least possible way, the lives or the health of their workpeople, if the apparatus in platinum should take a less expensive form.

Apothecaries will find, in these new methods of employing platinum, occasion and means of putting, at a trifling expense, their instruments under shelter from a host of vexatious and prejudicial alterations.

In order to give a just idea of the difficulties which may result in these sorts of applications of the nature of the solutions that were made use of, we will here report some experiments.

We have made use of six elements of the same pile employed for gilding; they were charged in the same manner, and were operated with under the same circumstances of temperature. The liquid contained 1 gramme of cyanuret of platinum dissolved in 100 grammes of water, with the addition of 10 grammes of yellow ferro-cyanuret of potassium.

In fine, we operated at 80° to 85° temperature, at which the gold deposited was elevated to 0.030 gr. a minute at least. With platinum, the deposit obtained in one minute would be so feeble that it could not be appreciated. It was necessary to prolong these proofs to four minutes at least.

Plate of Brass of 5 Centimetres on a side.-Liquor of 85° cent. Platinum deposited.

Thus, in twelve minutes, a plate which would have received 0.378 gr. of gold under the same circumstances, only took 0.003 gr. of platinum.

These details will render appreciable and full of interest the observation of M. de Ruolz, who has recognized them; and as we have previously said, if we make use of a solution of chloride of platinum in potash, the deposit will proceed with the same rapidity as that of gold, or silver at least. In fact, if the precipitation of platinum could not be accelerated, the expense necessary to apply this metal would be augmented to such a point as to place its use within very narrow limits. It is desirable, on the contrary, that these should become numerous and profitable, on one hand, for the interest of the platinum mines, which have hitherto wanted a market, and on the other hand, for the interests of the consumers, who will find in the metals covered with platinum objects at once remarkable for their unalterability, their beautiful appearance, and the safety obtained in employing them for all the purposes of life.

The extraordinary extensibility of gold is well known; it has already attracted the attention of Réaumur, and of many other philosophers since the time this illustrious naturalist made known

his observations. But we might admit that platinum is not possessed of the same faculty, or at least that its extensibility is much

less.

It is not, then, uninteresting to remark, that with one single centimetres may be square milligramme of platinum, a surface of 50 covered, which corresponds to Toooo of a millimetre, analogous, as we see, to the utmost tension of which we can form a just idea by direct observation.

Coppering.-M. de Ruolz has not limited his applications to the precious metals. Extending his processes to all the useful metals, he has tried to copper, to zinc, and to lead, several of the metals in common use.

Coppering applied on iron plates or cast iron, gives the means of making, with greater advantage, the joists of ships, if experiment confirm the ideas which have been made on this product.

It is evident, in every case, that to iron plates, iron, the cast metal, natural or softened, may be communicated all the properties of copper, as far as it concerns the colour, polish, and the resistance to the air; and that by the nature even of the interior matter the low price of the product is thereby insured.

The coppering is achieved, like silvering, by means of cyanuret of copper dissolved in alkaline cyanurets; but the precipitation of For the copper is more difficult than that of the precious metals. remainder, that which we have just said of platinum shows how great the influence of the solution may be in this respect.

With eight elements of the pile already described, charged as in the preceding cases, and keeping in the same conditions of temperature, we have obtained deposits of copper much more feeble than if we had been operating upon gold or silver.

We operated upon one solution, however, which contained 1 gr. of dry cyanuret of copper for 100 gr. of the solution.

Temperature of the Liquid, 30° cent.-Plate of Silver of 5 Centimetres a side.

Copper deposited.

Thus the copper, in being precipitated from its cyanuret, was deposited, like platinum, at the rate of 0.001 per minute for 50 square centimetres. This slowness will be, in practice, an obstacle, but which M. de Ruolz has no doubt previously studied.

In fact, the copper thus precipitated on iron will serve directly to preserve it, to give a beautiful appearance to objects of the locksmith's production, to balconies, balustrades, grates, chimney utensils, &c.

Besides, it can, we are assured, enable us to enclose iron in an envelope or case of brass. It is sufficient to make a deposit of copper and zinc on cast iron, then to heat the piece to a red heat in powdered charcoal. Brass is thus produced, and constitutes a metallic varnish less alterable than copper, and of a colour which we can vary at will.

In conclusion, at any time when we wish to go to the expense that the combustible which produces this latter operation exacts, we may be enabled to produce on the metals deposits in the alloys as easily as deposits of pure metal. This is a point of view which M. de Ruolz has not considered, but it is one to which we recommend his zeal and penetration.

The Precipitation of Lead.-In acting upon a solution of the oxyde of lead in potash, by means of the pile, we can lead iron plates, iron, and all the metals in general. The fabrication of chemical products will be benefitted by this discovery, by thus obtaining cauldrons of iron plates lined with lead, and where the solidity of the iron will be united to the resistance which lead offers to the chemical action of saline solutions and feeble acids.

In fine, there are but few circumstances in which lead obtains the preference over other metals, except for its low price and the facility with which it is managed. The new processes with which we are occupied will have, then, for their object rather to avoid the employment of lead than to increase it.

The new pro

Tinning. We have not yet said much of tin. cesses may extend its applications, by giving an easy and prompt means of tinning copper, bronze, brass, iron, and even cast iron, by operating with it cold, and on all kinds of utensils.

