making the powder, which he affures us anfwers fhort time, and filtered while hot, depofits the perfectly well.-Take of Sulphuret of antimony z parts Nitrate of potash I} Triturate thefe bodies well together, and heat them ftrongly in a covered crucible. IX. ACETATE OF ANTIMONY. (2968.) The acetic acid diffolves a small portion of the oxide of antimony, and the folution yields fmal! cryftals. This falt has been employed as an emetic. X. TARTRATE OF POTASH AND ANTIMONY. (2069.) This triple falt is ufually known by the name of tartar emetic, and it has been more employed in medicine than all the other preparations of antimony put together. It is faid to have been first invented by a Dudley Earl of Warwick; and it acquired great celebrity in Italy in confequence of the wonderful cures it effected. Many methods have been adopted for its preparation; but the one now generally employed is as follows.-Equal weights of the glass or of the peroxide of antimo. ny, and of tartar, are well mixed and boiled in ten or twelve times their weight of water, until the tartar be faturated. The folution is then filtered, and boiled until a pellicle appears on its furface. After which it depofits, on cooling, crystals in regular tetrahedrons, which are tartar emetic. As fome uncombined tartrate of potash remains in the folution, the evaporation ought not to be carried too far, otherwife its cryals will be depofited with those of tartar emetic. This falt efflorefces in the air; is foluble in 14 parts of cold wa ter, and in about 2 parts of boiling water. It is d compofed by heat, by alkalies and alkaline earths, by feveral of the metals, and by bitter and aftringent decoctions of plants, fuch as Peruvian bark, &c, and hence fhould not be administered in union with fuch bodies. From Thenard it appears that it is compofed of 563 tartrate of antimony, 100 kermes on cooling.-Thenard afcertained u 72 76 protoxide of antimony, 100 (2070.) After the mineral kermes have been pr cipitated from the folution, by any of the methods above defcribed, if an acid be dropped into t remaining liquid another precipitate takes plac of a beautiful orange colour, and hence calle Julphur auratum. According to Thenard this precipitate is composed of 1787 fulphureted hydrogen, 98.17 Goettling propofes to obtain this compound by diffolving two parts of fulphuret of antimon, and three parts of fulphur well mixed, in a bol folution of pure potash. The folution being ditted with water, is precipitated by weak fulphurk acid. Antimonial preparations are not now fo mach ufed in medicine as they were formerly, though few of them still maintain their ground. Its ondes are ufed to convey to glafs, porcelain, and ename fhades of brown, orange, and yellow colours, order to vary the colours, its oxides are often ed, in various proportions, with the oxides of ther metals. SECT. XVII. TELLURIUM (2011.) This metal has only been found in a t neral which occurs in a mine which yields g near Zalethna in Tranfylvania. Mineralogifts wer long at a lofs about this mineral and diftinguited it by the names of aurum problematicum, ar paradoxicum, aurum album. Muller, who exis ed it chemically, in 1782, concluded that this contained a new metal. Mr Kirwan, in the is cond edition of his Mineralogy, published gave it the name of fylvanite, from the name the country where it is found. Klaproth in 1 completely confirmed the conclufions of Mc and gave this new metal the name of telli which it now retains.-This metal occurs nat combined with gold, filver, iron, copper, and fres times a little fulphur. (2072.) It is very brittle, and may easily be t duced to powder. Its brilliancy is confiderable its colour intermediate between that of Zite lead; its texture laminated like antimony. cording to Klaproth, its fpecific gravity is 6'11 HYDROSULPHURET OF ANTIMONY.When hydrofulphuret of potash or ammonia is dropped into an acid folution of antimony, a beautiful orange coloured precipitate falls, which was ,much celebrated as a medicine about the beginning of laft century, under the name of Kermes mineral. It is commonly prepared by triturating in a mortar 16 parts of fulphuret of antimony, 8 parts of potash and one part of fulphur. The mixture is then melted in a crucible, and poured into (2073.) Its melting point is fomewhat an iron veffel. When cold it is reduced to pow- than that of lead. If the heat be incred der, boiled in a large quantity of water, and filter- boils, and flies off in vapour; and in clofe vele ed white hot. While cooling it depofits a yellow forms brilliant drops in the upper part of the powder, which is the kermes. The powder be- fel. Expofed to the blow-pipe ing well washed with water, is dried.