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то

SULPHUR RECOVERY.

show the need of a careful study of chemical engineering by those who have charge of the manufacture of heavy chemicals in this country, a more apt illustration than the recovery of sulphur from alkali waste could scarcely be imagined.

Fifty years ago and a similar period has more than once seen the completed cycle of several industries, from their rise to their fall again-the late Mr. William Gossage patented the use of alkali residuum for obtaining therefrom sulphuretted hydrogen by means of muriatic or carbonic acid. In Mr. Gossage's experiments the sulphuretted hydrogen was found to be contaminated with carbonic acid, and this latter gas was eliminated by exposing it to another portion of alkali residuum. We believe that this process, or at least one very similar in its operation was carried on for some time at the works of the Patent Alkali Company at St. Helens, but was eventually abandoned for several reasons. Gossage's patent, already alluded to, is dated August 17, 1837, No. 7,416.

In October of the next year, John Fowler (October 16, 1838, No. 7.831) obtained letters patent for reducing sulphate of lime to sulphuret of calcium, and evolving sulphuretted hydrogen from this by means of carbonic acid. As early as February, 1857, Gossage had found that the diluent gases accompanying the sulphuretted hydrogen interfered with the production of vitriol by its use, and by this discovery was led off from the right path into another series of experiments which did not turn out satisfactory, and so the subject has remained unsolved until the present day, when Mr. Alexander Chance has shown how the Gordian knot may be loosened.

And how has this come about? The chemical reactions which take place in the Chance process have been known to almost every chemical tyro for years; there is nothing new on that score. Mr. Chance does not create any new machinery which was not in existence before, so that his success is due to a dogged determination to overcome the difficulties which had proved unsurmountable to former experimentalists, by careful attention to details, and to carry out the

chemical operations already so well known to be perfect in the laboratory to equal success on the large scale. This is what we call chemical engineering.

But there is another side to look at. We fear that in many works there is not much inducement for the chemist to do any more work than is allotted to him, and we know ourselves of many instances where the chemist has been kept as a mere drudge, instead of allowing him to have a status in the works commensurate with the knowledge he is called upon to possess; and in not a few cases he has been the underling of the foreman, whose sole idea is that science and practice will not work together. The ammonia-soda process and the Chance sulphur recovery process should now teach manufacturers a lesson.

And when we come to that portion of the sulphur recovery process that relates to the recovery of the sulphur as such, is there anything new here? We have only to turn to the patent of Mr. Harrison Blair, of February 18, 1858, No. 313, relating to the "recovery of sulphur which has been used in the manufacture of soda-ash," to furnish us with the answer. We shall find therein described a process for the separation of the sulphur from its combination with hydrogen by means of combustion with such a quantity of air as will support a flame, but be insufficient to provide oxygen for the combustion of the sulphur therein contained. The details of this, worked out, constitute the Claus process.

The Chance process has been already described in these columns. It seems to be a comparatively simple one, and likely to be adopted by all who have money to spare for the capital outlay, but how far it may ultimately bless the Leblanc soda trade remains to be seen. The alkali makers have for a long time been seeking rest and finding none; in fact, they are now on the horns of a dilemma, and some of them are just saying that by adopting the process they may be jumping out of the frying pan into the fire.

First of all the new process will require a further expenditure of capital. Those who have not the money to spend will probably succumb under the oppression of still lower prices for soda, unless they are fortunate enough to participate in the compensatory advantages enjoyed by those who make bleach.

But when the capital is spent, will the pyrites companies step in and say, "You can have our sulphur for one penny per unit," or even less, so that they may have the copper in a convenient form for extraction. The open air calcinations in Spain will render it all the more necessary for the pyrites companies to give the sulphur contents free, or for a trifle, for the sake of the copper, but as most of the alkali makers have contracted for about three years ahead at 44d. per unit, the position cannot be materially changed in the meantime, unless the alkali makers who adopt the recovery process can, by their contracts, take a reduced quantity of pyrites commensurate with their requirements, and this is very questionable.

The law says caveat emptor, and the pyrites companies will naturally ask, "What does the bond say," or they may see how the wind blows and trim their sails for future fair weather by making a general reduction in price, and then those who have spent their money upon sulphur recovery will be worse off than those who have not.

This little cloud may be as yet no bigger than a man's hand, but it will undoubtedly be felt; and so also, most probably, will the production of alkali from sulphate of soda without the encumbrance of vat waste have to be calculated upon, before this or any other process for treating vat waste has become general. However this may be, an immediate saving of Ios, to 15s. per ton upon 60 % caustic soda is a fact

which the ammonia-soda process has to face, and an advantage which the makers of Leblanc soda must take advantage of or perish in the attempt.

