A, indigo. Now the instant that por-small quantity of it was ever made tion of the piece of cloth covered at any one time. Subsequently, with the resist paste meets the in- however, a means was discovered digo, the salt of copper it contains of applying this colour by means parts with its oxygen to the indigo, of blocks, and this has now nearly which renders it insoluble, and superseded the use of the pencil. prevents it having any effect on The little machine for this purthe cloth. When the rest of the pose is represented in the plate -pieces have acquired by frequent at the end of this article. dipping the requisite intensity of Fig. first and second, is a box for colour they are washed and passed containing the colour; B is a sieve, through diluted sulphuric acid; which floats within this box and and it is found that the parts co- on the top of the colour; cc.cc vered with the resist, paste have are four springs, which keep the been preserved of a good white, fine canvas of the sieve close down while all the other parts of the on the dissolved indigo; D, Fig. 2, cloth have become of a permanent is the tub containing the pencil blue. This is the general mode of blue, from which the box, A, is dying those blue calicoes which supplied as its contents are used by have white spots or figures; and the printer. D is constructed on by a subsequent dyeing in madder, the principle of the common bird figures of red or yellow are exhi- fountain, and is completely filled bited on a blue ground. In some with the prepared indigo at the sorts of work wax is used for a commencement of the process, and resist, but this is found to be very is then closely corked and sealed expensive, and though formerly to prevent the possibility of atmomuch in use, is now generally laid spheric air getting admittance to aside. The handkerchiefs called it. The tube is provided with a Bandanas, when dyed are pre- stop-cock in case the barrel should served from the effects of the in- by accident admit air and cause digo, by printing them with a pre- the box to overflow. By means of paration of tallow and rosin, on this sieve and the blocks the workthose parts which are to remain man applies the indigo, as already white; a part of the blue is after- described, when speaking of other wards discharged, and the hand- colours, at page 188. kerchiefs dyed yellow or orange, according to the pattern. If the ground, however, of the piece is to remain white, and to have only one object in indigo-blue, then the colour is imparted in the following manner: Twenty ounces of quick lime in lumps, as much subcarbonate of potash or the common potash of commerce, and ten ounces of orpiment (sulphuret of arsenic) are added to ten ounces of indigo finely ground in water. These proportions are mixed together with one gallon of water, the mixture is allowed to deposit its sediment, and then it is carefully thickened with gum senegal. This is what is called pencil blue, from the former practice of applying this colour with a pencil; and as it was necessary to use the indigo before it recovered its oxygen from the atmosphere, only a Besides the resist work, there is another process appropriately named discharge work. In this the cloth is first dyed of some uniform colour by means of a solution of some preparation of iron as a mordant, and one of the vegetable dyeing substances; it is then washed and dried, pressed and calendered. The colour is then discharged by the application of one of the mineral acids, previously prepared according to the nature of the dye intended to be discharged and the colour to be produced. Thus a piece dyed black with a decoction of Brazil wood, having for a mordant a solution of iron, when printed in any pattern with an acid solution of tin, discharges the iron portion of the dye, and the black is instantly changed to crimson. In the same way a piece dyed olive colour by decoction of weld, and iron as a mordant, is instantly changed, by a similar acid solution of tin, to a bright yellow. Different drabs and slate coloured stuffs, which have been coloured by means of iron, may also be changed; but the colour of the places discharged will depend on the substances with which the cotton was originally dyed. By this process, to which the dyer is wholly indebted to chemistry, and which depends altogether on the different affinities of the mordants of the colouring substances and of substances used to discharge the colours, almost any variety of shade may be produced, and for us to enumerate them all would be to refer to almost all the colours which the dyer uses. For a finer kind of discharge work, instead of the mineral acids and a solution of tin citric acid, the juice of lemons, is used, producing wherever it is applied a delicate white. To discharge the indigo from handkerchiefs, muriatic acid or nitro-muriatic acid is employed, which is mixed with gum or flour paste, and is then applied to the silk by means of a block, on which the desired pattern is cut, and a yellow colour is produced wherever it is applied. (To be concluded in our next.) TO MAKE A METALLIC WIRE RED HOT BY EXPOSING IT TO VAPOUR. EXPERIMENTS which serve for amusement, are not always those which are most instructive or most useful; but the one we are now to describe teaches the nature of flame, and has been applied by Sir Humphrey Davy to create light for the miner when the flame of his candle is extinguished. Take a platina wire, one-sixtieth or oneseventieth of an inch in diameter, coil it up at one end, and heat it red hot in a candle. Pour about 20 drops of sulphuric ether into a wine-glass, which will partly fill the glass by its vapour, and when the wire has ceased to be red hot, if brought pretty near to the surface of the ether, it will instantly begin to glow again, and continue ignited for some time. By agitating the