To a diluted colorless solution of chloride of gold, add a few drops of a solution of any salt of tin; or stir the solution of gold with a slip of metallic tin; in either case, the production of a beautiful purple or port wine color will be the immediate result. If the mixture is allowed to settle, it becomes colorless; a purple powder (which is an oxide of gold combined with a little tin) being precipitated. This powder is employed in the painting of china, and is called the purple precipitate of Cassius. For Silver. into a glassful of water, and add to it a grain of common salt. Mutual decomposition of the salts will take place, and chloride of silver (in the form of a white powder) will be precipitated. This precipitate is soluble in ammonia, and blackens on exposure to light. For Copper. Add a few drops of a solution of nitrate of copper to a test glass of water; the mixture will be colorless; pour into it a little liquid ammonia. The mixture will then assume a fine deep blue color. Another. Ferrocyanide of potassium gives a dense brown precipitate with the salts of copper. Let fall a drop of a solution of nitrate of silver This is very delicate. To Detect Copper in Pickles or Green Tea. Put a few leaves of the tea or some of the pickle, eut small, into a phial with 2 or 3 drs. of liquid ammonia, diluted with one-half the quantity of water. Shake the phial; when, if the most minute portion of copper be present, the liquid will assume a fine blue color. Or immerse a polished knifeblade; the copper will deposit upon it. For Iron. nary temperatures. It may therefore be used as To Determine whether Wheat Flour, or Bread be Mix with the flour to be tried, a little sulphuric acid; if chalk or whiting be present, an effervescence (arising from the discharge of the carbonic acid of the chalk) will take place; but if the flour Infusion of galls gives a bluish black, and ferro- be pure, no effervescence is produced. cyanide of potassium a blue precipitate. For Manganese. Sulphydrate of ammonia (made by passing a current of sulphuretted hydrogen gas through solution of ammonia until no more is absorbed), gives a flesh-colored precipitate. For Mercury. Protochloride of tin gives a grayish precipitate. A piece of gold introduced into a solution containing mercury and touched with a piece of iron, has the mercury deposited upon it. For Lead. Sulphydrate of ammonia gives a black precipitate; chromate of potassa and iodide of potassium, yellow. To make Oxygen. Heat in a retort, flask, or test tube, finely powdered chlorate of potassa, mixed with about onefourth its weight of black oxide of manganese. The gas must be collected by attaching a tube to the flask, the end of which dips under water; a jar full of water being inverted over the end of the delivering tube. To make Hydrogen. Act on zinc scraps with diluted sulphuric acid; say 1 part of acid to 10 of water. A common bottle with a perforated cork fitted with a glass tube or bit of pipe-stem, and another bottle to collect the gas, are all the apparatus required. In collecting the gas, the tube must reach quite to the top of the collecting vessel. Care must be taken that all the air has been driven out of each vessel before a light is applied, or an explosion will ensue. To make Laughing Gas. Heat gently in a flask or retort, nitrate of ammonia (made by adding carbonate of ammonia to nitric acid until no more gas comes off). It should be allowed to stand some time over water before being breathed. To make Carbonic Acid. Pour muriatic acid upon fragments of chalk or marble. The gas being heavy may be collected without the use of water, by simply allowing the delivery tube to pass to the bottom of the receiving vessel. To make Chlorine. Heat gently a mixture of muriatic acid and black oxide of manganese. It may be collected like carbonic acid. Care must be taken not to inhale it. To make Sulphurous Acid. To 12 oz. of sulphuric acid, in a glass retort, add 2 oz. of sulphur and apply a gentle heat. This is a cheap and easy process. To make Sulphuretted Hydrogen. Pour dilute sulphuric acid on sulphuret of iron. This is made by applying a roll of sulphur to a bar of iron heated white hot, or by heating in a erucible a mixture of 2 parts, by weight, of ironfilings and 1 of flowers of sulphur. Gun-cotton