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mixture be rather large, the platinum becomes red-hot. I could not but conclude, from this most remarkable phænomenon, that the finely-divided metallic platinum which is produced by the igneous decomposition of the ammonia-muriate, would perhaps exhibit this singular effect upon the detonating mixture; and, to my great satisfaction, this supposition was confirmed by the experiment. Some platinum powder, prepared from the saline precipitate just named, was wrapped up in white blotting-paper, and brought into contact with the hydrogen gas; and, as might be expected, no absorption took place, nor any other perceptible mutual action. Upon this I caused atmospheric air to have access to the platinum powder in contact with the hydrogen, and after the lapse of a few moments that remarkable reaction took place; viz. the gas diminished in volume; and in ten minutes all the oxygen of the atmospheric air admitted had condensed with the hydrogen into water. 1 afterwards mixed pure oxygen gas with the hydrogen in contact with the platinum; a condensation of both immediately took place, and the platinum heated tó such a degree, that the paper in which it was wrapped was suddenly charred. These experiments were repeated about thirty times on the same day, July 27, 1823, on which I discovered this remarkable phænomenon, and with the same success every time.

What useful applications of this discovery may be made in oxymetry, the synthesis of water, &c., I shall hereafter state more circumstantially. I shall at present merely observe, in conclusion, that the entire phænomenon must be considered as an electric one, that the hydrogen and platinum form a voltaic combination, in which the former represents the zinc ;--the first established instance of an electric alternation formed by an elastic fluid and a solid substance; the application of which will lead to further discoveries.

I obtained another interesting result in an experiment on the rela tion of the oxidized sulphuret of platinum to carbonic oxide. I found that this gas is always diminished to half its bulk when it comes into, contact with the sulphuret, and that the remaining gas is not carbonic oxide, but carbonic acid. The carbonic oxide gas is therefore decarbonized by the oxidized sulphuret of platinum, and thereby changed into carbonic acid.

SUPPLEMENT.*

I send you a short supplement to the paper communicated to you some days ago, on the newly discovered properties of several preparations of platinum. That the continuation of the experiments on this interesting subject would lead to new discoveries, was to be expected. I merely mention to-day, that I have succeeded in making the observed dynamic relation of the platinum powder to the hydrogen gas, appear in a very splendid manner by experiment. If hydrogen gas be suffered to issue from a gasometer through a capillary tube bent downwards, upon the platinum contained in a small glass funnel sealed at the bottom, so that the stream may mix with the atmospheric air before it comes in contact with the platinum, which is effected when the tube is from 1 to 1 or 2 inches distant from the platinum, the latter almost instantly becomes red- and white-hot, and

• From a letter of Professor Doebereiner to Professor Schweigger, dated Jena, August 3, 1823. New Series, VOL. VI. 2 H

remains so, as long as the hydrogen continues to flow upon it. If the stream of gas be strong, it becomes inflamed, particularly if it has already been mixed in the reservoir with some atmospheric air. This experiment is very surprising, and astonishes every beholder, when he is informed, that it is the result of the dynamic reaction of two species of matter, one of which is the lightest and the other the most ponderous of all known bodies. That I have already applied this new discovery to the formation of a new apparatus for procuring fire, and of a new lamp; and that I shall avail myself of it for much more important purposes, you may well suppose beforehand more of it in my next.-(Phil. Mag. vol. Ixii. p. 289, from Schweigger's Journal.)

From the Annales de Chimie et de Physique, t. xxiv. p. 91, we extract the following additional experiments by M. Dæbereiner:

I have found that the combustible energy of hydrogen is so much increased by contact with the powder of platina, that it will combine in a few minutes with all the oxygen of a mixture which consisted of 99 parts of azote and 1 of oxygen; an effect which cannot be produced by the strongest electrical sparks. I mix, however, for these. experiments, the powder of platina with potters' clay, and I moisten this mixture to form it into small balls of the size of a pea; I suffer these balls to dry in the air, and afterwards heat them to redness in an enameller's lamp. A ball of platina of this kind, although weighing only from 2 to 4 or 6 grains, is capable of converting any volume of the detonating gas into water, provided that after each operation it is carefully dried, and it may be employed for the same purpose more than a thousand times.

The compound gases containing hydrogen, such as ammonia, olefiant gas, carbureted hydrogen, muriatic acid gas, &c. do not combine with oxygen by the intervention of the powder of platina.

