The

The next ore in importance is the brown iron ore called Brown Hematite. In composition this ore is oxide of iron combined with water. Some of the finest specimens are from the Forest of Dean, Gloucestershire. Spanish and Portuguese ores seem to contain less combined water, and to hold a place between the ordinary brown hematites and the red ore.

Spathic or spathose iron ore is carbonate of iron. It is found in the Devonian series of rocks. This ore is renowned for producing the spiegeleisen in Saxony, which is imported for use in the Bessemer process. Somersetshire affords 27,556 tons, Northumberland and Durham 88,449 tons. I may observe here that spiegeleisen is another matter which presses itself upon the attention of the manufacturer of Bessemer metal. Until lately we were entirely dependent upon foreign countries, Germany or Sweden, for this beautiful pig-iron. But two years ago the Ebbw Vale Company succeeded in producing it. It is believed that the spathose ore is essential to its production, but I think as we have now interpreted in a scientific manner the old fashioned dogma about the nature of the ore giving a certain nature to the iron, it is quite possible to produce spiegeleisen from other ores than spathose. In this direction, if I may be allowed to speak critically, I think our local manufacturers have not shown sufficient enterprise.

Magnetic iron ore is a dense black ore. It is the real load stone, but little developed in this country. The Swedes here have the advantage. It is nearly always very free from the objectionable impurities of sulphur and phosphorus, and if the find of coal in Sweden justifies the expectations of some of our speculators, good times are coming for the ironmasters in Sweden.

Micaceous iron ore is brought to this country from Elba, where it has been worked from the time of the Romans. This ore in composition is exactly that of red hematite. By far the larger proportion of iron ores in this country is the kind known as argillaceous carbonates-the clay iron ores of the coal measures. These we must dismiss from the category of ores fit for producing Bessemer pig. The proportion of phosphoric acid they contain varying from 03 to 07 per cent. The same may be said of the hydrated oxides of Lincolnshire, Northampton, and other places, as well as the argillaceous carbonates of the Cleveland district. The latter contains 1'07, 186, 1'17 per cent of phosphoric acid. Wellingborough ore contains 126 per cent of phosphoric acid. From Scotland we have little hope of ore suitable for Bessemer pig. Ireland may furnish a little. Even now Antrim affords a valuable aluminous ore which is said to be free from phosphorus. It will be seen, therefore, that until phosphorus can be eliminated from pig-iron, or until these ores which lie in such vast quantities at our feet can be smelted, so as to keep the phosphorus out of the iron, we must look to foreign ores for a supply of Bessemer pig. In Sweden, according to Forbes, there are 800 square miles producing magnetic iron ore, or specular oxides containing from 40 to 68 per cent of metallic iron, without any trace of sulphur and phosphorus, upon a convenient line of railway. It is estimated that ore of about 60 per cent could be delivered in England at 25s. per ton. The Spanish and

In conclusion, I must deprecate any severe criticism on my figures. The general facts, I think, I have placed fairly before you. It would have been impossible, without much greater labour and more time for inquiry, to get accurately the quantity of iron ore really used for producing Bessemer pig. At least I have drawn attention to the necessity of augmenting its source in a town where such a manufacture cannot but be regarded with unusual interest.

ON THE UTILISATION OF WASTE COAL. By Dr. W. H. WAHL,

Secretary of the Franklin Institute.

THE desirability of effecting the economic utilisation of the coal waste daily accumulating in the anthracite-mining regions is universally conceded. This waste, to take a moderate estimate, is not far from 50 per cent of the total production. The question has for years attracted the attention of inventors, of those interested in the mining and transportation of coal, and others, the result being the announcement and testing, from time to time, of a number of plans for satisfactorily attaining this object. It is, however, only within the past few years that the growing importance of the problem has attracted general public attention to the attempts at its realisation. With every expansion of the industries dependent upon coal for their existence, and therefore highly sensitive to the price of this commodity, the necessity for its successful solution will be enhanced. Thus far, however, it may be safely asserted, no process has been devised for this purpose which could be operated with a reasonable amount of success-a declaration which is verified by the fact that, after a trial of a few months, each has invariably been abandoned, though it is very probable that there are some among the hundred odd patents granted in this country alone under this heading which, under the stimulus that would be afforded their owners by any considerable increase in the marketable value of coal, would prove to be of practical value.

