Part 11

Rub together in a _warm_ mortar, three parts of powdered niter, two of dry carbonate of potash, and one of flour of brimstone; place a small quantity of the mixture in an iron ladle, and heat it over the fire, when it will speedily melt, and then explode with a very loud noise; and if held under a foul chimney, will save the expense of a chimney sweep: but avoid cooking time.

Another salt of potash remarkable for the same property, in even a greater degree, is the _chlorate_ of potash.

EXPERIMENTS.

1. Triturate together in a _dry_ mortar a few grains of flowers of sulphur, with a small quantity of the chlorate of potash, and a succession of sharp explosions, like the crack of a whip, will be produced.

2. Substitute half a grain of phosphorus for the sulphur, and the action will be much more violent. The hand should be defended by a thick glove, and the eyes carefully guarded, in making this experiment.

3. Mix very carefully a little of this salt, reduced to powder, with a little lump sugar, also powdered, and drop on the mixture a little strong sulphuric acid, and it will instantly burst into a flame. This experiment also requires caution.

Want of space precludes us from considering the individual metals and their compounds in detail; it must suffice to describe some experiments, showing some of their properties.

The different affinities of the metals for oxygen, may be exhibited in various ways. The silver or zinc tree has already been described.

EXPERIMENTS.

1. Into a solution of nitrate of silver, in distilled water, immerse a clean plate or slip of copper. The solution, which was colorless, will soon begin to assume a greenish tint, and the piece of copper will be covered with a coating of a light gray color, which is the silver formerly united to the nitric acid, which has been displaced by the greater affinity or _liking_ of the oxygen and acid for the copper.

2. When the copper is no longer coated, but remains clean and bright when immersed in the fluid, all the silver has been deposited, and the glass now contains a solution of _copper_.

Place a piece of clean iron in the solution, and it will almost instantly be coated with a film of _copper_, and this will continue until the whole of that metal is removed, and its place filled by an equivalent quantity of _iron_, so that nitrate of _iron_ is found in the liquid. The oxygen and nitric acid remain unaltered in quantity or quality during these changes, being merely transferred from one metal to another.

A piece of zinc will displace the iron in like manner, leaving a solution of nitrate of zinc.

Nearly all the colors used in the arts, are produced by metals and their combinations; indeed, one is named _chromium_, from a Greek word signifying color, on account of the beautiful tints obtained from its various combinations with oxygen and the other metals. All the various tints of green, orange, yellow, and red, are obtained from this metal.

Solutions of most of the metallic salts give precipitates with solutions of alkalies and their salts, as well as with many other substances, such as what are usually called prussiate of potash, hydro-sulphuret of ammonia, &c.; and the colors differ according to the metal employed; and so small a quantity is required to produce the color, that the solutions before mixing may be nearly colorless.

EXPERIMENTS.

1. To a solution of sulphate of iron, add a drop or two of a solution of prussiate of potash, and a blue color will be produced.

2. Substitute sulphate of copper for iron, and the color will be a rich brown.

3. Another blue, of quite a different tint, may be produced by letting a few drops of a solution of ammonia fall into one of sulphate of copper, when a precipitate of a light blue falls down, which is dissolved by an additional quantity of the ammonia, and forms a transparent solution of the most splendid rich blue color.

4. Into a solution of sulphate of iron, drop a few drops of a strong infusion of galls, and the color will become a bluish-black--in fact, _ink_. A little _tea_ will answer as well as the infusion of galls. This is the reason why certain stuffs formerly in general use for dressing gowns for gentlemen were so objectionable; for as they were indebted to a salt of iron for their color, buff, as it was called, a drop of tea accidentally spilled, produced all the effect of a drop of ink.

5. Put into a largish test tube, two or three small pieces of granulated zinc, fill it about one third full of water, put in a few grains of iodine, and boil the water, which will at first acquire a dark purple color, gradually fading as the iodine combines with the zinc. Add a little more iodine from time to time, until the zinc is nearly all dissolved. If a few drops of this solution be added to an equally colorless solution of corrosive sublimate (a salt of mercury), a precipitate will take place of a splendid scarlet color, brighter, if possible, than vermilion, which is also a preparation of mercury.