SOCIETY OF CHEMICAL INDUSTRY.

ΑΤ
Ta meeting of the Liverpool section, University College,
Liverpool, on Wednesday, the 7th inst., Mr. Thomas
Fletcher, F.C.S., read the following paper on "A new com-
mercial application of oxygen":-

The want of some simple method of obtaining a powerful source of heat under perfect control is an experience, and often an unpleasant one, which all who have charge of machinery and chemical plant must have felt more or less frequently. Up to the present time the only practical methods have been either the use of a basket of live coke or a blowpipe connected to the nearest gas supply. Neither of these methods is satisfactory in many cases, and, to overcome the difficulty, I have devised some special forms of blowpipes which can be used with the ordinary coal-gas supply and compressed oxygen made by the Brin process. These blowpipes are essentially different from the usual form, and also from the well-known mixing jet, the latter requiring both gas and oxygen to be equally compressed, which at once excludes it as an emergency arrangement for repairs and accidents. It is pretty well known that air gas produced from gaseline vapour, when used with an air blast in a blowpipe, is peculiarly liable to be extinguished; the speed of combustion is sufficiently slow to enable the flame to be blown out, or away from the unburnt vapour, with the greatest ease, probably owing to the fact that the gasoline is not diffused through the air as a true gas, but as a vapour, which requires further heating and considerable expansion before it will burn. On this point I have a rather pretty experiment here, showing how the particles of vapour in the so-called air-gas, burning separately, the flames of the separate suspended beads of gasoline vapour being distinctly visible as independent centres of combustion. When we apply an oxygen blast to gasoline vapour this brittleness or want of persistence disappears, but owing to the air mixed with the vapour, the temperature obtainable is far lower than that from permanent combustible gases, and up to the present time high temperatures have not been obtained with blowpipes using the light petroleums owing to the necessary mixture of air to obtain the vapour. We must not forget, when gasoline or benzoline vapour is used, that it has one special point in its favour for some classes of work in the fact that the products of combustion are quite free from sulphur, which in many ways is a great source of trouble in laboratory work. The use of a petroleum or spirit spray, if it were practicable, would overcome the difficulty of the admixture of air; but the spray formed by an oxygen blast is of a most unpleasantly uncertain and explosive nature, so much so that after my own experience I can only give a strong caution as to the excessive care required to prevent disastrous accidents. A spray burner may start and work satisfactorily, and then suddenly, without any apparent cause, the whole apparatus may be shattered into fragments. When we burn a permanent gas, such as hydrogen or coal-gas, in a blowpipe with an air blast, the flame will bear a heavy air pressure on the jet, giving a correspondingly high temperature flame. If we take the same permanent gas, and use it with a jet of oxygen instead of air, the persistence and "toughness" of the flame is again greatly increased, the speed of traverse of flame backwards is so great that the amount of combustion which may be going on in a given space is almost unlimited, and enormously high temperatures can, therefore, be obtained with the greatest ease, the absence of nitrogen in the flame, of course, greatly assisting the result by reducing the loss of heat, and we gain also by the smaller area of flame containing a given number of available units of heat.

In the construction of powerful blowpipes for compressed oxygen, and coal-gas at ordinary pressures, the form of the jet is a very important matter. The centre jet, instead of being formed with a single hole (except in the very smallest sizes), should be flat on the end, and drilled with a circle of very fine holes, each large enough to pass from three to four cubic feet of oxygen per hour at a heavy pressure. The gas outlet which surrounds this jet should be an annular space about inch wide surrounding the jet, and should project inch beyond the tip of the jet, this projection being the same in all sizes and powers. Such an arrangement is useless

