TEMPERATURE AT WHICH OIL EMITS AN INFLAMMABLE GAS.

To the Editor of the Chemist. SIR,-Will you allow me, through the medium of your intelligent and amusing Publication, to ask, whethe difference of opinion, which caused such an acrimonious controversy between two scientific gentlemen some months since, has yet been decided. I have myself anxiously looked for it, but in vain. I mean as to the temperature at which oil emits an inflammable gas. I regretted exceedingly the warmth of expression with which each of the disputants supported his opinion; and considering the professional character of both pledged as to the issue, I am astonished that they should mutually have contented themselves with recriminatory abuse and invective, on a subject, the proof of which is as easy as the difference is palpable. I need not inform you, I allude to the evidence as given in the trial of the action, “ Severn, King, and Co. versus the Imperial Fire-office." Your friend,

ANTI-STAHL.

We believe the question has not been fully set at rest; but we understand that another trial is shortly to take place, when it most probably will be.-ED.

LITHOGRAPHY.

As soap forms an essential part of the ink used to trace the designs on stone, it is customary to wash the drawings, before going to press, with a weak solution of nitric acid, which, combining with the excess of alkali in the soap, renders the ink insoluble. But the acid solution sometimes attacks also the carbonates, which are a constituent part of the lithographic stones, and the most delicate parts of the drawings are destroyed. This is more particularly the case when the drawings consist of strong and delicate traits, or of a great difference in the intensity of their light and shade, in consequence of the different periods, or of stronger or weaker acids, which are then necessary to decompose the litho

graphic tints in the different parts of the drawing. To remedy this, M. Ridoffi employs nitrat of lime, perfectly neutral, in lieu of the acid solution, which decomposes the soap without injuring the stone. The nitrat is made by adding to the aquafortis of the shops pieces of the lithographic stones reduced to powder, as long as any effervescence arises; it is then weakened by adding rain-water, is filtered, and preserved for use.- -Bulletin des Sciences Technologiques.

TEST FOR GUM.

To the Editor of the Chemist. ders of your instructive little work, SIR,-If you, or any of the rea

can inform me of a convenient test for gum, when in solution, it will greatly oblige,

Your obedient servant, Woolwich, May 3. ALWIN.

P.S. I am aware that it may be detected by evaporating the menstruum in which it is held; but a test to ascertain its presence and quantity, without that trouble and time, would be of great service to me, and perhaps many more of your readers.

In answer to this question, we must observe, that silica is a very delicate test for gum. Silicated potash, added to a solution of gum, forms, with the gum, a white, flaky, and insoluble precipitate. A precipitate is formed, although the solution be very weak; the liquid remains transparent. Perhaps some of our readers may suggest a better test. We know of none.-ED. COMBUSTION OF IRON IN

VAPOUR OF SULPHUR. IF a gun-barrel, says Professor Hare, be heated red-hot at the butt end, and a piece of sulphur be thrown into it, on closing the mouth with a cork, or blowing into it, a jet of ignited sulphurous vapour will proceed from the touch-hole. Exposed to this, a bunch of iron wire will burn as if ignited in oxygen gas, and will fall down in the form of fused globules, in the state of protosulphuret. Hydrate of potash, exposed to the jet, fuses into a sulphuret of a fine red colour.Phil. Mag.

FROM ANTS.

THERE is a peculiar acid obtained from ants, called the formic acid. This is one of the modern discoveries of chemistry; and it is curious enough, says Mr. Brooke, that a discovery of modern chemistry should long have been practically employed in some parts of Norway to make vinegar. The method they employ in Nordlanden is simply this:-They first catch a sufficient quantity of these little animals by plunging a bottle partly filled with water up to the neck in one of these large ant-hills, into which they naturally creep, and are drowned. The contents are then boiled together; and the acid thus produced being strong and good, is made use of by the inhabitants as vinegar.

