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salts of silver. It is generally prepared by adding the metal to the diluted acid, in which case the silver is oxidized by decomposing a portion of the nitric acid, and that which remains undecomposed dissolves the oxide formed. It may also be prepared, but less advantageously, by dissolving the protoxide of silver in the dilute acid; in this case no nitric oxide is evolved, for no nitric acid is decomposed. The solution is colourless, and by evaporation colourless crystals are readily obtained, the primary form of which is a right rhombic prism. Nitrate of silver has a bitter metallic taste, is soluble in about its own weight of water at 60°, and in half its weight of boiling water; the solution is neutral to litmuspaper. Cold alcohol dissolves only a little of this salt, but when boiling takes up a considerable quantity of it, the greater part of which separates on cooling.

By the action of light, especially when in contact with organic matter, nitrate of silver is rendered of a dark colour, and is then insoluble in water. When moderately heated, nitrate of silver fuses, and being then cast in a mould in small cylindrical sticks, it constitutes the argenti nitras of the Pharmacopoeia, commonly called lunar caustic; if the heat applied be too great, the salt is decomposed, oxide of silver being left, which, if still more strongly heated, gives metallic silver. When sulphur, phosphorus, or charcoal is mixed with nitrate of silver, and struck on an anvil, detonation ensues, and metallic silver is obtained; the experiment should be made on very small quantities, Nitrate of silver is decomposed by simply placing charcoal or phosphorus in its solution, metallic silver being deposited in the crystalline state; the same effect is produced by several metals, and more especially copper, which is used in silver-refining for precipitating the silver from the nitrate in a pure state.

Chlorate of Silver may be obtained by dissolving protoxide of silver in chloric acid; the solution yields small rhombic crystals, which are soluble in four parts of water at 60°. This salt is not applied to any use.

Nitrate of silver is decomposed by sulphuric and phosphoric acids, and their soluble salts, sulphate and phosphate of silver, are thrown down. Potash and soda and the alkaline earths precipitate protoxide of silver; ammonia produces the same effect, but when added in excess, redissolves the oxide at first precipitated. Hydrosulphuric acid, hydrosulphates, and soluble sulphurets occasion the formation and precipitation of black sulphuret of silver.

Chlorine partially, and soluble chlorides and hydrochloric acid and hydrochlorates, perfectly, decompose nitrate of silver, chloride of silver being precipitated. It is on this account that nitrate of silver is employed, and with great accuracy, in both qualitative and quantitative analyses. Nitrate of silver is composed of

One equivalent of nitric acid

54

One equivalent of protoxide of silver 116

170

Equivalent Besides the uses already named, nitrate of silver is employed by precipitation with carbonate of soda, &c. for writing on linen; it is commonly called indelible ink.

Carbonate of Silver is prepared by adding a solution of carbonate of potash, or of soda, to one of nitrate of silver. It is a white substance, insoluble in water, but dissolved by ammonia, and decomposed by acids; it is blackened by exposure to light, and readily decomposed by heat. It is probably composed of

One equivalent of carbonic acid
One equivalent of oxide of silver

Equivalent

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22

. 116

138

Sulphate of Silver.-This salt may be formed by boiling finely divided silver in strong sulphuric acid, by dissolving the protoxide in dilute sulphuric acid, or by adding a solution of sulphate of soda to one of nitrate of silver, when it is thrown down as a crystalline precipitate.

Sulphate of silver is a colourless salt, soluble in about 90 parts of water at 60°; a saturated boiling solution deposits crystals on cooling, which are prismatic and anhydrous; when strongly heated, the acid is expelled, and metallic silver remains. It is sometimes employed as a chemical reagent, and is composed of

One equivalent of sulphuric acid
One equivalent of oxide of silver

40

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It is decomposed by chlorides and sulphurets, in the same manner as the nitrate of silver.