glass so as to diffuse the ether, the ignition, when it begins to slacken, will be increased. Sir H. Davy ascertained that the combustible mixture of coal gas and air had the same effect as the vapour of ether, and he applied this fact to use in the following method:-He suspended some fine coils of platina wire above the wick of the safetylamp, within the wire gauze cylinder. Should the flame be extinguished by the foul air, the glow of the metallic wire will continue to furnish the miner with a useful though feeble light; and as it is totally extinguished whenever the air is no longer respirable, it serves at the same time as an index of the purity of the air of mines. The experiment also shows, that there is, on common occasions, an invisible species of combustion going on; and that if we wish to make the most of our fuel in producing heat, we must cause it to burn briskly. DICTIONARY OF CHEMISTRY. (Continued from p. 189.) AIR, in chemistry, means atmospheric air, or the atmosphere. Formerly this term was applied to all kinds of gases, or permanently elastic fluids. Thus we have fixed air as a name for carbonic acid gas, called also choke damp by miners; and inflammable air for the name of hydrogen gas. Now, however, the term gas, in chemistry, is substituted for the word air, and the latter is restricted to the atmosphere. ALABASTER. Opaque semitransparent stone, composed of lime united with sulphuric acid. ALBUM GRÆCUM. A medicine made from the excrement of dogs; it consists chiefly of lime in combination with phosphoric acid. ALBUMEN. A chief constituent of animal bodies. It is so named from being found in great abundance in the white of eggs. It is distinguished from most other substances by its great liability to coagulate with heat. ALBURNUM. The soft part of the bark of trees, next the wood. It has been bark, and will become wood. ALCARRAZAS. The name of a coarse and porous species of pottery, used in Spain. It is made of about 36 parts of silica and 60 of a calcareous earth, mixed with alumina and a little iron. When these earths are mixed up with water, a small quantity of salt is added, and baked up with it. The vessels made of it are usually called Demi Johns; they are large, and employed to hold water, which, exuding through them, and constantly evaporating, keeps the portion which remains in the jar cool on the warmest day. Pottery of this description makes the best wine-coolers known. ALCHEMY. The art of transmuting metals into gold and silver, and preparing the elixir vitæ, or universal medicine. ALCHYMISTS. A sect who pretended to understand the art of making gold and silver. They are supposed to have existed from the third down to the beginning of the 19th century. Their place is now supplied by quacks, who impose on nobody but the most ignorant and credulous; the alchymists in their day imposed on the most enlightened and sagacious men. ALCOHOL. Spirits of wine; pure spirit. It is obtained by the distillation of liquids which have undergone fermentation, and by subsequent rectification, ALE is well known, by name at least, to our readers. It differs from beer chemically, by the sugar of the wort not having been thoroughly decomposed, and containing more mucilage. ALEMBIC. Another name for a still; a vessel used for chemical distillation. ALEMBROTH SALT. A salt consisting of ammonia, muriatic acid, and mercury. ALGAROTH, powder of, a preparation of antimony, which is violently purgative. ALKAHEST. The name which the alchymists gave to a pretended liquor, which was to dissolve all substances. Kunckel asked, “If it dissolve all substances, in what vessels can it be contained? ALKALESCENT. Tending to, or possessing alkaline properties. ALKALI. A general name for an important class of bodies, possessing the following properties :They neutralize, that is, destroy the distinguishing properties of, and are neutralized by, acids; they change vegetable blues or purples to green, reds to purple, and yellows to brown; have an acrid taste, corrode animal matter, with which they combine and are neutralized, and they are soluble in water. Formerly the term was restricted to potash, soda, and ammonia. Some chemists proposed to extend it to lime, barytes, and strontian; but this was not adopted; and now it is generally applied to a number of vegetable substances, such as morphia, quinina, &c. which have lately been discovered, ALKALI, fixed. Potash and soda. ALKALI, mineral. Formerly a name for soda. ALKALI, prussian, or phlogisticated. An old name for a combination of one of the fixed alkalies with prussic acid. ALKALI, volatile. Ammonia. ON THE HOT MINERAL WATERS OF THE CORDILLERAS OF VENEZUELA. By J. B. Boussingault and Mariano di Rivero. THE springs of Onoto issue copiously from gneiss. Their temperature is 44°.5 of the centigrade thermometer. Their height above the level of the sea is 702 metres. From the bottom of each reservoir bubbles of azotic gas arise, from time to time, in great abundance. The springs of Mariano have a temperature of 44o centig.; but in particular spots it is from 560 to 64°. They contain a very little sulphuretted hydrogen. They also rise from gneiss, and evolve azote. Silica is the predominating ingredient in solution. Their height above the sea is 476 metres:Annales de Chimie & de Physique, vol. xxiii. p. 272. CHEMICAL SOCIETY. To A. M. SIR,-Allow me to mention a few of my ideas regarding the Society which may be formed. It should not be composed of many members, perhaps not more than twenty. The members should meet once a week, at about half-past eight in the even ing; out of twenty members, twelve might be expected to attend. The subscription should be a small sum, about a shilling a month. The description of books, and apparatus, to be purchased with the money raised and all other matters re garding the interests of the