Chapter 5

The inseparable duties of studying the composition of the various animal and vegetable fabrics, as also their nature--when in contact with the various mineral, vegetable, animal, and gaseous bodies applied in the individual industries--should not devolve upon the heads, chemists, or managers of firms alone. It is most important that every intelligent workman, whom we cannot expect to acquire a very extensive knowledge of chemistry and perfect acquaintance of the particular nature and component parts of fabrics, should, at least, be able to thwart the possibility of the majority of accidents brought about in regard to the quality and aspect of materials treated by them.

In the treatment of wool the first operations are of no mean importance, and the whole subsequent operations and final results, almost as a whole, depend on the manner in which the fleece washing had been effected. In presence of suintine, as also fatty matters, as well as the countless kinds of acids deposited on the wool through exudation from the body, etc., the various agents and materials cannot act and deposit as evenly as might be desired, and the complete obliteration of the former, therefore, becomes an absolute necessity.

For vegetable fabrics a great technical and practical knowledge is already requisite in their cultivation itself, and before any operations are necessary at all. One of the greatest points is the ripeness of the fibers. It is almost an impossibility to produce delicate colors on vegetable fabrics which were gathered inopportunely. Numerous experiments have been made on cotton containing smaller or larger quantities of unripe fibers, and after the necessary preceding operations, have been dyed in rose, purple, and blue colors, and the beauty of the shades invariably differed in proportion to the greater or lesser quantities of unripe fibers contained in the samples, and by a careless admixture of unripe and unseasoned fibers the most brilliant colors have been completely spoiled in the presence of the former. These deficiencies of unripe vegetable fibers are so serious that the utmost precautions should be taken, not only by planters to gather the fibers in a ripe state, but the natural aspect of ripe and unripe fibers and their respective differences should be known to the operators of the individual branches in the cotton industry themselves.

The newest vegetable fabrics, as _ma_ (China grass), pina, _abaca_, or Manila hemp, _agave_, jute, and that obtained from the palm tree, must be tended with equal care to that of cotton. The _ma_, or China grass, is obtained from the _Boehmeria nivea_, as also from the less known _Boehmeria puya_. The fibers of this stalk, after preparing and bleaching, have the whiteness of snow and the brilliancy of silk. By a special process--the description of which we must for the present leave in abeyance--the China grass can be transformed into a material greatly resembling the finest quality of wool. The greatest advantage afforded in the application of China grass is, moreover, that the tissues produced with this fiber are much more easily washed than silks, and in this operation they lose none of their beauty or their quality.

The _abaca_ is produced from the fibrous parts of the bark of the wild banana tree, found in the Philippines. Its botanical denomination is _Musa troglodytarum_. The _abaca_ fiber is not spun or wrung, but is jointed end to end. The threads are wound and subsequently beaten for softening, and finally bleached by plunging in lime water for twenty-four hours, and dried in the sun.

The _pina_ is a fiber obtained from the leaf of the anana tree (_Bromelias ananas_), and is prepared in the same way as the abaca, but extreme care must in this case be observed in culling the fibers, in order to sort in accordance with their degree of fineness.

The Arabs manufacture the stuff for their tents with a mixture of camel's hair and the fibrous flocks (kind of wadding) obtained from the stalks of the wafer palm (the _Chamærops humilis_).

The tissues used by the Arabs are coarse and colored, but the palm fibers--when freed from gluten, which makes them adhere more strongly--are susceptible to divide in a most astonishing manner.

The _Agave americana_ is a coarse fiber, mostly used in France for the manufacture of Gobelin carpets and the production of ropes. Great efforts have been made to bleach it in a satisfactory manner, as is done with the _Phormium tenax_, but the former kind of fiber resists the ordinary treatment with lyes, etc., and an appropriate bleaching process has only been discovered quite recently.

Jute, which by many is confounded with _Phormium tenax_, or New Zealand lint, is a fiber which can be divided as finely as desired, and can be most beautifully bleached.

The jute or Indian _paat_ is generally known as a fibrous and textile fabric, obtained chiefly from Calcutta, and is similar in nature to the _Corchorus capsularis_, an Oriental species, known in Oriental India by the name of _hatta jute_ and _gheenatlapaat_. This fibrous plant has the property of dividing into the finest parallel fibers, which can be carded without difficulty, and may be said to have the excellent properties of linen, hemp, and cotton at once. When properly bleached, it has an aspect which is as beautiful as that of silk. A mixture of silk and jute can be easily worked together, and can also be mixed with such vegetable fibers as cotton and linen. An immense quantity of flannel and other stuffs are now manufactured and imitated with the different mixtures containing jute.

The _suun_ is a fiber of a plant in the form of a cane (_Crotalaria juncea_), and the paat or _suncheepaat_ is the thread of a species of spiral (_Corchorus olitarius_), sold under the name of jute tissues.