Sulphite of Silver may be obtained by adding sulphite of potash to a solution of nitrate of silver, or by digesting oxide of silver in a solution of the acid. It has the form of crys talline grains, and, unlike most other salts of silver, is stated to retain its whiteness when exposed to light. It is composed of One equivalent of sulphurous acid. 32 One equivalent of oxide of silver 116

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148

Equivalent Hyposulphate of Silver is prepared by digesting carbonate of silver in hyposulphuric acid. It crystallizes in prisms. Hyposulphite of Silver.-It is obtained by gradually adding a weak solution of nitrate of silver to a dilute one of hyposulphite of soda. It is a precipitate of a grey colour, and the supernatant liquor is stated by Herschel, who has particularly examined this salt, to be remarkably sweet, without any metallic flavour. It is also formed when chloride of silver is dissolved in a hyposulphite. This salt is very liable to spontaneous decomposition, and becomes black owing to the formation of sulphuret of silver. The hyposulphites have been advantageously employed in removing of the unchanged salt of silver in photogenic drawings. Hyposulphite of silver is composed of

One equivalent of hyposulphurous acid 48
One equivalent of oxide of silver

Equivalent

. 116

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Phosphate of Silver.-This is prepared by adding a solution of the common neutral phosphate of soda to one of nitrate of silver; a yellow precipitate is formed, which is quickly discoloured by exposure to light; becomes brown when heated, but regains its yellow tint on cooling; and when strongly heated, it melts. It is soluble in nitric and phosphoric acid. It is a subsesquiphosphate, composed of 1 equivalent of phosphoric acid 1 equivalent of oxide of silver

Equivalent

36

. 174

210

Pyrophosphate of Silver is obtained by heating neutral phosphate of soda so as to expel its water, and adding a solution of it to one of nitrate of silver. This precipitate is of a white colour. Like the preceding, it is composed of one equivalent each of acid and base.

We shall mention the properties of a few of the salts formed by the combination of the vegetable acids with oxide of silver.

Acetate of Silver.-It may be prepared by dissolving oxide of silver in acetic acid, or, as it is a salt of slight solubility, in water, by decomposing nitrate of silver with acetate of soda, when it is thrown down as a crystalline flocculent precipitate. It is a colourless salt, sparingly soluble in water, and decomposed at a red heat. It is occasionally used as a chemical re-agent. It consists of

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to a solution of nitrate of silver; the hydrogen of the acid uniting with the oxygen of the oxide of silver, water is formed, and the cyanogen and silver combine, and form cyanide of silver, which is precipitated. It is colourless, insoluble in water or solution of potash or soda, but readily taken up by ammonia. Nitric and sulphuric acid act but slightly upon it, unless concentrated and heated; hydrochloric acid decomposes it, and hydrocyanic acid and chloride of silver result, and this is one of the methods of procuring the last-mentioned acid, adopted in the London Pharmacopoeia. It is decomposed by hydrosulphuric acid, by which sulphuret of silver and hydrocyanic acid are obtained. It is composed of

One equivalent of cyanogen
One equivalent of silver

Equivalent

26 108

134

Ferrocyanide of Silver is obtained when ferrocyanide of potassium is added to nitrate of silver. It is a white insoluble substance.

Cyanate of Silver is formed when cyanate of potash is added to nitrate of silver. It is a white powder, slightly soluble in hot water, and also in ammonia. It blackens when heated, and burns with deflagration, and there are produced di cyanide of silver, cyanic acid, carbonic acid, and azotic gas.

Fulminate of Silver. Fulminating Silver.-This very explosive compound is formed by dissolving 60 grains of silver in half an ounce of nitric acid of specific gravity 1.38; to the solution are to be added two ounces of alcohol of specific gravity 0.88, and the mixture is to be heated in a capacious flask; a white flocculent precipitate soon begins to appear, and when ebullition commences, the flask is to be removed from the heat; the effervescence still continues, and when it has ceased, the product is to be collected on a filter, washed with cold water, and dried at a temperature not exceeding 100° Fahrenheit.

Fulminate of silver is a greyish-white crystalline powder. It becomes darker by exposure to light; it dissolves in about 40 parts of boiling water, and separates, as the solution cools, in minute crystals. In the quantity even of a half grain it detonates violently, either by the action of heat, electricity, strong sulphuric acid, or friction. When placed on one flint, and slightly touched with another, explosion also takes place. It has been known to detonate with great violence when a little has remained between a stopper and the neck of a bottle, on screwing in the stopper. It should be preserved therefore in small portions, in paper, in a widemouthed corked vial. It is composed of

One equivalent of fulminic acid

Two equivalents of oxide of silver

Equivalent

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68

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232

300

Alloys of Silver.-Little or nothing is known respecting the alloys of silver with the following metals:-Potassium, sodium, and the metals of the alkaline earths; manganese, cadmium, nickel, uranium, tellurium, titanium, cerium, chromium, and vanadium.