THE QUARTERLY JOURNAL OF SCIENCE versus MR. IVORY. WE take some little credit to ourselves for having been, we believe, the first to expose the want of good faith and candour which

is so plainly perceptible in the criticisms of the " Quarterly Journal of Science." We see by the Philosophical Magazine, that Mr. James Ivory, a very celebrated mathematician, also complains of the burlesque comparisons of the "Quarterly Journal." Burlesque on tables of refraction! After this, we shall expect to see the Elements of Euclid turned into ridicule in the Journal; and then, probably, the friends of the learned writer

may begin to think of placing him in safety.

TO CORRESPONDENTS.

In

The communications of a Chemist have been received. We are sorry that circumstances put it quite out of our power to comply with the request contained in the first part of the note of F. Smith. reply to the other part, we have to observe, that magnesia being only partially soluble in water, no definite proportion of these two ingredients can well be given; and he must have remarked, it is stated, that the magnesia is kept SUSPENDED, not dissolved, in the water, by constant stirring. About 1lb. of manganese is employed for 10 gallons of the water, in which as much magnesia has been put as it will dissolve, and such a quantity more as will give the water, when agitated, a milky appearance. The proportion of the muriatic acid to the manganese is stated in No. VI.

J. W., of Stockport, is informed, that the charge which he mentions is enormous, considering the value of both materials; but we cannot tell, in the individual case he mentions, whether it was a fair remuneration or not. If he turns to our No. V. p. 75, he will find a description of the mode of making oxymuriate, or chlorate, as it is now called, of lime. This substance is prepared on a large scale, for various purposes in the arts; and in transcribing the article relative to its employment as a manure, we had an eye to the waste chlorate being so used. We shall attend and shall be happy to learn from him to our Correspondent's other suggestion, the result of his own experiments.

mist has come to hand, but so late that The second communication of a Cheit was not possible to insert it in the present Number. We do not _think we shall even be able to find a place for request, therefore, it is left at our it in the next; and, agreeable to his publisher's.

A. B. shall appear in our next.

CHEMICAL APPARATUS.

GASOMETERS.

ONE of the principal instruments necessary for operating on the gases is a gasometer; and one of the most simple forms of this instrument is that represented in our plate. It is made of tinned iron, the surfaces of which are japanned, and consists of two principal parts; a vessel, A, somewhat bell-shaped, which is designed to contain the gas, and a cylindrical vessel of rather greater depth, B, in which the former is placed, and which is designed to contain the water by which the gas is confined. To diminish, however, the quantity of water, this cylindrical vessel has a cone within it, also of japanned tinned iron, C, adapted to the shape of the gas-holder, so that this latter, when pushed down, slides between this and the cylindrical vessel, and a small quantity of water fills up the space between them. The vessel designed to contain the gas is suspended by cords hung over pulleys, to which weights are attached, so as to counterpoise it. From a stop-cock at the under part of the apparatus, D, there runs a tube under the cylinder, which rises and passes through the cone, the opening by which it passes being soldered so as to be air-tight: it terminates by an open mouth at the upper part of the bell-shaped vessel, A. This tube, at the part where it is bent at right angles, to ascend as has been described, is connected with another which also runs under the bottom, and ascends on the outside, terminating in the stop-cock, E; so that from the one stop-cock to the other, through the gas-holder, there is an uninterrupted passage. When the instrument is to be used, the stopcock, E, is opened, and the vessel, A, pressed down, a sufficient quantity of water being in the outer cylinder; the air of the vessel is forced out by the pressure, and its place is occupied by the water in which it is thus immersed. When this is effected, the stop-cock is closed; and now, if we wish to introduce any gas into the appara

tus, a bent funnel, the mouth of which is placed in a vessel of water, is attached to the tube of the stop-cock, D, as represented in the figure, and this stop-cock is opened. If the extremity of a retort, or of a tube, conveying gas, as represented in the figure, terminate below the orifice of the funnel, the gas will rise along the tube, will ascend to the top of the gas-holder, and this being counterpoised, will, as the gas enters, rise in the water, until it is filled, a quantity of water remaining around the mouth of it, by which the air is confined. When the gas is to be expelled, the stop-cock at D is closed, that at E is opened, a flexible tube is adapted to it, and the gas-holder being pressed down, either by the hand or by its own weight, from the removal of the counterpoising weights, a stream of gas issues from the extremity of the flexible tube, and may be transferred into a jar, or be applied to any other purpose, and its quantity may be measured by the instrument being graduated by a scale marked on the brass rod, F.

