Chapter II: Part 2

To obtain the sugar from the sugar cane, it is first crushed between powerful rollers, by which all the juice is pressed out, this is immediately clarified by boiling it strongly with a small quantity of slaked lime, or it would speedily ferment, it is then put into evaporating pans, in which it is evaporated till it is ready to crystallize or granulate; from these pans it is ladled out into a cooler, and from thence into wooden boxes where it granulates; the next process is called “curing” this consists of draining the sugar of its molasses, for this purpose hogsheads or large broad barrels are arranged on a sloping floor, and having several holes at their lower part with a piece of plantain leaf put into them; through these holes the molasses runs out and is collected in a vessel for the purpose. The best kinds of sugar are partly purified by a process called “claying;” this consists in putting the sugar into conical earthen jars, with a hole at the point which is turned downwards; the top is piled up with a mass of wet clay, the moisture from which slowly sinks down, carrying with it most of the coloring matter of the sugar; the cone of sugar is afterwards dried, broken up, and each part ground up separately, as they form sugars of different value, the point being the brownest and the base of the cone the whitest.

Sugar is made from the beet root in the same way as from the cane, the roots being rasped up into a pulp by a wheel with a notched edge acting against them. Beet-root sugar crystallizes better than cane sugar; otherwise it is exactly like it, and purifies as well.

ALCOHOL, OR SPIRIT.

Alcohol, commonly called spirits of wine, is procured from any liquid which has undergone the vinous fermentation, such as wine and beer. The spirit used in England is procured from a wash made by pouring boiling water upon ground malt, as for making beer; this, when fermented and distilled, produces a colorless spirit, which, by being again distilled at a gentle heat, called rectifying, produces a very strong spirit; but even this contains some considerable quantity of water, and to get rid of this, for certain chemical purposes, it is necessary to add carbonate of potash, quick lime, or some other ingredient greedy of water, and again distil it. Brandy, rum, and whiskey, are but various forms of spirit colored and flavored with different substances. Brandy is distilled from wine; rum from the molasses, a sort of treacle produced in sugar making; and whiskey from malt. The strongest brandy does not contain more than one half of its bulk of pure spirit.

Alcohol, when pure, is a very limpid, colorless fluid, lighter than water, in the proportion that 792 bears to 1000. It is very volatile, boiling at 172 deg. of Fahrenheit, and highly inflammable, it dissolves resins and volatile oils, and is, therefore, used largely in perfumery. The well known lavender water and eau de Cologne, are solutions of volatile oils of various kinds in pretty strong alcohol, and what are called spirit-varnishes, are most of them solutions of various kinds of resin in strong alcohol, although some of them, as mastic varnish, are made with spirit of turpentine, a volatile oil, in place of alcohol.

STARCH.

Starch exists naturally in various kinds of grain, as wheat and barley, and in the roots and tubers of many plants, as potatoes. The process of extracting the starch, and separating it from the other constituents of the seed or root, consists, essentially, of crushing it, and wishing out the starch with cold water; the liquid resulting from this mode of treatment is of a milky whiteness, and deposits starch by sediment. This liquid is passed through five sieves to separate the husks and skins, and when the starch has settled, and the liquid fermented and become sour, it is drawn off; it is allowed to become sour as the gluten of the grain is more completely separated by so doing. The starch is repeatedly stirred, allowed to settle, and the water drawn off, till it is quite pure; the top of the starch is scraped to separate any slime adhering, and the pure starch dug out with wooden shovels and put in a box lined with linen, in which the moisture drains off; the cakes taken from these boxes are cut up into squares, put upon bricks, and dried by a gentle heat; the squares are then scraped clean and packed in paper for sale, in these packages it breaks up into pieces, so that when they are opened, the starch has that peculiar appearance so familiar, and almost resembling six-sided columns. Arrow-root is the starch obtained from a West Indian plant called _Maranta Arundinacea_.

Cassava and Tapioca are starches from the manioc, and Sago, from the sago palm. Starch, under the microscope, appears in the form of minute globules, and is quite insoluble in cold water, in which it falls to the bottom, leaving the water at the upper part quite clear; but water that is nearly boiling (that is to say at 160 deg. of Fahrenheit’s thermometer, or above), breaks or dissolves the granules, and the starch forms with it a sort of paste, this is the liquid used for stiffening linen and other articles in domestic laundry.

The starch sold in this country is colored blueish by smalt or indigo; but on the continent is used of its natural white color. If starch be baked in an oven at the temperature of about 300 deg. it becomes, to a great extent, soluble in cold water, forming what is called “British gum,” this is largely used for calico printing and other purposes; if boiled in water under great pressure, so that the temperature can be raised to the same degree, it is also changed into an adhesive sort of gum--this is the substance made use of by the government authorities to spread over the backs of postage and receipt stamps to make them adhere. The starch of grain during germination, or growth, becomes converted into sugar; the same effect can be produced by heating starch with diluted sulphuric acid.

SOAP.

Illustration: (‡ SOAP MAKING.)

Illustration: CUTTING SOAP.

Illustration: COPPERS FOR THE MIXING PROCESS.

