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BOOKS ON ELECTRO-METALLURGY.*

Not more than three years have elapsed since the first application to the mechanical arts of the chemical discovery, that metals can be precipitated from their solutions by the agency of the voltaic battery, in solid plates of perfect purity, of any thickness, and of the forms of the bodies on which they are deposited; and already there is scarcely a branch of manufacture connected with working in metals, which has not benefited by it. The many additions to our technical nomenclature to which this new process has given rise

of no learned society to be useful to bis fellow men, the art is honestly admitted to have "proceeded from the hands of Mr. Spencer," and is described as it came from his hands with considerable fairness-not in a perfect state, of course, (for what art was ever perfect all at once ?) but so far matured as to lead almost inevitably, to all the improvements which have followed each other in such quick succession; while, in the other, which is a London production, dedicated to the Consort of her Majesty, and writ

as Electrotype-Electrography-Electro- ten by a Fellow of the Royal Society, gilding-Electro-plating-Electro-tint, &c., are of themselves evidences of the multiplicity of uses to which it has been found subservient, and the extraordinary rapidity with which it has been turned to account. We doubt whether there is another such instance on record of a new art springing so quickly into full maturity, and being caught up so eagerly by so many different classes of persons.

On a former occasion (see vol. xxxiii. p. 20,) we stated our reasons for assigning to Mr. Thomas Spencer, of Liverpool, in preference to every other claimant, the merit of this exceedingly valuable addition to our manufacturing processes; and nothing has since transpired to induce us to modify in the slightest degree the opinion which we then expressed on this head. But though Mr. Spencer's title to be considered as the father of electrometallurgy, is now very generally recognized by the public, we are sorry to see that there still exists in certain scientific circles the same dogged reluctance, on which we before animadverted, to do justice to the humble "Carver and Gilder of Liverpool"-for no better reason, that we can discover, but the sin of being humble. We have now before us two publications on the new art, which may be considered as typical of these opposite states of feeling. In one, which is a Birmingham production, intended, like most Birmingham wares, for the million, and written by a person, who, like the hero of his subject, boasts the license

A Manual of Electro-Metallurgy. By George Shaw, 49 pp., 8vo., Groombridge, London.

Elements of Electro-Metallurgy, or the Art of Working in Metals by the Galvanic Fluid. By Alfred Smee, F.R.S., Second Edition, Revised, Corrected, Considerably Enlarged and Illustrated with numerous Engravings. Parts I. II. Palmer, London.

the name of Mr. Spencer is never once mentioned! A more flagrant instance of injustice and of venal subserviency to paltry class prejudices, we never met with. The offence smells the ranker, that it has been perpetrated by an individual, who, though not without some scientific eminence, owes all of that which he possesses, to having laboured assiduously in the very field of experimental investigation opened up by the genius of Spencer-who, but for the demand for a cheap and simple precipitating apparatus, occasioned by the extensive application of electrical science to the arts and manufactures, induced by Spencer's example, would never probably have invented the battery, with which his name is identified -and who, being himself an inventor, might have been expected to regard with some degree of fellow feeling, the claims of a brother inventor, instead of conspiring with an envious and scornful clique, to discredit and crush him.

Where there is an act of larcenygreat or petty-to be screened or palliated, falsehood is ever sure to be at hand to lend its aid. "The idea of electro-metallurgy," says Mr. Smee, " appears to have been first suggested by the use of Professor Daniell's battery, for during its action the outer copper vessel, which is the negative metal, becomes coated with an additional layer of metallic copper." Where, Mr. Smee, does this appear ? In no other page we are certain of the history of electro-metallurgy that ever was written. The fact of the deposition on the outer copper vessel, was, it is true, noticed by Professor Daniell, who even went so far as to point out to his pupils that the precipitated layer of metal exhibited im

BOOKS ON ELECTRO-METALLURGY.

pressions of any marks on the matrix with extreme fidelity, (so close did he go to the verge of the great discovery without hitting on it); but what the author of the rival treatise before us, Mr. Shaw, states on this head is not less true, namely, that the learned professor "never thought of applying this fact to any useful purpose," p. 16. Professor Daniell himself has nowhere alleged that he did, and is by far too honourable and candid a man to feel indebted to Mr. Smee for the false honour which he would parasitically thrust upon him.

