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mercury. 9. For what is it used? 10. What is said of fulminating powder? 11. Of mercury as a solid metal? 12. What is the description of the quicksilver mines in Peru? 13. How much must the temperature of mercury be reduced before it will become solid? (see Appendix.) 14. What is said of freezing mixtures?

LESSON 80.

Copper and Lead.

Concentrated, usually applied to fluids which are rendered stronger
by evaporating, by means of heat, a portion of the water they
contain.

Heterogeneous, dissimilar in nature. Homoge'neous, having the
same nature or principles..
Culinary, relating to the kitchen.

COPPER is a brilliant metal, of a red colour, very hard, sonorous, and elastic; and the most ductile of all the metals, except gold. Its malleability is also so great, that it is hammered into leaves, and sold in thin paper books in imitation of leaf-gold. It will not burn so easily as iron; which is evident from its not striking fire by collision. On this and other accounts it has been substituted for iron in the machinery which is employed in gun-powder mills. The salts of copper are numerous, and much used in the arts connected with chemistry. Concentrated sulphuric acid dis solves copper by the aid of heat, and thus the sulphate of copper or blue vitriol is formed. Copper exposed to the vapour of vinegar or acetic acid becomes acetate of copper or verdigris. All the salts of copper are poisonous, therefore great care should be taken not to taste wantonly the solutions. The uses of this metal are too various to be enumerated. Besides its employment to make boilers and other vessels of capacity, and to sheathe the bottoms of ships, it enters as a component part into several of the most valuable alloys. The most important of these alloys is brass, which is formed by the union of copper and zinc, though brass is never made with pure zinc, but generally with calamine, which is a native oxyd, or rather carbonate of zinc. Bronze and gun-metal are formed by the union of copper and tin in the proportions of a hundred parts of the former to ten or twelve of the latter. Bell-metal is also an alloy of tin with copper, but this usually contains one fourth

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of its weight of tin. Oxyd of copper is used by the colouredglass makers. It forms a beautiful green glass.

Lead is a metal of a bluish white colour, very brilliant when first cut with a knife, but it soon tarnishes by exposure to the air; it will mark writing-paper, though in a fainter manner than plumbago. It is malleable and ductile, but possesses very little tenacity. Lead may be mixed with gold and silver in a moderate heat, but when the heat is much increased, the lead rises to the surface, combined with all heterogeneous matters. Upon this property of lead is built the art of refining the precious metals. If melted lead be exposed to the atmosphere, a greyish-yellow powder begins to form upon the surface. By keeping it exposed for some time the powder becomes more yellow. In this state it is called massicot, or yellow oxyd of lead. By a second exposure this oxyd appears capable of combining with more oxygen. It gradually changes colour, and ultimately assumes a splendid red. In this state it is called minium or red lead. The process requires considerable management with regard to heat and the access of air. If the heat be too great or rapid, the lead becomes converted into a flaky substance, called litharge; and a still greater heat converts it into a clear, transparent yellow glass. Thin plates of lead, exposed to the fumes of vinegar at a certain temperature, are gradually corroded and converted into a heavy white powder, used as paint, and called white lead.

The ore of lead is so poisonous, that the steam arising from the furnaces where it is worked, infects the grass in all the neighbouring places, and kills the animals which feed on it. Culinary vessels, lined with a mixture of tin and lead, which is the usual tinning, are apt to communicate to acid foods pernicious qualities, and require to be used with great caution. The same may be said of liquors and other acid substances kept in glazed ware, and of wines adulterated with litharge, and such other preparations of lead as are sometimes used for the purpose of rendering them sweet.

QUESTIONS.-1. What is copper? 2. Why is it substituted for iron in some machinery? 3. What is said of the salts of copper? 4. What is brass? 5. What are bronze and gun-metal? 6. Bell-metal? 7. Describe lead? 8. Why is it used in refining metals? 9. How does lead become oxydized so as to form massicot, and minium? 10. What is litharge? 11. How is white lead formed? 12. What is said of the poisonous qualities of lead?

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Chalyb'eate, a term descriptive of those mineral waters which are impregnated with iron.

Pyrites, a name given to certain ores, as of iron, copper, tin, &c. which contain a large quantity of sulphur, and have a metallic lustre.