This very useful article is produced by a combination of tallow or oil with soda or potash; with soda, hard soap is formed; with potash, soft soap. The yellow soap of commerce has also an addition of resin or turpentine, and often palm oil, these give it its yellow color and peculiar smell; pure white soap is made by boiling a solution of soda with tallow or olive oil; ordinary soaps are generally made by mixing a solution of the soda of commerce, (carbonate of soda) with quick lime, this takes away the carbonic acid and makes the soda what is called “caustic;” this solution is drawn off, and kitchen stuff, tallow, turpentine, and sometimes palm oil, are added and boiled together, until all is converted into soap, but a large quantity of water remaining, it is necessary to separate the soap from this, for this purpose salt is added until the water becomes so heavy that the soap rises to the surface, whence it is removed into moulds or frames and allowed to cool, when it is cut into bars for sale.

Illustration: FILLING YELLOW SOAP.

Illustration: MOTTLED SOAP FRAMES.

Soft soap is made in the same way, using potash instead of soda, and, generally, a large quantity of train-oil. Castile soap is pure soda soap, and the blueish or red mottled appearance is produced by stirring in some sulphate of iron (green vitriol); when new it is of a blueish color, but gets red by exposure to the air.

Oils and fats combine with the oxides of several of the metals, and a combination of oxide of lead with olive oil forms a firm solid substance, or plaister, which, with the addition of a little resin, is used in surgery, and when spread upon linen or calico, forms the common adhesive plaister.

Oils and fats all consist of a combination of organic acids, (stearic, oleic, and margaric), with glycerine. When these fats are boiled with soda, potash, or metallic oxides, a combination of the oxide and fatty acid takes place, and this constitutes soap. The glycerine is then set free, and, when purified, forms a sweet, oily, colorless fluid, very similar to syrup, but not so sweet; it has lately been used for several purposes, especially as a remedy for chapped hands; a soap called “glycerine soap,” has lately been used for the same purpose; it is a soap made without separating the glycerine.

Illustration: MACHINE FOR CUTTING SOAP IN BARS.

The above illustration represents an ingenious contrivance for the purpose of cutting soap.

STEARINE.

The Stearine Candles, so much in use of late, are made of what chemists call “stearic acid.” It is extracted from tallow by the following process:--The fat is first melted, then boiled with water and quick lime; the lime forms a solid insoluble soap with the stearic acid of the fat. This, when cold, is dug out of the cistern and separated from the watery parts; it is then melted in a wooden cistern by means of perforated iron pipes, through which steam passes; the steam not only melts it, but condenses and runs to the bottom, thoroughly washing it; it is again allowed to cool, separated when it is mixed, stirred well with sulphuric acid and a large quantity of water, and allowed to settle. This separates all the lime, which settles to the bottom, leaving the stearine floating on the top, from whence, when cold, it is taken and again well washed with steam. The mass, after cooling, is cut into shavings by a machine consisting of a wheel, having knives attached to its edge; the shavings are put into hair-cloth bags and subjected to the most powerful pressure by means of the hydraulic press; each hair-cloth bag having a warm iron plate interposed between it and the next bag. The oily parts of the mass are, by these means, all pressed out; the remainder is again cut up and a second time pressed, leaving the pure stearine, white and crystalline like spermaceti.

SODA.

Illustration: (‡ SODA FURNACE.)

The Soda of commerce is a carbonate of soda, and it is made from sea salt. It is used in large quantities for the general purposes of washing and cleansing, and very extensively in bleaching and soap making. Soda occurs in two forms--soda ash and in crystals; the first is the crude soda before crystallization. To make soda, oil of vitriol (sulphuric acid) is poured, by degrees, on a layer of sea salt, in a sort of funnel connected with a tall chimney; on the addition of the vitriol, copious fumes of the hydrochloric acid are given off; this is the acid formerly called spirit of salt. When the furnace is heated and all the acid driven off, the dried residue is taken out, it is sulphate of soda. It was formerly the custom to allow the hydrochloric acid to pass up a very tall chimney so that it may be dispersed in the air; but such an injurious effect was produced on the surrounding vegetation that this could no longer be allowed; the plan adopted was, to cause the acid to be condensed by filling the chimney with coke, and causing water to trickle through it; the acid vapours, coming into contact with this porous wet surface, is condensed into a liquid, which runs down into a cistern placed to receive it. The sulphate of soda, when taken from the furnace and cooled, is next ground in a mill with rather more than its weight of chalk, and about half its weight of coal. This mixture is placed in a furnace and raised to a sufficient heat to partly fuse it, during which time it is stirred about; the black mass which results is called by the workmen “black ball.” It is taken out and put into a cistern; water is then poured over it, and after stirring, it is drained off and evaporated to a dry mass; this is impure soda. It is mixed with coal-dust, again burnt, again washed and evaporated, by this second process the soda ash is produced, which, being dissolved, filtered and evaporated, produces large crystals of soda. The large quantity of hydrochloric acid produced in the first part of the process, is used in the of making chloric of lime. A few years back, soda was got from the ashes of the plant called “salsola soda,” and sold in the form of an impure carbonate called “barilla.”

WINES.

Illustration: WINE MAKING.