for a gas and air blowpipe, as it extinguishes itself instantly, and some amount of experimenting has been necessary to arrive at the details now given. I have here three sizes of these blowpipes, requiring respectively about 7, 20, and 40 cubic feet of oxygen per hour; and with a small bottle of compressed oxygen, which can readily be carried under the arm, I will now give you some idea of their power. The quantity of oxygen required for each has not been measured by myself, but has been estimated from a bottle supplied by the Brin Oxygen Company, which I was informed contained 20 cubic feet, and which supplied the largest blowpipe at full power for half-an-hour continuously. The smallest of these blowpipes will fuse the end of a 3-16 wrought-iron rod: the next size will do the same with a inch wrought-iron rod, or will braze copper pipes inch thick about as quickly as a tinman can soft solder light sheet tinned iron. The largest will fuse a hole through a 4 inch wrought-iron steampipe, and will braze, and probably also weld, heavy flanges and couplings on work of the same size. Larger blowpipes can be easily made on the same lines, and it is now both possible and easy to braze and make repairs in parts of complicated machines without removal, in any place into which a man's hand can be got. The heat is so short and so quickly obtained that, with the assistance of wet cloths, polished work or wood lagging can be preserved without injury or mark, within two or three inches from a place where a heavy brazing repair has been done. Breakdowns in copper pipes or vessels can be made good and work restarted in a few minutes which under ordinary conditions would necessitate a stoppage for days. Using the same blowpipe and bottle of oxygen, I will show you, with a block of lime, an emergency light which will often be found useful; amongst other things it will enable you to get by photography a permanent record of any accident or unusual state of things in places where no natural light can be obtained, and where magnesium would fail owing to the dense fumes evolved. This light is, of course, anything but silent; but as we are now considering only works' emergencies, the noise is not of any great consequence. Turning now to the laboratory, as most of you will know, I have identified myself for many years with apparatus for the production of high temperatures for experimental purposes, and the cheap production of oxygen has advanced our powers in this direction very considerably. When any new application of a power is discovered, my own instinctive feeling turns at once to its application in the chemical laboratory, that source from whence a very large proportion of our commercial knowledge and power has originally sprung.

It is not only necessary that a new power shall be known in the laboratory; the most important point from a practical point of view is that it shall be easily and quickly applied to useful research by those whose time is limited, and the elements of time and personal trouble must be eliminated as much as possible,

My first attempts to utilise compressed oxygen for laboratory gas furnaces proved total failures, owing to the intensely local heat evolved, which entailed cutting and destruction of any and every crucible. The direct application of the heat to the contents is in many cases out of the question, and after some experimenting I found that the desired result could be obtained by mixing air with the oxygen blast, so as to increase the size of the flame, and spread the heat more evenly over the surface of the object to be heated. The form used for this purpose is similar to the well-known injector blowpipe, the air jet being, for a small laboratory furnace, inch bore and open at both ends, behind this is a small oxygen jet pointing directly along it; when the oxygen blast is turned on it carries along with it about four or five times its bulk of air. Having got so far, I was again blocked by the fact that no known casing suitable for gas furnaces would stand the heat obtained, even for a few minutes. The only kind of casings which can be satisfactorily used for laboratory gas furnaces are composed of a mixture of very refractory clay and ground cork or sawdust; when these are fired in a kiln, the woody matter is burnt out, and a porous material is left, which offers a most extraordinary resistance to the passage of high temperatures through it. It is, as is very well-known, an easy matter to fuse cast-iron in a crucible in a casing of this material only one inch thick, before the outside of the casing has time even to become slightly warm to the hand, The objection to this mixture is that the salts contained in the wood or cork are not burnt out, and they remain acting as a flux on the refractory clay, reducing its resistance to fusion to a very serious extent. This difficulty has, however, with the assistance of the Morgan Crucible Company, been at last overcome, and as the increase of

power in our guns leads to improvement in armour plates, so has the increase in power of our laboratory furnace burners led to an improvement in the resisting power of the crucible casings which have to withstand their destructive power. By the discovery of a very refractory clay, which has practically the same contraction as the porous mixture, it is now possible to line the furnace casings with a thin layer, which offers an extraordinary resistance both to fusion and also to the action of fluxes. That these casings are only in their preliminary stage, and not at their most perfect point, goes practically without saying, and only a few have been made up to the present time. One difficulty not yet perfectly overcome is the tendency of the refractory lining of the lid to tear loose owing to the thinness and the slight hold available, this is, however, only a question of detail which will shortly be overcome.

With the injector furnace, which is undoubtedly of great value for chemical research, I have been for some years held in check by the fusibility of the casings, and this has of necessity put a very definite limit to the power of the burners which could be employed. As this limit is now, or very shortly will be, greatly extended, there is an opportunity for further experiments on the air and gas burners for ordinary use, irrespective of the new power we have now at command. Using the combined air and oxygen burner with one of the new casings, you will see that any power, from the lowest to the highest, can be obtained with the greatest ease, and without attention, as one of the small oxygen cylinders will work this furnace at full power for about two and a half or three hours, and at lower powers for a correspondingly longer period.

I have already expressed an unfavourable opinion as to the use of gasoline or benzoline vapour for use in open blowpipes, but this objection does not exist with furnaces where the mixture is blown on to a surface at a high temperature, which ensures perfect combustion and persistence of the flame. The only working objection to the oxygen blast in gasoline or benzoline vapour furnaces at present is that a supply of air must be blown through the generator to produce the combustible vapour.