-Or fix parts takes fire, and burns with a lively blue f of potash may be diffolved in twenty parts of wa- whofe edges are tipped with green. It go ter, and after the folution is made boiling hot, one tirely off in white fmoke which Klaproth abfer aded. The folution being well ftirred, boiled a on charcoal, white fmoke is the oxide of tellurium; and it ar a alfo be obtained by diffolving the metal in nitric acid, and precipitating by potash. Or by diffolv. ing the metal in nitro-muriatic acid, and adding to the folution a great quantity of water. In ei ther cafe a white powder falls, which is the oxide of tellurium. This oxide eafily melts by heat into a ftraw-coloured mafs, of a radiated texture. If made into a paste with oil, and heated among charcoal, it is fo rapidly reduced to the metallic ftate, that an explofion takes place. (2074) Tellurium combines with fulphur by fulion, and its fulphuret has a leaden grey colour. It amalgamates with mercury by trituration.-This metal being in fmall quantity, and but lately difcovered, few of its acid combinations have been attended to. 1. SULPHATE OF TELLURIUM. (2075.) When one part of tellurium, and 100 of ftrong fulphuric acid are put into a clofe veffel, a folution takes place, and the liquid acquires a bright crimson colour. When water is dropped into the acid, the colour difappears, and the metal is precipitated in black flakes. Heat alfo deftroys the colour, and precipitates a white powder. This metal diffolves readily in diluted fulphuric a cid. The folution is colourlefs, and no precipitate is produced by adding water. II. NITRATE OF TELLURIUM. (2076.) This metal forms a colourlefs folution with nitric acid, which is not precipitated by water. By evaporation the folution yields fmall, white, light, needle-shaped, deneritical crystals. III. MURIATE OF TELLURIUM, (2077.) This metal diffolves readily in nitromuriatic acid, forming a colourlefs folution. On adding water, the white oxide is precipitated, and is again diffolved on adding more water. Alcohol alfo precipitates the oxide. SECT. XVIII. ARSENIC. (2078.) Though fome of the ores of Arfenic were known to the ancients, and ufed by them in painting, arfenic, in its metallic ftate was not known until about 1694. It was afterwards farther elucidated by Brandt, Mauquer, Monnet, Bergman, and Scheele. (2079.) The ores of arfenic abound very much in nature, and it is chiefly found combined with other metals, when they are faid to be mineralized by arfenic. When thefe ores are roafted, the arfenic is expelled from them, and is fometimes collected in long galleries where the powder depofits. But its ores are fometimes found forming veins in the primary mountains, and rarely in the fecondary. In thefe cafes it occurs. 1. Native, in dark colour. ed maffes, which exhibit the metallic luftre of the fracture. 2. The most frequent ore of arfenic is its fulphuret, which when of a yellow colour is called orpiment, and when of a red colour is called realgar. 3. It alfo, though rarely, occurs in the ftate of white oxide, or arfenious acid, when it obtains the name of white arfenic. (2080.) This metal and its oxide being very volatile, its prefence in any mineral may be detected by throwing a little of it on burning coals. If arfenic be prefent it will exhale a smell of garnic. To reduce it to the metallic ftate, its oxide is mixed with three times its weight of black flux, and is put into a crucible which has another crucible luted on its mouth. The lower crucible containing the mixture is exposed to heat, while the upper crucible is kept as cool as poffible by a plate of iron, or by blowing upon it with bellows. After the apparatus has cooled, a crystallized cruft of metallic arfenic is found in the upper crucible. (2081.) Arfenic has a good deal of brilliancy, and in colour fomewhat refembles Reel. Its fpecific gravity is & 31. It is extremely brittle, and can eafily be reduced to fine powder. It has no fmell when cold, but exhales