Wine is made from the juice of grapes. When the grapes are ripe, they are gathered and at once put into a press, by which all the juice is squeezed out, and the skins, stalks, and seeds left in the press. This juice, which is called “must,” is allowed to ferment, which it does of its own accord, in the countries where grapes most abound, and at the season of the year when they are gathered, without the addition of yeast or other ferment; in a few days nearly all the sugary matter contained in the “must” becomes converted into spirit, and it has now the pungent taste of wine; (if the wine is allowed to ferment too long, it is very apt to become sour), the wine is now put into casks and kept for a time, during which a slow fermentation goes on, and that substance, which is called “tartar,” is deposited in the form of a thick crust of an acidulus taste and brown color; when purified till it is quite white, it forms the cream of tartar of the druggists’ shop. The color of wine depends upon the color of the grapes used, whether white or black.

Wine, at a general average, contains about 20 per cent. of spirit or alcohol; when port wine is put into bottles, a slow fermentation continues to go on, and a crust of tartar is deposited similar to that described above, and it is the separation of this tartar which causes port wine to improve by age.

What are called British wines, are liquids mostly made by fermenting the juice of the fruits whose name they bear, as currant wine, gooseberry wine, &c.; but as the climate of this country is not favorable to the growth of grapes, or the spontaneous fermentation of their juice, the grape wine of England is very inferior to the foreign. The juice of any fruit required to make wine of, has to be fermented artificially; this is generally done by making it slightly warm, and floating on the surface a piece of bread soaked with yeast; the wines thus produced are very apt to become sour, and it is generally necessary to add brandy to preserve them. Many of the British wines sold in London are made of an impure weak spirit called “faints,” sweetened and flavored with various substances, as ginger, orange-peel, &c. and sell for ginger or orange wine.

VINEGAR.

Illustration: (‡ VINEGAR FERMENTATION YARD.)

Vinegar is produced by fermenting and exposing to the air any liquor which contains sugar, such as wine, infusion of malt, cyder, &c.; by the addition of yeast, this sets up a fermentation, by means of which the sugar in any of these liquors is converted, first into spirit, and afterwards into vinegar; this contains a certain quantity of acetic acid, which makes the vinegar sour. In warm countries, vinegar is made by simply exposing the poorer kinds of wine to the sun’s rays, when they ferment and become sour. In England, all the vinegar produced is made by fermenting wort made of malt, this is fermented for three or four days, and is then put into casks, with the bunghole left open for several weeks, or until it is thoroughly sour. In ordinary vinegar, there is about five or six parts only in the hundred of real acetic acid, but this acid, when pure, is so strong as to blister the skin when dropped on it; it is often extracted from vinegar for chemical purposes, and to smell too; for when scented, it constitutes aromatic vinegar. Vinegar, besides acid and water, contains a little unchanged spirit, much coloring matter, and some mucilage.

Illustration: BOILER OR COPPER.

Illustration: COOLING APPARATUS.

Vinegar is chiefly used as a condiment, and for making pickles, and has considerable powers of preserving vegetable or animal substances; if common vinegar be distilled, a weak colorless acid comes over, commonly known as white or distilled vinegar. It is a common thing to sprinkle a sick room with vinegar, under the impression that it has disinfecting properties, but this is an error; although the odour is very refreshing. Vinegar has, of late, been made by means of the vinegar plant, which is a fungus, causing a species of slow fermentation, and converting the sugar or treacle used into acetic acid.

Illustration: FILLING CASKS.

The heading of this section gives a good idea of the large scale on which vinegar is made; being an accurate representation of the extensive works of Messrs. Beaufoy & Co. at Lambeth.

COAL GAS.

Illustration: (‡ COAL GAS DISTILLERY.)

Illustration: SECTION OF RETORT.

Illustration: FIG. 1. (‡ RETORT FURNACE.)

Illustration: FIG. 2. (‡ RECEIVER TUBE.)

Illustration: FIG. 3. (‡ CONDENSER.)

Illustration: FIG. 4. (‡ RESERVOIR.)

Illustration: FIG. 5. (‡ GASOMETER.)

Gas, for lighting, is made from coal, by subjecting it to heat in iron tubes and collecting and purifying the gas which is produced; the following is a summary of the process:--The vessels in which the coal is put are called “retorts,” they are six or seven feet long, one-and-a-half broad, and one high, generally fitted up six to a furnace, in such a way that the flame may entirely surround them (see fig. 1); from each retort an iron tube passes, and these all dip into a large horizontal tube, reaching nearly to its bottom (fig. 2), this is the receiver for all the gas from the retorts; it is connected with a pit for tar and ammonical liquor, which copiously condenses from the hot newly-formed gas.

The object of causing the tubes to dip nearly to the bottom of the receiver is, that the fluid in it may close the end of each tube, and so prevent the gas returning when any of the retorts are opened for a fresh supply of coal; from the receiver, the gas passes by tubes bent up and down inside of a great cistern of water (fig. 3) kept cold by a constant change of its contents; this is the condenser, it causes the separation of all the tar and ammonia that remain; but the gas is still contaminated with sulphur, and this is got rid of by causing it to pass into a broad iron cylinder perforated with holes and dipping into a reservoir of lime and water mixed together and stirred about with a machine contrived for the purpose; the gas enters this lime mixture in hundreds of bubbles through the holes, and the sulphur the gas contains is attracted by the lime with which it unites.