CRYSTALLIZATION OF METALS.

Some of the metals assume certain definite forms in return from the fluid to the solid state. Bismuth shows this property more readily than most others.

EXPERIMENT.

Melt a pound or two of bismuth in an iron ladle over the fire; remove it as soon as the whole is fluid; and when the surface has become solid break a hole in it, and pour out the still fluid metal from the interior; what remains will exhibit beautifully-formed crystals of a cubic shape.

Sulphur may be crystallized in the same manner, but its fumes, when heated, are so very unpleasant, that few would wish to encounter them.

One of the most remarkable facts in chemistry--a science abounding in wonders--is the circumstance that the mere contact of hydrogen, the _lightest_ body known, with the metal platinum, the heaviest, when in a state of minute division, called spongy platinum, produces an intense heat, sufficient to inflame the hydrogen: of course this experiment must be made in the presence of atmospheric air or oxygen. If a small piece of the metal in the state above named be introduced into a mixture of oxygen and hydrogen, it will cause them to explode. A very small quantity of gas should be employed, and placed in a jar lightly covered with a card, or the explosion would be dangerous.

BEAUTIES OF CRYSTALLIZATION.

Dissolve alum in hot water until no more can be dissolved in it; place in it a smooth glass rod and a stick of the same size; next day, the stick will be found covered with crystals, but the glass rod will be free from them: in this case, the crystals cling to the rough surface of the stick, but have no hold upon the smooth surface of the glass rod. But if the rod be roughened with a file at certain intervals, and then placed in the alum and water, the crystals will adhere to the rough surfaces, and leave them smooth bright and clear.

Tie some threads of lamp-cotton irregularly around a copper wire or glass rod; place it in a hot solution of blue vitriol, strong as above, and the threads will be covered with beautiful blue crystals, while the glass rod will be bare.

Bore a hole through a piece of coke, and suspend it by a string from a stick, placed across a hot solution of alum; it will float; but, as it becomes loaded with crystals, it will sink in the solution according to the length of the string. Gas-coke has mostly a smooth, shining, and almost metallic surface, which the crystals will avoid, while they will cling only to the most irregular and porous parts.

If powdered turmeric be added to the hot solution of alum, the crystals will be of a bright yellow; litmus will cause them to be of a bright red; logwood will yield purple; and common writing ink, black; and the more muddy the solution, the finer will be the crystals.

To keep colored alum crystals from breaking or losing their color, place them under a glass shade with a saucer of water; this will preserve the atmosphere moist, and prevent the crystals getting too dry.

If crystals be formed on wire, they will be liable to break off, from the expansion and contraction of the wire by changes of temperature.

TO CRYSTALLIZE CAMPHOR.

Dissolve camphor in spirit of wine, moderately heated, until the spirit will not dissolve any more; pour some of the solution into a cold glass, and the camphor will instantly crystallize in beautiful tree-like forms, such as we see in the show-glasses of camphor in druggists' windows.

CRYSTALLIZED TIN.

Mix half an ounce of nitric acid, six drams of muriatic acid, and two ounces of water; pour the mixture upon a piece of tin plate previously made hot, and after washing it in the mixture it will bear a beautiful crystalline surface, in feathery forms. This is the celebrated _moirée métallique_, and, when varnished, is made into ornamental boxes, &c. The figures will vary according to the degree of heat previously given to the metal.

CRYSTALS IN HARD WATER.

Hold in a wine-glass of hard water a crystal of oxalic acid, and white threads, _i. e._ oxalate of lime, will instantly descend through the liquid suspended from the crystal.

VARIETIES OF CRYSTALS.

Make distinct solutions of common salt, niter, and alum; set them in three saucers in any warm place, and let part of the water dry away or evaporate; then remove them to a warm room. The particles of the salts in each saucer will begin to attract each other, and form crystals, but not all of the same figure: the common salt will yield crystals with six square and equal faces, or sides; the niter six-sided crystals; and the alum, eight-sided crystals; and if these crystals be dissolved over and over again, they will always appear in the same forms.

A LIQUID CHANGED TO A SOLID, AND HEAT FROM CRYSTALLIZATION.