Iron and silver combine with difficulty. They separate on cooling, the iron retaining about one-eightieth of silver, and the silver about one-thirtieth of iron. According to Faraday and Stodart, steel containing about one five-hundredth of silver forms a good alloy for cutting instruments. Iron and silver form a bluish-white granular alloy; tin and silver, a white, hard, brittle alloy. When cobalt and silver are fused together, they separate during cooling, each retaining a portion of the other. Lead and silver give a dull brittle alloy; antimony and silver, a white brittle alloy; arsenic and silver form a grey, brittle, granular compound, containing about 14 per cent. of the former metal. Bismuth and silver give a yellowish-white, brittle, lamellar alloy; molybdenum forms a compact, brittle, grey, granular compound with silver; and tungsten, a brown, slightly malleable button; copper and silver readily combine, and the silver is rendered harder by it without much deterioration of colour; the standard silver of this country is composed of 11 10 silver and 0.90 copper. Mercury and silver amalgamate readily, and this compound is sometimes employed for plating, but this operation is now being most advantageously carried on by precipitation by means of voltaic electricity.

Properties of the Salts of Silver.—The solutions of the salts of silver are recognised by the following, among other properties which have been occasionally mentioned:

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They give a white precipitate, insoluble in water or in dilute acids, but readily in ammonia, by chlorides and hydrochlorates; the precipitate becomes black by exposure to the light.

Metallic silver is precipitated by copper and the solution of protosulphate of iron; black sulphuret, by hydrosulphuric acid and hydrosulphates. A yellow precipitate by arsenious acid and phosphate of soda; a red-brown, by arseniates; a crimson, by chromates; and white, by the ferrocyanide of potassium.

With respect to the uses of silver it is scarcely requisite to say anything, as they are well known in its application to coin and the formation of vessels of great beauty and durability.

SILVER, PRODUCTION AND CONSUMPTION. Silver-ores are found chiefly in veins which traverse the primary and the older of the secondary stratified rocks, but especially the former; and also the unstratified rocks, such as granite and porphyry, which are associated with the above. Some of the richest mines in South America are situated in primary strata; also in limestone and in grauwacke, and in still more secondary strata. In some of the mines of Peru, and in those of Kongsberg in Norway and Freiburg in Saxony, silver has been discovered in masses weighing from 100 to 800 lbs. In the mines of Europe the veins are numerous and slender; in some of the mines in the Harz Mountains and in the Hungarian mines the veins occur in a small number of spots, and are of considerable dimensions. In three of the richest districts of Mexico there is only one principal vein, which is worked in different places. One of these veins, in the district of Guanaxuato, is from 130 to 148 feet wide, and it has been traced and worked to an extent of nearly eight miles.

In Mexico there were 500 mining establishments, called Reales, at the time of Humboldt's visit, and from 3000 to 4000 veins or masses were worked. The most common ores are the sulphuret of silver, antimonial silver, and muriate of silver.

The average richness of all the ores in Mexico is from 3 to 4 ounces per quintal of 102 lbs. In one of the Mexican mines a working of one hundred feet in length yielded in six months 432,274 lbs. troy of silver, equal in value to about 1,000,000. In Chili some of the mines yield only 8 oz. in 5000 lbs. of ore; but in the rich mine of Copiapo, discovered in 1832, the ore frequently contains 60 or 70 per cent. of silver. The average produce of the mines in Saxony is from three to four ounces in the quintal. The lead-mines of Craven in Yorkshire contained 230 ounces per ton; and those of Cardiganshire, worked in the reign of Charles I., yielded 80 ounces. The average proportion of the lead-mines of the north of England is 12 ounces per ton. Even when the proportion of silver is so low as eight ounces, or one grain per lb., it has been found profitable to separate it.

