strong solution of carbonate of potassa or oil of tartar, 1 oz.; let the whole stand until cold, then pour off the yellow liquor from the top, drain, agitate the residuum with boiling water in separate quantities, 1 quart; decant, drain, and dry. Product, an oz. The Society of Arts voted their gold medal to the author of this formula. 2. Add a little solution of acetate of lead to a decoction of madder, to throw down the brown colouring matter, filter, add a solution of tin or alum, precipitate with a solution of carbonate of soda or of potassa; proceed as before. 3. Ground madder, 2 lbs. ; water, 1 gall.; macerate with agitation for 10 minutes, strain off the water, and press the remainder quite dry; repeat the process a second and third time; then add to the mixed liquors, alum, lb. dissolved in water, 3 quarts; and heat in a water bath for 3 or 4 hours, adding water as it evaporates; next filter, first through flannel, and when sufficiently cold, through paper; then add a solution of carbonate of potassa as long as a precipitate falls, which must be washed until the water comes off colourless, and, lastly dried. If the alkali be added in 3 successive doses, 3 different lakes will be obtained, successively diminishing in beauty.

ORANGE LAKE.-Spanish annatto, 4 oz.; pearlash, lb.; water, 1 gall.; boil for half an hour, strain, precipitate with alum, 1 lb., dissolve in water, 1 gall., observing not to add the latter solution when it ceases to produce an effervescence or a precipitate; strain, and dry the sediment in small squares, lozenges, or drops. The addition of some solution of tin turns this lake on the lemon yellow; acids redden it.

RED LAKE.-Pearlash, 1 lb.; clean shreds of scarlet cloth, 3 lbs.; water 5 galls.; toil till the cloth is decoloured, filter the decoction, and precipitate with a solution of alum, as before. See Madder Lake.

YELLOW LAKE.-1. Boil French berries, quercitron bark or turmeric, 1 lb., and salt of tartar, 1 oz., in water, 1 gall., until reduced to one-half; then strain the decoction, and precipitate with a solution

of alum. 2. Boil 1 lb. of the dye-stuff with alum, lb.; water, 1 gall.; as before, and precipitate the decoction with a solution of carbonate of potash. See Orange Lake.

White Pigments.-ALUM WHITE. Powdered Roman a'um, 2 lbs. ; honey, 1 lb.; mix dry, powder, calcine in a shallow dish to whiteness, cool, wash, and dry. A beautiful and permanent white, both in oil and water.

DERBYSHIRE WHITE.-From chalk or heavy spar, by grinding and elutriation. MINERAL WHITE.-Precipitated car bonate of lead.

PEARL WHITE.-Fard's Spanish white. Trisnitrate of bismuth.

PERMANENT WHITE.-Artificial sulphate of baryta, prepared by precipitating chloride of barium with dilute sulphuric acid, or a solution of glauber salts. A good fast white unchanged by sulphurous fumes. Used to mark jars and bot. tles for containing acids or alkalies, as it is affected by very few substances; also to adulterate white-lead.

SPANISH WHITE. The softest and purest white chalk, elutriated, made into balls, and well dried. Used as a cheap white paint.

WHITE-LEAD.-Made by suspending rolls of thin sheet lead over malt vinegar, or pyroligneous acid, in close vessels, the evaporation from the acid being kept up by the vessels being placed in a heap of dung, or a steam bath. Commercial carbonate of lead, however prepared, is not the pure carbonate of lead, but always contains a certain proportion of hydrate. It is generally largely adulterated with native sulphate of baryta or heavy spar, and sometimes with chalk. The former may be detected by its insolubility in dilute sulphuric acid, or a solution of oxalic acid or oxalate of ammonia, after having been treated with sulphuretted hydrogen, or a hydrosulphuret, to throw down the lead. Pure carbonate of lead does not lose weight at a temperature of

212° Fahr.; 68 grains are entirely dissolved in 150 minims of acetic acid diluted with 1 fl. oz. of distilled water; and the solution is not entirely precipitated by a solution of 60 grains of phosphate of soda. The solution in nitric acid should not yield a precipitate when treated with a solution of sulphate of soda. Used as a superior white paint, and, in medicine, as an external astringent refrigerant, and desiccant. The particles of carbonate of lead prepared by precipitation, or by any of the quick processes, are in a somewhat crystalline and semitranslucent condition, and hence do not cover so well as that just noticed; also called fine white, and flake white. The following are some of the varieties of white-lead found in commerce.

