16 



CHEMISTRY. 



Kleracau 3. At far as we know at pment, chlorine hai not 

 the property of combining with azote. 



4-. The combination* of azote with the simple tub- 

 stance* arc not numerous, but tome of them are im- 

 portant. 



When putrid urine, wool, and many other animal 

 substances, are distilled, among other product*, there 

 U obtained a substance of a pungent odour and taste, 

 known by the names of hartshorn, volatile alkali, 

 ammonia. It may be obtained pure, by heating a 

 mixture of three parts of quicklime and one part of 

 the salt called sal ammoniac, in a glass flask, aud re- 



.ing the product over mercury. It is a gas. 

 When electric sparks are passed through it, its bulk 

 is doubled, and it is converted into a mixture of azo- 

 tic and hydrogen gases. Hence it is a compound of 

 these two substances. It consists of three parts by 

 measure of hydrogen gas, and one part of azotic gas. 



Azotic gas is said to have the property of dissol- 

 ving a little charcoal, which it again depusites when 

 allowed to stand over water. 



It disoolvcs likewise a little phosphorus, and in- 

 creases about one-fortieth part in bulk. When this 

 phosphureted azotic gas is mixed with oxygen gas, 

 it becomes luminous, in consequence of the combus- 

 tion of the dissolved phosphorus. 



Azotic gas is said likewise to dissolve a little sul- 

 phur when assisted by heat. Sulphuret-d azotic 

 gat is said to resemble sulphurated hydrogen gas in 

 us properties. 



CHAP. IV. 



Of Metals. 



Metals. METALS, one of the most important classes of bo- 



dies, and to which we arc indebted for most of our 

 improvements, are very numerous. Indeed, the pre- 

 sent state 'of chemical analysis leads to the opinion 

 that all bodies will ultimately divide themselves into 

 two sets ; namely, metals, and supporters of combus- 

 tion. 



1'ropertiefc 1. Metals are distinguished by a peculiar lustre, 

 well known by the name of the metallic hutre. They 

 are perfectly opake or impervious to light, even in 

 the thinnest plates to which they can be reduced. 

 The only exception U gold leaf. Its thickness does 

 not exceed T T'-Vr^ tn P art f an ' ncn > a d it allows 

 the light to pass through it. If other metals could 

 be reduced as thin, it is probable that they also would 

 be pervious to light. They may all be melted when 

 heated sufficiently. Some, as mercury, require very 

 little heat to melt them ; while others, as platinum, 

 require a great deal. Their specific gravity is ex- 

 ceedingly various. All the old metals are at least 

 five times heavier than water ; and some, as platinum, 

 more than twenty times heavier. But some of the 

 new metals discovered by Davy are much lighter 

 than water. They are the best conductors of elec- 

 tricity of all known bodies. None of them is very 

 hard ; but some of them may be hardened artificially, 

 so as to exceed must other bodies. Their elasticity 

 may likewise, iu somr c-i-ci, br artificially increased. 

 Some of them are malleable, or may be extended by 



the blows of a hammer, while others arc brittle. Elmnenw 

 Some of them are ductile, or may be drawn out into ' 

 wire, while others cannot. They differ considerably ^""^J" 

 from each other in their tenacity, or in the weight 

 which they arc capable of supporting without break- 

 ing. 



'2. Several of them take fire when heated, and burn Combine 

 with considerable splendour, and almost all of them with uxy- 

 may be burnt by peculiar contrivances. After fom- gen, 

 bustion, their appearance is totally changed : They 

 have lost the metallic lustre, and are converted into 

 earthy. like powders, formerly called calces, and now 

 oiidet. These oxides arc of various colours, white, 

 red, yellow, blue, &c. according to the metal, and 

 several of them are employed as paints. Most me- 

 tals are converted into oxides, merely by exposing 

 them for a sufficient length of time to the action of 

 heat and air, and all by the action of acids. 



When these oxides arc mixed with charcoal pow- 

 der, and heated, they lose their earthy-like appear- 

 ance, and are restored again to the metallic state. 

 This process is called reduction. Some metallic ox- 

 ides, as those of gold and silver, require only to be 

 heated in order to be reduced ; but most of them re- 

 quire also the presence of charcoal, or of some other 

 combustible substance. These oxides were at first 

 considered as simple substances, and the metals were 

 supposed to be composed of them and the principle 

 of inflammability, called phlogiston. But it was 

 shewn by the experiments of Lavoisier, that the 

 oxides are compounds, and that they are composed 

 of the metals from which they were obtained, united 

 to oxygen. Thus, oxide of gold is a compound of 

 gold and oxygen. It was the discovery of this fact 

 that induced chemists to substitute the word oxide 

 for calx. 



Must metals are capable of combining with various 

 doses of oxygen, and of forming various ox ides, which 

 it i>> of consequence to be able to distinguish. This 

 may be done by prefixing to the term oxide the 

 Greek ordinal numeral, expressing the peculiar ox.- 

 ide. Thus, protoxide of tin is the fir. -a oxide of tin, 

 or tin combined with a minimum of oxygen. Deut- 

 oxide of tin it the second oxide of tin, or tin com- 

 bined with two doses of oxygen. The terms trit- 

 oxide, tetroride, pentoxide, &c. are to be under- 

 stood in the name way. The hist oxide of a metal is 

 called Peroxide. Peroxide means a metal combined 

 with as much oxygen as it can take up, or a metal 

 saturated with oxygen. 



3. Metals combine with the simple combustibles, -,,] w [,|, 

 and form compounds, many of which are of consider- curabutti- 

 able importance. These compounds are denoted by ble*. 

 a word formed from the simple combustible present, 

 and terminating in uret. Thus, sulphtiret of tin is a 

 compound of sulphur and tin. In like manner, car- 

 buret and ji/iosji/nirct of iron, means iron combined 

 respectively with carbon and with phosphorus. Hy- 

 drogen gas dissolves some of the metals. These so- 

 lutions are denoted by prefixing the metal converted 

 into an adjective before tl: word hydrogen. Thus, 

 arse it oil hydrogen gas. mean., a ..Union of arsenic in 

 hydrogen gas. When hydrogen combines with a 

 metal, and forms a solid compound, it is denoted by 

 the term hydrogurct . 



1 