The pure metal is separated from the ore by various processes; by mechanical division, roastings to separate the sulphur and other volatile matter, and melting at different stages of purification, with the addition of fluxes of various sorts. Refining is performed by amalgamation with quicksilver, the two metals being afterwards separated by distilling off the quicksilver.

The produce of the Mexican mines averaged annually 4,800,0007. from 1793 to 1803, of which nineteen-twentieths were silver. In the first ten years of the present century the average annual value was about 5,000,000l., the quantity of pure silver annually produced in that time being 1,440,650 troy lbs. The mines of Potosi in Peru are the most famous in South America. [POTOSI.] The produce of the Chilian mines in 1832 was about 1,000,000 ounces. At the commencement of the present century Humboldt estimated the annual produce of the silver-mines of Chili, Peru, Buenos Ayres, and New Grenada, at nearly 700,600 lbs. troy, valued at 2,074,4767. sterling.

The annual average of both gold and silver coined in the different mints of Spanish America was estimated, in 1810, at 8 millions sterling, namely, in Mexico 24 millions of dollars; Lima, 6 millions; Potosi, 44 millions; Santa Fé and Santiago, each 1 million; and Popayan and Guatemala, nearly 1 million. The proportion of silver to gold coined at all these mints was stated as 30 to 1; but the proportion of silver to gold produced from all the American mines was as 62 to 1; and from the mines of all countries as 52 to 1. In a work published at Paris in 1807 by M. Brongniart, the value of the gold and silver brought annually into circulation

from all parts of the world was estimated at nearly 46 mil-, and the other extending the inquiry from 1809 to 1829, lions of dollars; of which 36 were from the mines of Spanish complete this part of the subject. The investigations of America, 44 from those of Portuguese America, and 54 from Humboldt, and the personal inquiries of Mr. H. G. Ward the mines of the Old World. (Report of Bullion Com- (Mexico in 1827), with the scattered notices of other writers, mittee, 1810.) are collected and arranged by Mr. Jacob, whose work must always be valuable for reference in all questions relating to the history of prices. Several chapters of the work are devoted to this topic in connection with the increased supply of the precious metals after the discovery of America, and the rise of prices which occurred in Europe in the sixteenth century. The gold and silver coin in Europe, in 1492, Mr. Jacob estimates at 34,000,0007., which was increased in the course of the next 112 years by 138,000,0002., making the total gold and silver currency in 1599, allowing for abrasion, &c., 172,000,000l. In book i., chapter xi., of the 'Wealth of Nations,' there is a Digression concerning the Variations in the Value of Silver during the course of the Four last Centuries.'

The most productive mines in Europe are those in Saxony, Austria, Hungary, Norway, Russia, and Spain. The mines in Saxony have been worked since the tenth century. The average annual produce of all the European mines in the last twenty years of the eighteenth century did not exceed 600,0007. in value. In the early part of the thirteenth century the mines of Schneeberg in Saxony are said to have yielded 600,0007. annually; but taking the average of all the mines of late years, the annual produce does not, according to the estimate of Mr. Jacob, exceed 400,000 lbs., or 100,000%. in value. The mines of Chemnitz and Kremnitz in Hungary have been worked about a thousand years. Those of the Tyrol have long ceased to be productive. The mine of Kongsberg in Norway was probably the richest in Europe during the middle of the last century. It yielded 649,270 lbs. troy, value nearly 2,000,000, in the forty years from 1728 to 1768. The silver of Russia is obtained from the refining of stream gold found in the Ural Mountains, and from lead-ores. Silver-mines were worked in Spain from a very early period by the Phoenicians, Carthaginians, Romans, and Moors; but they are now abandoned as unprofitable.

Native silver and several of the other varieties of the ores are met with in some of the Cornish copper-mines, and silver is extracted from the ore of English lead; but with these exceptions, and very small quantities which are occasionally found of this metal, silver cannot be considered as constituting one of the mineral treasures of the United Kingdom. A vein of silver-ore and the sulphuret was worked in Stirlingshire during the latter part of the last century, and from 40,000l. to 50,000l. were obtained, when the vein was lost. In 1607 a silver-mine was worked in Linlithgowshire. The silver-mines of Asia have ceased to be very productive in modern times. There are mines in Armenia, but none are known to exist in Persia, nor in any part of the East India Company's possessions. Silver-mines are worked in China; and Mr. Davis remarks (Chinese) that the great quantities of silver brought to Lintin for many years past, to be exchanged for opium and exported to India, prove that there must be abundant sources in the empire. Silver is not obtained in any part of Africa.