DUTCH WHITE-LEAD.-1. From flake white, 1 cwt.; chalk, 3 cwt. 2. (Ordinary.) Flake white, 1 cwt.; chalk, 7 cwt. These form the best white-lead in the shops.

2. ENGLISH WHITE - LEAD.-Flake white lowered with chalk; covers badly, and the colour is inferior to the preceding. FRENCH WHITE-LEAD. From litharge dissolved in vinegar and the lead thrown down by a current of carbonic acid gas from coke. Does not cover so well as flake white.

HAMBURG WHITE.-From flake white, 1 cwt; chalk, 2 cwt. Also sold for best Dutch white-lead.

VENETIAN WHITE.--From flake white, or pure white-lead and chalk, equal parts. SULPHATE OF LEAD.-From an acetic or nitric solution of litharge precipitated by adding dilute sulphuric acid, and the white powder washed and dried. The clear liquid decanted from the precipitate is poured on fresh litharge, when a second solution takes place; this may be repeated for any number of times.

CHINESE WHITE.-Take as much as is required of zinc white finely ground, put it on a marble or glass slab, mix it into a cream of the required consistence by adding mucilage of gum tragacanth, grinding with a glass muller. For quantity required to fill an ordinary sized Chinese white bottle, add to above 10 or 12 drops of thick mucilage of gum arabic

and 5 or 6 drops of pure glycerine; grind well together, and fill bottle by aid of palette knife. Make tragacanth mucilage by putting a small piece, size of a horse bean, into oz. of cold water, letting it remain a day or two till gum swells up and absorbs water, then beat into a pulp. It will easily regrind when dry with a little fresh medium. As required consistence depends much on habit and practice, we do not specify any exact proportions. It is easy to add white or medium to suit taste. The cost when thus made is very trifling.

WHITING. The same as prepared chalk, but prepared more carelessly, in horse-mills.

WILKINSON'S WHITE.-From litharge ground with sea water until it ceases to whiten, and then washed and dried.

Green Pigments. BARTH'S GREEN. -Yellow lake, Prussian blue, and clay, ground together.

BREMEN GREEN.-This is properly green verditer, but other preparations are frequently sold under the name.

BRIGHTON GREEN.-Sulphate of copper, 7 lbs., add sugar of lead, 3 lbs. ; each separately dissolved in water, 5 pints; mix the solutions, stir in whiting, 24 lbs., set the paste on chalk stones, and when dry grind it to powder.

BRUNSWICK GREEN.-A saturated solution of sal ammoniac, 3 parts, is poured over copper filings or shreds, 2 parts, contained in a vessel capable of being closed up, and the mixture is kept in a warm place for some weeks, when the newly-formed green pigment is separated from the unoxidized copper, by washing the mixture on a sieve; it is then washed with water, and slowly dried in the shade. Colour very deep and rich. The lighter shades are produced by the addition of sulphate of baryta. In another method a solution of crude carbonate of ammonia or bone spirit is added to a mixed solution of alum and blue vitriol, as long as it affects the liquor; in a short time the precipitate is collected, washed, and dried. The various shades of green are produced by using different quantities of alum, which "pales" and "cheapens" it.

CHROME GREEN.-Prepared by melting in a crucible equivalent quantities of anhydrous boracic acid and bichromate of potassium, and treating the fused mass with water. The hydrated oxide thus produced is washed and finely triturated. Common chrome green is a mixture of chrome yellow and Prussian blue.

is a common practice to add pint of lime water and oz. of gum arabic to every pint of either of the above juices. Powdered arsenious acid, 11 oz.; carbonate of potassa, 1 lb.; boiling water, 1 gall.; dissolve, filter, and add the solution, as before, to another solution of crystallized sulphate of copper, 2 lbs., in water, 3 gall. Product, 1 lb. A very fine grass-green colour.

GELLART'S GREEN.-A mixture of cobalt blue and flowers of zinc with some yellow pigment.

IRIS GREEN.-A pigment prepared by grinding the juice of the petals of the blue flag with quicklime. It is very fugitive.

MOUNTAIN GREEN.-Native green carbonate or bicarbonate of copper ground to powder, either with or without the addition of a little orpiment or chrome yellow. That of the shops is commonly prepared by adding a solution of carbonate of soda, or of potassa, to a hot mixed solution of sulphate of copper and alum. Green verditer is commonly sold for this article.