The gas now rises to the top of this reservoir, which is, of course, air tight, and from thence passes for use to the gasometer; this is the store-house where the gas is kept to supply the service pipes _b_, _c_, under the streets. The gasometer is made of plates of iron rivetted together. The lower part of this cylinder (see figs. 4 and 5) is received into a circular deep channel cut in the ground (_b b_, fig. 5) and filled with water, so that the gasometer _d_, which is suspended and balanced by means of the chains and weights _e e_, may be raised or depressed at pleasure.

When the gasometer is quite down, the inside of its top, _a_, rests on the ground; when the gas enters, it raises it up till the lower edge is but a few inches below the water, and is prevented from rising higher by frames which support it; when some of the weights, _d d_, are removed, the huge cylinder, _a_, slowly sinks down and forces the gas through the tubes, _c c_, to be burnt by thousands of consumers. About four cubic feet of gas is produced from every pound of coal used; the gas is lighter than air in the proportion of 650 to 1000, and it is owing to this lightness that balloons ascend when filled with it, not from any peculiar power it has of ascending, but because the air, being heavier, presses downwards and forces it up. When gas is mixed with air it becomes very explosive, and when any escape is suspected in a room, the windows of the room should be opened _at the top_, and the door also opened, before any light is introduced; a few minutes will then suffice to ensure safety.

One ton of good coal produces--

1 Chaldron of Coke, weighing 1494 lbs.
12 Gallons of Tar ” 135 ”
12 Gallons Ammoniacal liquor 100 ”
9500 Cubic feet of Gas, weighing 291 ”
Loss (chiefly water) ” 220 ”
--------
2240 lbs.

A cubic foot of gas weighs 514 and a-half grains.

TAR.

Illustration: (‡ TAR FACTORY.)

Tar is one of the results left in the distillation both of wood and coal; in places where wood is plentiful and tar in request, it is produced by burning the wood for that purpose; and in some of the pits in which charcoal is produced, an arrangement is made to collect the tar also. Coal-tar and wood-tar are different in some respects, and are both distilled to procure the napthas which bear the respective names. From wood-tar, creasöte is also extracted, and it is this substance which gives the peculiar tarry flavor to provisions cured or preserved by being smoked over wood fires, such as ham, bacon, or herrings. Tar is used as a sort of paint for covering wood-work and cordage, when much exposed to wet, which it resists better than anything else at the same price; but the tar chiefly used for these purposes, is that produced by burning fir or deal wood and condensing the tar in a pit below the stack of wood, it is called Stockholm tar, as it comes chiefly from that place.

ACETIC ACID, OR WOOD VINEGAR.

Acetic acid forms a considerable article of commerce. It is not only used in medicine and the culinary art, but is extensively employed in forming acetate of iron for dyeing and calico printing. To prepare it, large iron cylinders, about eight feet long and three in diameter, are embedded in brickwork in a row, and in such a manner that furnaces placed below may heat them red-hot; these cylinders have a tube leading from each into a main tube, where the liquid products from each cylinder are received for condensation; the other end of the cylinder has a plate of iron fitting closely to it. The cylinders are filled with logs of wood, either oak, beech, birch, or ash, the door is closely fastened and the joints smeared with clay; the fires are now lighted and kept up all day, till the cylinders are red-hot; at night they are allowed to cool. About seven or eight hundred weight of wood is put into each cylinder. In the morning, the charcoal, into which the wood is now converted, is withdrawn, and a fresh charge supplied; from this charge of wood about thirty or forty gallons of liquid is condensed in the main tube from each cylinder, the remainder being charcoal and gases which pass off; the liquid is acid, brown, and very offensive, and contains acetic acid, tar, and several other ingredients, among which may be named creasote; it is from this source all the creasote, so famous for the cure of toothache, is obtained. The next process is to purify this liquid; it is first distilled, and this separates much tar, it is then mixed with lime, evaporated to dryness, and heated to expel the remaining tar and other impurities; it is next mixed with sulphate of soda and water and the whole stirred together, the soda, now in unison with the acetic acid, is washed out from the lime and strained quite clear; it is afterwards evaporated till it crystallizes, and vitriol (sulphuric acid) then added; finally, the acetic acid is distilled over, and the acid left in unison with the soda, forming sulphate of soda, to be used in a similar process for the next batch of acid; the acetic acid is now quite colorless, transparent, and very sour, possessing a fragrant and agreeable smell. This acid is not pure acetic acid, but contains a considerable quantity of water. The acetic acid of commerce, mixed with seven times its bulk of water, forms an acid of about the strength of malt vinegar, perfectly wholesome, and, to many, more agreeable as a condiment.

Pure acetic acid may be made by mixing dry acetate of potash with oil of vitriol in a retort, and distilling the acetic acid into a very cold receiver; this, when flavored with various volatile oils, forms the aromatic vinegar sold by druggists. It is a very strong acid, and if applied to the skin will quickly blister it.

VARNISHES.