Mr. Shaw gives a summary of Mr. Spencer's part in the affair, which, though it might reasonably have been in a more commendatory vein, presents in a few words the literal truth of the case. After sundry quotations from Mr. Spencer's published papers on the subject, he thus proceeds:

"We learn by the above extracts that Mr. Spencer was experimenting with a voltaic arrangement similar to that of Professor Daniell, and that in detaching the precipitated copper, he found, as that gentleman and others had done, that every impression was transferred to the precipitated copper. It is true, accident presented the fact to him in a much more forcible form than that in which it had been presented to others; the want of a proper piece of copper to complete the arrangement occasioned Mr. S. to introduce a penny as a substitute, and on detaching the precipitated copper, he found the head and letters distinctly marked upon it; so that a fac simile of the coin was produced quite unintentionally on the part of Mr. Spencer, and this new application of the voltaic battery was presented to him in a manner so forcible that it was impossible to neglect it. Mr. Spencer pursued the subject, and so far succeeded in his experiments as to be able to furnish processes by which medals and plates may be copied, and some non-conducting substances coated with copper."-p. 17.

Be it so-since the fact is so that it was by "accident" Mr. Spencer made the discovery, still it was an accident of that happy sort which happens to but one or two men in an age, and which by the universal consent of mankind entitles him to whose lot it falls, to be looked upon with all the respect, honour, and gratitude due to the chosen instrument of any great revelation by Nature to her children. It was just such an accident as that which led to the discovery of the

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only basis of all sound philosophy, the theory of gravitation. But as the fact of the fall of the apple was not merely observed by Newton, but reflected and reasoned on by him, till he reared upon it that glorious superstructure which takes in the entire universe; so in like manner Spencer saw in the facsimile which he accidentally obtained of the penny piece, a thing which was more than simply curious-to be shown about and talked about, and then no more; he saw at once that it was but a sample from a mint that was inexhaustible he "pursued the subject," as Mr. Shaw states-he pondered it well-he made experiment after experiment, till he was able to furnish processes by which medals and plates, as well as penny pieces, may be reproduced in copper by the voltaic agency. Here, at least, there was no accident; Mr. Spencer did what we cannot be sure many men would have done under the same circumstances he turned a most fortuitous incident to admirable practical account. One metal he brought quite under subjection to the new power; and but left it to others to add the rest.

Mr. Smee is of course perfectly well aware of all this, and were he not more actuated by a desire to curry favour with those by whom Spencer has been so shamefully slighted, than by sentiments of justice and generosity, he could not possibly have passed Mr. Spencer and his services over so entirely unnoticed as he has done. It would be to ascribe, however, far more importance to Mr. Smee's silence than really belongs to it, to suppose that it can be of the least permanent injury to Mr. Spencer's reputation. The only person certain to be damaged by it is Mr. Smee himself, whom it exhibits in the unenviable light of a person possessed of all the will to extinguish another's well-earned fame, but happily without the power.

The reader will not expect us to recommend him to seek for the "Elements" of electro-metallurgy in a work so destitute of the first great element of all philosophical enquiry, truth, as that of Mr. Smee. Willingly we could not do so; and fortunately there is no occasion. The first edition of Mr. Smee's Elements is confessedly so defective, that to adapt the second-Parts I. and II. of which are now before us to the advanced state of the art, the author is obliged to promise, be

sides much general revision and amendment, the addition of "one-third original matter." But while Mr. Smee is revising and amending and adding, and has as yet not reached half way in his task (for this new edition is to consist of seven Parts,) Mr. Shaw has stepped in with a "Manual" of the art, so comprehensive and complete as to leave Mr. Smee nothing of importance to tell. The student of electro-metallurgy will find in Mr. Shaw's small work every information and assistance that is to be procured through the medium of books; the principles of it expounded with correctness and clearness, though of necessity with brevity, and the practice of it in all its numerous ramifications traced with a judicious and discriminating hand. It will not of itself make a man a perfect electro-metallurgist, but combined with that knowledge which experiment alone can impart, it will certainly enable any one (which is all the author could hope to accomplish) to practise the art with workmanlike proficiency and success.