PRUSSIAN GREEN.-The sediment of the process of making Prussian blue from bullock's blood or horns, before it has had the hydrochloric acid added to it. It is also prepared by pouring liquid chlorine upon freshly-precipitated Prussian blue. As sold, this pigment is generally a mixture of Prussian blue and gamboge.

VIENNA or SCHWEINFURT GREEN.— Arsenious acid, 8 lbs., is dissolved in the least possible quantity of boiling water, and added to verdigris, 9 or 10 lbs., diffused through water, at 120° Fahr., the pap of the latter being first passed through a sieve; the mixed ingredients are then set aside till the mutual reaction produces the proper shade. 2. Sulphate of copper, 50 lbs., and lime, 10 lbs., are dissolved in good vinegar, 20 gall., and a boiling-hot solution of white arsenic, 50 lbs., is conveyed as quickly as possible into the liquor; the mixture is stirred several times, and then allowed to subside, after which it is collected on a filter, dried, and powdered. The supernatant liquor is employed the next time for dissolving the arsenic.

MANGANESE GREEN. - Prepared by mixing intimately 3 or 4 parts caustic barytes, moistened with water, 2 parts nitrate of barytes, and 2 of oxide of manganese; then introducing the mixture into a crucible heated to dull redness, and when it has fused, pouring it out, pul

washing it with cold water, and drying it in an atmosphere which contains no carbonic acid. It answers well for paper hangings, being applied by means of thin glue, and for some other purposes, white of cgg being used instead of the glue.

Yellow Pigments. CHROME YELLOW.-1. Add a filtered solution of nitrate or acetate of lead to a like solu

tion of neutral chromate of potash, as long as a precipitate falls; then collect this, wash it well with clean soft water, and dry it out of the reach of sulphuretted vapours. 2. Dissolve acetate of lead in warm water, and add a sufficient quantity of sulphuric acid to convert it into sulphate of lead; decant the clear liquid, wash the residuum with soft water, and digest it with agitation in a hot solution of yellow neutral chromate of potash, containing 1 part of that salt to every 3 parts of sulphate of lead; decant the liquid, which is a solution of sulphate of potash, and carefully drain, wash, and dry the newly-formed pigment. The product contains much sulphate of lead, but covers as well, and has as good a colour as pure chromate of lead, whilst it is much cheaper. The shade may be varied by increasing or lessening the quantity of the chromate.

KING'S YELLOW, or ORPIMENT. -A native sulphuret of arsenic. It is prepared artificially by sublimation from a mixture of arsenious acid and sulphur; or by collecting the precipitate when a stream of sulphuretted hydrogen gas is passed through a solution of arsenious acid.

NAPLES YELLOW.-1. Powdered metallic antimony, 3 parts by weight, oxide of zinc 1, red-lead 2, mixed, calcined, ground to a fine powder and fused in a closed crucible; the fused mass is ground to a fine powder and well washed. Washed diaphoretic antimony 1 part, red-lead 2, grind with water to a stiff paste, and expose in a crucible to a red heat for 4 or 5 hours.

2.

Blue Pigments.-ULTRAMARINE. -Pure lapis lazuli reduced to fragments about the size of a pea, and the colourless pieces rejected; 1 lb. is heated to redness, quenched in water, and ground to an impalpable powder; to this is added, yellow resin, 6 oz.; turpentine, beeswax, and linseed oil, each, 2 oz., previously melted together; the whole is next made into a mass, which is kneaded in successive portions of warm water, as long as it colours it blue; from these it is deposited on repose, and is then collected, well washed with clean water, dried, and

sorted according to its qualities. The first water, which is usually dirty, is thrown away; the second gives a blue of the first quality; and the third and following ones yield samples of less value. Ultramarine is the most costly, but at the same time the most splendid and permanent, of our blue pigments, and works well in oil.

ULTRAMARINE ASHES.-Obtained from the resinous mass from making ultramarine, by melting it with fresh oil, and kneading it in water containing a little potash or soda; or, by burning away the wax and oil of the mass and well grinding and washing the residue with water. Very permanent, but much less brilliant than ultramarine.

