infects, and the gall plant, which contains camphor, is commonly called flea-bane in this country from the ufe to which it is fometimes applied. XXII. BIRD-LIME. (2379) This viscous fubftance exudes from the bark and leaves of feveral plants. It is faid to abound in the berries of the miletoe. It is ufually prepared by boiling the middle bark of the holly, feven or eight hours, until it becomes foft. It is then put into a hole in the earth, covered with ftones, and left to ferment or rot for a fortnight or three weeks. This fermentation changes it to a mucilaginous confiftency; and it is now pounded to a paste in mortars, and well washed with river water. It is foluble in ether, and in boiling alcohol. Its colour is greenifls, its flavour four, its confiftence gluey, ftringy, and tenacious. It has hence been much employed in catching fma!! birds. It reddens vegetable blues. It foftens, but does not diffolve in boiling water. Concentrated folution of potash forms a fpecies of foap with bird-lime. XXIII. RESINS. (2380) Refins derived their name from common rofin, which is the most abundant of any of this clafs of fubftances. Refins are fuppofed to have the fame relation to the volatile which wax has to the fixed oils, and to be formed in confequence of a combination of oxygen with volatile cils. Accordingly when a volatile oil is long expofed to the air it acquires the properties of a refin, in confequence, it is thought, of its combining with oxygen. The fame change takes place more rapidly when oil of turpentine is expofed to oxymuriatic It is foon converted into a yellow refin. Refins often exude fpontaneoufly from trees, or flow from artificial wounds. They are frequently at first combined with a volatile oil from which they are feparated by diftillation. They are folid brittle fubftances, commonly of a yellow colour. Their tafte resembles that of volatile oils, but they have no fmell unless they contain foreign ingredients. They are all heavier than water. They are all non-conductors of electricity, and by fric tion are electrified negatively.` gas. (2381.) When heated they melt, and when ignited, they burn with a yellow flame, emitting at the fame time much fmoke. They are infoluble both in hot and in cold water, but when they are melted in water, or combined with volatile oil and diftilled with water, they become opaque and lefs brittle than formerly. This every fhoemaker knows who prepares his rolin by working it in a quantity of rofin in their foap, which ge yellow colour, a peculiar fmell, and males, more foluble in water. In volatile altai thiya ly form an imperfect folution. (2383.) Mr Hatchett fira difcovered t are foluble in acids. Sulphuric acid ben, pt. on them in powder, firft diffolves the n by the affiftance of heat, gradually content into artificial tannin and charcoal, wid like mineral coal. The compound being and the tannin feparated by alcohol from 100 grains of the following refins, chett obtained the following proportions coal by this procefs: Copal 67 Maftich 66 Elemi 6; Tacamahac 61 Amber 56 Rona 45 The fame bodies when expofed to a red clofe veffels yield very little charcoal. Th lowing is the quantity obtained by Mr from 100 grains of feveral of them. Maftich Amber Rofin 4'50 grains 3'50 0'65 (2384) Nitric acid of the specific pay diffolves refin with the affiftance of bes changes its nature. It is precipitated b If the acid be in fufficient quantity, ard digefted on a refin, a yellow vifcid fe obtained which is equally foluble in water cohol. At laft the nitric acid converts ref artificial tannin. Muriatic acid alfo diffolve flowly. Mr Hatchett recommends acetic an excellent folvent of refins for vegetab (2385.) By deftructive diftillation carbureted hydrogen gas, carbonic acid a acidulous water, and mach empyreu When volatile oil is expofed to the air t converted into refin, partly into the camphoric acids, while a portion of water formed. It has hence been inferred t confifts of volatile oil, combined with and deprived of a portion of its hydroge know if any fubftance contains refin, p ric ether upon it in powder, and expo light. If refin be prefent, the ether wa brown colour. We fhall now enumerate the more useful refins. (2386.) Refin is obtained from the p ris, or Scotch fir, from the pinus ab fir, from the larix, and baljama. W bark is ftripped from the fir trees in become encrufted with a white brittle confifting of rofin united to a fmall port (2382.) They are, with only two exceptions, fo- The yellow rofin is made by meltag lubie in alcohol, efpecially when it is heated, ing this fubftance in water, and it is m which takes up about one third of its weight of than the others because