Mr. Spencer, as we have seen, effected by the electric agency the precipitation of copper only, and left to subsequent experimenters the honour of bringing the nobler metals under its dominion; or to state the case more correctly, perhaps, he was joined in the pursuit by others whose success was greater, only because Spencer had cleared the way for them. Works of art are now multiplied in gold and silver with as much facility as in copper. The following instructive sketch of the means by which this is effected we quote from Mr. Shaw.

"Platinum may be precipitated from its chloride, gold from its combination with chlorine, iodine,* bromine, and cyanogen,* or from its oxyde dissolved in potassa or soda, and silver may be precipitated from its cyanide, acetate, sulphate, or the solution of most of its salts in ammonia.

The chloride of platinum is made by the addition of spongy platinum, or the ordinary metal in small pieces, to nitro-muriatic acid or aqua regia; the latter is composed of one part of concentrated nitric acid, and two parts of muriatic (hydrochloric) acid. Chlorine is liberated, and is the real solvent.

The chloride of gold may be prepared in the same way, and from the concentrated

The reader must bear in mind that the use of these salts for plating or coating metallic bodies with a film of gold or silver has been patented.

solution, oxyde of gold may be precipitated by the addition of caustic potass. The bromide of gold is formed by the simple addition of gold to bromine. The cyanide of gold is easily procured, by dissolving either metallic gold, or the oxyde of that metal, in a solution of cyanide of potassium. If metallic gold be used, it must be in a state of minute division, and its solution may be promoted by the application of heat: it is, however a very tedious operation. The oxyde dissolves very readily. Two ounces of the cyanide of potassium may be dissolved in a pint of water, and the oxyde of gold added till the solution will take up no more. The cyanide of potassium may be made in various ways. It may be formed by the direct union of its elements; if potassium be heated in cyanogen it burns with a beautiful flame; cyanogen is absorbed, and the cyanide of potassium formed. This process cannot be used for its production in large quantities. The simplest and most economical mode of forming it is to heat the salt known by the names of prussiate of potass, ferroprussiate of potass, and ferrocyanide of potassium. It is known in commerce as prussiate of potash. It should be put in a close vessel, and heated to redness, and, after cooling, the addition of water will dissolve away the cyanide of potassium, which may be obtained in crystals by the ordinary process. The latter, however, is not necessary, as it must be used in the state of solution.

The compounds from which silver can be reduced are thus prepared. The cyanide, by the addition of oxyde of silver to the solution of cyanide of potassium, the acetate by adding oxyde of silver to acetic acid, or a solution of acetate of potassa to the solu tion of nitrate of silver. Sulphate of silver may be procured by boiling silver in sulphuric acid, or adding sulphate of soda to nitrate of silver, and the carbonate is precipitated when carbonate of potassa is added to a solution of nitrate of silver. The latter is prepared by dissolving silver in nitric acid, diluted with an equal quantity of water. The oxyde of silver is prepared from this solution by adding a solution of caustic potass, or soda, or lime water. An olive coloured precipitate falls, which is the oxyde. The carbonate of silver and most of the other salts of that metal, which are insoluble in water, dissolve very readily in a solution of ammonia, and the metal may be reduced from such solutions; but they possess no advantages; and the fact, that the detonating compound called fulminating silver is produced by the solution of the salts of silver in ammonia, is sufficient to induce the experimenter to reject them.