(Genesis, xlv., 22.)

The proportional value of gold to silver was 12 and 10 to 1 from the Anglo-Saxon times to the discovery of America. it is at present 14.28 to 1. In antient Greece the propor tion varied from 15 and 10 to 1, and in Rome from 12 and 7 to 1. Herodotus (iii. 95) estimates it at 13 to 1. Since the discovery of America the proportion throughout the world has been 17 and 14 to 1. (Kelly's Cambist.) Mr. Jacob gives the amount of silver coined in each reign from the time of James I. :

James I.
Charles I. and the
Commonwealth
Charles II.

James II.

£

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William and Mary,

and William III.

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(13 years)

618,212

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Anne
George I.
George II.
George III. from
1760 to 1809
1809 to 1820

63,419 6,933,346

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Gold and silver appear to have been in request from the earliest ages. Abraham was rich in silver and in gold. He bought a field for a burial-place, for which he paid 400 shekels of silver, delivered by weight, according to the currency of the merchants." (Genesis, xxii., 14-16.) Joseph, his great-grandson, was sold by his brethren for twenty pieces of silver (Genesis, xxxviii., 29); and when aftewards they went to Egypt to purchase corn, they brought silver in their sacks' mouth.' the book of Job (xlii., 11-12), we read of silver passing from hand to hand as money. The writer of that book was acquainted with the fact that silver was found in veins and gold in particles, though the country in which he lived did not produce the precious metals. It is said (1 Kings, x.) that in the days of Solomon silver was nothing accounted of, and that the king made silver to be as stones in Jerusalem.' Darius Hystaspes, king of Persia, annually collected 9880 talents of silver, besides gold, as tribute from Asia and Africa; subsequently tribute came in also from the islands of the Mediterranean and from Europe as far west as Thessaly. Herodotus states (iii. 96) that the gold and silver were melted and poured into earthen vessels, and that the earthen vessels were then removed, which left the metal in a solid mass: when any was wanted, a piece was broken off as the occasion required. Silver was coined at Rome 266 B.C., before gold had been so employed. [COIN.] For further information on the production and uses of the precious metals, the reader may refer to Mr. Jacob's elaborate History of the Consumption of the Precious Metals, 2 vols. (1831). Chapter ii. contains an account of the mines of the antients, and their modes of mining and smelting. Chapter x. is an inquiry into the production of the precious metals during the middle ages, from the dissolution of the Western Empire to the discovery of America. Another chapter is on the produce of the mines at the epoch of this discovery; also one from this period to the opening of the mines of Potosi, in 1564; and two other chapters, one on the produce of gold and silver from 1700 to 1809,

1828

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copper the maximum of hardness is produced by one-fifth of copper. One lb. of standard silver of the English coinage contains 11 oz. 2 dwts. of pure silver and 18 dwts. alloy, or 925 parts of pure silver in 1000 parts of standard silver. [MONEY.] For purposes connected with the manufacture of various articles of use and ornament the alloy is greater. At Birmingham rolled sheets are made which do not contain more than 3 or 4 dwts. of silver to each lb. of the inferior The rolling of silver in contact with the inferior metals is performed by powerful flatting-mills. A bar of copper is made quite smooth and clear on one of its surfaces, and is then sprinkled over with glass of borax, and there is laid upon it a plate of fine silver, and the two are carefully bound together by wire. The mass is then exposed to a full red heat, which melts the borax and causes the silver to adhere to the copper. The ingot is now passed through a rollingpress and formed into a plate, both the silver and copper extending uniformly during the whole process, at the conclusion of which they are inseparably joined. The art of silver-plating was introduced at Sheffield about the middle of the last century. Another mode of plating is called 'silvering,' when an amalgam of silver and mercury is well rubbed upon the surface of the copper; by the application of heat the mercury is driven off, and the silver remains behind, adhering firmly to the copper, and capable of being highly polished.