The difficulties in the way of effecting the utilisation of the anthracite waste are very great. They involve not only the question of economy of manufacture, which is absolutely controlled by the ruling price of coal at the mines, and which, from a financial standpoint, must necessarily stamp any such plan with a speculative character, but they reside also in the chemical and physical nature of the material.

The processes for the utilisation of the anthracite waste consist universally in the employment of a foreign material or materials, which shall serve the purpose of a cement to bind the loose particles of the waste together. The cements heretofore used have been both of mineral (incombustible) and of organic (combustible) character. In the majority of instances, as is usually the case with a field of invention just ripening into importance, the patentees of such processes display a characteristic ignorance of, or lofty indifference to, the conditions of the problem they profess to solve. The number and variety of substances which have been secured by inventors, either as cements, or to aid in the cementation or combustion, is well calculated to surprise one unfamiliar with the literature-if such an expression is allowable when applied to patent office records of the 'subject. The several alkaline substances and their

objectionable clinker. For reasons to be specified below, the writer is of the opinion that no process employing a mineral cement will ever be more than indifferently successful, not excepting the clay process, of which so much is anticipated.

For a number of years the bituminous or semi-bituminous waste from the mines of Germany, France, and Belgium, has been to a considerable extent successfully utilised by mixing with it from 15 to 30 per cent of ordinary moist clay, and pressing this plastic mass into forms of any desired shape and size. The product thus obtained, though of inferior heating quality, still secures a ready market, owing to the high price of coal in the countries named, where it finds employment not only for household purposes but also for steam generation. Quite recently a similar process, by which the percentage of cementing clay is reduced to a minimum, has been brought out in America by a Belgian engineer familiar with the methods employed abroad. His plan, according to description, is to employ about 7 per cent of clay with the dust, and, after thoroughly mixing the materials, to bring the mixture into a pressing machine, where it is pressed into cylindrical forms of convenient size under considerable pressure. In order to protect the product from the disintegrating effects of rain or dampness, the inventor passes the lumps thus formed through a bath of resin dissolved in benzine, obtaining in this way thin hide of resin upon the surface of the lumps, which effectually serves the purpose of excluding the water.

This plan, from its simplicity, aided doubtless by the favourable opinion expressed of its merits by a committee of the Franklin Institute, has received the favourable consideration of the Lehigh Coal and Navigation Company. The adandoned works of a former unsuccessful company, which will be named hereafter, situated at Nesquehoning, Carbon County, Pa., have lately been secured by the Lehigh Company, for the purpose of giving the plan a thorough trial. The expensive machinery of their predecessors has been, or is now, in process of being modified to suit the present plan.

The same inventor has laboured zealously in this field for a number of years in the South, having for some time successfully manufactured at Nashville, Tenn., an artificial fuel by the same general process from the Southern bituminous coals, until certain business complications conspired to raise the price of the waste to so high a figure that the manufacture was abandoned.

The other plans (employing a mineral cement) as yet made public include those using an alkaline silicate (water-glass), either alone or in connection with a chloride of calcium or magnesium, or both, an hydraulic cement, plaster-ofParis, &c. As far as the knowledge of the writer extends, none of these have yet passed through the ordeal of practice, and should this have occurred with any one of them it has simply resulted in a failure. All such attempts must prove unsuccessful, from the fact that either the combustible character of the coal waste is so considerably reduced by the mixture with it of from 10 to 20 per cent of non-combustible materials that the product can only be burned with difficulty, necessitating either constant attention or an artificial draught, or the cement employed fuses in the heat of the furnace, and, coating the cemented particles with a liquid glass, prevents the access of the

It is well known that coal of any description, and especially when in the finely-comminuted condition of dust, if exposed for some time to the combined action of air and moisture, gradually deteriorates in heating quality. This deterioration is produced, first, mechanically, by the slow admixture with it of dust and dirt carried by the winds; and, secondly, by a slow process of oxidation, analogous to the rusting of iron, which infallibly attends the exposure of any readily oxidisable substance to atmospheric influence. From both of these causes, the heating quality of the coal waste is slowly reduced (or its percentage of ash, to state the case in other words, is slowly increased), and this reduction in quality grows greater and greater with the time of its exposure. With bituminous lump, Varrentrapp estimates, from careful experiments, that the loss of heating power, from chemical causes alone, may even reach 25 per cent, and, for purposes of gas production, 45 per cent. With anthracite lump, the deterioration from this cause alone will be far less than with bituminous; but, from both the causes named, it must be evident that, with the anthracite in form of waste, the deterioration must in most cases be considerable enough to gravely influence the success of any plan having in view its manufacture into artificial fuel. By the employment of dust from freshly mined coal, or of a judicious mixture of the old waste with the new, the difficulty from this source may be partially overcome; but no scheme having for its object the utilisation on a large scale of the vast waste heaps of the anthracite region, can afford to be blind to the objection here named, since it is mainly from more or less deteriorated materials that the product to be utilised must be obtained.