The nature of the moulds or surfaces on

BOOKS ON ELECTRO-METALLURGY.

which the deposit is to take place requires attention. There are very few of the salts of gold and silver which do not suffer decomposition by contact with other metals. Thus, if a piece of copper, brass, &c., be immersed in a solution of any of these salts, a precipitation occurs upon it, sometimes in the form of a perfect layer of silver or gold, and at others in the form of a dark powder. In using such metals it is advisable to make all the connexions with the battery before introducing the surface on which the deposit is to take place, into the solution. When such a course is adopted, the mould or surface receives a thin film of gold by voltaic action, immediately on being introduced, and there is very little action upon it. If this precaution be not taken, the precipitation alluded to will take place, and the surface to receive the deposit will be injured: as much metal will be dissolved from it, as is equivalent to that deposited upon it. Although the whole of the salts of gold before mentioned may be reduced for the reduction of that metal upon a surface of gold, and those of silver upon a silver surface, yet, with every precaution, many of them are wholly unfitted for reduction upon baser metals, such, for example, as copper, brass, or iron. Those least objectionable, are the cyanide of gold, and the solution of its oxyde in potassa or soda, and the cyanide of silver and its ammoniacal solutions. The cyanide of silver possesses no action on iron, and may be therefore advantageously used for its reduction upon that metal."-Manual, p. 45.

The platinized silver battery invented by Mr. Smee, of which we gave a description in vol. xxxii. p. 540, is, we believe, more extensively used than any other, but Mr. Shaw gives some good reasons for considering it not so well adapted as that of Professor Daniell to the reduction of the noble metals.

"The character of the deposit of gold or silver is influenced by the state of the current employed, as in the case of copper, and the remarks made on this subject, when treating of the reduction of copper, are applicable in general to the reduction of other metals. There are, however, two or three circumstances in relation to this subject, which require especial attention. The solution of cyanide of silver cannot have its conducting power increased by the addition of sulphuric acid, as decomposition of the salt would take place; hence, the only means we have of regulating the flow of electricity are the quantity of the cyanide in the solution, its temperature, and the intensity of the battery. The solution of two ounces of the cyanide to a pint of water, and saturated

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with oxyde of silver, answers exceedingly well, and as the maintenance of an elevated temperature is very inconvenient, it is necessary to use a battery possessing considerable intensity three or four cells of the acid battery will answer the purpose; but a Daniell's battery is far more convenient, and cannot be too strongly recommended for the purpose in question. When the arrangements are properly made, the deposited silver is of a beautiful whiteness, and tolerably smooth on its surface. If the flow of electricity be too great, the silver is of a dirty yellow or brown colour. The remedy is so obvious from what has been already said, that it is unnecessary to do more than thus allude to it."-Manual, p. 48.

For beginners, also, Mr. Shaw pronounces Daniell's battery to be greatly superior.

"The experimenter is strongly recommended to use, in his early experiments, a Daniell's battery in preference to every

other.

He is much less likely to fail in his operations by its use; and, from the extreme regularity of its action, the character of the deposit is not likely to change, even during a long experiment. As a general rule, it may be remarked that there is greater danger of failure from a deficiency of power than from excess; the black deposit occasioned by the latter is at once apparent, but the brittle metal produced by the former may more easily escape observation."-Manual, p. 36.

The following remarks on batteries in general, are also well deserving attention

"Before dismissing the subject of voltaic batteries, we would remark, that whatever form is given to an instrument of this kind, the amount of electricity generated by the consumption of a given amount of zink is the same in each; they differ only in the rapidity with which the development of the voltaic power takes place. In the invention of Daniell a flow of electricity of extreme uniformity is produced. We have a torrent of surprising intensity, but of transient duration, in the battery of Mr. Grove; and a copious flow of electricity of moderate intensity in the common acid battery and that of Mr. Smee: but we repeat (for it cannot be too strongly urged upon the reader) that in all these instruments a like amount of this subtle agent is obtained by a like consump. tion of materials, the intensity alone being affected by the arrangements of Daniell and Grove. In Smee's battery this is not at all increased; the mechanical form of the surface of the negative plate only facilitates the escape of the hydrogen therefrom,"-Manual, p. 15.

The voltaic precipitation of copper has been turned to useful account for many other purposes besides the multiplication of coins, medals, &c. One of the most remarkable of these is the production of plain copper plates for engraving, with the following account of which we must conclude.

