A manual of electro-metallurgy

Preface To The First Edition

The following pages contain the principal facts of the Art of Electro-Metallurgy.

The author has endeavoured to introduce everything interesting to the experimenter in this novel art ; but has at the same time sought to make the work as brief as possible, by the omission of some of the minute details of manipulation. To the beginner this may appear discouraging, but in the end he will find it to his advantage ; for although by giving minute directions in the manipulatory processes, a person wholly unacquainted with the principles on which those processes are founded, may possibly succeed in his experiments, yet the probability is that he would fail in the majority of cases, and would find himself compelled to master the principles of the science of Voltaic Electricity, before he could proceed to his experiments with certainty of success.

The author would not be understood to mean that the subject of manipulation has been neglected ; on the contrary, he has endeavoured to introduce all that is essential ; and he iv.

believes that a careful perusal of the foUowiug pages, combined with that knowledge which experiment alone can give, will enable any one to practice the Art of Electro-Metallurgy, as far as it is at present developed.

As the facts stated in this work (with a few trifling exceptions,) have been experimentally verified by the author, he feels little doubt of their general accuracy.

The present edition has been considerably enlarged by the introduction of recent discoveries in the art. The extent to which improvements have been introduced since the publication of the first edition, has rendered a more systematic arrangement necessary; the work has been divided into chapters, and many other alterations have been made, which, it is hoped, will make it more convenient and useful.

li.

f

RECEIVE Electro-Metallurgical Deposites . 101

Chap. IX. — On the various arrangements of Electro-Metallurgical Apparatus 112

Chap. X. — On the circumstances which influence the quality and quantity of Electro-Metallurgical Deposites 129

Chap. XI. — On Electro-Gilding, Plating, &c. and the production of Works of Art by Electro-Metallurgy 149

Chap. XII. — On the production of Printing Surfaces by

Electrical agency 152

Chap. XIII. — On various applications of Electro-Metallurgy 168

Chap. XIV. — On colouring Metallic Surfaces . . . 183

Chap. XV. — On the value and probable results of Electro- Metallurgy 189

A MANUAL

OF

ELECTRO -METALLURGY.

Chapter I. Introduction And History

1. In reviewing the early history of the physical sciences, we cannot but be struck with the fact, that many discoveries, which now either minister to our wants, or add to our enjoyments, lay for a long time after their announcement wholly neglected, or at best, served but to swell the pages of the historian. It is not so, however, in modern times; no sooner is a discovery now made, than its application to some useful purpose is attempted ; and at this moment there are, probably, hundreds anxiously watching the progress of discovery, eager for the announcement of some fact, which may be made available for purposes of use or ornament.

2. No department of science more strikingly exemplifies these remarks, than that branch of the science of electricity which the following pages are intended to illustrate, namely, the precipitation of metals by voltaic agency. During the short period that has elapsed since the constant battery of Professor Daniell was made public, a fact presented by the action of that instrument, has given rise to a new application of the voltaic battery, which has already effected the most important changes in the production of works of art. In treating of the voltaic battery, we shall fully describe the invention of Professor Daniell ; it will suffice to notice in this place, that

B the solution of sulphate of copper used in the excitation of that instrument, suffers rapid decomposition, and that the metallic copper which is precipitated, attaches itself closely to the copper cylinder in which the solution is contained, and it is found, on detaching the precipitated metal, that it had been deposited in such intimate contact with the copper cylinder, that the most minute marks are faithfully copied. The application of this fact constitutes the electrotype, — the earliest branch of the art of electro-metallurgy.

3. From this it would appear, that the history of the art is so simple as to require no comment, and so modern as to admit of no dispute ; such, however, is not the case. It is a subject which has given rise to the most angry discussions, and concerning which even now opinion is strangely divided.