Mr. Jacob estimates the annual consumption of silver in the United Kingdom at 3,282,046 oz., valued at 820,5217. The consumption for watch-cases is about 506,000 oz. annually: 100,000, each weighing on an average 24 oz., are stamped annually at the London Assay-office; 60,000, each weighing 2 oz., are stamped at Birmingham; and 80,000, of the same weight, are stamped at the other assay-offices in the kingdom. About 900,000 oz. are used by coach-makers, harness-makers, and saddlers' ironmongers. In articles of small size, such as thimbles, of which hundreds of thousands are annually made; chains for watch-guards, pencilcases, necks of smelling bottles, locks of pocket-books, instrument cases, and portfolios, and small portions to handles of penknives and razors, the silver used is under the weight which subjects it to the stamp duty of 1s. 6d. an oz., but a very considerable quantity of silver is employed in these minor objects. Leaf-silver for gilding is made two and a half times thinner than gold, and the gold-beaters require a considerable quantity of the metal for this purpose. Some articles are washed' with silver. Mr. Jacob distributes the total consumption as follows:

That paying duty

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That used in watch-cases
That used in plating

That for other minor purposes

1,275,316 oz. 506,740

900,000

500,000

3,282,046

The value of the stock of silver in the hands of the manufacturers and dealers is estimated by the same authority at 3,280,000l. The value of ornaments and utensils of the precious metals in Europe and America, if brought to the crucible, Mr. Jacob values at 400,000,0007., or one fourth more than the value of the coined metais. The annual consumption of gold and silver in Europe and America for or namental purposes he states to be nearly 6,000,000Z., that of Great Britain being valued at 2,457,000. In McCulloch's 'Dictionary of Commerce,' it is stated that Mr. Jacob's calculations are generally too high. Silver forms by far the largest proportion of the value of domestic utensils in which either of the two precious metals are used. In England the gold currency is of much higher relative value than that of silver [CURRENCY]; but in most other countries this is not the case. The coinage of silver and gold in France is estimated at 100,000,0007., a very large proportion of which is of silver. Since the peace, the number of silversmiths and persons engaged in working silver and gold into articles of ornament and use has greatly increased on the Continent; and the increase of the same class is probably also considerable in the United Kingdom. See the articles ANDES, CHILE, MEXICO, PERU, POTOSI, for an account of the South American mines; AUSTRIA, HUNGARY, SAXONY, &c., for those of Europe.

(Jacob's Inquiry into the Production and Consumption of the Precious Metals, 2 vols., London, 1831; Humboldt's New Spain; Personal Researches, &c.; Ward's Mexico, &c.)

P. C., No. 1362.

SILVER, Medical Properties of. In a purely metallic state silver has no action on the animal frame, and the only salt much used is the nitrate, termed also lunar caustic. This is always fused in proper moulds, from which it is turned out in the form of cylinders, about three inches long, and the eighth of an inch in diameter. They are at first white, but quickly become of a dark grey or black colour, from combining with organic matter in the air. To prevent this the cylinders are generally wrapped up in blue paper. When nitrate of silver is brought in contact with any part of the human frame, it causes first a white mark, which gradually changes to blue, purple, and at last to black. This occurs more rapidly if moisture be present; and is owing to a chemical combination of the metal with the albumen and fibrin of the animal tissues. If the part be wetted, and the caustic applied several times at short intervals, vesication results. Nitrate of silver acts therefore locally as an irritant and corrosive. When taken internally in small doses for a considerable time, such as six or twelve months, it is absorbed and deposited in various parts of the body, and when it is deposited in the rete mucosum of the skin it causes discolorations, which in most cases prove permanent. It has been employed frequently with success, but often with failure, in the treatment of epilepsy, chorea, and some forms of angina pectoris, as well as morbid sensibility of the stomach. Larger doses can be borne when it is administered in the form of pill than in solution. The pills should be made with mucilage and sugar, but not with bread-crumb, as the common salt, or chloride of sodium, decomposes the nitrate and renders it inert. In cases of poisoning by nitrate of silver, common salt is a ready and effectual remedy. The liability of nitrate of silver to produce discolorations of the skin in persons taking it internally constitutes a serious objection to its employment, and there appears little necessity for giving it, since any case of epilepsy likely to be benefited by it will generally receive equal good from the use of oxide of zinc, without the risk of stains or other inconvenience. It has been suggested that the use of nitric acid internally as well as externally may remove the discolorations; but it is better not to incur the chance of causing them, than trust to the remote chance of removing them by such an expedient.