it contains a fa warm water. refin. If the alcohol be diftilled off, the refin remains unchanged. Or if water be poured into the folution, the refin falls in the fate of a white of oil. The larix yields Venice t balfamea the balfam of Canada. (2387.) Maftich is obtained from the powder. They are alfo foluble in fulphuric ether. lentifcus, a tree which grows in the L efpecially in the drying oils. They are alfo gene- incifions are made in the tree, from wha Most of them are foluble in the fixed oils, and particularly in the inland of Chirs T avy foluble in oil of turpentine and other vola- exudes, which concretes into thi tile oils. They are foluble in the fixed alkaline tains nearly a fifth of caoutchouc, f folutions, and hence the foap manufacturers put refin may be feparated by folut chewed in Turkey, as we chew tobacco, and is (2287) Sandarach is obtained from the juni- (2391.) Animé is obtained from the hymenaa (2392.) Ladanum or labdanum exudes from the lujereticus, a fhrub which grows in Syria and the 'ecian iflands. Water diffolves about th of which feems to be gum. Part of the remainris foluble in alcohol. It generally contains out 4th of its weight of extraneous matters. 2393.) Botany Bay refin is obtained from the Trois refinifera, a fingular fort of tree which w's near Botany Bay, and other parts of New uth Wales. It exudes fpontaneously, or from unds made in the bark of the tree. Two-thirds it are foluble, by digeftion, in alcohol. The reining third is extractive matter foluble in wa, and woody fibre. It is partially foluble in aline folutions, and it burns like rolin." 2394.) Black popular refin was firft pointed out Schroeder, who obtained it from the buds of black poplar, by boiling them in water, and erwards preffing them. The buds yield about of their weight of this refin, which is very fi Mar to the refin of Botany Bay. vapour by the heat of a fand-bath, the ccpal melts, and drops like oil into the alcohol, and is fudden. ly diffolved. Atter the drops ceafe to be diffolved by the alcohol, it is unneffary to continue the procefs, because the alcohol is now faturated with the copal. By a fimilar procefs copal may be combined with oil of turpentine. Copal was firft ufed as an ingredient in varni.hes by the Fresch. It afterwards found its way into Holland, where the mode of preparing it was much improved. But the modes by which it is prepared have hitherto been kept a fecret among workmen, and are hardly known in the British ifles. (2397.) Lac.-Though this fubftance has long been known in the arts, very little is known refpecting its origin. It is faid to be deposited on various fpecies of trees in the Eaft Indies, by an infect called chremes lacca. It feems to form the nefts of thefe infects, and it appears doubtful whether it be formed in their bodies, or be merely an exudation occafioned by their punctures in the tree. In its original ftate it is called flick-lac, which is of a deep red colour. When broken, and boiled in water, the water diffolves a great part of this colouring matter, and the decoction is ufed as a red dye. What remains undiffolved is called feed-lac, which is of a brown colour. Al cohol diffolves the greatest part of what the water has left. What the water leaves melts by heat, and being formed into thin plates is known under the name of hell-lac. (2398.) To Mr Hatchett we are indebted for an accurate analysis of the three fpecies of lac, and the following Table exhibits his results in parts of a 100. 100'0 100'0 2395) Green refin, conftitutes the colouring tter of the leaves of trees, and of almost all nts. It is infoluble in water, but foluble in alhol, by which it may be extracted from the ves of plants. If the leaves be immersed in ymuriatic acid, they foon affume a withered pearance, but the colouring matter acquires properties of refin in greater perfection. 2396.) Copal is faid to be obtained from the scopallinum, a tree which abounds in feveral ts of North America. It is faid alfo to be proed from various trees in Spanish America. It white fubftance, fometimes opaque, often rly tranfparent. It has long been reckoned a m, because it is of difficult folution in alcohol, of turpentine, and in the fixed oils. But it (2400.) Amber is thought to be of vegetable ots when heated, and as Mr Hatchett difcover-rigin, and though it differs from refin in fome par is foluble in acids and in alkalies. With ni- ticulars, it agrees with it in most of its propertie. acid it forms artificial tannin, and exhibits all It is a light, hard and brittle fubftance, of a yellow ufual properties of the refins. It is therefore colour, and nearly tranfparent. Though ufually claffed with the refins. If copal be fufpend- taftelefs, and without fmell, it emits a fragranit by a thread ove the furface of alcohol, in a odour when pounded or heated. It cannot be le veffel, well corked, and the alcohol raifed in melted without losing weight, and changing its YYY ? (2399.) Lac is of very extenfive ufe in India. In Europe, befides furnishing a red dye, it forms the bafes of fealing wax. Black wax is formed by melting certain proportions of fhell lac with oil of turpentine, and ftirring into the folution a fufficient quantity of ivory black. Red wax is formed in the fame manner, with vermilion to give the colour. A portion of bleached bees wax is often ufed to fave the expense of lac.