"Plates for engraving may be made by depositing the metal upon a burnished piece of copper. In this case, the precipitated plate will have a burnished surface like the copper on which it is deposited; or it may be precipitated on a plate not so prepared, and be afterwards treated exactly as ordinary copper is for the use of the engraver. Copper-plates intended for etching,,when made by the electrotype process, are so superior to those of ordinary copper, that there can be no doubt the former will very soon completely supersede the latter. The electrotype metal is absolutely pure, and hence, in all chemical processes, is more uniformly acted upon than any other. The electrotype itself will demonstrate this. The copper forming the positive pole in the decomposition cell invariably presents a black surface during its solution, and a quantity, more or less, of scaly matter, consisting of charcoal and other impurities, is invariably left behind where thick plates are thus operated upon; but, if a piece of electrotype copper is used as a positive pole, its surface does not for a moment lose the beautiful orange colour so peculiar to it; and, after the largest masses have been dissolved, not a particle of impurity is left behind-nay, the beautiful transparency of the liquid is not in the slightest degree impaired. Hence it is that, in the process of etching, the common or impure metal proves a source of anxiety, and often disappointment to the engraver, while he uses that precipitated by voltaic agency with the absolute certainty of success. When the acid is applied to the former, its action is frequently intense in one place and feeble in another, and the etching is of necessity irregular; but with the latter the utmost uniformity of action prevails, and a corresponding regularity in the product results."-Manual, p. 37.

THE SMOKE NUISANCE.

At a Public Meeting held last week at the Victoria Gallery, Manchester, the Rev. Dr. Molesworth in the Chair, it was resolved to establish a "Manchester Association for abating the Smoke Nuisance."

Mr. Henry Houldsworth, who addressed the meeting at great length and with much ability, stated that he had had Mr. Williams's apparatus under trial for six months, and that it had diminished the quantity of

smoke produced by full three-fourths. Indeed, he had no doubt that, by proper attention and a little judgment on the part of the fireman, nine-tenths of the smoke might be prevented. In answer to a question put by the Chairman as to the saving in fuel resulting from Mr. Williams's plan, Mr. Houldsworth said, "I can state, with very considerable confidence, that there is no excess in the consumption of coal. I must say that we have been partial smoke-burners for twenty years; so far back as the time of Mr. Josiah Parkes, who, it will be remembered, did something on this subject, we have admitted air into our furnaces in two places; but, not understanding the principle as well as now, we did not admit it in the most judicious manner. But when Mr. Williams examined our furnaces, he at once said, 'I cannot expect to save so much in the consumption of fuel here as in some places, because I see you already manage your furnaces much better than most that I have seen; but I shall expect to save about 15 per cent." Now, we find that we actually do save 5 per cent. In the last month, I find that the quantity of coals which we consumed was 60 tons less than in the same month of last year; and I am not aware of any cause for this reduction but the change in the management of the furnaces."

Mr. Hall. I should like just to ask Mr. Houldsworth, as he says he believes there is no excess in the consumption of fuel on Mr. Williams's plan, whether he means to say that there would be any saving?

Mr. Houldsworth.-I have stated that we have saved about 5 per cent., but whether we are to attribute it to that or other causes, I cannot say. I know of no other cause to which I can attribute it; but the saving is so small that I should not feel myself strongly justified in saying that there was any saving. In our case, we have burnt, in one month, 5 per cent. less than in last year; and I am not aware of any other change that has been made.

Mr. Hall. I am much obliged to Mr. Houldsworth for his admission of that fact.

In reference to Mr. Hall's plan for the prevention of smoke, Mr. Houldsworth observed: Mr. Hall also introduces the atmospheric air in such a position as to cause it to mix with the gases, and produce the same effect; but I will say this, that there are certain conditions of the fire when a uniform admission of air, which is the principle of both these inventions, does not entirely prevent the smoke. I find, from my own experience, that this is the case when the fire is low; our fire burns for eight or ten hours, but twice a day it is essential that the fire should run down, in order that it may be cleaned out; and this is

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