The cotton tissues lose about twenty-five per cent. of their weight in bleaching, five per cent. of the substances are dissolved through alkalies, and the other twenty per cent., which are not attacked directly through the alkalies, are removed through chlorine, acids, and the water itself. The linen and hemp tissues contain eighteen per cent. of substances which are soluble in alkalies, and they lose from twenty-seven to thirty per cent. of their weight when taken through the consecutive bleaching operations.

The substances do not alone include the substances contained in the fabric originally, but also such as are deposited in the preliminary treatment of the fabrics, as dirt from the hands of the operator, and gluten soluble in warm water; as also glue or gelatine, potash or soda, starch, albumen, and sugar, used by weavers, etc., and which are all soluble in water; further, such as greasy matters, calcareous soap, coppery soap, resinous or gummo-resinous matters, and the yellow and green coloring matters contained in textile fabrics, which are soluble in caustic soda; and finally, the earthy constituents which are soluble in acids.

The nature and composition of silk and wool is diametrically opposed to that of the former. The silk is more of a gummy nature, and is susceptible to decompose into a kind of gelatinous mass if specially treated.

The yellow coloring principle in silk was found only to be contained in a very small proportion, and consisting of several distinct bodies.

The wool contains, first, a fatty matter which is solid at an ordinary temperature, and perfectly liquid at 60° C.; secondly, a fatty matter which is liquid at 15° C.; thirdly, a fibrous substance which essentially constitutes the wool in the strict sense of the word.

The wool at least contains three important principles, as it will be known that the fibrous substance disengages sulphur and hydro-sulphuric acid without losing its peculiar properties; and it, therefore, appears probable that the sulphur entered as an element in the composition of a body which is perfectly distinct from the fibrous substance aforementioned.

In treating wool with nitric acid, and taking all possible precautions to determine as accurately as possible the quantity of sulphuric acid produced by the contents of sulphur in the wool by the reaction with chloride of barium, it will be found to contain from 1.53 to 1.87 per cent. of sulphur.--_Wool and Textile Fabrics._

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THE PRODUCTION OF AMMONIA FROM COAL.[1]

By LUDWIG MOND.

[Footnote 1: A paper read at the annual general meeting of the Society of Chemical Industry, London, July 10, 1889.]

As exemplifying to a certain extent the application of methodical research to an industrial problem, I propose to bring before you to-day an account of the work I have been engaged in for many years in relation to the procuring of new and abundant supplies of ammonia, and to investigations connected therewith.

Through the classic researches of Lawes and Gilbert, who proved, in opposition to no less an authority than Liebig, that ammonia is a most valuable manure which enables us not only to maintain, but to multiply, the yield of our fields, and thus to feed on the same area a much larger number of inhabitants, the immense importance of an abundant supply of ammonia, more particularly for the Old World, with its teeming population and worn-out soil, has been apparent to every one.

For many years Europe has paid to South America millions upon millions of pounds for ammonia in the shape of guano, and more recently, since the supply of guano practically ceased, for nitrate of soda, which effectually serves the same purpose as ammonia. During the past year South America exported 750,000 tons of nitrate, of which 650,000 went to Europe, representing a value of not less than 6,500,000l.

The problem of saving this immense expenditure to Europe, of making ourselves independent of a country so far away for the supply of a material upon which the prosperity of our agriculture--our most important industry--depends, by supplying this ammonia from sources at our own command, is certainly one of the most important which our science has to solve.

It is more than 100 years since Berthollet ascertained that ammonia consists of nitrogen and hydrogen, two elements which we have in great abundance at our command, and innumerable attempts have been made during this century to produce this valuable product by the direct combination of the elements, as well as by indirect means. It has been equally well known that we are in possession of three abundant sources of nitrogen:

(1.) In the shape of matter of animal origin.

(2.) In the shape of matter of vegetable origin.

(3.) In the atmosphere, which contains no less than 79 per cent. of uncombined nitrogen.

In olden times ammonia was principally obtained from animal matter, originally in Egypt by the distillation of camel dung, later on from urine, and from the distillation of bones and horn. The quantity so obtained was very small and the products very expensive. The introduction of coal gas for illumination gave us a considerable and constantly increasing supply of ammonia as a by-product of the gas manufacture, and until recently all practical efforts to increase our supply of ammonia were directed toward collecting and utilizing in the best possible manner the ammonia so obtained. The immense extension of the coal gas industry all over the world has in this way put us into possession of a very considerable amount of sulphate of ammonia, amounting in Europe now to 140,000 tons per annum. In recent years this has been augmented by the ammonia obtained by the distillation of shale, by the introduction of closed ovens for the manufacture of coke, combined with apparatus for condensing the ammonia formed in this manufacture, and also by the condensation of the ammonia contained in the gases from blast furnaces working with coal. But all these new sources have so far added only about 40,000 tons of sulphate of ammonia to our supply, making a total of 180,000 tons per annum, of which about 120,000 are produced in the United Kingdom, while we still import 650,000 tons of nitrate of soda, equivalent to 500,000 tons of sulphate of ammonia, to make up our requirements.