as a Filter. Gun-cotton, carefully prepared, is scarcely acted, on by the most energetic chemical agents at ordi Another Method. Pour boiling water on some slices of bread, and then pour into the water some sulphuric acid; if there be any chalk in the bread, an effervescence will ensue as before; but if none be in it, no effervescence will take place. To Prepare Soda Water. Soda water is prepared (from powders) precisely in the same manner as ginger beer, except that, instead of the two powders there mentioned, the two following are used: For one glass, 30 grs. of carbonate of soda; for the other, 25 grs. of tartarie (or citric) acid. To Prepare Ginger-Beer Powders. Take 2 drs. of fine loaf sugar, 8 grs. of ginger, and 26 grs. of carbonate of potassa, all in fine pow der; mix them intimately in a Wedgwood's ware mortar. Take also 27 grs. of citric or tartaric acid (the first is the pleasantest, but the last is the cheapest). The acid is to be kept separate from the mixture. The beer is prepared from the powders thus: Take two tumbler-glasses, each half filled with water; stir up the compound powder in one of them, and the acid powder in another, then mix the two liquors; an effervescence takes place, the beer is prepared and may be drunk off. The effervescence is occasioned by the discharge of the carbonic acid of the carbonate of potass. If the beer is allowed to stand for a few minutes it becomes flat; this is owing to its having lost all its carbonic acid. The cost of these powders is 20 cents a dozen sets. To Determine whether Water be Hard or Soft. To ascertain whether or not water be fit for domestic purposes, to a glassful of the water add a few drops of the solution of soap in alcohol. If the water be pure, it will continue limpid; if hard, white flakes will be formed. To Preserve Phosphorus. Keep it in places where neither light nor heat has access. It is obtained from druggists in rolls; these are put into a phial filled with cold water, which has been boiled to expel air from it, and the phial is enclosed in an opaque case. Expeditious Method of Tinning. Plates or vessels of brass or copper are rapidly and firmly coated with tin by boiling them with a solution of stannate of potassa, mixed with trimmings of tin, or by boiling them with tin-filings and caustic, potash or cream of tartar. PREVENTING AND REMOVING BOILER INCRUSTATIONS. The following substances have been used, with more or less success, in preventing and removing the incrustations which are formed by using hard water: Krause's Anti-incrustation Powder for Steam Boilers. Powdered charcoal, sal soda, alum, each 1 lb. sawdust, 8 lbs. Mix. Most of the secret incrustation powders sold are but modifications of this. Potatoes. By using about 1-50th of potatoes to the weight of water in a boiler, scale will be prevented, but not removed. Their action is mechanical; they coat the calcareous particles in the water, and prevent them from adhering to the metal. Extract of Oak Bark. A mixture has been used of 12 parts of chloride of sodium, 2 parts of caustic soda, extract of oak bark, of potash, for the boilers of stationary and locomotive engines. The principal agent in this case appears to be the tannin or the extract of oak bark. Pieces of Oak Wood, Suspended in the boiler and renewed monthly, prevent all deposit; even from water containing a large quantity of lime. The action depends principally upon the tannic acid. Sawdust. Mahogany and oak sawdust has been used to prevent and remove scale; but care must be exercised not to allow it to choke up pipes leading to and from the boiler. Catechu contains tannic acid, and has also been used satisfactorily for boilers. A very small quantity of free tannic acid will attack the iron; therefore, a very limited quantity of these substances should be employed. Slippery-Elm Bark. This article has also been used with some sucBess in preventing and removing incrustations. Soda. which is made of parchment-paper, afloat on the surface of water (dialysis); after a few days silica, combined with water, will be found in the box. It may be used for the preservation of building-stone, or to render wood fire and water proof. Stoppers of Bottles for Chemical Re-agents. Paraffine is the best material for lubricating the stoppers of bottles containing caustic alkali, as it is not acted upon by chemical agents under ordinary circumstances, and lubricates perfectly. To Loosen Tight Stoppers. 