Varnishes are solutions of various resinous substances that will dry with a bright surface on exposure to the air. They are used to protect different substances from the action of the atmosphere, and to give them an elegant bright surface; woods and painted work are the chief things varnished; metals are coated with a kind of varnish called “lacquer,” this is to prevent the bright surface of the metal from being dulled by the air or damp, and to give an artificial appearance to some metals; tin, for instance, if lacquered with yellow lacquer, acquires somewhat the appearance of brass. Mastic varnish is the varnish generally used for paper and pictures; it is made by dissolving gum mastic in oil of turpentine. Copal varnish is that most generally used for carriages and wood, it is made by adding boiled linseed oil to melted copal, and afterwards thinning it with oil of turpentine. A common varnish, fit for many purposes, may be made by adding common resin to oil of turpentine, and warming it till dissolved. Lacquers are made by dissolving shellac and various other gums in strong spirits of wine, and in some cases coloring it, either yellow, by means of gamboge, or red, by dragon’s blood (a kind of resin). French polish is nearly the same as lacquer, but the mode of applying it is different; the grain of the wood is first filled up by means of drying oil and chalk rubbed in, when this becomes thoroughly dry, a rubber of flannel is covered by a piece or two of clean old linen, and some of the polish put on it, just enough to moisten it, and then a little oil, this is slowly rubbed round and round, the varnish adhering to the wood, and the oil preventing the rubber sticking to it, and at the same time, polishing the surface of the varnish as it dries. This process requires a good deal of art to produce a perfect surface. Old work, before being varnished with any varnish that contains oil (as copal varnish), should be thoroughly freed from grease or greasy matter, or the varnish will never dry. Good varnish should dry in twenty-four hours so that dust will not adhere to it.

OILS.

Illustration: PRESSING LINSEED FOR OIL.

Oils, whether animal or vegetable, have pretty much the same properties. The vegetable oils are got by crushing and pressing certain seeds, as linseed; the animal oils are obtained chiefly from the whale and seal tribe, or from fish, as the cod and sturgeon. They are viscid and of a pale yellow color, lighter than water, and therefore float upon it, and are very combustible. Oils are used for a multiplicity of purposes: for burning in lamps, for making paints and varnishes, preventing the friction of machinery, in making soap, and numerous other processes. Oils are generally divided into fixed and volatile oils; as an example of the first, linseed oil may be selected; of the last, oil of lavender.

Some of the fixed oils are called drying oils, and it is this kind that are used for varnish making; as linseed oil possesses the properties of this class very perfectly, it may serve as a description of all. Linseed oil has the power of drying when spread out in a thin layer, becoming of a resinous consistence like varnish, and upon this quality depends the drying powers of paint, for the other non-drying oils, as olive oil, may be exposed to the air for months without drying at all; the drying powers of linseed oil are greatly increased by boiling it with litharge (oxide of lead). This forms the drying or boiled oil used in painting, and is employed in making varnishes, printers’ ink, and for other purposes. Oiled silk is formed by brushing silk over with this oil and exposing it to the air till it is dry; this oiled silk is the same that is used for sponge-bags and bathing-caps. Of the non-drying oils, the chief are those used for burning in lamps, as sperm oil. Salad oil is expressed from the olive, and is called olive oil. Of the volatile oils, the most useful is oil of turpentine, commonly called spirit of turpentine; it is got by distilling common turpentine (the concrete juice of trees of the fir and pine tribe), it has a strong odour, is very inflammable, and is volatile, that is to say, if spread out, will evaporate, leaving nothing behind; this oil is capable of mixing with drying oils, and it not only increases their drying powers, but, by thinning them, makes them more applicable to many purposes. Oil of turpentine dissolves resin and many resinous substances, and forms useful varnishes with them. Mastic varnish is mastic dissolved in oil of turpentine; it is the varnish always used for varnishing pictures. Many of the volatile oils are used as perfumes, and the odour of plants and flowers depends upon the volatile oil which evaporates from them, as lavender, cloves, and others. Peppermint water, dill water, and cinnamon water are produced by distilling water mixed with the substances, and is simply water containing a small quantity of the volatile oil of these substances in solution; but eau-de-Cologne and lavender water, although called “waters,” are mixtures of volatile oils and spirit of wine, and contain no more water than is comprehended in the spirit used.

INKS.

Inks are fluids of various kinds suitable for writing with pens. The chief inks in use are black, blue, and red writing inks, and indelible or marking ink, intended for marking linen which has to be washed. Indian ink is not used as an ink, properly so called. All the black inks in use are composed of green vitriol (sulphate of iron), in union with some astringent vegetable matter, the best is the gall-nut, although, for cheapness, logwood and oak bark have each been used. An excellent black ink may be made by putting into a gallon stone bottle twelve ounces of bruised galls, six ounces of green vitriol, and six of common gum, and filling up the bottle with rain water, this should be kept three or four weeks before using, shaking the bottle from time to time. Blue ink has lately been much used, it is made by dissolving newly-formed Prussian blue in a solution of oxalic acid. To make it, dissolve some yellow prussiate of potash in water in one vessel, and some sulphate of iron in another, adding a few drops of nitric acid to the sulphate of iron; now mix the two liquids, and a magnificent blue color will appear in the form of a light sediment; this is to be put upon a paper filter, and well washed by pouring over it warm water and allowing it to run through; a warm solution of oxalic acid should now be mixed with it, and the Prussian blue will dissolve into a bright blue ink.