4. The earliest recorded process in electro-metallurgy is contained in the Philosophical Magazine.* Brugnatelli relates, in a letter to Van Mons, that he had deposited a film of gold on ten silver medals, " by bringing them into communication by means of a steel wire with the negative pole of a voltaic pile, and keeping them, one after the other, immersed in aramoniuret of gold newly made and well saturated." This announcement of a process identical with those now extensively used, attracted no attention at the time it was made, and its existence has only been recently pointed out by Mr. Brayley.

5. The earliest experimenters with the voltaic pile, observed the precipitation of metals in the voltaic circuit. The precipitation of copper was distinctly noticed by Mr. Nicholson in a paper entitled " Account of the New Electrical Apparatus of Sig. Alex. Volta, and Experiments performed with the same. W. N."t The following passage is extracted from this paper. " When copper wires were used for the broken circuit, with muriatic acid diluted with 100 parts of water

♦ Phil. Mag. 1805, f Nicholson's Journal, July, 1800, p. 179.

in the tube, no gas nor the least circulation of the fluid was perceived, when the distance of the wires was two inches- A short tube with two copper wires very near each other, in common water, was made part of the circuit, and showed, by the usual phenomena, that the stream of electricity was rapidly passing. The wires in the muriatic acid were then slided within a third of an inch of each other. For the sake of brevity, I avoid enumerating the effects which took place during several hours, and simply state, that the minus wire gave out some hydrogen during an hour, while the plus was corroded, and exhibited no oxide, but a deposition of copper was formed round the minus or lower wire, which began at its lower end ; that no gas whatever appeared in this tube during two hours, though the deposition was going on, and the small tube showed the continuance of the electric stream; and that the deposition at the end of four hours formed a ramified metallic vegetation, nine or ten times the bulk of the wire it surrounded. In this experiment it appeared, that the influence of electricity increasing the oxidability of the upper wire, and aflFording nascent hydrogen from the lower, caused the latter to act as the precipitant of a solution of one and the same metal."

6. Voltaic precipitation of the metals was observed about the same time by Mr. Cruikshank, as the following extracts from his paper, " Some Experiments and Observations on Galvanic Electricity," will shew.* "The tube was filled with a solution of the acetite of lead, to which an excess of acid was added, to counteract the effects of the alkali. When the communication was made in the usual way, no gas could be perceived, but after a minute or two, some fine metallic needles were perceived at the extremity of the wire connected with the silver. These soon increased, and assumed the form of a feather, or rather, that of the crystals of the muriate of

* Nicholson's Journal, July, 1800, p. 187.

b2 ammonia. The lead thus precipitated was perfectly in its metallic state and very brilliant ; a little gas escaped from the wire connected with the zinc, and it was considerably corroded as usual. A solution of the sulphate of copper was next employed, and with the same result, the copper being precipitated in its metallic form by the wire connected with the silver. In this instance the metal did not crystallize, but formed a kind of button at the end of the wire, which adhered so completely to the silver, that it was found impossible to separate it. The most beautiful precipitate, however, was that of silver from its solution in the nitrous acid. In this case, the metal shot into needle-like crystals articulated or joined to each other as in the ai-hor DianasP The same philosopher also remarks as follows, in his "Additional Remarks on Galvanism :"* — " Having found that the solutions of metals in acids were decomposed by this influence (voltaic electricity), I next wished to ascertain if their solutions in alkalies, more particularly in ammonia, could be decomposed in the same way. For this purpose, I added to a dilute solution of the nitrate of silver some pure ammonia, until the mixture smelled strongly of the latter substance. This mixture was introduced into a glass tube secured by corks in the usual way, and silver wires applied. When the tube was placed in the circle of communication, a very rapid production of gas took place from the wire connected with the silver extremity of the machine, although but little or none escaped from the zinc wire during the whole process."