A strong saline solution excluded from the _air_ will frequently crystallize the instant that air is admitted. For this purpose make a solution of Glauber's salt (sulphate of soda) in boiling water (3 lbs. of the salt to 2 lbs. of water); bottle and cork quickly; also tie over the neck a piece of wet bladder. When perfectly cold, or even a few days afterwards, remove the cork, and the salt will immediately crystallize, shooting out the most beautiful crystals, at last becoming nearly solid: at the same time the whole becomes warm, in consequence of the latent heat generated by the change of the liquid to the solid state. If the liquid will not crystallize quickly on removing the cork, tie a crystal of Glauber's salt to a bit of wire, touch the surface of the liquid, and the crystallization will then generally occur.

ANOTHER EXPERIMENT.

Heat some blue vitriol (sulphate of copper) in an iron ladle till all the water contained in the crystals is driven off, and the color changes to a gray. Take the lumps out without breaking them, and lay the dried blue vitriol on a plate; if this be moistened with water, steam is produced; and if a slice of phosphorus is then laid on the sulphate of copper, it ignites, demonstrating again that the condensation of a liquid produces heat. The addition of the water restores the blue color, thus proving that water was necessary to the composition of blue vitriol.

A SOLID CHANGED TO A LIQUID, AND INTENSE COLD FROM THE LIQUEFACTION.

Mix five parts by weight of powdered muriate of ammonia, commonly termed sal ammoniac, five parts of niter in powder, and sixteen parts of water. A temperature of twenty-two degrees below the freezing point of water is produced; and if a phial of water, or any convenient metallic cylinder containing water, be surrounded with a sufficient quantity of the freezing mixture, ice is obtained. The ice clings to the interior of the tube, but may easily be removed by dipping it in tepid water.

This experiment is the reverse of the last, and proves that a sudden reduction of a solid to the liquid condition always affords cold.

An amusing combination of two experiments may be made by putting some fresh-burned lime into one tea-pot and this freezing mixture into another. When water is poured on the one containing lime, it gives out steam from the spout; while the addition of water to the other produces so much cold, that it can hardly be kept in the hand. Thus heat and cold are afforded by the same medium, water.

MAGIC OF HEAT.

Melt a small quantity of the sulphate of potassa and copper in a spoon over a spirit lamp; it will be fused at a heat just below redness, and produce a liquid of a dark green color. Remove the spoon from the flame, when the liquid will become a solid of a brilliant emerald green color, and so remain till its heat sinks nearly to that of boiling water; when suddenly a commotion will take place throughout the mass, beginning from the surface, and each atom, as if animated, will start up and separate itself from the rest, till, in a few moments, the whole will become a heap of powder.

SUBLIMATION BY HEAT.

Provide two small pieces of glass; sprinkle a minute portion of sulphur upon one piece, lay thin slips of wood around it, and place upon it the other piece of glass. Move them slowly over the flame of a lamp or candle, and the sulphur will become sublimed, and form gray nebulous patches, which are very curious microscopic objects. Each cluster consists of thousands of transparent globules, imitating in miniature the nebulæ which we see figured in treatises on astronomy. By observing the largest particles, we shall find them to be flattened on one side. Being very transparent, each of them acts the part of a little lens, and forms in its focus the image of a distant light, which can be perceived even in the smaller globules, until it vanishes from minuteness. If they are examined again after a certain number of hours, the smaller globules will generally be found to have retained their transparency, while the larger ones will have become opaque, in consequence of the sulphur having undergone some internal spontaneous change. But the most remarkable circumstance attending this experiment is, that the globules are found adhering to the upper glass only; the reason of which is, that the upper glass is somewhat cooler than the lower one: by which means we see that the vapor of sulphur is very powerfully repelled by heated glass. The flattened form of the particles is owing to the force with which they endeavor to recede from the lower glass, and their consequent pressure against the surface of the upper one. This experiment is considered by its originator, Mr. H. F. Talbot, F.R.S., England, to be a satisfactory argument in favor of the repulsive power of heat.

HEAT PASSING THROUGH GLASS.

