As it appeared, from these experiments, that either nitrogen, hydrogen, or perhaps ammonia, was absorbed, MM. Savart and Porzos heated 49 grs. of the altered copper in a small porcelain retort, but could obtain no liberation of gas, although the heat was high and the copper fused. When cold, the copper was found in one lump, but between it and the porcelain was a substance, partly imbedded in the glaze of the porcelain, of a yellow brown colour, and having a greater specific gravity than copper itself. The copper re-weighed amounted to 48.9; having lost of its weight, and abandoned the largest part of the substance which had been combined with it. When potassum was made to act upon the substance adhering to the porcelain, it appeared to have an action exactly like that of the same metal on ammonia.

M. Savart then remarks, that these experiments, imperfect as they are, accord with and support those of MM. Davy and Berzelius, who, by other researches, have been led to consider azote as an oxide of a base, and this substance, which they have called ammonium, may be the body which has formed alloys with the copper and iron in the experiments described.-Annales de Chimie, xxxvii. 326.

7. Preparation of liquid Ammonia.-Bizio.-A tubulated retort is to be put into a sand-bath, and connected with a small balloon placed on a little furnace; a tube is to proceed from the balloon to a flask which is to be supplied with a safety tube, and with another tube dipping into a mercurial bath. Equal parts of sal ammoniac and hydrated lime are to be used; the lime is to be made into a cream with water, and put into the retort, and then the powdered sal ammoniac added; after being well mixed the retort is to be closed; water, equal in weight to the sal ammoniac, is to be put into the flask; the retort in the sand-bath to be heated, and the balloon moderately warmed. As the ammoniacal gas is disengaged it will be absorbed by the water in the flask. By managing the fire properly, and distilling the portion of impure ammonia in the balloon, pure ammonia of the s. g. of .910 will be obtained, 16lbs. being produced for every 10lbs. of sal ammoniac employed. M. Bizio says, that the ordinary processes do not give more than one-half of this quantity.-Bull. Univ. C. xii. 88.

8. Solubility of certain Substances in Sulphuric Acid.-Vogel observed, that anhydrous sulphuric acid dissolved sulphur, forming a blue, green, or brown solution, according to the quantity present. Water precipitated the sulphur.

Müller found, a long while ago, that pulverized tellurium dissolved readily in concentrated sulphuric acid, forming a transparent deep red solution; no gas or peculiar odour was developed; water precipitated the tellurium.

Selenum dissolves in sulphuric acid, forming a green soluAPRIL-JUNE, 1828.

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tion precipitated by water. An analogy holds between these three substances in this respect.

Iodine, according to Bussy, also dissolves in sulphuric acid.Annales de Chimie, xxxvii. 189.

9. On the Presence of Columbium as well as Titanium in Iron Slag. -The iron slag of Königshütte, in Upper Silesia, has been examined by Professor Hünefeld, in consequence of its having been shown by Karsten to contain abundance of titanium, like that first pointed out by Wollaston in the iron slags from South Wales. But besides titanium, Professor Hünefeld found great reason to believe in the presence of columbium, or, as he calls it, tantalium, in considerable quantities. Besides the cubes of titanium, he found in the slag, 1. Granules of metal melted into it of the shape of beans or spheres, weighing from 2 to 30 grains. 2. Cavities of different sizes, the sides of which, when filed, had a steel lustre. 3. Grains of metal sprinkled through the slag, of a globular or oblong shape, with a metallic lustre, and a colour between those of silver and tin. In their chemical properties, they resembled the small lustrous metallic bases before described; they scratched glass, gave a shining powder, and seemed, therefore, to be tantalium, such as we have found it hitherto described. 4. Melted grains of metal partly globular, with a tint verging upon the colour of brass. 5. Portions of melted slag, of a dark rose-red colour, which exhibited a fine lustre when filed, and were hard and tough, but not malleable.