7. " After some time, a quantity of greyish flakes, evidently of metallic silver, were separated by the wire which gave out the gas, and a dark grey powder was deposited on the zinc wire ; at this period of the process much less gas was disengaged, although a considerable quantity still appeared at the silver wire. After some hours, the apparatus was removed j

* Nicholson's Journal, July, 1800, p. 254.

at this time a very considerable quantity of metallic silver was deposited, and the zinc wire was encrusted with a blueish black substance. On endeavouring to remove this crust with the finger, part of it exploded, although still moist." .... " This experiment was repeated, and instead of a solution of silver, nothing but pure ammonia was introduced into the tube, which answered exceedingly well ; for the silver of the zinc wire, after being corroded &c., was immediately taken up by the vol. alkali and afterwards deposited in its metallic form by the silver wire." " I next filled the tube with an ammoniacal solution of copper, and employed copper wires. In a very short time after this had been exposed to the action of the machine, the upper part of the fluid in contact with the silver wire became considerably paler, and copper was precipitated. In about an hour, the whole of the fluid in this part of the tube became as colourless as distilled water, so completely had the metal been precipitated. The precipitated metal was also the purest I had ever seen. From these experiments it would appear, that the galvanic influence might be employed with success in the analysis of minerals, more particularly in separating lead, copper and silver, from their different solutions. A very small quantity of a metal may likewise be detected in this way, as I have found from direct trial."

8. From the time Brugnatelli's experiment was announced, till the year 1830, no experiments on the application of electricity to the deposition of metals for the purposes of art were published. On the 2oth of November in that year, a paper by Mr. Edmund Davy was read before the Royal Society, in which he distinctly states that he had gilded, silvered, coppered, and tinned various metals by the voltaic battery ; and although he does not give the disposition of the apparatus for reducing these metals, he describes accurately the means to be taken for procuring depositesof mercury, copper, lead, arsenic, and those metals the salts of which constitute the more common poisons, and he states, that in a future communication he shall enter into the application of these facts to the purposes of gilding, plating, &c. ; but so far as the author is aware, the concluding part of his paper never appeared. There is, however, sufficient evidence of Mr. Davy's familiarity with the voltaic precipitation of the metals, in the paper from wdiich the subjoined extracts are made, as well as such information as would have enabled any one to carry out the practical application of voltaic precipitation to useful purposes, had the value of such precipitations been as evident then as it is now. Mr. Davy's paper will be found in the Philosophical Transactions of the Royal Society for the year 1831, p. 147. The following are extracts.

9. " On a Simple Electro-chemical Method of ascertaining the Presence of different Metals, applied to detect minute quantities of Metallic Poisons. By Edmund Davy, F.R.S., ^6'." (Read Nov. 25, 1830.) — " It is now nearly a quarter of a century since the late Sir Humphry Davy, by a train of masterly researches, developed the general principles of electro-chemical action, which subsequently led him to many fine discoveries and important practical applications. Some years since, I repeated most of the interesting experiments noticed in his excellent Bakerian lecture, ' On the Chemical Agencies of Electricity.'"* On the decomposition of metallic salts by the voltaic battery. Sir Humphry is very brief. He clearly ascertained, however, that " when metallic solutions were placed in the circuit, metallic crystals or depositions were formed on the negative surface," and that " the metals passed towards the negative surface, like the alkalies, and collected round it." ' In the course of my experiments on this subject, phenomena occurred which led me to think that some novel results might be obtained by instituting a series of experiments on metallic salts, using, as a voltaic arrangement, the feeble

* Phil. Trans, of the Royal Society, 1807.

power produced by the contact of small slips of dilFereut metals with solutions of the common metallic salts. Operating in this manner, I could readily detect very minute quantities of different metals, coat platina with gold, silver, copper, &c., or cover gold with a surface of these metals, and tin,

copper, brass, iron, &c."" " Circumstances which it is

unnecpssary to mention have hitherto prevented me giving greater publicity to these facts The fear of trespassing too much on the time of the Society, induces me to limit the present paper to one part only of the subject. At no distant period I promise myself the pleasure of communicating the remaining part, which will embrace the different electro-chemical experiments I have made on the other metals and their compounds, together with the application of the facts to the processes of gilding, silvering, tinning, &c."