Red ink is made by boiling chips or raspings of Brazil wood in vinegar, and adding a little alum and gum; it keeps well, and is of a good color. A red ink of more beautiful appearance, but not so durable, may be made by dissolving a few grains of carmine in two or three tea-spoonfuls of spirit of hartshorn.

Marking ink is made by dissolving nitrate of silver in water, and then adding some solution of ammonia, a little gum water, and some Indian ink to color it. Printers’ ink is made by grinding drying oil with lamp-black.

CHARCOAL.

Illustration: (‡ CHARCOAL OVENS.)

Charcoal is made by burning wood in such a manner that but little air shall be admitted during the operation, that is to say, only sufficient to keep up the combustion of the more easily destroyed parts of the wood, leaving a black residue called charcoal. The best charcoal is made when the wood is quite excluded from the air, as in making acetic acid, but where large quantities of charcoal are used for common fuel, as in France, of course this process is too expensive. The usual way is to pile up billets of wood and cover the whole with turf; when fired, the wood consumes gradually and the charcoal is left behind. Charcoal is light and porous, and of a shining black color; it weighs about one quarter as much as the wood used, and burns without flame or smoke, giving out a strong heat. When charcoal burns, it combines with part of the air, and is converted into a gas called carbonic acid, which, although invisible, is much heavier than air, and is a deadly poison; it is therefore necessary, where charcoal is burning, to always have some opening at the _bottom_ of the room. Many fatal accidents have arisen from people sleeping in a small room with a pot of burning charcoal, and no outlet for the poisonous vapour but the chimney, up which it will not pass on account of its weight. Charcoal enters into the composition of gunpowder, and is used for several other purposes. It is an excellent sweetener of foul water, and a few pieces should always be kept in the top of the filter when the water has any bad odour, or in the cistern or butt, where a filter is not used; powdered charcoal has also the power of taking away the color of many liquids, as well as the bad smell; vinegar, if warmed with powdered charcoal, and then strained, will be almost colorless. Water butts are sometimes burnt or charred inside, that the water may be the better preserved in them.

Chemically considered, charcoal consists of carbon with a certain amount of earthy matter (the ashes or earthy part of the wood from which it was made), but these ashes may be easily removed by maceration in an acid; the charcoal then remains unaltered in appearance and consists of carbon, but its structure is exceedingly porous.

CEMENTS.

In various processes, cements of different descriptions are required for a variety of purposes. The common cement used in building, which is called mortar, is made of sand and quicklime mixed with water. Roman and Portland cements consist of certain kinds of clay burnt and ground. Plaster of Paris forms a useful cement, it is to be mixed with water to the consistence of cream, and it hardens in a few minutes. Glue is an invaluable cement for wood and many other purposes, it also joins any kind of broken glass or china that will not have to be subjected to much wetting. Shellac dissolved in spirit is a useful cement; and isinglass, dissolved in weak spirit, and having some gum ammonicum added to it, forms the “diamond cement” for uniting china. China and glass which require to be much wetted, are best united by being made very hot and having the broken edges rubbed with a piece of shellac, this melts on them, and forms, while hot, a sort of cement; if they be immediately applied and pressed firmly and accurately together, and then permitted slowly to cool, they will unite so as to be almost as strong as before breaking.

COKE.

Illustration: (‡ COKE OVENS.)

Coke is produced by the partial burning of coal, in the same way that charcoal is from wood. The great source of coke is the gas manufactory, where it is sold in large quantities, being the result left in the retorts after the gas has all been driven off; but the consumption of coke by locomotive engines, &c., where coal would not be admissible on account of the smoke produced, has become so great that it is necessary to burn coals for its production; this is done by a range of ovens fitted up for that purpose, having iron doors which can be closed to any extent required so as to regulate the draught of air. Dr. Ure gives the following in his account of the coke ovens belonging to the London and North Western Railway Company:--“An excellent range of furnaces for making a superior article of coke for the service of the locomotive engines of the London and Birmingham Railway Company, has been erected at the Camden Town Station, consisting of eighteen ovens, in two lines, the whole discharging their products of combustion into a horizontal flue which terminates in a chimney-stalk one hundred and fifteen feet high. Each alternate oven is charged, between eight and ten o’clock every morning, with three-and-a-hall tons of good coals, a wisp of straw is thrown in on the top of the heap, which takes fire by the radiation from the dome, which is in a state of dull ignition from the preceding operation, and inflames the smoke then rising from the surface by the reaction of the hot sides and bottom upon the body of the fuel, in this way the smoke is consumed at the very commencement of the process, when it would otherwise be most abundant. The coke being perfectly freed from all fuliginous and volatile matters by a calcination of upwards of forty hours, is cooled down to moderate ignition by sliding in the dampers and sliding up the doors, which had been partially closed during the latter part of the process. It is now observed to form prismatic concretions, somewhat like a columnar mass of basalt. These are loosened by means of iron bars, lifted out upon shovels furnished with long iron shanks, which are poised upon swung chains with hooked ends, and the lumps are thrown upon the pavement, to be extinguished by sprinkling water upon them from the rose of a watering can, or they may be transferred into a large chest of sheet iron set on wheels, and then covered up. Good coals, thus treated, yield eighty per cent. of an excellent, compact, glistening coke, weighing fourteen cwt. per chaldron.”