a ftrong smell of garlic when heated, which diftinguishes it from all o ther metals. It rifes in vapour, without melting at 356° and is the moft volatile of all the metals Its cryftals are tetrahedrons. It is not altered un der water, but foon becomes black, and falls into powder when expofed to the air. (2082.) It is the most combustible of all the metals, and it burns when heated in an open veffel with a pale blue flame. It exhales when heated in the form of a white powder, which is the protoxide of arfenic. This is extracted during the procefs of roafting the ores of other metals, and is known in commerce under the names of arfenic, or white arfenic. Chemifts call it quite oxide of arfenic. Fourcroy arfenious acid, because it poffeffes the properties of an acid. It is a white brittle fubftance, of a glaffy appearance. It is foluble in 80 times its weight of water at 60o, and in 15 of boiling water. It reddens vegetable blues, has an acrid tafte, but afterwards leaves an impreffion of fweetnefs. It is a moft virulent poifon; when flowly evaporated cryftallizes in regular tetrahedrons. It combines with metals and generally renders them brittle. It fublimes at 383°, with a strong garlic fmell. It is foluble in from 70 to 80 parts of alcohol, and in oils. According to Prouft it is composed of 75*2 arfenic, 24'8 oxygen. 100 (2083.) But arfenic combines with a higher dofe of oxygen than the one just defcribed, and when charged with a maximum of oxygen it forms arfenic acid, which was explained (864, 865, &c.) and need not be here repeated. (2084.) Arfenic combines with all the imple combuflibles. If four parts of granulated zinc, and one part of arfenic, be mixed, and have fulphuric acid poured upon them which is diluted with twice its weight of water, abundance of hydrogen gas efcapes in combination with arfenic. This arfenical hydrogen gas is colourlefs, of a garlic fmell, extinguishes flame and animal life. A 100 cubic inches of it weighs 16'4 grains. It burns with a blue flame and it explodes when two parts of this gas and three of oxygen are brought in contact with a lighted taper. The product is water and white oxide of arfenic. Oxymuriatic acid diminishes its blufh, and caufes it to depofit yellow flashes. Nitric acid fuddenly mixed, caufes it to evolve red fumes, and an explosion takes place with flame. *Rrr2 (2085 (2085.) Arfenic unites readily with fulphur. If a mixture of these bodies be melted in a covered crucible, a red vitreous mafs is obtained, which is a fulphuret of arfenic. This mixture abounds in rature, and is ufually called realgar. It has a fearlet colour, and is often cryftallized in tranfparent prifms. Its specific gravity is 3*225. It is often ufed as a paint, but Macquer affirms it to be poisonous. (2c86.) If white oxide of arfenic be diffolved in muriatic acid, and fulphureted hydrogen be added in folution, a fine yellow powder is precipitated. Or it may be formed by fubliming arfenic and fulphur with a heat not fufficient to melt them. This mixture is alfo found native, and is ufually called orpiment. Its fpecific gravity is 5'315. Chemifts differ about its nature; but it is now generally underftood to be a fulphuret of arfenic. (2087.) Arfenic combines with moft of the metals, but as few of its alloys are applied to ufe, a minute defcription of them does not feem neceflary. With gold it combines moft readily, when its fumes are made to act upon a plate of gold heated red hot. The alloy is grey and very brittle. With platinum and filver it forms brittle alloys. With mercury it forms a grey amalgam, after they are long ftirred over a fire. (288) With copper arfenic combines, when they are melted in a clofe crucible, with fome common falt to exclude the air. A little bimuth is commonly added, and when the proportion of the arfenic is small the alloy is ductile and malleable. It is commonly called white copper, and white tombac, and is ufed for various purpofes. Iron combines with arfenic, and this compound occurs native, and is known by the name of mispickel. Arfenic deftroys the magnetic virtue of iron. Tia combines with arfenic, and the alloy is whiter, harder, and more brittle than tin, unless the proportion of arfenic be very finall. Lead combines with about of arfenic. The alloy is hard and black and is used for making fmall hot. Arfenic likewife