When a jet of hydrogen was directed upon a mixture of powder of platina and nitrate of platina and ammonia, the mixture became redhot with a crackling noise and the emission of sparks. The same effect occurred with the black powder of platina, which zinc separates from the solution of that metal. This powder is a mixture of oxide and reduced platina. This powder possesses the property of gradually converting alcohol, when oxygen is present, into acetic acid.

Among the other metals which I have hitherto tried, nickel, prepared by decomposing the oxalate, is the only one which has the property of converting a mixture of oxygen and hydrogen into water, and this takes place very slowly.

II. On the Ignition of Platina by Hydrogen Gas. By Mr. A. Garden. (To the Editor of the Annals of Philosophy.)

Oxford-street, Nov. 20, 1823.

DEAR SIR, The very curious phænomenon, recently observed by Doebereiner, that a jet of hydrogen gas when brought into contact with metallic platina at common temperatures, produces a temperature equal to that of ignition, has already been noticed by other chemists, namely, by Messrs. Dulong and Thenard, in France; and by Faraday and

Herapath, in England: but these philosophers do not mention that any other than substancès actually in the metallic state are capable of exhibiting a similar appearance.

*

After repeating several of the experiments already published, I was induced to submit a number of other bodies to the action of the hydrogen jet. Some I found to have their temperature slightly increased, and the greater number not at all: but the most remarkable increase which I have observed has been with the ore of iridium; this substance, when previously heated to redness and suffered to cool, becomes red-hot by a stream of cold hydrogen, in the manner of spongy platina, and appears to retain the property of so doing equally well.

The circumstance of these bodies becoming heated to incandescence in our atmosphere of medium temperature, naturally suggests the idea of employing them for the instantaneous production of fire and light ;† but, in order that this may be done with tolerable certainty, so as to be really useful, it becomes necessary that the effect shall take place at pretty low temperatures. To ascertain this point I made the following experiments:

A quart bottle filled with hydrogen gas was placed in an earthenware wine-cooler, and the space between the sides of the bottle and of the cooler was filled up with ice, broken into small fragments, a small piece of spongy platina was exposed upon a slip of foil of the same metal, and laid upon the surface of the ice; in this state the whole was left in an apartment (at 52°) for about three quarters of the hour; at the end of this time the temperature of the platina foil was found to be 35°, which, with the spongy metal, was covered with a considerable film of moisture.

A jet of gas was now made to pass from the bottle through a capillary tube upon the spongy platina, the moisture immediately began to evaporate, and the metal quickly became heated to whiteness, kindling the hydrogen as it issued from the orifice of the tube.

From the result of this experiment (which was made, not so much with a view to determine the minimum temperature at which the effect could be produced, as to see whether it would take place at the usual degrees of atmospheric temperature in this climate,) it has appeared that a very ready and elegant mode of obtaining light may be obtained.

I have constructed several lamps for the purpose upon a very simple principle, and from the certainty which I have hitherto observed, I have reason to believe that they will answer most completely. When I have satisfied myself as to the most convenient form, I shall probably trouble you'with a sketch of it, and also with the results of a few more experiments upon the subject.

I remain, dear Sir, your's truly,

A. GARDEN.

* I mean the black powder which remains after the action of nitro-muriatic acid upon crude platinum, and which also contains osmium.

Dæbereiner says, that he has already applied his discovery to this purpose.

2н 2

III. On the Fusion of Charcoal, Graphite, Anthracite, and the Diamond. By Professor Silliman.

(Concluded from p. 316.)

In a second letter immediately succeeding that already given, dated April 15, 1823, Dr. Silliman states :

Having last year caused to be constructed an aparatus, capable of containing fifty-two gallons of gas, for the supply of your compound, or oxy-hydrogen blow-pipe, and capable of receiving a strong impulse from pressure, I have been intending, as soon as practicable, to subject the diamond and the anthracite to its intense heat. Although their being non-conductors, would be no impediment to the action of the blow-pipe flame on them, still, obvious considerations have always made me consider the success of such experiments as very doubtful. I allude, of course, to the combustibility of these bodies, from which we might expect that they would be dissipated by a flame sustained by oxygen gas.