-This fubftance alfo makes a confpicuous figure in the com pofition of varnishes. A folution of a 100 grains of lac in 4 ounces of water, in which 20 grains of borax are alfo diffolved, and a fufficient quantity of lamp black is ftirred in the mixture, conftitutes Chinese Ink. appearance (2406.) An equally briiliant, but map and folid varnish is obtained from Sandarach Elemi Animé appearance. In a ftrong heat it burns, leaving a Pulverifed glafs 2401.) Refin from bitumen.-Mr Hatchett afcertained that when mineral bitumen, fuch as that which is diftilled from pit-coal, is digefted in nitric acid, it acquires the properties of a refin. Its fracture is then dark brown, and it acquires a refinous luftre. VARNISHES. (2402.) As refins form the bafis of varnishes, it may not be improper to conclude this branch of the fubject with a fhort account of thofe which are in moft frequent ufe.--The object of varnishes is to prevent the action of air and water on the warnifhed bodies. In moft cafes it is alfo defireable that they thould be tranfparent, fo as not to obfcure the colours of the bodies to which they are applied. They fhould not crack nor fcale off, and they fhould be fufceptible of a fine polish. It is alfo neceffary that the folvent of the relin ufed as a varnish, should be capable of drying. The folvents ufually employed in making varnishes, are alcohol which forms what are called drying varnishes, volatile or effential oil, which forms what are called effential varnishes, and the drying fixed oils which form the fat varnishes. Frequent ly more than one folvent, and different refins are mixed in the fame varnish. Powdered glafs is alfo recommended by Mr Tingry to give them more confiftency. The mixture is commonly made in a glafs matrafs immerfed in a veffel of boiling water, and is stirred with a stick until the combination be completed. The materials, when neceffary, are previously liquified in feparate bottles by expofing them to the fteam of boiling water. After the combination is effected, the varnish is poured off, and filtered through cotton. (2403.) Chaptal, in his Chemistry applied to the Arts, recommends, on the authority of Tingry, the following varnishes, which dry of themfelves. (2404.) A very brilliant varnish for pasteboard, boxes, pen-cafes, &c. 4 Camphor ..33 602 02. 6 (2407.) For wainfcot, iron-work, gras luftrades, &c. Sandarach Shell-lac Rofin Pure turpentine Alcohol 32 (2408) For waxing tables and other fa melt over a flow fire. White wax Add effence of turpentine pre viously liquified nue to fir until the compofition become Sandatach. 4 Maftich. . I Benzoin..! Turpentine. : Alcohol 1 CL (2410.) Various colouring fubftances, Dragon's blood in tears I This varnish is ufed for covering m inftruments, utenfils of copper, mom, When applied to metals they fhould be p heated. ly (2411.) A beautiful golden colour mi conveyed to vafes, and utenfils formed “ various compofitions of name of brafs, &c. Amber Gamboge Dragon's blood copper, triturated en aves the varnish in a hard and brittle ftate, crack and scale off, unless corrected by the ingredients. In the compofition of the ef varnishes the volatile oil of turpentine is only used as the principal folvent of the reThis oil, like alcohol, efcapes in vapour; art remains in union with the refins, and ys to the varnish greater pliability, and renhe varnish lefs apt to crack and fcale off, hofe varnishes where alcohol is the principal t. It therefore follows that varnishes where turpentine is the principal folvent, are beft ed for pictures, leather, and fuch bodies as pofed to be bent, folded, or to be dafhed a hard fubftances. 13.) The following varnish is recommended Aures. 14.) Another varnish for leather, wood, and is compofed of Seed lac Oz. grs. 4 Gamboge 36 36 2 5 32 Pure turpentine Pulverized glass Oil of turpentine 15.) Copal varnish, as Tingry difcovered, e formed by diffolving copal in ether, in llowing manner.