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ful in case of accident to destroy the partition wall between the house and the establishment which contains the steam-engine.

The commission also proposes that an exact account should be kept by authority of all the accidents which happen to steam-engines of every construction, and to publish this statement, mentioning the causes and effects of such events, the name of the manufacturer of the steam-engine, and this (they observe) is the most efficacious of all methods to prevent the misfortunes which result from the use of steamengines, whether of low, middling, or high pressure.-(Ann. de Chim.)

X. On the Phosphates of Lead. By N. J. Winch, Esq. Hon. MGS. (To the Editor of the Annals of Philosophy.)


Newcastle-upon-Tyne, Jan. 23, 1823. From an itinerant dealer, who collects minerals at the lead hills in Scotland, I lately procured a variety of the phosphate of lead, which I suspect is not described in any of our mineralogical arrangements, or scientific journals. The ore in question is of as bright and deep an orange-red colour as the chromate of lead, and consists of groups of simple six-sided prismatic crystals, from an eighth to a quarter of an inch in length, filling cavities in pale-yellow crystalline phosphate of lead. The crystals are brittle, possess an adamantine lustre, and are accompanied by grey, white, and lemon-coloured carbonates of lead, together with galena. Placed on charcoal before the reducing flame of the blowpipe, it decrepitates, and immediately becomes nearly black; then easily fuses into a pale-grey enamel. On borax being added, it melts with effervescence, and the glass formed is of a yellowish milky hue while cooling, but transparent and colourless when quite cold, with air bubbles and globules of lead dispersed through it. Here it may not be amiss to mention the results obtained by means of the blowpipe by some of the most able writers on mineralogy, on testing this ore. Brongniart, at p. 201, vol. ii. says, "Le plomb phosphaté ne fait aucune effervescence dans les acides, et se fond au chalumeau sur le charbon en un globule qui prend un surface polyédrique en si figeant. Il n'est point reductible en plomb sans l'addition d'un peu potasse et de charbon." Berzelius on the Blowpipe, at p. 158, observes, "Phosphate of lead alone on charcoal fuses in the exterior flame; the globule crystallizes; and, after cooling, has a dark colour. In the interior flame, it exhales the vapour of lead, the flame assumes a bluish colour, and the globule on cooling forms crystals with broad facets inclining to pearly whiteness. At the moment it crystallizes, a gleam of ignition may be perceived in the globule. With borax, it behaves like oxide of lead." Phillips's account of this process, at p. 256, is as follows: "Before the blowpipe on charcoal, phosphate of lead usually decrepitates; then melts, and on cooling forms a polyedral globule, the faces of which present concentric polygons. If this globule be pulverized and mixed with borax, and again heated, a milkwhite enamel is the first result. On the continuance of the heat, the globule effervesces, and at length becomes perfectly transparent, the lower part of it being studded with metallic lead." In the third edition of Jameson's Mineralogy, vol. ii. p. 372, the same account is given; but in the second edition, vol. ii. p. 368, that author observes, "Before the blowpipe, phosphate of lead does not fly into pieces, but

becomes white, and melts very easily into a greyish globule, but without being reduced even with charcoal. From my own experiments, I have found, 1. That orange-red phosphate of lead behaves in some respects differently from all the varieties tested by these eminent writers. 2. That minute green crystals from Suvside lead mine in Nitherdale, Yorkshire, gave the same results as detailed by Berzelius and Brongniart, but more particularly by Phillips. 3. That opaque peagreen botryoidal phosphate from Germany, and pale-yellow from the lead hill mines, in the reducing flame first became white, and on a stronger heat being applied, melted into a grey opaque globule. With the addition of borax, it effervesced, burned, and was at length reduced into a glass, milky while cooling, but transparent when cold, and containing small globules of lead. Thus it appears, that the crystallized and botryoidal, the orange-red, pale-yellow, and green phosphates of lead, are variously affected by the action of fire, which leads to the conclusion that different ingredients, as well as ingredients in very different proportions, must enter into the composition of the several varieties of this ore; and in its description, it is not sufficient to mention how any single variety behaves under the influence of the blowpipe. I remain, Sir, your obedient servant,


XI. Maclureite, or Fluo-silicate of Magnesia, a new Mineral Species from

New Jersey.