combines with nickel, zinc, antimony and bismuth. (2089.) Arfenic poffeffing the property of combining with oxygen, and affuming the properties of an acid itfelf, in this ftate it combines with many of the oxides of other metals, forming arfenical falts. But when the other acids act upon arfenic,, they oxidize it, and the falt formed is feldom foJulle in water. It hence feems unnecellary to enter into the falts of arfenic. III. METALS BRITTLE AND OF DIFFICULT SECT. XIX. COBALT. the fubject by the labours of Lehmann, Bergma Taffaert, Thenard and others. (2091.) The ores of cobalt are not abundant, hence this metal is of confiderable value. They abound chiefly in Germany, Sweden, Norway, and Hungary. They have alfo been found in Brit and France, tho' in very fmall quantity. Its e are either alloys with other metals, or they are ides, or falts. The moft abundant of these org and the only one wrought for ufeful purpo is of a white colour, and it is chiefly alloyed w arfenic. To reduce the metal, the ore is firft ed, and is then mixed with black flux and c mon falt, and expofed to a forge heat in a cruci lined with charcoal. The cobalt obtained in thi manner always contains a portion of arfenic, el, iron, and other metals. Many procelles bet been adopted for purifying it by acid fot but as thefe fill retain a degree of uncertainty, forbear entering into them. (2c92.) The pureft cobalt has little brillians, a of a grey colour with a fhade of red. It is k times fibroùs, fometimes granular ometimes i ated, according to the heat employed in its for Its (pecific gravity is 77. It is fo brittle th may cafily be reduced to powder. It mobs a 130° of Wedgewood, but does not evaporat any heat that has been applied to it. It cry in irregular prifms. It is attracted by the m and Wenzel found it might be converted into magnet fimilar to thofe made from iron. Bu feems doubtful whether this property may no owing to iron in its compofition. (2093.) It is not changed in the air, nor doesit decompofe water. When kept red hot in an en veffel, it gradually imbibes oxygen, and is cor ed into a blue powder, which becomes deeper deeper, until it appears black. With exceflive the cobalt takes fire and burns with a red far Thenard afcertained that cobalt combines w three different dofes of oxygen and forms th diftinét oxides. (2094.) The first oxide may be formed by folving cobalt in nitric acid, and precipitating means of potash, This oxide has a blue co but by drying in the open air, it becomes ba If this black powder be kept half an hour cherry red heat, the oxygen abforbed in drying expelled, and it is converted into a fine bu lour. The fecond oxide of cobalt is obtained cautiously drying the first oxide in the ope without the affifiance of heat, after its prep tion from acid folution by potafh. It then afir an olive green colour, If either the fift or free oxides be dried in the open air, with the aft of heat they gradually affume a flea-brown col which at laft becomes black. Thisisthethird on of cobalt. The fecond and third oxides emit cs muriatic acid gas with effervefcence, when t are diffolved in muriatic acid. Hence the mo tic acid deprives thefe oxides of a part of their or gen. (2000.) NONE of the metals which follow feem to have been known to the ancients. The name cobait or cobelt feems to have been derived from cobolus, a fancied evil fpirit which the German miners fuppofed to haunt their mines andto do a great deal of mifchief. Since the 15th century the mineral (2095.) Of the fimple combuflibles, cobalt or which had obtained this name, has been employed ly combines with fulphur and phofphorus, We to tinge glafs of a blue colour. But it was not fulphur it does not directly combine, unes the known to contain a new metal until it was exa- fulphur be previously combined with put mined by Brandt, a celebrated Swedish chemift in The fulphuret has a yellowish white colour, F 1733. Much additional light was thrown upon phorus combines with cobalt when firalles are dropped upon the metal heated red hot. he phosphuret is white and brittle, more fuble than cobalt, and is decompofed by heat. (2006.) Cobalt feems capable of combining ith most of the metals, ut as its alloys have it been much examined, and none of them applied to any ofe, we reckon a particular feription of them unneceffary. The order