10. These experiments of Brugnatelli and Davy having been completely lost sight of, do not affect the merit of succeeding experimenters ; and the art cannot be said to have originated until after the origin of the constant battery.

11. It has already been remarked (2), that in Daniell's battery, metallic copper is precipitated on the copper cylinder containing the solution of the sulphate of that metal. This precipitated copper is not very intimately attached, for, by the application of a very moderate force, it may be torn off". This fact was known to Mr. Dauiell, who shewed that the detached metal had been deposited in such close contact with the matrix, that it exhibited impressions of marks on the latter with extreme fidelity ; he did not think, however, of applying this fact to any useful purpose. In the course of experiments made with this battery, other philosophers observed the same fact.

12. Mr. Warren de la Hue makes the following remarks in a paper " On the Effects of a Battery charged with Sulphate of Copper," published in the London and Edinburgh Philosophical Magazijie for 1830. " The zinc plate is always partially covered with a coating of copper, which, however, is not detrimental to the power of the battery ; the copper plate is also covered with a coating of metallic copper, which is continually being deposited ; and so perfect is the sheet of copper thus formed, that on being stripped off, it has the polish, and even a counterpart of every scratch, of the plate on which it is deposited."

13. In May, 1839, it was announced that Professor Jacobi, of St. Petersburgh, could employ the voltaic battery in the reduction of copper for various purposes ; and to his art was given the name of Volta- Plastics.

14. The first account of the result of Jacobi's experiments which appeared in England was contained in a paragraph in the Athenaeum for May, 1839, and was as follows : — " Galvanic Engraving in Relief. — While M. Daguerre and Mr. Fox Talbot have been dipping their pencils in the solar spectrum, and astonishing us with their inventions, it appears that Professor Jacobi, at St. Petersburgh, has also made a discovery which promises to be of little less importance to the arts. He has found a method, if we understand our informant rightly, of converting any line, however fine, engraved on copper, into a relief, by a galvanic process. The Emperor of Russia has placed at the Professor's disposal funds to enable him to perfect his discovery." Immediately after this announcement, the following letter appeared in the Mechanics^ Magazine."^

15. Engraving by Galvanism. — Sir, — Observing in the last page of a recent number of your Magazine a notice extracted from the Athenmim, relative to a discovery of Professor Jacobi, its perusal occasioned the recollection of some experiments performed about the commencement of last summer, with the view of obtaining impressions from engraved copper plates by the aid of galvanism, which led me to infer some analogy in principle with those of the Russian Professor, and may, probably, give me the right to claim priority in its discovery and application. These experiments were abandoned from the want of that most important element in pursuits of this nature, time ; the writer's share of the said element being occupied in a manner more imperative than pleasing. I regret, however, not having made it the subject of an earlier communication, as this would have placed my pretensions beyond doubt ; but inasmuch as the notice alluded to is given from memory, and is undescriptive, while I may be enabled to exhibit the modus operandi, my assertion may be at least partially substantiated.