The external employment of this agent is not liable to any objection when used cautiously, while its advantages are very great. It is the most powerful direct antiphlogistic agent known. All subacute inflammations in any part to which it can be immediately applied will subside under its influence. In inflammations not merely of the skin, but of mucous membranes when they occur in parts which are accessible, its influence is great, and speedily manifested. Many of the cases of croup which in an advanced stage are unmanageable, begin in the back part of the throat (fauces), and if these parts are freely touched with a pencil dipped in a strong solution of nitrate of silver, the farther downward progress of the inflammation may be arrested. The same treatment is applicable to the erythematous inflammation which frequenily begins either externally, and spreads through the mouth or nose to the fauces, and thence down the esophagus, or originates in the fauces, leading to very serious results. Erysipelatous inflammation occurring in any part of the body may be effectually limited by nitrate of silver. For this purpose a complete circle should be formed round the inflamed part, but on the sound skin. For this case the solid cylinder, moistened at the end, is best. The circle must be perfect, or the morbid action may extend, escaping at the smallest breach. Chronic inflammation, and even ulceration of the eyes, may be removed by nitrate of silver applied in different forms. Old indolent ulcers are stimulated to a healthy action by its use; and many cutaneous diseases removed by it. Recent burns have the severe pain often very much mitigated by it; but it must not in any of these cases be applied to too large a surface at once, as ill effects have followed such a practice. To specify all the uses of nitrate of silver would be impossible here, but one more deserves to be extensively known. It is the best application to chilblains, especially at first; but even after they break, it disposes them to heal.

When a solution of nitrate of silver is made, distilled water should invariably be used. The neglect of this rule causes many of the solutions applied to the eye to be not only useless, but hurtful. Oxide of silver has been recently strongly recommended as an antispasmodic, and not liable to the objections which attach to the nitrate.

VOL. XXII-E

SILVER, GERMAN. [TUTENAG.] SILVER-GRAIN. In making a horizontal section of the trunk of any tree, a number of straight lines will be seen radiating from the central pith through the wood to the bark. These rays are called by botanists medullary rays or plates, and by persons who work on wood silver-grain. They are composed entirely of cellular tissue, which is of a compressed form, and thence called muriform, and often do not consist of more than a single layer of cells, although in some trees, as Aristolochias, the layers are very numerous. In longitudinal sections of the stem they give it a remarkable satiny lustre, which constitutes the great beauty of some woods, as the plane and the sycamore. The great variety that is seen in the character of different woods appears to depend on the nature of the silver-grain, for the woody and vascular tissues do not present sufficient difference to constitute any obvious peculiarity. Thus in the cultivated cherry the plates are thin, and their adhesion to the bark slight, so that a section of this wood has a pale, smooth, homogeneous appearance: but in the wild cherry the silvergrain is much thicker; it adheres closely to the bark, and is arranged with great irregularity, so that this wood when cut has a deeper colour, and a twisted, knotted, irregular appearance. In the two species of oak the same kind of differences are observable. In Quercus sessiliflora the rays are thin and distant from each other, so that when a wedge is driven into the end of the trunk the plates of wood do not readily break into each other; but in Quercus pedunculata the rays are hard, and are so close together that the wood may be split up without any difficulty. [STEM.]

SILVIC ACID, a substance which with pinic acid [PINIC ACID] constitutes the greater portion of colophony, or common rosin. When this substance is digested in cold alcohol of specific gravity 0-833, the pinic acid dissolves, but the silvic acid remains insoluble in alcohol until it is boiled; on cooling, it separates in crystals of considerable size, the form of which, according to Unverdorben, is a rhombic prism terminated by four facets, but Laurent represents it as an acute rhomboid, the edges of which are usually serrated.