Instead, therefore, of employing in the cementation of the waste a substance incombustible in itself, and which directly adds so much to the percentage of ash, and still further detracts from the heating quality of the waste, the path seems pointed out to inventors to seek about for some cementing material which, being itself combustible, will improve the heating qualities of the poor waste, and which must be free from certain collateral objectionable features incident to the problem. This fact seems to have been recognised long ago, as the list of combustible cements given previously would indicate. Whatever of historical record there has come to our knowledge with regard to their trials, however, is equally unfortunate with the mineral cement processes. In some of the European countries only, have the attempts to employ coal-tar, pitch, resin, and kindred substances to bind the loose particles of dust into a coherent mass been successful. In America it has several times been essayed to apply such a process to the utilisation of anthracite waste, but all have signally failed.

Several years ago a company was formed with this object in view, by whom the extensive works at Nesquehoning, Carbon County, Pa., referred to in a former portion of this article, were erected. They employed a mixture of waste anthracite with coal-tar; this, after the most thorough mixture which could be attained (with the aid of heat), was pressed into suitable forms, and subsequently transferred to an oven, in which it was subjected to a baking process. From the testimony of several engineers, superintendents, and others who used it, it appears that the product, in spite of the increment given to its heating quality by the addition of coal-tar, was but an inferior steam generator. Whether the only partial carbonisation of the tar by the baking process allowed the offensive coal-tar odour to be perceived or not, is a contingency not known to us; but it will readily be granted that, unless this carbonisation was complete, the introduction of the product for the household was im

NEWS

possible from the outset. It is most probable that the complicated character of the process, and the number of details requiring personal attention of workmen, aside from any consideration of the quality of the product, rendered the expense of its manufacture too great to permit of a successful competition with coal, and contributed mainly to the abandonment of the enterprise, which shortly followed. The failure of this, the best organised effort of any yet made to solve the problem of the waste heaps, would seem to indicate that, though similar plans have been, and are still, in successful operation in continental Europe, the cost of mining coal with us is yet too low to permit of the employment of a tarry or resinous cement to utilise our anthracite waste, even admitting that the fuel produced were of a satisfactory quality.

Of the other patented processes, but few are worthy of mention; the great majority read too much like kitchen recipes to deserve serious consideration, as a glance at the list will show.

It is of interest to note that the first reasonable process to utilise this material originated with Mr. Bessemer, in England, where the demand for some such process will be more than ever urgent, now that the English coals have lately risen so considerably in price. Mr. Bessemer's process is for the manufacture of an artificial fuel from bituminous waste, by employing a peculiarly constructed furnace, having a device somewhat like an endless chainpump arranged horizontally, upon the successive sections of which the bituminous material, without foreign admixture, is led in from a hopper above, and is taken continuously from the furnace in a semi-caked plastic condition, and pressed in suitable forms or moulds, which are then ready for use. This plan has received considerable praise from scientific critics, of which it is indeed well worthy. It is now stated to be in successful operation in several large manufactories in England. There remain, finally, to be mentioned several American processes for utilising coal waste by the use of Grahamite as a cement, which, as far as a judgment of their merits may be formed without the crucial test of practice, may ultimately prove to be satisfactory.

With us, however, for the present, this field of industry lies fallow for want of a cultivator.-American Gas-Light Journal.

OUTLINE OF A NEW EXPLANATION OF THE ACTION OF SUNLIGHT ON IODIDE OF SILVER.* By Dr. J. EMERSON REYNOLDS, Professor of Analytical Chemistry, and Keeper of the Mineral Department in the Royal Dublin Society.