Whilst experimenting, it is the nature of chemists to consider the expense after the money is all gone; in fact, if this were not fortunately the case, very little original work would be done, and, to follow this old-established rule, now the oxygen is gone we will consider the expense. In the first place, owing to the great concentration of the heat, the loss in use is exceeding small, the nitrogen, which in an ordinary blowpipe frame is a source of great waste, is partly or entirely absent, and as a consequence the coal-gas consumed is in practice only about one-sixth of that required to do the same work if an air blast is used. The oxygen, if made on a large scale, can be produced by Brin's process at a cost varying from 2s. to 7s. per 1,000 cubic feet, depending on the quantity made.

In the steel bottles the compressed gas is now sold at from 2d. to 3d. per cubic foot, which is, of course, a high price for work on anything like a commercial scale; but if we keep a few small bottles of compressed oxygen ready for emergencies, their value may, in some case, be more than a thousand times their cost, and the expense becomes, therefore a minor consideration.

It may be well to mention, whilst dealing with this subject, that compressed liquid nitrous oxide has been used for small blowpipes for platinum working, but it is not only very much more costly than compressed oxygen, but it is also not so satisfactory. With the oxygen, repairs of platinum vessels in the laboratory become a very easy matter, and the ordinary forms of blowpipes can be used for this purpose, provided a small jet is used and the outer cap is kept about in. in advance of the jet. This is necessary to obtain a rough flame for general heating, a fine pointed flame being liable to cause perforation of the vessel instead of producing a broad welding surface. If the compressed oxygen is to be at all freely or generally used, the price charged must be greatly reduced, and judging from the first cost of the gas, I certainly can see no reason why so high a price should be charged, as the bottles last practically for ever, and the cost of compressing must be very small.

iron or steel door in existence. Chilled iron or steel were powerless to resist the small blowpipe Mr. Fletcher used, which would penetrate thick iron and steel plates as readily as ordinary carpenters' tools would penetrate wooden doors. The apparatus was devised by Mr. Fletcher for works' repairs, and was noisy in action; but, as he explained, the apparatus could be made silent, and small enough to carry in a hand-bag. This is a very serious matter for bankers and others who have valuable property, and one which will have to be taken up at once by the safe and strong room makers. It is very well-known that the professional burglar is ready to utilise the latest applications of science for his own ends; in fact, Mr. Fletcher's furnaces designed to assist in chemical research are well-known as being used by receivers of stolen goods to reduce plate and jewellery to ingots, and these furnaces may be seen in the detectives' museum at Scotlandyard.

Bankers have already taken the alarm, and have visited Mr. Fletcher's works with the object of seeing the extraordinary ease with which large openings can be fused in heavy iron or steel plates. It is hardly necessary to state that Mr. Fletcher plainly declares his intention not to devise a silent form of the apparatus, which naturally would be required only for burglars' use, but the light-fingered profession will no doubt take the matter in hand, and most probably succeed in making the apparatus silent, a modification which Mr. Fletcher states can be made.

During an interview with Mr. Fletcher on this very serious matter, he informed us that the present danger is possibly not so great as it appears, owing to the fact that the apparatus necessary to manufacture and prepare the silent arrangement is both costly and large, and as the person who prepares it must have fixed machinery and plant, he will most probably be one of the last to whom the enterprising burglar would apply for his apparatus.

RECOVERY OF THE SULPHUR FROM ALKALI WASTE.

SIR

DISCUSSION ON MR. CHANCE'S PAPER.

IR FREDERICK ABEL said although not a manufacturing chemist he had dealt somewhat in practical chemistry, and not long ago had the opportunity in company with Professor Dewar of inspecting the process now described. Some years ago when he saw at Oldbury the attempt to bring the Shaffner and Helbig process to a practical success he was much delighted with the progress then made, and imagined it would be as great a success practically as it was theoretically, but this did not prove to be the case. Undismayed by this, Mr. Chance and his partners, like typical Englishmen, had persevered until they had achieved the results which had now been described. He had examined this process with the greatest interest, and although at first sight he might have been a little dismayed by the elaboration of the apparatus, he was reassured by witnessing the ease by which the process was conducted by the workmen in charge, who simply opened one stopcock and shut another, and tested the richness of the gas in sulphuretted hydrogen from time to time. During the time he spent in the inspection sulphur was concentrated in one vessel and afterwards in another, so that the manufacturers were able from time to time to use the sulphuretted hydrogen gas either for the manufacture of sulphuric acid, or for the production of sulphur, as desired. He was charmed to see that a combination of simple chemical reactions and of simple chemical engineering brought about such excellence, and congratulated Messrs. Chance on what appeared to be the ultimate success which had attended their efforts. With his former colleague Mr. Stevenson, he had at one time to inquire a great deal into the bête noir of alkali makers' waste, and quite apart from the question of mercantile profit, had been gratified in watching the progress made towards the recovery of sulphur, which had been in so many ways a mischief rather than an advantage to scientific and practical chemists.