Silvic acid melts below 212°; is insoluble in water, but dissolves readily in hot alcohol and in æther, and is precepitated by water; it is soluble also in all proportions in the volatile and fixed oils. Concentrated sulphuric acid dissolves and water precipitates it from the acid; by the action of nitric acid it is converted into another resinous acid when it has been precipitated from alcohol by water; ammonia dissolves this acid readily, and the silvate of ammonia formed, as well as that of potash and of soda, is soluble in water; most silvates are however insoluble in it, but many of them are dissolved by alcohol and by æther; the silvate of magnesia especially is taken up by alcohol; the silvates of silver and lead are colourless and insoluble in water.

Silvic acid may be regarded as an oxide of oil of turpentine; its composition, as stated by the chemists above named, is as follows: it will be observed that there is no great difference between them, but they do not agree as to

its constitution:

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vermin; but if taken internally it causes stupor and other narcotic symptoms; it should therefore be carefully distin-. guished from the former.

SIMARUBA CEA, a natural order of plants belonging to the gynobasic group of polypetalous Exogens. The plants of this order are trees or shrubs, with alternate exstipulate usually compound leaves, and mostly without dots. The flowers are whitish-green or purple, on axillary or terminal peduncles, hermaphrodite, or occasionally unisexual. The calyx is 4 or 5 parted; petals four to five, twisted in æstivation; stamens twice as many as the petals, arising from the back of an hypogynous scale; ovary 4 to 5 lobed; style simple; stigma 4 or 5 lobed; fruit a drupe; seeds pendulous, exalbuminous, with a superior short radicle drawn back within thick cotyledons. With one exception they are all natives of Africa, India, and tropical America. This order was formerly included under Rutacea, but their differences from that order appear to many of sufficient importance to constitute a separate family. A. de Jussieu says, 'They are known from all Rutaceous plants by the coexistence of these characters, namely, ovaries with but one ovule, indehiscent drupes, exalbuminous seeds, a membranous integument of the embryo, and by the radicle being retracted within thick cotyledons.'

The plants of this order are all intensely bitter. The Quassia on this account is used in medicine. [QUASSIA.] Simaruba versicolor is so bitter that no insects will attack it; and when all other specimens of plants in dried collections have been attacked by Ptini, &c., specimens of this plant have been left untouched. The Brazilians use an infusion of this plant in brandy as a remedy against the bites of serpents.

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SIMARU'BA is the bark of the root of the Simaruba amara (Aublet), S. officinalis (of Dec. and Pharm. Lond.'), a tall tree, native of Guayana, and also of Jamaica, if the tree found in that island be not a distinct species. It is imported in bales containing pieces a foot or more in length, tolerably broad, and generally formed into rolls the whole length of the piece. Externally it is rough, warty, and has a dirty-yellow cuticle marked with transverse ridges; the epidermis below this is of a whitish-yellow colour. Internally smooth, with a greyish yellow colour. It is devoid of odour, but intensely bitter. Its chief constituents are quassite, resin, a volatile oil having an odour like benzoin, ulmin, mucilage, and some salts. It is tonic and demulcent in small doses, and therefore useful in the later stages of dysentery, but in larger doses it is emetic. The bark of the root of Simaruba versicolor (St. Hilaire) is very like that above described, and is used externally by the Brazilians as a wash to ill-conditioned ulcers, and to destroy

Quassia amara.

a, brauch, showing flowers and compound leaves: b, flower; c, stamens separated, attached to hypogynous scale; d, stamens surrounding ovary; e, ovary seated on a stalk, to which the stamens are attached.

SIMBIRSK, a government of Asiatic Russia, is situated between 52° and 57° N. lat., and between 42° 20′ and 50° 20' E. long. It is bounded on the north by Kasan, on the east by Orenburg, on the south by Saratow and Pensa, and on the west by Nischnei Novgorod, The area is 24,000 square miles. The surface is in general an undulating plain, but on the right bank of the Volga there is a range of hills, composed of clay, marl, limestone, and freestone, which rise to the height of 400 feet. The principal river of this government is the Volga, which enters it from Kasan, about the middle of the northern frontier, and runs in a direction nearly south to Stavropol, where it turns to the east; and there, after being joined by the Sok, coming from Orenburg, it makes a semicircular bend, and at Sa mara turns due west, in which direction it proceeds as far as the town of Sysran, when it again turns to the south. It is at this bend that the eminences on the Volga are highest, though they accompany the river in its whole course from north to south. Beyond the bend the surface of the country

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