The instrument connected with the gasometer in the plate, is a convenient one for procuring gases from any solid substance, by the application of a strong heat. It is an iron bottle, A, into which is fitted, by grinding, a tube bent at an acute angle. To this a smaller tube is adapted, the extremity of which can be adjusted to various heights, by a circular joint in the middle of it, at b. The bottle containing the materials from which the elastic fluid is to be disengaged, is placed in à furnace, or in a common fire, so as to be raised to a sufficient heat; the gas issues at the extremity, and may be conveyed into the gasometer, or received in an inverted jar on the shelf of the pneumatic trough. At the end of the operation, the gas ceasing to be produced as the heat diminished, the water would be pressed into the tube, and might rise into the bottle, if the joinings were not opened. The easiest way of obviating this, is by having a small

stop-cock in the tube, as at c, which may be opened when the production of the gas has ceased.

THEORY OF WATER-SPOUTS.

(Concluded from p. 122.)

On the 28th of May, 1788, (says Dr. F. Buchanan) I observed a curved spout come from the cloud; at the same time, or at the next moment, I observed a thick cloud or fog arise from the sea: very soon afterwards, the spout rushed down and joined the cloud which had arisen from the sea, and at the same time this rose higher. The body of the spout tapered gradually downwards, and was seemingly more dense than the cloud from which it descended, but not more dense or black than clouds often are. The fog coming from the sea was of the same colour as the spout, and resembled the smoke of a steam-engine. During the whole time, the surface of the sea under the spout was evidently in a violent agitation, and full of white waves; at the same time a noise was heard like that of an immense waterfall. From the formation of the spout till it reached the cloud arising from the sea, appeared about two minutes. For two or three days the weather had been very unsettled, the wind seldom remaining two hours in one quarter, and sometimes blowing hard, and at others sinking into a perfect calm. Sometimes the sky was clear, and at others it rained heavily. Our latitude was about 20° 44' S. On the 8th of January, 1789, the Doctor observed another; to the southward of it was heavy rain. About half an hour afterwards there was another, also with rain. In looking at this with a glass, I at first took it to be hollow, but I soon discovered that this was owing to the middle appearing lighter than the sides. It lasted about ten minutes, the rain continuing all the time, and seemed nearly as dense as the spout. The weather was very unsettled, with frequent showers. Lat. 3° 38' N., long. 135° 26' E. The Doctor describes another,

which he saw in April, in the southern Atlantic Ocean, when the weather was also squally and showery.

We also know, Mr. Editor, that water-spouts, as they are called, are frequent on land.

"We

"In the north of England (we are told, in the late Number of the Quarterly Review) a water-spout is called a burst." (In German they are also called bursts, but cloudbursts.-Wolkenbruch.) "A cloud is attracted to the side of a mountain, in some manner not yet explained, and discharges its waters at once, instead of letting them fall in rain. This occurs frequently in the mountains of Cumberland and Westmorland. The name of water-spout, however, has not been applied to them without a reason; the appearance and motion of the cloud bearing some resemblance to what is observed at sea." happened," continues the writer in the Quarterly Review," to see one burst upon Helvellin, at the distance of about eight miles; a sort of arm or spout, shaped like a funnel, descended from the bottom of the cloud, and was twice or thrice retracted before it appeared to touch the side of the mountain, when the whole cloud fell. Bursts such as this are said to be very frequent in North America." In August 1823, a very remarkable burst, or water-spout, as it is called, took place in the arrondissements of Dreux and Mante. The waterspout was described as having its broad base on the ground and its summit lost in the clouds. It consisted of a thick and blackish vapour. Advancing along with the storm, it tore up trees by the roots, destroying seven or eight hundred in the space of a league, and at last burst with great violence on the village of Marchepoy. half of the houses were instantly demolished, and some of the ruins were carred half a mile by the violence of this aërial torrent. People were blown away by the whirlwind, and hailstones fell as large as a man's fist. Carts, heavily laden, were broken to pieces, and their

One