My first trials were made by placing small diamonds in a cavity in charcoal, but the support was, in every instance, so rapidly consumed, that the diamonds were speedily displaced by the current of gas. I next made a chink in a piece of solid quick lime, and crowded the diamond into it; this proved a very good support; but the effulgence of light was so dazzling, that, although through green glasses I could steadily inspect the focus, it was impossible to distinguish the diamond in the perfect solar brightness. This mode of conducting the experiment, proved, however, perfectly manageable; and a large dish, placed beneath, secured the diamonds from being lost (an accident which I had more than once met with), when suddenly displaced by the current of gas; as, however, the support was not combustible, it remained permanent, except that it was melted in the whole region of the flame, and covered with a perfect white enamel of vitreous lime. The experiments were frequently suspended, to examine the effect on the diamonds. They were found to be rapidly consumed, wasting so fast, that it was necessary, in order to examine them, to remove them from the heat, at very short intervals. They exhibited, however, marks of incipient fusion. My experiments were performed upon small wrought diamonds, on which there were numerous polished facets, presenting extremely sharp and well-defined solid edges and angles. These edges and angles were always rounded and generally obliterated. The whole surface of the diamond lost its continuity, and its lustre was much impaired; it exhibited innumerable very minute indentations, and intermediate and corresponding salient points; the whole presenting the appearance of having been superficially softened, and indented by the current of gas, or perhaps of having had its surface unequally removed, by the combustion. In various places, near the edges, the diamond was consumed, with deep indendations, and occasionally where a fragment had snapped off, by decrepitation, it disclosed a conchoidal fracture and vitreous lustre. These results were nearly uniform, in various trials; and every thing seems to indicate that were the diamond a good conductor, it would be melted by the deflagrator; and were it incombustible, a globule would be obtained by the compound blow-pipe.

In one experiment, in which I used a support of plumbago, there

were some interesting varieties in the phenomena. The plumbago being a conductor, the light did not accumulate as it did when the support was lime, but permitted me distinctly to see the diamond through the whole experiment. It was consumed with great rapidity; a delicate halo of bluish light, clearly distinguishable from the blow-pipe flame, hovered over it; the surface appeared as if softened, numerous distinct but very minute scintillations were darted from it in every direction, and I could see the minute cavities and pro jections which I have mentioned forming every instant. In this experiment I gave the diamond but one heat of about a minute; but on examining it with a magnifier, I was much surprised to find that only a very thin layer of the gem, not much thicker than writing paper, remained, the rest having been burnt.*

I subjected the anthracite of Wilkesbarre, Penn, to similar trials, and by heating it very gradually, its decrepitation was obviated. It was consumed with almost as much rapidity as the diamond; but exhibited, during the action of the heat, an evident appearance of being superficially softened; I could also distinctly see, in the midst of the intense glare of light, very minute globules forming upon the surface. These, when examined by a magnifier, proved to be perfectly white and limpid; and the whole surface of the anthracite exhibited, like the diamond, only with more distinctness, cavities and projections united by flowing lines, and covered with a black varnish, exactly like some of the volcanic slags and semi-vitrifications. The remark already made, respecting the diamond, appears to be equally applicable to the anthracite, i. e. that its want of conducting power is the reason why it is not melted by the deflagrator, and its combustibility is the sole obstacle to its complete fusion by the compound blowpipe.

I next subjected a parallelopiped of plumbago to the compound flame. It was consumed with considerable rapidity, but presented at the same time, numerous globules of melted matter, clearly distin guishable by the naked eye; and when the piece was afterwards examined, with a good glass, it was found richly adorned with numerous perfectly white and transparent spheres, connected also by white lines of the same matter, covering the greater part of the surface, for the space of half an inch at and around the point, and presenting a beautiful contrast with the plumbago beneath, like that of a white enamel upon a black ground.

In subsequent trials, upon pieces from various localities, foreign and domestic (confined however to very pure specimens), I obtained stilr more decided results; the white transparent globules became very numerous, and as large as small shot; they scratched window glass were tasteless-harsh when crushed between the teeth, and they were

* In Tilloch's Phil. Mag. for November 1821, vol. lyiii. p. 386, I observe the following notice by Mr. John Murray -"By repeatedly exposing a diamond to the action of the oxy-hydrogen blow-pipe in a nidus of magnesia, it became as black as charcoal, and split into fragments which displayed the conchoidal fracture.

"It will be found, that this gem affixed in magnesia soon flies off in minute fragments, exhibiting the impress of the conchoidal form.

"In lately exposing the diamond fixed on a support of pipe-clay, to the ignited gas, I succeeded in completely indenting it :-examined it after the experiments, it exhibited proofs of having undergone fusion."

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