This mineral was discovered, several years ago, near Sparta, in Sussex County, New Jersey, by the late Dr. Bruce. It was at first supposed to be sphene; but subsequent investigations led to its being ranked with condrodite, a mineral discovered in Sweden, and analyzed by M. d'Ohsson, whose results, confirmed by Berzelius, were as follows:

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The new mineral, however, though it resembles condrodite in external characters, differs essentially from it in chemical composition, as was proved from an analysis, which appears to have been made with care and skill, by Mr. Henry Seybert, of Philadelphia.

Though the pulverized mineral gives no indication of fluoric acid, when acted upon by an excess of heated sulphuric acid, and though other processes failed to detect it, yet fluoric acid was distinctly traced in the silica, remaining after the calcined mineral had been first boiled with nitromuriatic acid (which converted it into a jelly), and then heated with water acidulated with muriatic acid. The silica, thus obtained, effervesced violently with sulphuric acid, and gave fluosilicic acid in abundance, disengaged, it should appear, from the insoluble compound of potassa, silica, and fluoric acid, described by Gay-Lussac

and Thenard. The constituents of the mineral were determined to be as follows:

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(Silliman's American Journal, vol. v. p. 2.)

XII. Combustion of a Stream of Hydrogen Gas under Water. Mr. Thomas Skidmore, of New York, has discovered that if the flame produced by the combustion of hydrogen gas, issuing in combination with oxygen from the compound blowpipe of Dr. Hare, be plunged below the surface of water, it continues notwithstanding its submersion in, and actual contact with, that fluid, to burn, apparently with the same splendour as it does in the common air. The only discoverable difference is, that when the flame burns into water, it seems, if the expression may be allowed, to conglobate its figure; whereas in the air, it assumes the shape of a long slender conical pencil. Care is required that the flame be introduced slowly and gently into the water, in order to avoid the recession of the flame into the interior of the tube, at its first entrance, which is apt to take place if suddenly immersed. To obviate this evil more effectually, tubes of a fine capillary bore are best adapted.

When a piece of cork or pine wood was applied to the submersed gaseous flame, it gave out a brilliant light, and this appearance continued till the recession took place, which, in some instances, might be for a minute or two. Small pieces of copper wire, 1-40th of an inch diameter, became red-hot when exposed to the flame under water in full day-light. The discoverer of this property of the flame of the compound blowpipe suggests its application to the purpose of a submarine instrument of naval warfare, and thinks there are no difficulties in the way of its being so employed that may not be easily overcome. -(American Journal.)

XIII. Fusion and Volatilization of Charcoal.

The fusion and evaporation of charcoal has been effected in America with the assistance of Dr. Hare's galvanic deflagrator. Prof. Griscom, of New York, describes the experiment in the following terms: "With a deflagrator, of considerable size and in good order, these experiments are, in fact, extremely easy; and with well prepared charcoal will never fail in a single instance. The surface of the fused charcoal is brilliant, with a metallic and frequently iridescent lustre. Upon the charcoal on the copper side, there is no appearance of fusion, but a crater-shaped cavity extremely well defined, with the proper fibrous and porous appearance of charcoal; every thing indicating that the charcoal is wasted from this pole, and transferred to the other. It seems to pass in the state of vapour, to be accumulated or condensed

on the positive pole, and then to undergo fusion by intense heat. In about three seconds, a decisive result is obtained.

Charcoal, which has been thus fused, is found to have acquired a great increase of specific gravity. It sinks readily in strong sulphuric acid, though common charcoal floats readily in water with at least half its volume out. It is rendered also very difficult of combustion, but may be burned away, leaving no residuum if heated by a powerful lens in a vessel over mercury filled with oxygen gas. The gas produced was ascertained to be pure carbonic acid. Strong sulphuric acid may be boiled without effect on charcoal which has been fused. Even the strongest nitric acid in the cold does not act upon it, and at a boiling temperature, the action is very slight, and ceases the moment the heat is withdrawn.-(American Journal.)