The following experiment is also by Mr. Talbot: Heat a poker bright red hot, and having opened a window, apply the poker quickly very near to the outside of a pane, and the hand to the inside; a strong heat will be felt at the instant, which will cease as soon as the poker is withdrawn, and may be again renewed, and made to cease as quickly as before. Now, it is well known that if a piece of glass be so much warmed as to convey the impression of heat to the hand, it will retain some part of that heat for a minute or more; but in this experiment the heat will vanish in a moment. It will not, therefore, be the heated pane of glass that we shall feel, but heat which has come through the glass, in a free or radiant state.

METALS UNEQUALLY INFLUENCED BY HEAT.

All metals do not conduct heat at the same rate, as may be proved by holding in the flame of a candle at the same time, a piece of silver wire and a piece of platina wire, when the silver wire will become too hot to hold, much sooner than the platina. Or, cut a cone of each wire, tip it with wax, and place it upon a heated plate, (as a fire-shovel,) when the wax will melt at different periods.

SPONTANEOUS COMBUSTION.

Mix a small quantity of chlorate of potassa with spirit of wine in a strong saucer; add a little sulphuric acid, and an orange vapor will arise and burst into flame with a loud crackling sound.

INEQUALITY OF HEAT IN FIRE-IRONS.

Place before a brisk fire a set of polished fire-irons, and beside them a rough unpolished poker, such as is used in a kitchen, instead of a bright poker. The polished irons will remain for a long time without becoming warmer than the temperature of the room, because the heat radiated from the fire is all reflected, or thrown off, by the polished surface of the irons, and none of it is absorbed. The rough poker will, however, become speedily hot, so as not to be used without inconvenience. Hence, the polish of fire-irons is not merely ornamental, but useful.

EXPANSION OF METAL BY HEAT.

Provide an iron rod, and fit it exactly into a metal ring: heat the rod red hot, and it will no longer enter the ring.

Observe an iron gate on a warm day, when it will shut with difficulty; whereas it will shut loosely and easily on a cold day.

EVAPORATION OF A METAL.

Rub a globule of mercury upon a silver spoon, and the two metals will combine with a white appearance; heat the spoon carefully in the flame of a spirit lamp, when the mercury will volatilize and disappear, and the spoon may then be polished until it recovers its usual luster: if, however, the mercury be left for some time on the spoon, the solid texture of the silver will be destroyed throughout, and then the silver can only be recovered by heating it in a ladle. Care must be taken to avoid the fumes of mercury, which are very poisonous.

A FLOATING METAL ON FIRE.

Throw a small piece of that marvelous substance, potassium, into a basin of water, and it will swim upon the surface and burn with a beautiful light, of a red color mixed with violet. When moderately heated in the air, potassium takes fire, and burns with a red light.

ICE MELTED BY AIR.

If two pieces of ice be placed in a warm room, one of them may be made to melt much sooner than the other, by blowing on it with a pair of bellows.

SPLENDID SUBLIMATION.

Put into a flask a small portion of iodine; hold the flask over the flame of a spirit-lamp, and from the state of bluish-black crystals, the iodine, on being heated, will become a violet-colored transparent gas; but, in cooling, will resume its crystalline form.

MAGIC INKS.

Dissolve oxide of cobalt in acetic acid, to which add a little niter: write with this solution; hold the writing to the fire, and it will be of pale rose color, which will disappear on cooling.

Dissolve equal parts of sulphate of copper and muriate of ammonia in water; write with the solution, and it will give a yellow color when heated, which will disappear when cold.

Dissolve nitrate of bismuth in water; write with the solution, and the characters will be invisible when dry, but will become legible on immersion in water.

Dissolve, in water, muriate of cobalt, which is of a bluish-green colour, and the solution will be pink; write with it, and the characters will be scarcely visible: but, if gently heated, they will appear in brilliant green, which will disappear as the paper cools.

Dissolve in water a few grains of prussiate of potash; write with this liquid, which is invisible when dry; wash over with a dilute solution of iron, made by dissolving a nail in a little aqua fortis; a blue and legible writing is immediately apparent.[4]

CHAMELEON LIQUIDS.