1. Tap the stopper gently, upwards and sidewise, with a bit of wood. crack of a door or a drawer, and work the bottle 2. Fasten the upper part of the stopper in the gently from side to side. 3. Fasten a string firmly around the stopper (see KNOTS), attach it to a fixed body, and jerk the bottle suddenly downward. 4. When the stopper adheres on account of the solidification of matters dissolved in the liquid in the bottle, a little of the same liquid poured around the base of the stopper, and allowed to remain awhile will often dissolve the hardened matter, and free the stopper. 5. The most effectual way, but one requiring care, is to heat the neck of the bottle evenly and rapidly over an alcohol or gas-flame. The neck expands sooner than the stopper, and it is very rarely that any difficulty is found in the removal of the latter. If the bottle contain inflammable The carbonate of soda has the sanction of Pro-liquids, it is safer to wrap a cloth dipped in boilfessors Kuhlman and Fresenius, of Germany, ing water around the neck, instead of exposing it Grace Calvert, of England, and others. It is satisfactorily employed for the purpose. Tin Salt. The chloride of tin is equal to the muriate of ammonia, and is similar in its action in preventing scale. Extract of Tobacco, and Spent Tanner's Bark Have been employed with some degree of satisfaction. The sulphate, not the carbonate, of lime, is the chief agent in forming incrustations. By frequent blowing off, incrustations from carbonate of lime in water will be greatly prevented. Ammonia. The muriate of ammonia softens old incrustations. Its action is chemical; it decomposes the scale. About 2 oz. placed in a boiler, twice per week, have kept it clean, without attacking the metal. to the naked flame. To Remove Ink from Paper. Wash alternately, with a camel's-hair brush, dipped in a solution of oxalic acid and cyanide of potassium. Artificial Tourmalines. Dissolve 50 grains of disulphate of quinine in 2 fl. oz. of acetic acid, and 2 oz. of proof-spirit, warmed to 130° Fahr., in a very wide-mouthed flask or glass beaker; then slowly add 50 drops of a mixture of 40 grs. of iodine in 1 oz. of recti. fied spirits; agitate the mixture, and then set it carefully aside for 6 hours, in an apartment maintained at a temperature of about 50° Fahr. The utmost care must be taken to avoid any motion of the vessel; indeed, all accidental vibrations should be guarded against by suspending the vessel by a string, or by allowing it to rest on a mass of cotton and wool. If, in 6 hours, the large lamwith a spirit lamp, and when it has become clear, inæ of the salt have not formed, warm the fluid add a few drops of the solution of iodine in spirit. The large lamina form on the top of the fluid, and should be removed carefully by gliding under one of them a circular piece of thin glass. The specimen should be drained by resting the edge of the glass on a piece of bibulous paper, but it must not be touched on account of its extreme fragility; if any small crystals adhere to its surface, they must be washed off by pouring over it a few drops of watery solution of iodine. When dry the specimen should be placed for a few minutes under a bell-glass by the side of a watch-glass, containing a few drops of tincture of iodine; and, lastly, a very little fluid Canada balsam should be dropped Specimens may thus be obtained of extreme thinon it, and a thin glass cover applied without heat. Curious Mode of Silvering Ivory. Immerse a small slip of ivory in a weak solution of nitrate of silver, and let it remain till the solution has given it a deep yellow color; then take it out and immerse it in a tumbler of clear water, and expose it in the water to the rays of the sun. In about 3 hours the ivory acquires a black color; but the black surface on being rubbed, soon be-ness, and an inch in diameter, or even larger, comes changed to a brilliant silver. possessing scarcely the slightest color, and yet completely polarizing transmitted light. Soluble Silica. Add to soluble glass (water-glass) an excess of muriatic acid; put it into a box, the bottom of New Materials for