Many processes have from time to time been proposed to obtain ammonia from other sources. The distillation of turf, which contains upward of 3 per cent. of nitrogen, has received much attention, and a large number of inventors have endeavored to produce ammonia from the nitrogen of the air; but none of these processes has to my knowledge been successful on a manufacturing scale.

My attention was called to this subject at an early part of my career. Already, as far back as 1861, I undertook experiments to utilize, for the production of ammonia, waste leather, a waste material of animal origin at once abundant and very rich in nitrogen, containing from 12 per cent. to 15 per cent. of this element. Distillation in iron retorts yielded about half the nitrogen of this material in the form of ammonia, the carbon remaining in the retorts containing still from 6 per cent. to 8 per cent. Distillation with a moderate quantity of hydrate of lime increased the yield of ammonia only by 1 per cent. to 1½ per cent. A rather better result was obtained by distilling the ground residual carbon with hydrate of lime, but this operation proceeded very slowly, and the total yield of ammonia still remained very far below the quantity theoretically obtainable, so that I came to the conclusion that it was more rational to utilize the leather, reduced to powder by mechanical means, by mixing it directly with other manures.

A few years later I became connected with a large animal charcoal works, in which sulphate of ammonia was obtained as a by-product. Here again I was met with the fact that the yield of ammonia by no means corresponded with the nitrogen in the raw material and that the charcoal remaining in the retorts contained still about half as much nitrogen as had been present in the bones used.

From this time forward my attention was for many years given exclusively to the soda manufacture, and it was only in 1879 that I again took up the question of ammonia. I then determined to submit the various processes which had been proposed for obtaining ammonia from the nitrogen of the air to a searching investigation, and engaged Mr. Joseph Hawliczek to carry out the experimental work.

These processes may be broadly divided into three classes:

(1.) Processes which propose to combine nascent hydrogen with nitrogen at high temperatures or by electricity, with or without the presence of acid gases.

(2.) Processes in which nitrides are first formed, from which ammonia is obtained by the action of hydrogen or steam.

(3.) Processes in which cyanides are first formed and the ammonia obtained from these by the action of steam.

We began with an investigation of those processes in which a mixture of steam and nitrogen or of steam and air is made to act upon coke at a high temperature, sometimes in the presence of lime, baryta, or an alkali, sometimes in the presence of hydrochloric acid.

Very numerous patents have been taken out in this direction and there is no doubt that ammonia has been obtained by these processes by many inventors, but as I was aware that coke contains a considerable quantity of nitrogen, frequently as much as 1.5 per cent., which might be the source of the ammonia obtained, I determined to carry on the investigation in such a way as to make quite certain whether we obtained the ammonia from the coke or from the nitrogen of the atmosphere, or from both. For this purpose we made for every experiment carried on by a mixture of nitrogen or air with steam another experiment with steam alone, carefully excluding nitrogen from the apparatus. A very large number of experiments carried on at carefully determined temperatures, ranging from 500° to 1,200°C., and in which the directions given by the various inventors were most carefully observed, all led to the same result, viz., that the quantities of ammonia obtained were the same whether nitrogen was introduced into the apparatus with the steam or whether steam alone was used, thus proving conclusively that the ammonia obtained was derived from the nitrogen contained in the coke.

Further, on carefully determining the nitrogen in the coke used, it was found that the quantity of ammonia we had obtained in burning coke in a current of nitrogen and steam very nearly corresponded with the total nitrogen in the coke, so that we subsequently made our nitrogen determinations in the coke by simply burning it in a current of steam.

A process belonging to this class, proposed by Hugo Fleck, in which a mixture of carbonic oxide, steam, and nitrogen is made to pass over lime at a moderate red heat in order to obtain ammonia, was also carefully tried. It was claimed for this process that it produced nascent hydrogen at temperatures at which the ammonia is not dissociated, and for this reason succeeded where others had failed. We found that a considerable amount of hydrogen was obtained in this way at a temperature not exceeding 350°C., and that the reaction was nearly complete at 500°C.; but although we tried many experiments over a great range of temperatures, we never obtained a trace of ammonia by this process.

Among experiments with processes of the second class, based upon the formation of nitrides and their subsequent decomposition, the nitrides of boron and titanium had received most attention from inventors. The nitride of boron, which is obtained by treating boracic acid with carbon in the presence of nitrogen, when acted upon by steam, forms boracic acid again and yields the whole of its nitrogen in the form of ammonia, but the high temperature at which the first reaction takes place, and the volatility of boracic acid in a current of steam, make it impossible to utilize this reaction industrially.