IF utility were made the standard of estimation, iron would hold the first place in the class of metals, and would be counted more valuable than gold, as it appears indispensably necessary to the carrying on of every manufacture. It appears to be one of the principal means of civilizing mankind. There has never been an instance of a nation, acquainted with the art of manufacturing iron, which did not in time attain to a degree of civilization infinitely be yond the inhabitants of those countries where this metal was wanting, or its use unknown. It is plentifully and universally diffused throughout nature, pervading almost every thing, and is the chief cause of colour in earths and stones. It may be detected in plants and in animal fluids. There is a great variety of iron ores, which have different names given them by the workmen, and are of very different qualities. They are chiefly composed of the oxyds of iron and clay. This metal is susceptible of two degrees of oxydizement: the scales, which are detached from forged iron by a high degree of heat, are in the state of black oxyd, and the common rust of iron is the red oxyd. If a bar of iron be heated red-hot, and a stick of sulphur applied to it, a fluid substance will drop from its end, which is found to be a compound of sulphur and iron, and in chemistry is called sulphuret of iron. Iron-filings mixed with sulphur, and made into a paste with water, in a certain time become very hot, and even produce flame. This mixture is sometimes buried under the ground to produce an artificial volcano. In this experiment the water is decomposed, the oxygen unites with the iron to form an oxyd of iron, and with the sulphur to form sulphuric acid, while the hydrogen combines with another portion of the sulphur, and produces sulphuretted hydrogen gas, which occasions the flame. Green vitriol or copperas, which is of so much use in dyeing, in colouring

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hats, and in other manufactures, is a sulphate of iron. With the prussic acid, iron forms that beautiful paint, known in commerce and the arts by the name of prussian blue.

Tin must have been known very early, as it is mentioned by Homer, and also in the books of Moses. It is a white metal, of little elasticity, and small specific gravity. It is not very ductile, but so malleable that it may be beaten out into leaves thinner than paper. Tin-foil, as it is termed, is usually about one-thousandth part of an inch in thickness. Tin enters into combination with many of the metals, and forms alloys with them, some of which are of great importance. The amalgam of mercury with tin is used in silvering mirrors. Pewter, which was formerly much used, is an alloy of tin and lead. In tinning iron the plates are immersed in the melted tin, and are either moved about in the liquid metal, or are dipped several different times. They are then taken out, and rubbed to remove the impurities from the surface. Tin is consumed in large quantities by the dyers. It is employed to give a brightness to several articles used in forming reds and scarlets. Substances which produced to the ancients only faint and fleeting colours, give us such as are brilliant and durable, by the use of a solution of this metal.

QUESTIONS.-1. What is said of the utility of iron? 2. Of its abundance? 3. Of its oxyds? 4. Of its sulphuret? 5. How may an artificial volcano be produced? 5. How do you account for this? 7. What is green vitriol and prussian blue? 8. Describe tin. 9. What is said of the alloys of tin? 10. Of tinning iron plates? 11. Of the use of tin by dyers?

LESSON 82.

Zinc, Manganese, and Antimony.

Sublimation, a process whereby certain volatile substances are raised by heat, and again condensed by cold into a solid form: thus are obtained flowers of arsenic and flowers of sulphur.

ZINC is a very combustible metal, and when broken, appears of a shining bluish white. It is one of the most abundant metals in nature except iron, and in Wales its ore was employed till lately in mending the roads. It is used in

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China for the current coin, and for that purpose is employed in the utmost purity. When zinc is heated it readily attracts oxygen; and at a white heat, the absorption of oxygen is so rapid and violent, that the oxyd immediately sublimes, and for this reason it has acquired the name of flowers of zinc. It is frequently combined with copper or tin, in various proportions, and these mixtures constitute some of the most useful compound metals. It is used in medicine, is the base of white vitriol, and its carbonate or oxyd may be advantageously substituted for white lead in house-painting.

Manganese is a brilliant metal, of a darkish white colour, inclining to gray, of considerable hardness, and of difficult fusibility. When exposed to the air, it absorbs oxygen with rapidity and falls into powder. It abounds in this country; but on account of its great affinity for oxygen, it has never been discovered in a metallic state. Its oxyd is easily procured; but the pure metal can only be obtained by art, and in order to preserve specimens of it, it is necessary to varnish them, or to keep them immersed in oil, or ardent spirits. Its oxyds are used in preparing the bleaching liquor, in purifying glass, and in glazing black earthen ware. It is also employed, in some cases, to give colours to enamels in the manufacture of porcelain. The black oxyd is much used by chemists for producing oxygen gas, which, by the application of a red heat, it yields in great abundance.

Antimony is a brilliant, brittle metal, of a silvery white colour, which has not much tenacity, and is entirely destitute of ductility. It may be entirely volatilized by heat. It is also susceptible of vitrification, and produces a hyacinthcoloured glass. Antimony is combined with some other metals in making types for printers. Its oxyds are employed in medicine, and in colouring glass.

Arsenic is generally found in combination with sulphur, oxygen, and many of the metals. Its colour is bluish, or greenish white, becoming, on exposure to the air, dark, almost black; it is extremely brittle, and at the same time the softest of all metals. It is one of the most active of mineral poisons.

Beautiful shades of various colours may be given to different substances by solutions of arsenic. So that the substance which is most injurious to the animal economy, appears to be endowed with properties for embellishing the

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