Buttons. Excellent buttons, and even handsome cameos, may be made with tale or steatite, provided, after they are made, they be heated for several hours at a nearly white heat. By this strong calcination the steatite gets so hard that it strikes fire with flints, and resists the best tempered file. They may be polished by emery, tripoli, and jeweller's putty; and colored by mineral or organic matters; chloride of gold colors them purple; nitrate of silver, black; exposure to the reducing flame increases very much the brilliancy of the color. ARTIFICIAL COLD. When a solid body becomes liquid, a liquid vapor, or, when a gas or vapor expands, heat is abstracted from neighboring bodies, and the phenomena or sensation of cold is produced. Evaporation produces cold, as is seen familiarly in the chilliness caused by a draught of air blowing on the moist skin. Water may be cooled to 60°, in warm climates, by keeping it in jars of porous earthenware; a flower-pot, moistened and kept in a draught of air, will keep butter, placed beneath it, hard in warm weather. In India water is exposed at night in shallow pans, placed on straw in trenches, and freezes even when the thermometer does not fall below 40° Water may be frozen by its own evaporation under the receiver of an air-pump over sulphuric acid; the process is a delicate one, and not adapted for use on the large scale. Twining's ice-machine freezes water by the evaporation of ether, aided by the vacuum produced by a pump worked by a steam-engine. The same ether may be used over again indefinitely. The apparatus works well, but, in case of a leak, the ether vapor, mixed with air, would explode; there is always danger of fire. Carré's Apparatus Freezes by the evaporation of liquid ammonia, the ammoniacal gas produced being absorbed by water which will take up over 500 times its bulk of the ammonia, which it gives out again on heating. As liquid ammonia boils at 42° below zero, an intense cold is produced. This apparatus is efficient, but as the internal pressure rises sometimes to over 100 lbs. to the inch, it is not quite safe, although no accidents have yet been reported. Compressed Air. Air, when compressed, gives out heat which is re-absorbed when it is allowed to expand. By forcing the air into a strong receiver and carrying off the heat developed by a stream of water, it may, on expanding, re-absorb enough to reduce the temperature below 32°. It is thus used in the paraffine works in England, and would be an excellent method of at once ventilating and cooling large buildings. Freezing Mixtures Depend upon the conversion of solid bodies into liquids. There are two classes, those used without ice and those in which it is employed. Where extreme cold is required, the body to be frozen should be first cooled as much as possible by one portion of the mixture, and then by a succeeding one. Without Ice.-Four oz. each of nitre and sal ammoniac in 8 of water will reduce the temperature from 50° to 10°. Equal parts of nitrate of ammonia and water, from 50° to 4°. The salt may be recovered by evaporation and used over again. Equal parts of water, crystallized nitrate of ammonia, carbonate of soda, crystallized and in powder, from 50° to 7°. Five parts of commercial muriatic acid and 8 of Glauber's salt, in powder, from 50° to 0°. With Ice.-Snow is always preferable. Ice is best powdered by shaving with a plane like a carpenter's, or it may be put into a canvas bag and beaten fine with a wooden mallet. Equal parts of snow and common salt will produce a temperature of -4°, which may be maintained for hours. This is the best mixture for ordinary use. Three parts of crystallized chloride of calcium and 2 of snow will produce a cold sufficient to freeze mercury, and to reduce a spirit thermom. eter from 32° to -50°. The chloride may be recov ered by evaporation. There are many other freezing mixtures given in the books, but none are so cheap and efficient as the above. ANTISEPTICS AND DISINFECTANTS. Antiseptics are bodies which prevent or retard decay; disinfectants those which are supposed similarly to retard or prevent the spread of disease, whether epidemic or contagious. The latter term, however, is popularly applied to deodorizers or bodies which remove the offensive smell accompanying decaying