Illustration: (‡ OVEN TOOLS.)

Coke burns without smoke, and not so rapidly by far as charcoal, it is, moreover, considerably cheaper than that article is.

GUNPOWDER.

Gunpowder is a mixture of nitre, sulphur, and charcoal, and the more completely they are mixed, the more finely ground, and the purer they are, the more perfect will be the gunpowder. The proportions used of these ingredients differ slightly in different powder mills; but the average is about seventy-four parts nitre, ten sulphur, and fourteen charcoal, by weight; the sulphur and nitre can easily be completely purified, but the charcoal differs very much in almost every specimen, and charcoal that has been burnt long ago and exposed to the air and moisture is almost unfit for the purpose, that charcoal which has the least ash when burnt is found to be the best, and the charcoal which has been made in iron cylinders, is better than that made in the usual way, when each of the ingredients are separately powdered and sifted through a kind of sieve of silk called a bolting machine (such as is used in dressing flour), they are mixed in the proper proportions and taken to the mill, where they are moistened with water and ground to a smooth paste, this is pressed hard and then broken up into pieces which are put into a copper sieve, the bottom of which is perforated with small hole; a flat wooden ball is put into each sieve with the pieces of damp powder, and the sieves are all put into a circular motion by machinery, this causes the wooden ball to turn round in the sieve and so rub the damp powder through the little holes; it is collected below in small grains or “corns,” this process is called “corning,” this is now dried, and then put into a “reel” (a sort of barrel which turns round) and the grains, by rubbing against each other, become smoothed on the surface; the dust is now removed by a sieve, too fine to let the grains through; the powder is now fit for use.

Gunpowder was first known in England about five hundred years ago. It is not only used to discharge firearms, but in the more peaceful occupations of quarrying stone, mining, and to get rid of rocks both below and above water; these processes are called “blasting.”

GUN COTTON.

To prepare gun cotton, make a mixture of three parts sulphuric acid and one part nitric acid; when this has cooled (for it becomes hot on mixing), put into it some cotton wool, and let it be stirred about with a glass rod, then taken out, and all the superfluous acid strained from it; it is then to be covered up for an hour or so. It should now be thoroughly washed in cold water, so that all the acid be removed; to ensure this completely, let it be afterwards washed in a very weak solution of potash, and then dried by a very gentle heat, produced by either steam or hot water; when dry, soak it in a solution of nitre and dry it again. It is now so explosive that great care is required in its management, being about three times as explosive as gunpowder.

PHOSPHORUS.

This substance, since the general use of lucifer-matches, has become an important article of manufacture; whereas, but a few years ago, it was a mere chemical curiosity. It is prepared by mixing bone ashes with sulphuric acid, straining off the liquid part, and evaporating it to a syrupy consistence; with this, about a quarter of its weight of powdered charcoal is mixed, and the whole stirred and evaporated to a dry powder; this is put into earthenware retorts, which are connected by copper tubes to receivers filled with water; the retorts are raised to a white heat and maintained at this high temperature as long as any phosphorous passes into the receivers, the water in which is kept warm, so that the phosphorous melts and runs to the bottom, from whence it is taken and strained through chamois leather bags, under warm water, and then cast in glass tubes into sticks. Phosphorous is of a whitish color, like wax, is easily melted, readily takes fire even by slight friction, and, in the air, gives off fumes which in the dark appear luminous. It is chiefly used in the manufacture of lucifer matches, and, mixed with flour, butter, or sugar, is used to poison rats, mice, and other vermin, under the name of “phosphorous paste.” Phosphorous is poison, and most dangerous stuff to handle, minute particles often getting under the nails and causing painful sores.

WHITE LEAD.

Illustration: WHITE LEAD BED.

Illustration: FIG. 1. (‡ LEAD GRATE.)

White Lead is used in very large quantities by painters, not only as white paint, but to mix with and qualify every shade of color, and to give body to them. It is prepared by different processes, and several patents have been taken out for improvements in its manufacture; but the most usual, and, perhaps, the best process, is as follows:--A layer of spent tan (from the tanner’s pits) is spread out three or four feet thick, and in it a number of earthen pots are arranged in rows, each partly filled with a mixture of vinegar, water, and treacle, or some other acid fermenting liquid, each of these pots is covered with a piece of lead made in the form of a grating (fig. 1), and over all these a flooring of boards, and then again a layer of tan, pots covered with lead, and boards, two or three times repeated; this is called a white lead bed, and is left for several weeks; the tan ferments and gets warm, causing the acid vapours to rise and corrode the lead, at the same time giving off carbonic acid. At the end of about three months the leaden covers are found to have become completely changed into a white shining substance (carbonate and oxide of lead), this is washed from impurities and ground in a mill, under water, to a fine powder. It is the white lead of commerce; but what is familiarly called white lead, is this substance ground up with linseed oil into a thick paste so as to be ready for the use of painters.