of alinities of cobalt with metals, according Bergman, is the following. (2100.) When ammonia is added in excefs to a folution of nitrate of cobalt, no precipitate enfues. The folution being evaporated to drynefs, and water again added, a red folution is obtained, which, by flow evaporation, yields regular cubes of a red colour. Thefe cryftals are compofed of nitric acid, oxide of cobalt, and ammonia. IV. MURIATE OF COBALT. (2101.) The muriatic acid acts feebly on cobalt even when affifted by heat. But it readily dif folves its oxides, and when a little nitric acid is added, a folution is eafily obtained of the metal itfelf. The concentrated folution is of a fine green colour, but becomes red when diluted with wa ter. By evaporation the folution yields fmall des liquefcent crystals of muriate of cobalt. (2102.) If muriate of cobalt be fo much diluted with water that lines drawn with it upon paper are not visible, they affume a beautiful green colour when gently heated. Thus this falt forms the most curious of all the fympathetic inks. A firefcreen which reprefents winter, with trees deftitute of foliage, may have leaves and verdure drawn upon it with this ink, which are not vifible until the fercen be placed before the fire, when it will fuddenly exhibit all the verdure of fummer.' When allowed to cool, the verdure again difappears and it may be revived as often as we pleate, provided it be not heated beyond a certain point. If this fhould happen, the lines, or figures, drawn by the ink acquire a permanent brown colour. Below this point, which renders the colour permanent, the vividnefs of the green is in proportion to the degree of heat to which it is expofed. Matheories have been adopted to account for this, but as none of them appear to be fatisfactory, we fhall not enter into them.-This fympathetic ink is commonly prepared by diffolving the zaffre of commerce in nitro-muriatic acid, and expelling the excess of acid if any there should be, by heat, After which water is added, and the muriate of cobalt diluted to the proper conliftency. ny V. ACETATE OF COBALT. (2103.) The acetic acid does not act upon the metal, but diffolves the oxide of cobalt, forming a deliquefcent falt which does not cryftallize. This falt is red while cold, but becomes blue when heated. When diluted it forms a sympathe tic ink, the lines and figures drawn by which are colourlefs when cold, but become blue when heated.-It does not feem neceffary to detail any more of the falts of cobalt. (2104.) The oxide of cobalt is much ufed for conveying a beautiful blue colour to glass, and for painting on porcelain and enamels. It is neceffary that the proportion of oxide of cobalt should be very fmall, or the colour of the glafs or porce. lain will be black, or approaching to black. The intensity of the blue may be varied ad infinitum by varying the proportions of the cobalt. For fine porcelain, the purer oxides of cobalt are ufed. For glafs, coarfe pottery, and enamels, zaffre is commonly ufed, which is oxide of cobalt reduced to fine powder, and diftended by a mixture of fand. When zaffre is fufed along with filica and an alkali, glafs of a deep blue colour is obtained, which is known by the name of malt. When this is reduced to powder, and agitated among a large quantity of water, the firft portion which drops down is called coarfe azure. Four quantities are separated in this way; and the laft, which is the fineft is called azure of four fires. Thefe powders are used in painting, and for various purposes. Except for chemical experiments, cobalt is never ufed in its metallic ftate, SECT. XX. MANGANESE. (2105.) THOUGH a mineral under this name had long been known, and was fo much used by glafs-makers, to convey tranfparency to their glafs, that it often went by the name of glass-makers Joup, it was firft fufpected to be a peculiar metal by Kaim of Vienna in 1770. Bergman and Scheele added confirmation to the conjectures of Kaim; but the perfon who first fucceeded in reducing it to the metallic form was Dr Gahn, about 1774. His experiments were confirmed by Haeman in 1702, Hielm in 1985, and Bindheim in 1789. (2106.) The orcs of manganefe are very abundant, and are found in Spain, France, Britain, Germany, Norway, Sweden, Siberia, and many other countries. They are all reducible to two general claffes, Oxides, and Carbonates. The oxides are of two kinds, 1. Grey oxides. 