-Half an ounce of copal, fine powder, is gradually dropped into a ontaining two ounces of ether. The flash clofed, and agitated for about half an hour, en left to repofe. When afterwards agitathe liquid exhibit a wavy furface, and ap auddy, more ether muft be added, as the in is imperfect. The ether diffolves from a o a fourth of its weight of copal, The varus formed is of a pale citron colour. It is d with a brush, and the fubftance on which read thould be covered with a flight coatany volatile oil, to prevent the too rapid ration of the ether. The oil may be afterwiped off by a linen cloth. This varnish fuch a hard coating on wood and metals, that hardly be defaced by either friction or blows. 6.) Copal varnish may also be prepared by on in the effential, or volatile oils. When turpentine is used as the folvent, it is previneceffary to expofe the oil to the fun, for months, in bottles clofely ftopped, having pty space of fome fingers breadth between and the cork. Eight ounces of this preoil are put into a matrafs, immerfed in boilater, and afterwards one ounce and a half wdered copal is gradually dropped into the fs, during which the matrafs is moved round the water. After the folution is effected, atrafs is removed from the bath, allowed to fome days, and the liquid is filtered through This varnish has nearly the fame properith that which was last defcribed; but its fuccefs depends much on the state of the oil em ployed as the folvent. (2417.) Other volatile oils are used as helps in the folution of copal for varnish-For example two oz. of effential oil of lavender being heated in a matrafs over a gentle fire, one ounce of powdered copal is added in small parcels, and the liquid ftirred with a flick until the copal difappears. Six ounces of oil of turpentine, heated nearly to the boiling point, are then poured in at three different times, and the mixture is ftirred inceffantly until the combination be completed.-This varnish is folid, and of a brilliant golden colour, but lefs drying than the preceding. (2418) Another varnish is prepared by putting fix ounces of oil of lavender into a matrafs, with one dram of camphor, and heating them until they boil. Then two ounces of powdered copal are added, in very finall portions, with conftant ftirring of the liquor. After the copal is well incorporated, a fufficient proportion of boiling oil of turpentine is gradually added, and the boiling and flirring are continued until the mixture has acquired the neceflary confiftency. (2419.) Fat varnishes are chiefly employed to cover iron, copper, and utenfils made of other metals. The oils chiefly employed as folvents are lint-feed rendered drying by the means which were defcribed when treating of that oil, and nut oil. A portion of oil of turpentine, or other effential oil, is commonly added to facilitate the drying. But the fat varnishes are fo flow in drying that the workmen are obliged to dry the articles covered with them by the heat of ftoves.-A very good varnish is made by adding 8 oz. boiling lintfeed oil to 16 of copal melted in a matrafs, 16 of oil of turpentine. The two firft ingredients being well flirred, the matrais is removed from the fire, and fhaken until the heat abates. Then the heated oil of turpentine is added, the whole well ftirred, and while yet hot is paffed through a linen cloth. This varnish fhould be kept in wide mouthed bottles, and it improves by keeping. (2420.) Another hard, durable, and beautiful varnish may be formed by digefting together 6 oz. of copal 24 6 drying lintfeed oil Venice turpentine oil of turpentine. (2421.) Since balloons were invented many experiments have been made to procure a varnish fufficient to retain the gas. Caoutchouc is preferable to all known fubftances for this purpose; but as ether is the only folvent from which it parts with its properties unaltered, this folvent is too expensive for general ufe. The method commonly adopted is to liquify the caoutchouc cut into fall flips, in a matrafs over a fand bath, and then to add boiling lintfeed oil, and after they are well ftirred and incorporated, heated effential oil is added. Each of the three ingredients are in equal proportions. After the varnish cools, it is paffed through a linen cloth. Lintfeed oil, and nut oil, when rendered very drying, acquire all the properties of varnish, and are after ufed to cover balloons without any addition. XXIV. GUAIACUM. XXIV. GUAIACUM (2422.) Is obtained from the guaiacum officinale, a tree in the West Indies, whofe wood is uncommonly hard and heavy. It exudes fpontaneously, or billets being bored longitudinally, and heated at one end, the melted fubftance runs out at the other. It has long been used in medicine, particularly in venerial complaints. It is a folid fub ftance refembling a refin, of a mixed brownish, reddish, or greenifh colour; and it becomes green by expofure to light in the open air. When pounded, or melted by heat, it diffufes a fragrant odour. About nine per cent of it are foluble in water, and the diffolved part poffeffes the properties of extractive., Alcohol diffolves guaiacum readily. Liquid oxymuriatic acid precipitates the folution of a fine pale blue colour, which is permanent, and renders it probable that guaiacum cóntains indigo in its compofition. It is alfo foluble in fulphuric ether, and in the fulphuric and nitric acids.