No.3 was the most striking of these products. The grains scarcely lost anything in aqua regia, preserved their lustre, and did not crumble. Similar granules, which remained behind in another experiment with the same solvent, scratched glass, and, when beaten and broken with a hammer, made red-hot with caustic potash, and treated by the blowpipe as well as with humid tests, did not give any indications of titanium. A portion, however, which had been melted with potash, and acidulated with nitric acid, the solution exposed for several days to the air, and afterwards filtered, was, by means of a solution of galls, precipitated rather abundantly of a dirty orange colour, whilst hydrosulphuret of potash produced a scarcely perceptible turbidity.

Numbers 1, 2, 4, and 5 seemed to be different mixtures of iron, titanium, and columbium.—Phil. Mag. N. S. iii. 121.

10. On Electrical Phenomena produced by Pressure, and the Cleavage of Crystals, by M. Becquerel.-In continuing researches commenced, and in part published some years since, on the developement of electricity by pressure, M. Becquerel's object has not been to ascertain whether the electricity was due to any other cause than that which is effective when friction is resorted to, but to see how pressure, which may be considered as an element of friction,

affects the developement. The instrument he used was a balance of torsion, the wire being of platina, exceedingly fine, and drawn by Wollaston's method. By the aid of this instrument it was ascertained, that when badly conducting substances were experimented with, and a convenient velocity of separation obtained, the intensity of the electricity disengaged was proportional to the pressure, i. e. a double pressure gave a double intensity; the law, however, diminishes no doubt as the pressure is increased, either as the molecules lose their faculty of being compressed, or as the surfaces of contact alter. By submitting different mineral substances to the pressure of the same body, their electric relation has also been ascertained, and in this way it was found that Iceland spar had thrice the power of sulphate of lime.

When two bodies are pressed together, and the pressure is then diminished without the contact being changed, the electric effect remains some time after the partial removal of the pressure, ac→ cording to the conducting power of the bodies; so that they may be removed from each other, and yet retain an electricity greater than that due to the last pressure. A disc of cork was pressed against a crystal of Iceland spar with a force of 4 kilogrammes; the pressure was then reduced to two kilogrammes, and a minute after the pieces were separated: the electricity of the cork was then 170; that produced by the original pressure would have been 250: so that it is sufficiently evident the effect of the greater pressure had remained some time after the pressure itself was lessened. If, on repeating the experiment, in place of separating the two pieces, the pressure is restored to 4 kilogrammes, then diminished, and again restored several times, the disc of cork will ultimately be found to have an electricity of 250, or no more than that due to the highest pressure given.

Hence it results, that if two bodies, one a bad conductor of electricity, are pressed against each other with a certain force, and the force be diminished and increased several times without any change in the place of contact, each of these bodies, when freed from the compression, will exhibit only the quantity of electricity due to the highest pressure. The effect is to complete in each body that quantity of electricity which it should receive in proportion to the highest pressure.

Electricity due to Cleavage.-Different bodies, which adhere together, exhibit electricity upon their surfaces when separated, the two bodies being in opposite states. Glass and gum-lac produce this effect with mercury, and guin-lac with glass. In the phenomena of compression also, when adhesion takes place, as between two pieces of cork, the electricity is greater than when there is no adhesion. These effects are eminently distinguishable when cork or elder-pith is pressed against the polished faces of a diamond.

The electrical phenomena due to pressure and those of cleavage

have a great analogy with each other. When plates of mica or sulphate of lime are suddenly separated, each surface is electrical, the two being contrary to each other; if they be put together again, and slightly pressed, upon separation they exhibit the same electrical phenomena as before. Hence the pressure which mechanically causes the approximation of the particles produces the same effects as the force of aggregation, which in reality only occasions a more immediate contact of the same particles.

Every substance, regularly crystallized, possesses the same property as mica and sulphate of lime. To obtain the effect, it is necessary that the cleavage be regular and perfect; if it be irregular, some plates take one electricity and some another, and the effects are no longer distinctly observed.