16. " It is well known to experimentalists on the chemical action of voltaic electricity, that solutions of several metallic salts are decomposed by its agency, and the metal procured in a free state. Such results are very conspicuous with copper salts, which metal may be obtained from its sulphate, (blue vitriol) by simply immersing the poles of a galvanic battery in its solution, the positive one becoming gradually coated with copper. The phenomenon of metallic reduction is an essential feature in the action of sustaining batteries ; the effects, in this case, taking place on more extensive surfaces. But the form of voltaic apparatus which exhibits this result in the most interesting manner, and relates more immediately to the subject of the present communication, may be thus described : — It consists of a glass tube, closed at one extremity with a plug of plaster of Paris, and nearly filled with a solution of sulphate of copper ; this tube and its contents are immersed in a solution of common salt. A plate of copper is placed in the first solution, and is connected, by means of a wire and solder, with a zinc plate, which dips into the latter. A slow electric action is thus established through the pores of the plaster, which it is not necessary to mention here; the result of which is the precipitation of minutely-crystallized copper on the plate of that metal, in a state of greater or less malleability, according to the slowness or rapidity with which it is deposited. In some experiments of this nature, ou removing the copper thus formed, I remarked that the surface in contact with the plate equalled the latter in smoothness and polish, and mentioned this fact to some individuals of my acquaintance. It occm-red to me, therefore, that if the surface of the plate was engraved, an impression might be obtained. This was found to be the case ; for on detaching the precipitated metal, the most delicate and superficial mai-kings, from the fine particles of powder used in polishing to the deeper touches of a needle or graver, exhibited their correspondent impressions in relief with great fidelity. It is therefore evident that this principle will admit of improvement, and that casts and moulds may be obtained from any form of copper.

17. " This rendered it probable that impressions may be obtained from those other metals having an electro-negative relation to the zinc plate of the battery. With this view, a common printing type was substituted for the copper plate and treated in the same manner ; this also was successful ; the reduced copper coated that portion of the type immersed in the solution. This, when removed, was found to be a perfect matrix, and might be employed for the purpose of casting, where time is not an object.

18. "It appears, therefore, that this discovery may be turned to some practical account. It may be taken advantage of in procuring casts from various metals, as above alluded to ; for instance, a copper disc may be formed from a cast of a coin or medal, in silver, type metal, or lead, &c., which may be employed for striking impressions in soft metals. Casts may probably be obtained from a plaster surface surrounding a plate of copper ; tubs [tubes ?] or any small vessel may also be made by precipitating the metal around a wire, or any kind of surface to form the interior, which may be removed mechanically, by the aid of an acid solvent, or by heat."

19. On the 8tli of May, 1839, Mr. Thos. Spencer, of Liverpool, announced to the Polytechnic Society of that town, that he had a communication to make to the society relative to the application of electricity to the arts, and that he then gave notice of that communication, in consequence of a j)aragraph having appeared in the public prints, announcing that Professor Jacobi had applied the voltaic battery to the production of works of art.

20. Mr. Spencer's first communication to the public was on the 12th of September, 1839. His paper was to have been read at the meeting of the British Association in Birmingham, but, for some unexplained reason, it was suppressed. It was subsequently read before the members of the Liverj)ool Polytechnic Society on the day above mentioned. In this paper (which was afterwards published) Mr. Spencer details the circumstances which suggested to him this application of voltaic electricity. He observed, during one of his experiments, that a copper plate which he had been using as a negative element in a voltaic arrangement, in which a solution of sulphate of copper was employed, had become covered with the precipitated metal in every part, excepting in two or three places where by accident some drops of varnish had fallen ; it immediately occurred to him, that if a plate of varnished copper, having a design made upon it by a pointed instrument so as to remove the varnish, were made the negative plate of a voltaic arrangement, the copper would be precipitated on the parts where the metal was exposed, so that on removing the varnish the design would be left in relief j experiment confirmed the correctness of his conjecture.

12. In the same paper, Mr. Spencer relates another experiment which suggested to him that application of voltaic electricity, which is at present known as the Electrotype. " The members of the society," says Mr. Spencer, alluding to the Liverpool Polytechnic Society, at a meeting of which the paper was read, " will recollect that on the first evening it met.

I read a paper on the ' Production of Metallic Veins in the Crust of the Earth,' and that among other specimens of cupreous crystallization which I produced on that occasion, I exhibited three coins; one wholly covered with metalhc crystals, the other on one side only. It was used under the following circumstances : — When about to make another experiment, and being desirous of using the piece of wire used in the first instance, I pulled it off from the coin to which it was attached. In doing this, a piece of the deposited copper came off with it; on examining the under portion of which, I found it contained an exact mould of a part of the head and letters of the coin, as smooth and sharp in every respect as the original on which it was deposited."