organic matter. Antiseptics. Salt, spices and sugar are too well known to require comment. Professor Morgan's method of salting meat is to inject the brine into the aorta, or main artery; this process is highly recommended on the score of simplicity and economy. lutions. The latter does not shrink or alter the Alcohol and glycerine are used as preservative socolor of animal or vegetable substances preserved Goadby's Solutions. in it. 1. (For ordinary use in preserving specimens.) Alum, 1 oz.; bay salt, 2 oz. ; corrosive sublimate, where there is a tendency to mouldiness, use 2 1 gr.; water, 1 pt. In very tender tissues, or grs. of corrosive sublimate. Bay salt, lb.; corrosive sublimate, 1 gr.; water, 2. (For objects containing carbonate of lime.) 1 pt. 3. (For old preparations.) Bay salt, lb.; arsenious acid (white arsenic), 10 grs.; water, 1 pt. Dissolve by the aid of heat. When there is a tendency to softening, add 1 gr. of corrosive sub limate. Reboulet's Solution. 4 parts; water, 16 or 20 parts; to be diluted as Nitre, 1 part; alum, 2 parts; chloride of lime, may be necessary. For pathological specimens. Stapleton's Solution. Alum, 24 oz.; nitre, 1 dr.; water, 1 qt. Is made by adding scrap zinc to muriatic acid so long as any gas (hydrogen) is evolved. If it be required neutral, add carbonate of soda until a slight precipitate is seen. It is largely used in the preservation of timber, and in embalming, being in the latter case injected into the aorta. Kyan's Solution Is a strong solution of corrosive sublimate in water; used for the same purposes as Burnett's, but now generally superseded by the latter. Coal Tar Is used to preserve wood; it is boiled and applied as a paint, or forced into the pores of the wood under pressure. Disinfectants. The only true method to prevent the spread of contagious or epidemic diseases is thorough cleanliness. Abundance of air to date the poison, and the removal of organic effete After Ly liberal use Charcoal of water or soap and water, are effectual. Lime | der contains 5 to 8 per cent. each of lime and of acts by destroying organic matter and absorbing carbolic acid, and 70 to 80 per cent. of fuller's earth. certain offensive gases. Hence the use of whitewashing. Sulphurous acid checks organic change or fermentation. A high temperature, say 240° Fahr., is useful in disinfecting clothes, letters, etc. Condy's Solution acts by destroying organic matter; solutions of chloride of zinc, corrosive sublimate, persulphate or perchloride of iron act by coagulating certain organic matters and preventing further decay; they also absorb sulphuretted hydrogen. Chloride of lime (bleaching salt), chlorine, nitrate of lead, and copperas are merely deodorizers. Pastils (see PERFUMERY), burned sugar, vinegar, and burning tar, merely disguise offen sive odors. Condy's Solution. A saturated solution of permanganate of potassa is one of the most efficient and elegant of all disinfectants. A teaspoonful in a soup-plate of water, exposed in a room, quickly removes any offensive smell; when the pink color disappears more must be added. It has been used to remove the smell of bilge-water, and guano from ships. It speedily cleanses foul water and makes it drinkable. A teaspoonful to a hogshead is generally enough, but more may be added, until the water retains a slight pinkish tint. This will disappear, by putting a stick into the water for a few minutes. Ledoyen's Solution. Litharge, 13 oz.; nitric acid, s. g. 1.38, 12 oz., previously diluted with water, 6 pts. It contains nitrate of lead, and is merely a deodorizer. Chlorine. Free chlorine is seldom used, on acount of its offensive and suffocating qualities. Chloride of lime contains hypochlorite of lime and chloride of calcium and lime. It is made into a paste with water; acids cause it to evolve chlorine. Eau de Javelle is made by adding to chloride of lime 1 part, water 15 parts, and agitate at intervals for an hour; then dissolve 2 oz. carbonate of potassa in pint water. Mix the solutions, and when the mixture has settled pour off the clear part. Or, by passing a stream of chlorine through a solution of carbonate of potassa to saturation. It contains hypochlorite of potassa and chloride of potassium. Labarraque's Solution. Pass chlorine through a solution of carbonate