Mr. STEVENSON, M.P., said he had had the advantage on two occasions of visiting and examining very closely the experimental plant at Messrs. Chance's works at Oldbury. The best testimony he could give as to his appreciation of the process was that he persuaded his partner to at once put it into operation. What induced him to come to that conclusion was this: They were all aware of the series of attempts made from the time of Mr. Gossage's downwards to get rid of this bête noir, sulphuretted hydrogen gas, which

was not only a waste product, but far worse, it was a positive nuisance in many places. He had always felt that if it had not been for the existence of this gas, which was such a nuisance in Lancashire, very likely the Royal commission on noxious vapours would not have been called into existence, and Mr. Chance in showing them the way not only to get rid of this waste, but to turn it to profitable account, conferred a very great advantage not only on the alkali trade but on the public at large, who never entirely sympathised with the efforts of manufacturers in promoting the industry of the country. Previous efforts to produce sulphuretted hydrogen from waste in a combustible form so as to make sulphuric acid of brimstone might have failed because they attempted to obtain a continuous supply of sulphuretted hydrogen, and the great merit and ingenuity of Mr. Chance's process was that the supply was not continuous but intermittent. He felt very much puzzled at first sight at the combination of taps and pipes, and after visiting the works for the first time requested Mr. Chance to put on paper a complete round of operations lasting through an entire day, recording hour by hour the taps which were opened and the gases evolved. In order to make the thing clear to his own mind, without which he should not have understood it, he made a sketch of these operations on paper which Mr. Chance had adopted as his diagram; and what struck him about it was the remarkable symmetry of the operations-although there was apparently an extraordinary complication there was a law of symmetry and uniformity pervading them which took his fancy very much. It would be seen that when the inert gases were being produced there were always six vessels in series; but when the rich gases were being evolved there were only four vessels in series, and that held good all the way through. Again, the time during which the inert gases escaped was about half the time of that during which the rich gases evolved. There were necessarily some variations, but on the average the inert gas escaped for about one hour to one hour and twenty minutes, and the rich gases for from two hours to three and a half hours. He was also struck by the entire absence of smell of sulphuretted hydrogen, for there was nothing whatever to give any idea of that particular manufacture which was being carried on. He felt that the alkali trade had never adequately acknowledged the great services which Mr. Chance rendered some years ago by threatening the producers of pyrites, who had a combination-which at one time he had even ventured to call a conspiracy against alkali makers to keep up the prices. At one time Mr. Chance did a great service in the trade for which he received no return, but for the far greater service he had now rendered he believed he would get a substantial acknowledgment.

Mr. ALFRED E. FLETCHER (Inspector of Alkali Works) desired to congratulate Mr. Chance on the admirable manner in which he had developed this process, and on the lucid and clear manner in which he had explained it. It was only another illustration of the thoroughness of everything which Mr. Chance undertook. It was particularly interesting to see why Mr. Chance had succeeded where others had failed, and how he had followed the steps originated by Mr. Gossage, whose experiments had never been forgotten, and yet had succeeded where he had failed. It seemed to him that the three principal points to be noted were these: first in reducing the tank waste to the consistency of cream by mixing it with water, whereas Mr. Gossage used the material dry; secondly, that he did not simply force the carbonic acid through the mixture, but by watching the result had found a means of separating the poor gas from the rich. The sulphuretted hydrogen did not come off in a constant stream; the first portions were absorbed, and after an interval it came off sufficiently pure to be of use. He had also introduced a third point of importance in employing a gasholder, which had nothing to do with the production of sulphuretted hydrogen, but was most essential in utilising it afterwards. It had been suggested that the apparatus looked complicated, but it was most simple in working, and they had been told that the gases were watched until the appropriate richness was obtained, those who had not seen it would probably like to know how it was done. There was no elaborate arrangement of burettes and test tubes, but simply a Bunsen burner, on to which the sulphuretted hydrogen was turned. As long as it burnt the man in charge knew there was sufficient sulphuretted hydrogen coming off, and when the light went out he stopped it. In the same way when he wanted to know if it were rich enough he tried to light the burner, and if it would light the gas was rich enough to send into the gasholder. The Claus kiln was not