AZURE BLUE, or PARIS BLUE.-1. Sulphur, 2 parts; dry carbonate of soda, 1 part; mix well; gradually heat them in a covered crucible to redness, or till the mixture fuses, then sprinkle in, by degrees another mixture of silicate of soda and aluminate of soda (containing 72 parts of silica and 70 parts of alumina), and continue the heat for an hour. The product contains a little free sulphur, which may be separated by water. 2. Kaolin, 37 parts; sulphate of soda, 15; carbonate of soda, 22; sulphur, 18; charcoal, 8; intimately mixed and heated from 24 to 30 hours, in large crucibles; the product is then heated again in castiron boxes, at a moderate temperature, till the required tint is obtained; it is finally pulverized, washed, and dried. 3. Take crystallized carbonate of soda, 1075 grs.; apply a gentle heat, and, when fused in its water of crystallization, shake in finely-pulverized orpiment, 5 grs., and, when partly decomposed, add as much gelatinous hydrate of alumina as contains 7 grs. of anhydrous alumina ; finely-sifted clay, 100 grs., and flowers of sulphur, 221 grs., are next to be added; the whole placed in a covered crucible, and at first gently heated, to drive off the water, but as soon as this is effected, raised to redness, the heat being so regulated that the ingredients only "sinter" together, without actually fusing; the mass is then to be cooled, finely pulverized, suspended in river water, and brought upon a filter

the product has now a very beautiful delicate green or bluish colour, but on being heated in a covered dish, and stirred about from time to time, until the temperature reaches that of dull redness, at which it must be kept for one or two hours, it changes to a rich blue. If the heat of the first calcination has been properly regulated, the whole of the mass taken from the crucible will have uniform colour; but if too little heat has been used, and the ingredients have not been properly mixed, there will be colourless parts, which should be rejected; if too much heat has been used, or the mass allowed to fuse, brown parts will appear, especially if the crucible is of a bad kind, or easily destroyed; these must also be rejected.

COBALT BLUE.-Prepared by slowly drying and heating to dull redness a mixture of freshly-precipitated alumina freed from water as much as possible, 8 to 10 parts; arseniate or phosphate of cobalt, 1 part. By daylight it is of a pure blue, but by artificial light the colour turns on the violet.

PRUSSIAN BLUE.-Mix alum, 2 parts, with sulphate of iron 1 part, add water sufficient to dissolve. Then make a solution of yellow prussiate of potash, add to it a little sulphuric acid, and when mixed drop in the first solution until the precipitate falls slowly; wash well on a filter and dry. Or add a solution of protosulphate of iron to one of red prussiate of potash; wash and dry.

SAXON BLUE.-Dissolve in 1 gallon of water 1 oz. sulphate of iron and 8 oz. alum; add together separate solutions of prussiate of potash and ordinary pearlash, until the mixture ceases to deposit a precipitate. After the deposit has stood for some time it should be collected, washed thoroughly, and dried.

Black Pigments.-IVORY BLACK. -Take any quantity of ivory-turner's waste or ivory dust, place in a closed crucible and expose for a sufficient time to strong heat. Cool the crucible, remove and powder its contents, wash in warm water and dry. An inferior pigment termed Bone Black is made by treating bones in a similar manner.

LAMPBLACK.-Cooley's 'Cyclopædia' has the foilowing receipts for the preparation of this useful pigment. 1. A conical funnel of tin-plate furnished with a small pipe to convey the fumes from the apartment, is suspended over a lamp fed with oil, tallow, coal-tar, or crude naphtha, the wick being large and so arranged as to burn with a full smoky flame. Large spongy, mushroom-like concretions of an exceedingly light, very black, carbonaceous matter gradually form at the summit of the cone, and must be collected from time to time. The funnel should be united to the smoke-pipe by means of wire, and no solder should be used for the joints of either. 2. On a large scale, lampblack is made by burning bone-oil, previously freed from its ammonia, or common coaltar, and receiving the smoke in a suitable chamber. In one process the coaltar is violently agitated with lime water until the two are well mixed, after which it is allowed to subside, and the lime water having been drawn off, the tar is washed several times with hot water. After subsidence and decantation, it is put into stills, and rectified. The crude naphtha in the receiver is then put into a long cast-iron tube furnished with numerous large burners, underneath which is a furnace to heat the pipe to nearly the boiling point. Over each burner is a sort of funnel which goes into a cast-iron pipe or main, which thus receives the smoke from all the burners. From this main the smoke is conveyed by large pipes to a succession of boxes or chambers, and thence into a series of large canvas bags arranged side by side, and connected together at top and bottom alternately. Fifty to eighty of these bags are employed; the last one being left open to admit of the escape of the smoke, which has thus been made to traverse a space of about 400 yards. As soon as the bags contain any considerable quantity of black, they are removed and emptied. The black deposited in the last bag is the finest and best, and it becomes progressively coarser as it approaches the furnace. The state of minute division in which the carbon exists in good

H