22. We learn, by the preceding extract, that Mr. Spencer was experimenting with a voltaic arrangement similar to that of Professor Daniell ; and that, on detaching the precipitated copper, he found, as that gentleman and others had done, that every impresssion 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 ; and this new application of the voltaic battery 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.

23. The letter of Mr. Jordan in the Mechanics' Magazine attracted so little attention, that it had been overlooked ; and probably would have remained unknown, had not Mr. Dircks, of Manchester, called attention to it in a recent number* of that journal. It will be observed that Mr. Jordan anticipated all the most important parts of Mr. Spencer's communication, and must now take the position so long occupied by Mr. Spencer— that of the author of the earliest successful application of electricity to the arts.

24. In studying the history of the art of electro-metallurgy, it should be borne in mind that the individual who will eventually be regarded as the originator of the art, cannot claim to be ranked as a discoverer the art in question consists of the application of facts, already matters of notoriety, to some useful or ornamental purpose. The announcements of Mr. Jordan and Mr. Spencer contain no discovery, so far as obtaining impressions by galvanism is concerned, for the announcements of De la Rue and others contain every fact which those gentlemen pointed out ; but while the philosophers contented themselves with noticing the exactness of the impression produced by voltaic precipitation, even to the "polish" and counterpart of "every scratch," the printer and the carver and gilder apply themselves to the production of impressions of printers' type and medals by the same action. To them, then, belongs the merit, usually reserved for practical men ; that of applying facts which had hitherto been unapplied ; of creating a new, beautiful and valuable art from materials until then neglected, although within the reach of all.

25. The position which Mr. Spencer has so long occupied, as the earliest English experimenter in this art, and which now clearly belongs to Mr. Jordan, cannot but excite the surprise of all who are interested in this art. It is surprising that the letter of Mr. Jordan to the Mechmiics' Magazine should have been so long overlooked, and still more surprising that Mr. Jordan should have permitted the honour with which the origin of so important an art is associated to be appropriatecl by anotlier. The supineness of Mr. J ordan is equalled by that of his friends, for it now appears that his claim to the origin of the art of electro-metallurgy was known to many individuals.

26. Besides the names of Mr. Jordan and Mr. Spencer, several names new to the history of electro-metallurgy are introduced by Mr. DirclvS, in the paper already referred to. Mr. Bessemer is mentioned as having precipitated crystalline copper on lead castings more than ten years ago. Mr. John Dancer, of Manchester, also produced a design by attaching paper to a metallic plate and depositing copper thereon ; the deposite was formed only on those parts which were not covered by paper, so that on tearing off the precipitated copper, the design was cut out, as it were, of the precipitated sheet of copper. Mr. Dancer also produced designs by impressing his name on a copperplate, and depositing copper on the indented plate.

27. There can be little doubt that the precipitation of metals by voltaic agency, particularly on the large scale on which this phenomenon presents itself in the constant battery, has suggested to many individuals the possibility of the useful application of the voltaic battery to the arts, although but few have pubhshed their views respecting such application. It has been demonstrated to the author of this treatise, on the most conclusive evidence, both documentary and personal, that the late Mr. Woolrich, of Birmingham, succeeded in applying coatings of copper to various articles by means of the voltaic battery ; and that, in one instance at least, he succeeded in gilding an article by voltaic precipitation from the ammoniacal solution of gold, before the published experiments of Mr. Jordan and Mr. Spencer appeared. Mr. Woolrich, however, never published an account of his experiments, as, from the imperfect nature of the voltaic batteries then in use, the deposition of copper was considered too troublesome to be valuable ; and, from the same cause, he was unable to repeat his experiments on gilding. There are, no doubt, many individuals who similarly experimented, but the historian has only to do with published experiments ; and the present instances are only adduced to show that voltaic precipitations were so strikingly brought before experimenters in electrical science, that it would have been impossible for them to have been much longer neglected.