society to be determined by ballot. $ it must be conducted with gravity and decorum. My opinion is, that the Society should take an experimental system of chemistry, Henry's, for instance, and go regularly through it; performing all the experiments contained therein, as far as their skill and apparatus would permit; and that every member, in his turn, should give a LECTURE, illustrative of the experi ments performed. Each lecture,, with the experimental illustrations, to be the business of one evening. › Let no one laugh at the idea of a parcel of students becoming professors, or exclaim," If the blind lead the blind," &c.; for be it remembered, that they are to have a guide. I feel persuaded, that this plan would be practicable and useful. The LECTURE, at first, might be a mere reading of what the author of the system they went by said › in illustration of his own experi ments. But the eloquence of every lecturer would gradually improve,. as well as his practical skill in the manipulations; so that, after a s time, when things got in a proper train, amusement and instruction would certainly be obtained by every member at every meeting. A fair chance would thus be opened for every one to improve, as › well as be improved. I shall at present say nothing of the advan tages which would arise from pos- › sessing a choice, scientific library; the books composing which of course would be circulated among.. the members. J. G. THE following very liberal offer was accompanied by the writer's real address; it seems well worthy of the attention of our readers; and such as are disposed to join the proposed Society should hasten to declare themselves. SIR,-In furtherance of A. W.'s proposition, I beg leave to offer the use of a large room and my small collection of books, utensils, &c. twice or three times a week for twelve months. Supposing a Society to be formed, and to be furnished with a moderate apparatus and library, the next thing to be considered is, how are the members to study? They cannot all meet, and each set about some experiment according to his own faney, for then every thing would be confusion. If the Society is to be continued, the business of May 28, SILICON. M: BERZELIUS, the celebrated Swedish chemist, has announced in a letter to Sir H. Davy, read before the Royal Society, that he has succeeded, by acting on dry silicated fluate of potash by potassium, in obtaining the base of silica in an insulated state. Among other substances which the fluate yielded, was hydroguret of silicon; and when this was heated in a crucible, the hydrogen was burned off, and the silicon obtained pure. In this state Professor Berzelius examined it, and found it resembled charcoal in one point, namely, varying in its combustibility as it was obtained in different states of aggregation. In its state of greatest density, it may be made incandescent without burning. It is difficult to effect its complete combustion, but 200 parts of silicon unite with 208 of oxygen to form silica. It will not burn when heated with nitre, but is brought into combustion by carbonate of potash. It burns when ignited in chlorine, forming a colourless, transparent fluid, having the smell of cyanogen. It burns also in vapour of sulphur, producing a grey sulphuret. QUERIES. To the Editor of the Chemist. SIR, Can any of your numerous correspondents inform me of the method of dissolving India rubber, (I mean nearly to a liquid,) so that it can be shaped at pleasure, and returned to its former consistency. Yours, A SUBSCRIBER and READER. TO, DISSOLVE CAOUTCHOUC, OR INDIA RUBBER. BOIL it for an hour in water, cut it into slender threads, boil it again for about an hour, then put it into rectified sulphuric ether, which has been well washed with water, and cork the vessel closely up. In a few days it will be totally dissolved; and, ifether enough have been employed, the impurities will all fall to the bottom. If the solution be spread on any thing, the ether quickly evaporates, and leaves a coating of caoutchouc, unaltered in its properties. By this means it may be made into almost any shape by means of moulds. Or it may be made into tubes and such shapes, by cutting it into a uniform slip, of proper thickness, and winding it spirally round a glass or metal rod, and then boiling it for some time, when it will be found that its. edges will adhere without any alteration of its properties. Pieces of it may also be made to unite very firmly by softening them with heat, and pressing them together. SIR, I should be happy to learn, through the medium of your Publication, what preparation those bladders undergo that are used for holding gas, with the method. of preparing them. May 24. 66 Yours, P. SIR, I lately read in an old book the following method of making an oil paper for copying drawings, &c. and which might afterwards be written or painted on; now, Sir, I shall be obliged to you, or any of your readers, who can inform me if such a paper is in use? if it answers well? and what the expense is of preparing it?The receipt for making it is as follows:- Take fine vellum or writing paper, and rub it over with also stone oil, and petroleum, taking cotton dipped in naphtha, called care that the naphtha is white; wipe off the superfluous oil, and hang the paper up in a warm place, or near the fire, till the oil has: completely penetrated it; after this rub it over with wheat bran, and it is fit for use, being as trans→→ parent nearly as glass. When it has been used for copying the outline of any thing, which it is afterwards required to fill in, the paper may be entirely freed from the oil by exposing it to the heat of a coal fire, and if done where there is a draught so much the better. By this process," says the writer of the receipt," the paper may be made as clear as before, and may afterwards be drawn on with water |