the surgeon but not to the man who wanted to make b.a.l.l.s and hairpins and knife handles out of it. In England Alexander Parkes began working on the problem in 1855 and stuck to it for ten years before he, or rather his backers, gave up. He tried mixing in various things to stiffen up the pyroxylin. Of these, camphor, which he tried in 1865, worked the best, but since he used castor oil to soften the ma.s.s articles made of "parkesine" did not hold up in all weathers.

Another Englishman, Daniel Spill, an a.s.sociate of Parkes, took up the problem where he had dropped it and turned out a better product, "xylonite," though still sticking to the idea that castor oil was necessary to get the two solids, the guncotton and the camphor, together.

But Hyatt, hearing that camphor could be used and not knowing enough about what others had done to follow their false trails, simply mixed his camphor and guncotton together without any solvent and put the mixture in a hot press. The two solids dissolved one another and when the press was opened there was a clear, solid, h.o.m.ogeneous block of--what he named--"celluloid." The problem was solved and in the simplest imaginable way. Tissue paper, that is, cellulose, is treated with nitric acid in the presence of sulfuric acid. The nitration is not carried so far as to produce the guncotton used in explosives but only far enough to make a soluble nitrocellulose or pyroxylin. This is pulped and mixed with half the quant.i.ty of camphor, pressed into cakes and dried. If this mixture is put into steam-heated molds and subjected to hydraulic pressure it takes any desired form. The process remains essentially the same as was worked out by the Hyatt brothers in the factory they set up in Newark in 1872 and some of their original machines are still in use. But this protean plastic takes innumerable forms and almost as many names. Each factory has its own secrets and lays claim to peculiar merits. The fundamental product itself is not patented, so trade names are copyrighted to protect the product. I have already mentioned three, "parkesine," "xylonite" and "celluloid," and I may add, without exhausting the list of species belonging to this genus, "viscoloid," "lithoxyl," "fiberloid," "coraline," "eburite,"

"pulveroid," "ivorine," "pergamoid," "duroid," "ivortus," "crystalloid,"

"transparene," "litnoid," "petroid," "pasbosene," "cellonite" and "pyralin."

Celluloid can be given any color or colors by mixing in aniline dyes or metallic pigments. The color may be confined to the surface or to the interior or pervade the whole. If the nitrated tissue paper is bleached the celluloid is transparent or colorless. In that case it is necessary to add an antacid such as urea to prevent its getting yellow or opaque.

To make it opaque and less inflammable oxides or chlorides of zinc, aluminum, magnesium, etc., are mixed in.

Without going into the question of their variations and relative merits we may consider the advantages of the pyroxylin plastics in general.

Here we have a new substance, the product of the creative genius of man, and therefore adaptable to his needs. It is hard but light, tough but elastic, easily made and tolerably cheap. Heated to the boiling point of water it becomes soft and flexible. It can be turned, carved, ground, polished, bent, pressed, stamped, molded or blown. To make a block of any desired size simply pile up the sheets and put them in a hot press.

To get sheets of any desired thickness, simply shave them off the block.

To make a tube of any desired size, shape or thickness squirt out the mixture through a ring-shaped hole or roll the sheets around a hot bar.

Cut the tube into sections and you have rings to be shaped and stamped into box bodies or napkin rings. Print words or pictures on a celluloid sheet, put a thin transparent sheet over it and weld them together, then you have something like the horn book of our ancestors, but better.