WHITE light is known to exert a very marked influence upon a very large number of chemical substances; but certain salts of silver are known to be specially subject to the action of the more refrangible rays of the spectrum. When light acts for a considerable time on iodide, bromide, or chloride of silver, evident decomposition occurs; but when the action is stopped before any sensible effect has been produced, the silver salt can be shown to have suffered profound change, in consequence of which its relations to chemical agents are almost wholly altered. All who have practised the beautiful and interesting artscience of photography well know that advantage is taken of this subtle action of light in the familiar operation of "taking a negative." A layer of iodide of silver (or of iodide, bromide, and nitrate of silver) is exposed for a short time in a camera to an image formed by a lens; the silver layer, on removal, is apparently in the same condition after as before exposure; but when an acidulated solution of ferrous sulphate is applied, the parts which have been exposed to the action of light become dark, while the other portions of the film are unaffected. *Communicated by the Author, having been read before the Royal

Dublin Society.

Notwithstanding numerous and well-directed investigations, the nature of this "latent image" remains a mystery. Quite recently, however, some remarkable experiments upon the action of light on chlorine have been published by Dr. Budde, of Bonn, which appear to me to give a very distinct clue to the modus operandi of light, more particularly on the iodide of silver. I propose now to lay before the Society, in the first instance, a brief account of Dr. Budde's experiments, and his conclusions, and then to state the explanation of the nature and relations of the "latent image" on iodide of silver, which I have ventured to build upon the work of the German physicist.

It has been long well known that the blue and violet rays of solar light can determine the union of chlorine and hydrogen gases. The two bodies are freely miscible in the dark, without any chemical action taking place; but in diffused daylight the two gases slowly combine, and produce hydrochloric acid. If the mixture be exposed to direct sunlight, the same effect is obtained instantaneously, and a violent explosion is the consequence. The cause of this union under these conditions has not hitherto been traced out; but Dr. Budde has obtained the following remarkable evidence of the direct action of blue and violet light on pure chlorine gas:

A quantity of chlorine gas was passed into a tube closed at one end, the gas being confined by a column of oil of vitriol saturated with chlorine, and the operation, of course, conducted as nearly as possible in the dark. A prismatic spectrum was formed in the usual way by means of a prism, and the several coloured rays, from red to ultra violet, allowed to fall in succession on the tube containing the chlorine, the latter being fixed in such a position that any alteration in volume which might take place during the experiment could be at once detected and estimated with the aid of an observing telescope, placed at a suitable distance. The red rays were allowed first to fall on the tube, but the effect produced was comparatively slight, as the maximum increase in the length of the gas column did not exceed theth of an inch. The permanent expansion was greater in the more refrangible rays, until the maximum effect was obtained in the violet rays, the expansion being at least ten times greater than in the red rays, and this increase in volume was permanent. If the alteration of volume were caused by heat, the expansion | should be temporary, and, further, the effect ought to be much greater in the red than in the violet rays. It is evident that the observed expansion might have been due to the decomposition of the sulphuric acid by the chlorine; but this source of error seems to have been fairly eliminated by substituting for the sulphuric acid saturated with chlorine the tetrachloride of carbon. The same result was obtained with the latter as with the former liquid.

If the experiments are to be fully trusted, chlorine is proved to have its volume permanently increased by exposure to the violet rays.

Dr. Budde concludes, from the results of his experiments, that sunlight, or rather the violet rays, act by decomposing the molecules of the chlorine, setting free the component atoms of which the so-called "molecule " is supposed to be built up. The atoms must occupy a greater space when separate than when combined forming the molecule, and are also in a peculiarly favourable condition for entering into combination with those of a new body. The rapid combination of chlorine and hydrogen under the influence of sunlight is, therefore, no longer difficult of explanation.

If Dr. Budde's conclusion be accepted for chlorine, it clearly follows that all the cases known to photographers, in which light brings about chemical change, may be explained simply and naturally on the hypothesis of the partial or complete separation of the atoms of which the molecule of a given compound may be built up. We her seem to break new ground, and to get a clue to a soun

theory of the latent image, which shall serve to explain the phenomena relied on by the supporters respectively of the present vibratory and chemical hypotheses. I would now venture to suggest an explanation of the action of light on iodide of silver which, prima facie, seems to be complete.