of soda (1 lb. in water 1 qt.) to saturation; or, to a mixture of chloride of limelb., and water 3 pints, add 7 oz. crystallized carbonate of soda, in 1 pt. of water. Proceed in all respects as for Eau de Javelle. These solutions will remove fruitstains from linen. Iron Compounds. Perchloride of Iron is made by dissolving iron in muriatic acid, and while boiling add nitric acid as long as red fumes are evolved. It is a powerful styptic. Monsel's Solution, subsulphate of iron, is made by dissolving copperas 12 oz. (troy), in water 12 oz., adding sulphuric acid 510 grs., and then while boiling adding nitric acid as long as red fumes come off. It is much used as a styptic and astringent, and is a cheap and powerful deodorizer. Copperas mixed with its weight of lime is a cheap and popular agent in deodorizing sinks. Carbolic Acid, Or coal-tar creosote, coagulates organic matter; is a powerful antiseptic and deodorizer. It is used mixed with lime. Ridgewood's disinfecting pow Is a useful deodorizer and purifier; it acts by its densing the latter as well as the oxygen of the air attraction for organic matter and gases. By conanimals buried in charcoal are rapidly converted in its pores it causes rapid combination. Small into skeletons, while no offensive smell is noticed charred casks; foul water is purified by filtration even in warm weather. Water is best kept in through charcoal. Meat lightly tainted is restored by wrapping in powdered charcoal; animal charfor these purposes. Animal charcoal is an anticoal is the best. Lampblack is nearly worthless dote to all animal and vegetable poisons; it rapidly removes organic coloring matters and also vegetable bitters from solution. Pieric acid is not thus removed, and may in this way be detected when used instead of hops in brewing. Noxious Vapors. To prevent the effects of noxious vapors from wells, cellars, fermenting liquors, etc., procure a free circulation of air, either by ventilators, or opening the doors or windows where it is confined, or by keeping fires in the infected place; or throwing in lime, recently burnt or powdered. Old wells, vaults, and sewers, which have been long shut up from the air, are generally occupied by vapors which soon prove fatal to persons breathing them. The property which these vapors have of extinguishing flame, affords the means of detecting their presence, and thereby avoiding the danger of an incautious exposure to them. When such places, therefore, are opened to be cleaned out or repaired, a lighted candle should be let down slowly by means of a cord, before any person is suffered to descend; and if it burns freely until it gets to the surface of the water, or other matter covering the bottom, the workmen may then venture down with safety. But, if without any accident, the candle is extinguished, and continues to be so on repeated trials, then the air of the place is highly noxious. Parchment Paper Is made by immersing unsized paper for a few seconds into a mixture (cold) of 2 parts, by measure, of commercial sulphuric acid, and 1 part of water; then washing in water, and afterwards in dilute solution of ammonia. It is water-proof, about 6 times as strong as paper, and may be used in all cases as a substitute for parchment, which it resembles. The same effect is produced by soaking paper in a solution of neutral chloride of zine, s. g. 2100. It is then treated as before. This paper is used in Mr. Graham's process for dialysis. New Mode of Preparing Paper for the Use of Draughtsmen, etc. glazed earthen vessel, containing cold water, some Reduce to a powder, and dissolve quickly in a gum tragacanth, having been well worked with a wooden spatula, to free it from lumps. There must be a sufficient quantity of water, to give to this diluted gum the consistence of a jelly. Paper, and some sorts of stuffs, upon which, if this composition be smoothly applied, with a pencil or either water or oil colors; in using water colors, a brush, and dried before a gentle fire, will receive they must be mixed with a solution of the above gum. This cloth or paper, so prepared, will take any color except ink. When it is intended to retouch any particular part of the drawing, it should be washed with a sponge, or clean linen, or a pencil (containing some of the above-men |