White lead is a very poisonous substance, and produces the disease called painters’ colic, when taken into the system in minute quantities and for a long time, so that all who have much to do with this dangerous substance, as house-painters and artists, should be extremely careful that their hands are well washed frequently, and especially before going to meals. Cisterns of lead, used for containing water, very soon become coated inside with a thin film of sulphate of lead, this prevents the water from acting further on the lead, and the water from such cisterns is never found to be poisonous; but, if distilled water were used, it would act rapidly on the lead, corroding it, and causing a deposit in the water of white lead, which would render such water dangerous in the extreme.

PRUSSIAN BLUE.

This beautiful blue color is made by mixing solutions of sulphate of iron (green vitriol) and prussiate of potash together, when the Prussian blue falls in the form of a precipitate, or moist powder, of a pale greenish color, but which, by exposure to the air and the addition of a little nitric acid, becomes intensely blue; but the Prussian blue of commerce is never pure, for the solution of prussiate of potash is used as it comes from the factory, before being crystallized, and contains carbonate of potash, to get rid of which, alum is added, and the result is, the formation of a considerable amount of alumina, which is a white earth produced from the alum, and which falls down in the precipitate mixed with the Prussian blue, which is thereby increased in bulk and but little injured in color; when a larger quantity of this alumina is purposely produced, the result is a blue of a rather less intense color, called “Antwerp blue.” The chemical name for pure Prussian blue is percyanide of iron. Chinese blue is this substance in its purest state.

PRUSSIATE OF POTASH.

Prussiate of potash is the commercial name given to what chemists call “ferrocyanide of potassium,” it is used largely for the production of Prussian blue, and also in the art of electro-plating, which, of late, has greatly increased the demand for its manufacture, and many patents have been taken out for various modifications in the form of production, the result, however, is the same, and it occurs in commerce in magnificent crystals of a square form, with bevelled edges, and of a yellow color; there is, however, another kind called the “red prussiate,” which is much used in the process of calico printing. Prussiate of potash is made by heating together carbonate of potash, scraps of iron, and any kind of animal refuse, as blood, horns and hoofs, clippings of skin or old woollen rags; these are stirred together, and the heat raised, till they form a sort of paste of a black color, which, when cold, is thrown into water and all the soluble parts washed out; this fluid is filtered till quite clear, evaporated, and set aside that crystals may form; these are dissolved and again crystallized. The red prussiate is made by passing chlorine over the yellow prussiate in powder dissolving and crystallizing.

The most deadly of all poisons, prussic or hydrocyanic acid, is obtained from the ferrocyanide of potassium, or prussiate of potash, by adding diluted sulphuric acid and distilling the vapour into an ice-cold receiver. This experiment should never be made by any but those well conversant with such matters.

SULPHATE OF IRON.

Also called “Green Vitriol” and “Green Copperas,” is a combination of sulphuric acid and oxide of iron, and may be made by putting iron filings or pieces of iron into a mixture of sulphuric acid and water, and when all action has ceased evaporating the liquid, and setting it by till crystals form--these are of a pale green color. The sulphate of iron of commerce is formed by exposing the iron pyrites found in the coal districts to the air till it falls to powder; water is then poured over this substance, and the fluid collected and evaporated. Sulphate of iron is used chiefly to form the black dye so much in demand to dye cloth, and also in making writing ink.

SULPHATE OF COPPER.

This substance is also known by the names, “Blue Vitriol” and “Blue Stone.” It is a combination of sulphuric acid with oxide of copper, and may be made by uniting those substances; but what is used on a large scale for commercial purposes is obtained from the waters which flow into copper mines where “copper pyrites” abound; this water is evaporated, and the sulphate of copper crystallizes. Sulphate of copper has of late been in great demand for the electro-deposition of copper.

CHLORIDE OF LIME.

Chloride of lime or “bleaching-powder” is made for the purposes of bleaching calicoes, linens, &c., and also for purifying foul air, which it does by giving out chlorine, a gas capable of uniting with and changing the injurious properties of foul air (which generally contains some combination of sulphur and hydrogen). Chloride of lime is made on the large scale by mixing hydrochloric acid with black oxide of manganese. This mixture gives off chlorine. This is made to pass over a layer of slaked lime, which absorbs it greedily, and becomes converted into the bleaching powder. The hydrochloric acid used is a product resulting from the manufacture of soda, and was formerly wasted; it is now used in large quantities for the process above described. “Burnett’s Disinfecting Fluid” is a solution of chloride of zinc. It is made by dissolving scraps of zinc in hydrochloric acid; hydrogen gas is given off, with effervescence, and the liquid remaining is the solution of chloride of zinc, which acts like chloride of lime, by giving off chlorine; for the chloride is slowly decomposed by the air, the oxygen of which takes the place of the chlorine, uniting with the zinc to form oxide of zinc, while the chlorine is set free.

SULPHURIC ACID.

This was formerly called “Oil of Vitriol,” because it has an oily consistence, and was originally distilled from green vitriol. Sulphuric acid is one of the most useful chemical agents known; scarcely a process in chemical manufacture can be performed without its assistance. Sulphuric acid is colorless, and very heavy, being nearly double that of water (the proportion is 1·842, while water is 1,000); it is powerfully acid, even when largely diluted with water, and during this mixture with water gives out great heat, a mixture of equal parts will become hotter than boiling water; if it be mixed, however, with snow instead of water, it becomes extremely cold (below zero).