XIV. Alteration of the freezing Point of Thermometers by being long kept.

It is asserted (Annales de Chimie et de Physique, Nov. 1822, p. 330), that a thermometer on which the freezing point has been. exactly marked, becomes incorrect in process of time, at the end of a year for example, and indicates, when plunged into melting ice, a temperature a little above freezing, as if the bulb had become smaller. This fact, originally observed by Bellani, of Monza, in the Milanese, was confirmed by Pictet's experiments in six different thermometers. In one of these, made 40 years ago, the freezing point had risen to +01 centigrade. M. Flaugergues, the astronomer, after satisfying himself of the fact, has endeavoured to assign a reason for it in the diminishing elasticity of the glass of the thermometric ball, which, like all other springs, loses its force by being kept long in a state of tension."

A correspondent of the Editor of this journal has been induced, by the foregoing notice, to examine several thermometers which he has had for many years; but has not been able to discover the deviation above remarked. Two of these, made by Crichton, of Glasgow, having very small cylindroidal bulbs, have been in his possession nearly twenty years. In these, the freezing point is marked by a file on the stem, and when plunged into thawing snow, not the smallest change is observable in the height at which the mercury now stands. In one or two others, out of ten which were examined, there did appear a little deviation from the freezing point marked upon them; but they had not been constructed by makers of any eminence, and had probably been inaccurate from the first. The change, therefore, though scarcely to be questioned on such testimony, appears not to be universal.

XV. Excrement of the Boa.

Prof. Psaff found that the fresh solid excrement of the boa is insoluble in cold water, but dissolved by about 800 times its weight of boiling water. The greater part of what is dissolved is deposited as the water cools, and this deposit is partly pulverulent, and partly on fine shining scales, circumstances which characterise uric acid.

With nitric acid, the general phenomena exhibited by uric acid were also produced, but the Professor observed, that when evaporated with nitric acid to a certain point, and before purpuric acid is formed, the solution deposits a considerable quantity of crystallized nitrate of ammonia; after the first portion of crystals were separated by evaporat

ing the solution, a further quantity was obtained; when after this, the solution was evaporated to dryness, no purpuric acid was obtained; but, on the contrary, if the solution in nitric acid be immediately evaporated to dryness, purpuric acid is formed.

The excrement of the boa contains ammonia, and in so great excess that it may be considered as a suburate of ammonia; when distilled with a weak solution of potash, water containing ammonia is condensed in the receiver; when the experiment was repeated with uric acid, no ammonia was obtained. When the excrement is burnt, the ashes are found to contain oxide of iron and carbonate of lime, but no phosphate of lime.-(Schweigger's Journal.)

XVI. Heliotrope.

According to Dr. Brandes and Firnhaber, the heliotrope is composed of

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It, therefore, resembles chalcedony on silica being slightly mixed with other bodies.-(Ibid.)

XVI. Carbonate of Magnesia and Iron, &c.

Prof. Walmstadt, of Upsal, has analysed carbonate of magnesia from Hartz containing the carbonates of iron and manganese. The texture of this mineral is foliated, and its primary form is a rhomboid of 108° 15', differing of course still more from calcareous spar than rhomb spar. The results of the analysis were:

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XVII. On the Absence of Carbonic Acid in the Atmosphere over the Sea

M. Vogel found that atmospheric air taken over the sea half a mile from the sea-shore off Doberan, contained so little carbonic acid, that a solution of pure barytes was hardly made turbid by it; while the same bulk of air taken on shore produced a considerable quantity of carbonate of barytes.

M. Vogel repeated these experiments in 1822 in the Channel, two leagues from Dieppe, where he emptied a large bottle with distilled water, and tried the air afterwards with a solution of pure barytes, which became so little turbid that it hardly could be perceived; when the experiment was repeated on shore, the solution of barytes became extremely

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