It is well known that the atom of a chemical element is a sharply-defined relative quantity, but that the atoms of unlike matter often differ materially in the amount of chemical work they can perform; thus an atom of sulphur can represent 6 atoms of hydrogen in combination; nitrogen 5; carbon 4; boron 3; and oxygen 2 atoms of hydrogen; silver, on the contrary, only 1. But this so-called "equivalence" of an element is not absolutely fixed, for, in some of its compounds, nitrogen represents only 3 atoms of hydrogen-in ammonia, for instance-and in others, as in nitrous oxide, but I. This variation is now commonly accounted for by supposing that pairs of points of attraction on the atom of a polyequivalent element disappear by neutralising each other, and thus lie hidden in certain forms of combination. If we represent the atom of nitrogen by a circle, its pentequivalent, triequivalent, and monequivalent conditions may be thus shown :

N

In Nitric Acid.

In Ammonia.

N

In Nitrous Oxide. These points of attraction are now usually termed "bonds." Iodide of silver consists of 1 atom of silver and I of iodine, Now, the atom of silver is known to be equivalent to only I atom of hydrogen; but the study of organic and other iodine compounds teaches us that the atom of iodine is equivalent to 3 of hydrogen, though in most compounds only appearing to be equivalent to 1 hydrogen atom. Representing graphically the atoms of silver and of iodine respectively by equal circles, and the equivalence of each atom by lines projecting from the circumference as usual now in graphic formula, we may represent ordinary iodide of silver in the following way:

Ag

Here one of the three "bonds" or centres of attraction of iodine is united with the single bond of silver, the other two neutralising each other, as indicated by the dotted line, and so remaining latent. Up to this point I have advanced nothing new; but it is necessary to recognise these preliminary matters in accounting for the action of light on iodide of silver.

Common experience leads us to the conclusion that in many cases the action of light chiefly consists in the severance of the union of unlike bodies held in combination by comparatively feeble affinity; and the highly interesting investigations of Dr. Budde would seem to go farther, and to prove that the same kind of action is inimical to the exercise of the still more feeble attractive force which tends to unite the atoms of like matter in molecules. We have only to extend the statement to the union of bonds in a single atom-as in the case of iodine -and we gain a perfectly intelligible conception of the nature of the influence exerted upon iodide of silver by light, and the cause of the well-known difference in chemi

After, as before, exposure the compound is iodide of silver; but two of the three attractive powers of the iodine are now free from each other's control, and ready to enter into new combinations. It is evident that change may now take place in either of two directions. First, the atom of iodide of silver may attract two additional atoms of silver or other analogous body to itself in so-called development; or, secondly, a complete separation of iodine from silver may arise, owing to the exercise of the superior power of the two free bonds of the former over the one attached to the silver atom. It appears by no means improbable that the first condition obtains in acid development with excess of silver, while in alkaline developement the action is more likely to be chiefly of the second kind.

Up to the point at which it is necessary to assume that light is capable of severing the union between the latent "bonds" of iodine, the theory is in harmony with the current of thought in chemistry. But it is not yet generally admitted that a "bond" can remain free or unsatisfied. The existence of such apparently anomalous compounds as nitric oxide and certain of the chlorine oxides has, however, led some chemists to think that certain "atomicities" in a compound may remain free, and ready to enter into new combinations on a favourable opportunity presenting itself. The experiments of Dr. Budde on chlorine strongly support such a view; and,. further, when we carefully consider the action of chlorine on olefiant gas, under the influence of sunlight, I see no difficulty in supposing light actually to have the power of severing the union between the latent "bonds" of an atom. I venture to think that this could take place even more easily in some cases than could the separation between the atoms of the molecule of a simple body, orthe much more difficult case-of the disunion of the unlike atoms of a compound such as iodide of silver. If, then, the last, and as must be admitted, the least likely case to occur is that which we can, in several compounds, actually observe, we are clearly warranted in assuming the much easier, and, a priori, the more probable, change to take place also.

Let us now apply the theory stated above to the explanation of some of the facts of development. I shall take at present only the case of acid developmentwith iron, for example-in the presence of excess of silver in the solution flooding the film. The acid present prevents the immediate deposition of metal; but still the exercise of even a very slight attractive power is capable of separating the silver from the liquid. The existence and exercise of the surplus chemical energy of the iodine atom of the exposed iodide of silver is amply sufficient to account for the attraction to the exposed iodide only of the metal silver, and this without assuming that the iodide of silver itself suffers any decomposition; in fact, the process appears to consist in the formation of a sub-iodide of silver by addition of silver to the exposed iodide, not by abstraction of iodine, as might be supposed. If such a definite compound be produced in the manner indicated, its formula most probably is Ag3I, for each of the three