-Mr Brande obtained from 100 parts of this fubftance by diftillation, (2423) This fubftance differs from the refins in containing a much greater proportion of charcoat; in forming oxalic acid when treated with nitric acid, but no tannin as is the cafe with the refins; and in the various changes of colour it undergoes, which feems a confequence of combining with various proportions of oxygen. XXV. BALSAMS. (2424.) Balfams poffefs the general properties of refins, but differ from them in yielding a portion of benzoic acid when heated or digefted in acids. Though infoluble in water, they often yield benzoic acid when boiled in that liquid. The ftrong acids diffolve them, and the aikalies act upon them nearly as on the refins. Their name is derived from the celebrated balm or balfam of Gilead. They are either liquid or folid. The liquid balfams yet known are five in number. (2425.) Opobalfamum or halm of Gilead, is obtained from the amyris Gileadenfis, a tree which grows in Arabia, especially near Mecca. It is fo much efteemed by the Turks that little or none of it ever reaches this country. Of courfe its properties are not known in Europe, except from fome vague reports. (2426) Copaiva is obtained from incifions made in the trunk of the copaifera officinalis, a tree which grows in South America, and in fome of the West India Inlands. It is of a yellowish colour, tranf. parent, at firft refembles oil, but gradually ac very little water are obtained. The berg to conclude that the balfam is do when it is diftilled from an infofion in that the oil and the refin are formed t procefs. Diftilled at the temperature yeilds oil, acidulous water, a fmall p carbonic acid, and much olefant galuble in the fulphuric and nitric which convert it into artificial tarai. feems nearly allied to turpentine. (2427.) Balfam of Tolu is obtained fro made in the bark of the toluifero bal which grows in South America. Ita fmell, is of a reddish brown colour, becomes folid and brittle. Diftilled yields very little volatile oil, but co water its taste and fmell. If the dif continued, benzoic acid fublimes. found it to be foluble in the alka when diffolved in the fmalleft pothe folution of potash, it loft its own fire. ed a moft delicious odour, refembling pink. This fmeil he found to be ret hence this preparation feems likely to perfume. Sulphuric acid, by digeftion bout 54 per cent. of this fubftance into portion of artificial tannin is formed, able quantity of pure benzoic acid i tric acid acts upon it nearly in the upon the refins. Benzoic acid fubi repeated digeftions it is converted tannin. (2428.) Balfam of Peru is obtained water the twigs of the myroxylon pen which grows in the warm parts of S and which abounds in refin. Its ta acrid, its fmell agreeable, its color confiftence that of honey. Water, been boiled fome time, depofits or c tals of benzoic acid. Diftilled from a with a heat gradually raifed, fome firft fublimed; next fome water d ver. At 550° the balfam begins much benzoic acid is fublimed, ter, much oil and gas come over perature reaches 617°. The gas nic acid mixed with a portion of c increafing the heat a brownish a at laft a black oil of the confifter a confiderable quantity of gas, P carbonic acid, but the greatest p olefiant.-Sulphuric acid convers to charcoal, the proportion of no lefs than 64 per cept. of the orf the balfam. The refidue is artic nitric acid evolves the pruffic the balfam into artificial tannin. cafion, by digeftion, a copious zoic acid. (2429.) Styrax is obtained by b the liquidambar fyraciflua, Virginia and feveral parts of a tre quires the confiftence of honey. It has a pungent tree called rofa malles by the ti tafte, and agreeable fmell, and when mixed and island of Cobrafs in the Red S diftilled with water, it yields from a half, to 34th is boiled in falt water to of its weight of volatile oil. The refiduum is refin. lime, and then put into cas But when diftilled from a water bath, without being colour, an agreable fmell, and mixed with water, only a few drops of oil and abforbs oxygen from the air |