There seemed to be a better chance for a process patented by M. Tessier du Mothay, who proposed to bring a mixture of nitrogen and hydrogen into contact with titanium nitride and thus to form ammonia continuously. Titanium is the only element of which we know at present several combinations with nitrogen, and the higher of these does, on being acted upon by a current of hydrogen at an elevated temperature, produce ammonia and a lower nitride of titanium; but this lower nitride does not absorb nitrogen under any of the conditions under which we tried it, which explains the fact that if we passed a current of hydrogen and nitrogen over the higher nitride, we at first obtained a quantity of ammonia corresponding to the quantity which the nitride would give with hydrogen alone, but that the formation of ammonia then ceased completely.

Thus far we had quite failed to get the nitrogen of the air into action.

With the third class of processes, however, based upon the formation in the first instance of cyanides, we found by our very first experiments that the nitrogen of the atmosphere can be easily led into combination. A few experiments showed that the cyanide of barium was much more readily formed than any other cyanide; so we gave our full attention from this time to the process for obtaining ammonia by means of cyanide of barium invented by MM. Margueritte and Sourdeval. This process consists in heating a mixture of carbonate of barium with carbon in the presence of nitrogen, and subsequently treating the cyanide of barium produced with steam, thus producing ammonia and regenerating the carbonate of barium. A great difficulty in this process is that the carbonate of barium fuses at high temperatures, and when fused attacks fireclay goods very powerfully.

We found that this can be overcome by mixing the carbonate of barium with a sufficient quantity of carbon and a small quantity of pitch, and that in this way balls can be made which will not fuse, so that they can be treated in a continuous apparatus in which the broken briquettes can be charged from the top, and after treatment can be withdrawn from the bottom.

We found that the formation of cyanides required a temperature of at least 1,200° C., and proceeded most readily at 1,400° C., temperatures which, although difficult to attain, are still quite within the range of practical working, and we found no difficulty in obtaining a product containing 30 per cent. of barium cyanide, corresponding to a conversion into cyanide of 40 per cent. of the barium present.

We found, however, that the cyanide when exposed to the atmosphere at a temperature above 300° C. is readily destroyed under reformation of carbonate of barium, so that it is absolutely necessary to cool it down to this temperature before exposing it to the atmosphere, a fact of great importance that had hitherto been overlooked.

The operation for producing ammonia and regenerating the carbonate of barium by acting upon the cyanide with steam offers no difficulty whatever, and if the temperature is not allowed to exceed 500° C., the results are quantitative. The regenerated carbonate of barium acts actually better than the ground witherite used in the first instance, and if care is taken that no impurities are introduced by the pitch which is used to remake the briquettes and to replace the small amount of carbon consumed at each operation, I see no reason why it should not continue to act for a very long time.

The cyanide is not acted on by carbonic oxide, but carbonic acid destroys it at high temperatures, so that it is not possible to produce it by heating the briquettes directly in a flame free from oxygen, but containing carbonic acid. The process has, therefore, to be carried out in closed vessels, and I designed for this purpose the following apparatus:

Clay retorts of moderate dimensions and thin walls are placed vertically in a furnace, passing through the hearth as well as through the arch of the furnace. These are joined at the bottom to cast iron retorts of the same shape as the earthenware retort. Through a cast iron mouthpiece on the top of the retort the material was introduced, while in the cast iron retort below the material was cooled to the necessary temperature by radiation and by the cold nitrogen gas introduced into the bottom of it. The lower end of the cast iron retort was furnished with an arrangement for taking out from time to time small quantities of the material, while fresh material was in the same proportion fed in at the top. As a source of nitrogen I used the gases escaping from the carbonating towers of the ammonia-soda process. The formation of cyanide of barium from barium carbonate, carbon, and nitrogen absorbs a very large amount of heat--no less than 97,000 calories per equivalent of the cyanide formed--which heat has to be transmitted through the walls of the retort. I therefore considered it necessary to use retorts with very thin walls, but I did not succeed in obtaining retorts of this description which would resist the very high temperatures which the process requires, and for this reason I abandoned these experiments. I was at that time not acquainted with the excellent quality of clay retorts used in zinc works, with which I have since experimented for a different purpose. I have no doubt that with such retorts the production of cyanides by this process can be carried out without great difficulty.

I believe that the process will prove remunerative for the manufacture of cyanogen products, which, if produced more cheaply, may in the future play an important role in organic synthesis, in the extraction of noble metals, and possibly other chemical and metallurgical operations.

The process certainly also offers a solution of the problem of obtaining ammonia from the nitrogen of the atmosphere, but whether this can be done with satisfactory commercial results is a question I cannot at present answer, as I have not been able to secure the data for making the necessary calculations.