The kind of electricity acquired by the different surfaces varies according to circumstances not yet ascertained. The topaz has only one cleavage, and that perpendicular to the axis of the crystal, but no regularity is observed in the nature of the electricity; for sometimes the surface towards one end and sometimes that towards the other, takes the same electricity.-Annales de Chimie, xxxvi. 265.

11. On the Velocity of Sound in Water.-Experiments on the velocity of sound in water have been made by M. Colladon on the Lake of Geneva, and are connected with researches by himself and Sturm on the compressibility of fluids. The space through which the sound passed was about 45,000 feet (13487 metres). The sound was produced by striking a large bell suspended in the water, and was heard by means of a peculiar apparatus, so constructed that the person who listened for it could also observe the signal at the bell, and both set going and stop the time-piece. The mean of several experiments was 9.4 seconds, for the whole distance: on dividing the distance by the time, the velocity of sound on the water of this lake was 1435 metres, or 4708 feet per second.

The water being examined, gave one six-thousandth of its weight of saline matter; and its specific gravity at 40° Fahr. was 1.00015.

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M. Colladon remarks that the sound of a bell heard at some distance under water is strikingly distinct from that of the bell in air, being a short, brief noise, similar to that produced by striking two knives together. If the distance be increased, still the character is preserved, and it is impossible to distinguish whether the original blow is strong but distant, or nearer and weaker. It is only within the distance of 200 metres that the ringing of the bell is heard in air the reverse of this takes place; the blows struck upon a bell are easy to distinguish near at hand, but at a distance melt into one continuous sound. This phenomenon depends upon the nature of the sonorous vibrations in water. In fact, it is known that in the vibratory motion of a fluid the duration

1.

of the motion of a particle is equal to the radius of the spherical portion of the fluid supposed to be agitated at the origin of the motion, divided by the velocity with which the sound is transmitted. The first of these qualities is necessarily smaller in water than in air; the second greater: from whence it follows, that the duration of the sound should be much less when transmitted by water than when by air.

A second remark is, that sound is not transmitted from water to air when the direction of the vibrations forms a very small angle with the surface at which the two fluids meet. When the bell 6.56 feet below the surface was struck, the sound could be heard in the air at the surface of the water at the distance of 200 metres (656.17 feet); but at a greater distance it diminished rapidly, and at 400 or 500 metres could not be distinguished. If, however, the head were immersed a little way in the water, or a trumpet-formed tube, full of air and closed by a diaphragm, were immersed, so that the diaphragm should be perpendicular to the line extending directly to the bell, then the sound could be heard even at ten or twenty times that distance.

The agitation of the waves produced no alteration in the velocity, duration, or distinctness of the sound under water, when a tube like that just mentioned was used to render them audible. Some of the experiments were made at very stormy periods, but with no observable difference on these points.-Annales de Chimie, xxxvi. 236.

12. Extraordinary Experiments on Heat and Steam, by Mr. Perkins. Under this title are described in the last number of this Journal, (p. 461,) some results, stated to have been obtained by Mr. Perkins, from an American journal. The details are so circumstantial that we cannot resist the inclination of quoting another experiment of the same kind from the French journals.

A generator is said to have cracked when very hot, but no vapour or water issued out until the temperature was allowed to fall, and then the rush of steam by the aperture formed was tremendous. This was supposed to be because the heat repelled the water and vapour to a certain distance from the metal, and, virtually, stopped the crack; accordingly, another day, the generator was heated red hot at the cracked part, and water introduced in the usual way: neither steam nor water came out at the crack during the whole of the day, the generator being at work all the time; but in the evening, on cooling it, the same effects happened as before.

As some persons still retained doubts, all these, it is said, were removed by the following experiment: a hole, the eighth of an inch in diameter, was made in one of the extremities of one of the tubes of a generator, and an iron tube, three feet long, one inch external and half an inch internal diameter, screwed over it. The