2. Black oxides. The grey oxides are most abundant; the black oxides are generally found intermixed with the former. Of both there are feveral varieties, and they are often found crystallized. The car bonates are rare, and are of a red colonr, hence called red ore of manganefe, which by exposure to the air changes to yellowish brown. Thefe ores occur, chefly in veins, both in primary and fecondary mountains. (2107.) To reduce manganefe to its metallic ftate, a crucible must be coated internally with charcoal powder mixed with water or oil. The oxide of manganefe must be reduced to fine powder, made into a paste with oil, and placed in the crucible above charcoal, and the whole crucible filled with charcoal powder. Another crucible is now luted on, and the whole fubjected to the most violent heat that can be procured, for about an hour. The charcoal attracts the oxygen of the oxide, and when the apparatus cools, the metal is found at the bottom of the crucible in globules difperfed among the fcoriæ. Its weight amounts to about one third of that of the oxide employed. (2108.) Manganefe generally contains a portion of iron, from which it can hardly be feparated. When pure it is of a granular texture, brilliant, and of a greyish white colour. According to Bergman, its specific gravity is about 6850. It is very brittle and melts at 160° of Wedgewood. When reduced to powder, it is attracted by the magnet, owing perhaps to iron in its compofition. (2109.). Expofed to the air, and efpecially when heated in an open veffel, it rapidly attracts oxygen, and becomes grey, violet, brown, and at laft black. By combining with three proportions of oxygen, it feems capable of forming three different oxides, the white, the red, and the black. (2110.) The firft or white oxide, may be formed by diffolving the black oxide in nitric acid, with the addition of a little fugar. The fugar con with the excefs of oxygen, and efcapes is ch nic acid gas, while the white oxide is differe the acid. By adding a folution of potat, precipitated in thefn of a white powder. white oxide if expofed to the air focn attra gen, and reverts to the ftate of black oxide, cording to Bergman it contains 80 manganefe, 20 oxygen. 100 (2111.) The fecond, or red oxide is obtain making the black oxide of manganefe into a p with fulphuric acid, and heating them in a tr A great quantity of oxygen gas comes orar, the oxide being deprived of part of its oxyge folves in the acid. Diftil to drynefs, and the water on the refidue, and pafs it through a f A folution of fulphate of manganefe is of a red colour. On adding an alkaline fo this oxide is precipitated in the form of a ro der. Expofed to the air, the red oxide of nefe likewife attracts oxygen, and is convers to the black oxide. Its conflituents, acc to Bergman are 74 manganefe, 26 oxygen. 100 (2112.) The third, or black oxide, abo nature, and was the firft fubftance which obe the name of manganefe. It may be foon for by expofing the metal, or any of the pr oxides after precipitation from an acid, to t or to moderate heat, in an open vefiel. We black oxide is heated to rednefs in an earth iron retort, it gives out a great quantity of gas, which may be collected in proper velle it approaches the state of red oxide. The oxide yields no oxygen gas, (fee 512, 13) bleachers who ufe great quantities of oxy tained from the black oxide of mangane cause the fame material to reabforb from t the portion of oxygen of which they had cr it. This oxide melts in a very violent heat green coloured glafs. According to Fourre black oxide is composed of 60 manganefe, 40 oxygen. 100 (2113.) Of the fimple combuftibles, can only be combined with phofphorus, indeed found native phofphuret of mang an ore of tellurium, but Bergman was tot effect this combination by art. He fucced deed in combining eight parts of the black t with three of fulphur, which formed a comp of a green colour. (2114) The phosphuret of manganefe formed by melting equal parts of the me of phofphoric glais, or by dropping bita p phorus upon red hot manganefe. This is much more fufible than the metal itfel, white colour, brittle, granular, and cryftal It is not altered by the air, but heat burns of t phosphorus, and oxidizes the metal, (2115) Manganefe combines with mary |