Again, for a long time the workpeople who tin pins have, without knowing it, made use of a truly galvanic process, for they put among the pins grain tin, and water charged with cream of tartar. The two metals constitute a real pile, where the negative pole formed by the pins attract the tin to such a degree that it becomes dissolved, and being obliged to precipitate itself, the pins are thus covered with the tin.

The tinning of iron, as well as zinc, would be impossible by such a process; it is then neeessary to have recourse to a real pile, independent of the metals employed.

On the contrary, in order to copper the metals which are negative with respect to tin, we can make a voltaic pair with the tin itself and the metal to be tinned, and by making use of cream of tartar to dissolve the tin, as is practical in the process of tinning pins, from a solution of the oxide of tin in potash, as propssed by M. Böttiger.

Cobaltizing Nickelizing.—The Academy will remark with some interest the metallic pieces covered over with nickel or of cobalt among the specimens on its bureau.

Cobalt, whose colour approaches so near to platinum, has been employed in the recovering of musical instruments of copper, and it furnishes, in these cases, a metallic varnish agreeable to the eye, durable, and at a cost very little enhanced. However, all our experiments lead us to believe that platinum, gold, or silver, will obtain the preference; but cobalt will be able to find its place in such applications as a means of varying the tints.

Experience has proved, again, that by thus changing the surface of sonorous instruments, and by recovering the metals which form them with a coat of another metal, we do not modify in any point their properties, in a musical point of view. The most practised ear cannot recognize any change in this respect.

Nickel has especially been tried upon objects in the locksmith's branch, or in ornaments for harness. As it is not dear, and there does not require much to resist the air, it is well to note here that this metal may be applied very well on iron—a fact which may possibly become important in its application to locks for great security, to large clocks, to counters, and even to many parts of machines which we wish to preserve from the action of the air, without being obliged to grease them often.

Zincing. Among the processes of M. de Ruolz, those which he applies to the zincing of metals, and of iron in particular, have highly interested your Commission.

The zinced iron acquires the faculty of resisting the oxydizing action of the air, and especially of humid air or of water. The fact is, that the zinc, which is more oxydable than the iron, preserves this metal from oxydation, and is scarcely at all oxydized itself; for when it becomes covered with a layer of sub-oxyde, all ulterior alteration is arrested.

In the greater part of the applications attempted by M. de Ruolz, the metal deposited is found on the contrary negative, with regard to the metal thus covered. All the guarantees which the metallic varnish promises in similar cases depends on its perfect integrity or connexion; for if it enters upon any point whatever, and the humid air can arrive at the interior of the metal, the superficial layer, far from being a preserver, will become, on the contrary, a determining cause of oxydation.

Zinc, applied on iron, preserves it doubly then, as long as it is in contact, like varnish, and when it is performed by a galvanic action. This particularity accounts for the success which the zinced iron, in all its applications where iron, or iron plates, being employed cold, have not lost any of their tenacity, and might support a supplement of expense.

În general, the zinced iron ought not to be employed for containing cold water; the galvanic action of the two metals determines

very rapidly the oxydation of the zinc, and the iron in its turn becomes red with a singular activity. This remark is intended, and ought to direct artisans to the employments they may make of the new processes, and is doubly sufficient to make them avoid mistakes except in very rare circumstances, but even then, less susceptible of being apprized of it by experiment alone.

The zincing of iron has hitherto been performed by immersing the iron in a bath of zinc, which is melted with some inconveniencies besides. The iron becoming attached to the zinc, thus constitutes a very brittle superficial alloy the iron then loses its tenacity, a circumstance which is not at first perceived, until we attempt to zinc a very fine wire of iron or of iron plates very thin. Besides, the surface thus clothed with a layer of a metal slightly fusible, is always deformed.

Thus, by this process, we cannot zinc a fine wire of iron; it would become fragile and misshapen. Nor can we zinc balls or bullets; they would be misshapen, and no longer of the same calibre. The zincage of iron is not, by this process, applicable to objects of art: all their forms would be destroyed.

The industrial arts, the military art, the fine arts, will receive, then, with a high degree of interest, the processes of M. de Ruolz, by which is accomplished, and that economically, the zincing of iron, steel, and cast iron, by means of the pile with the solution of zinc ; by operating with the solution cold, and in respecting, consequently, the tenacity of the metal; by applying it in very fine layers, and by the preserving of the general forms of the objects, and even the aspect of their smallest details.

There is, then, nothing to hinder us from zincing the iron wire employed in numerous ways, and which, far from rusting, will be preserved, at any rate, during many years, without doubt. Thus, the cords of suspension bridges and lightning conductors may be made of iron wire covered with zinc. We may say as much for metallic cloths employed in the fabrication of sieves, bolters, and of those which we apply in the construction of safety lamps. In the latter case, even the workmen charged in the mines with the care of cleaning the lamps, will be enabled, without sensible expense, to be supplied with everything that is necessary to restore the zinc, from time to time, without dismounting the lamp.

All the parts of machines, whose dimensions are so strong or so small as to render improper the zincing by the hot method, will be, on the contrary, susceptible of being easily zinced by the humid method.

The thinnest plate may receive this preparation without becoming cased; this will permit of the production of artificial slates of plate zinc perfectly applicable, and applicable with great economy, to the roofs of buildings.

The Commission were desirous of being convinced that it was possible to zinc cast-iron, and bullets in particular. It was certain