Put a small portion of the compound called mineral chameleon into several glasses, pour upon each water at different temperatures, and the contents of each glass will exhibit a different shade of color. A very hot solution will be of a beautiful green color; a cold one, a deep purple.

Make a colorless solution of sulphate of copper; add to it a little ammonia, equally colorless, and the mixture will be of an intense blue color; add to it a little sulphuric acid, and the blue color will disappear; pour in a little solution of caustic ammonia, and the blue color will be restored. Thus may the liquor be changed at pleasure.

THE MAGIC DYES.

Dissolve indigo in diluted sulphuric acid, and add to it an equal quantity of solution of carbonate of potassa. If a piece of white cloth be dipped in the mixture, it will be changed to blue; yellow cloth, in the same mixture, may be changed to green; red to purple; and blue litmus paper to red.

Nearly fill a wine-glass with the juice of beet-root, which is of a deep red color; add a little lime-water, and the mixture will be colorless; dip into it a piece of white cloth, dry it rapidly, and in a few hours the cloth will become red.

WINE CHANGED INTO WATER.

Mix a little solution of subacetate of lead with port wine; filter the mixture through blotting-paper, and a colorless liquid will pass through; to this add a small quantity of dry salt of tartar; distil in a retort, when a spirit will arise, which may be inflamed.

TWO COLORLESS TRANSPARENT LIQUIDS BECOME BLACK AND OPAQUE.

Have in one vessel some dilute hydrosulphate of ammonia, and in another a solution of acetate of lead; they are both colorless and transparent; mix them, and they will become black and opaque.

TWO COLORLESS FLUIDS MAKE A COLORED ONE.

Put into a wine-glass of water a few drops of prussiate of potash, and into a second glass of water a little weak solution of sulphate of iron in water; pour the colorless mixtures together into a tumbler, and they will be immediately changed to a bright deep blue.

Or, mix the solution of prussiate of potash with that of nitrate of bismuth, and a yellow will be the product.

Or, mix the solution of prussiate of potash with that of sulphate of copper, and the mixture will be of a reddish-brown color.

CHANGE OF COLOR BY COLORLESS FLUIDS.

Three different colors may be produced from the same infusion, merely by the addition of three colorless fluids. Slice a little red cabbage, pour boiling water upon it, and when cold decant the clear infusion, which divide into three wine-glasses: to one, add a small quantity of solution of alum in water; to the second, a little solution of potash in water; and to the third, a few drops of muriatic acid. The liquor in the first glass will assume a purple color, the second a bright green, and the third a rich crimson.

TO CHANGE A BLUE LIQUID TO WHITE.

Dissolve a small lump of indigo in sulphuric acid by the aid of moderate heat, and you will obtain an intense blue color; add a drop of this to half a pint of water, so as to dilute the blue; then pour some of it into strong chloride of lime, and the blue will be bleached with almost magical velocity.

VERITABLE "BLACK" TEA.

Make a cup of strong green tea; dissolve a little green copperas in water, which add to the tea, and its color will be black.

RESTORATION OF COLOR BY WATER.

Water being a colorless fluid, ought, one would imagine, when mixed with other substances of no decided color, to produce a colorless compound. Nevertheless, it is to water only that blue vitriol, or sulphate of copper, owes its vivid blueness, as will be plainly evinced by the following simple experiment. Heat a few crystals of the vitriol in a fire-shovel, pulverize them, and the powder will be of a dull and dirty white appearance. Pour a little water upon this, when a slight hissing noise will be heard, and at the same moment the blue color will instantly reappear.

Under the microscope the beauty of this experiment will be increased, for the instant that a drop of water is placed in contact with the vitriol, the powder may be seen to shoot into blue prisms. If a crystal of prussiate of potash be similarly heated, its yellow color will vanish, but reappear on being dropped into water.

[5] TWO LIQUIDS MAKE A SOLID.

Dissolve muriate of lime in water until it will dissolve no more; measure out an equal quantity of oil of vitriol; both will be transparent fluids; but if equal quantities of each be slowly mixed and stirred together, they will become a solid mass, with the evolution of smoke or fumes of muriatic acid.

TWO SOLIDS MAKE A LIQUID.