m 



CHEMISTRY. 



COPPER. 



Tin* meul WM well known to the ancients, and is men- 

 tioned in the work* of biblical and general history. Its 

 pecifio graMty U 878 ; iU symbol, Cu ; and the equiva- 

 lent- 317. 



Copper U found in the rocky districts of mart parU of 

 the worl<l, fitln r in the metallic state or OonUnad with 

 sulphur and carbon. In some parts it is found in the 

 metallic state in immense masses ; a specimen weighing 

 above one ton, and containing 96 per cent, of pure 

 copper, may lie seen in the Polytechnic Institution, 

 Regent-street, London. When combined with Milpliur, 

 called copper pyrtta ; and as a carlwnate, it forms 

 that beautiful substance called malachite. The chief 

 source of copper in this eonntry in in the mines in Corn- 

 wall Australia, New Zealand, America, Western Africa, 

 Russia, and Sweden also produce it in large quantities. 

 A very ingenious use of old iron pots and pans is effected 

 in the water running from the copper mines. The old 

 iron is collected in London, and shipped to Cornwall, and 

 on being thrown into water containing copper in solution, 

 the iron is dissolved, and the copper is thrown down in 

 the state of a brown powder. It is afterwards melted 

 and cast into bars. This plan is easily illustrated by 

 dipping any iron article into a solution of blue vitriol 

 (sulphate of copper), when the metal will be coated with 

 copper, a portion of the iron having been dissolved away. 

 Whan the ores of copper are employed, they are first 

 roasted, to drive off the sulphur ; and after smelting, t< .1.- 

 rably pure copper is obtained, in quantities proportional 

 to the richness of the ore. 



In the metallic state, copper is recognised by its red- 

 dish-yellow colour. It can be highly polished, but soon 

 tarnishes. It is soluble in many acids, and may be de- 

 tected in solution, by the addition of a little smelling-salts 

 (carbonate of ammonia), which produces a blue colour. 



It is hugely employed in a variety of ways. As a 

 metal, it is fashioned into vessels for domestic use, which 

 are, however, highly dangerous if they are not coated 

 romplrttly with tin, because a portion of tho metal dis- 

 solves and forms a poisonous salt. In the manufacture 

 of pickles and preserves, this often occurs; but cop]>.-r 

 may be detected by the means already named. In the 

 absence of medical advice, abundance of sugar or the 

 vntoiltd white of an egg may be taken as an antidote. 



Alloyed with zinc, the well-known metal brass is pro- 

 duced, lironce and gun-metal are a mixture of CO]>]T 

 with about one is weight of tin. Bell-metal U 



composed of four or five part* of copper to one of tin. 

 An alloy of copper, instead of tho im-tal itself, called 

 Mnntz's metal, is extensively employed for nln-athing 

 ship*' bottoms. 



The combinations of copper are numerous, and many 

 of them are extensively employed in the arts and manu- 

 factures. It combines with oxygen in vari< >us ] . i . 

 Two equivalents of tho metal with one of oxygon ((.'<. 

 produce the sub-oxide, which may be procured by heating 

 the chloride with carbonate of soda in a crucible. 

 compound so produced by fusion, is then to be plunged 

 Id water, when tho sub-oxide separates. It is chicil y 

 nerd to colour glass, and a singular property exists in 

 reference to it. If it be burned in at a coiiiparnth.-iy 

 low temperature, and for a short period, but a slight rod 

 tint is afforded. If the heat be increased, and the j 

 of burning extended, tho colour is deepened. In an 

 instance which came under our notice some years 

 resulting from thn destruction of the Glasgow Polytechnic 

 by fire, a piece of cut-glass of about four cubic inches' 

 capacity, which had previously been of but a light niliy 

 tint, was converted into so dark a colour by the 

 that when chipped into the thinnest pieces, it appeared of 

 the deepest ruliy red. 



The protoxide of copper (Cu O), which is extensively 

 employed in organic analysis, may be readily obtained by 

 basting strongly the nitrate in a crucible, when a black 

 pr<lii<-<-l. Full directions for its use for 

 that purpose will be subsequently given. A binnxido oi 



copper, and sn acid called cuprio acid, have Ixxsn disco- 

 vered ; 1'iit they are not of special chemical importance, 

 except that the latter is somewhat analogous to the ferric 

 acid, of which wo shall speak hereafter. 



There are two compounds of copper with chlorine* 

 mib and the proto-chlorid>j. The latin- <-. 

 by dissolving tho oxide of copper in hy ! 

 when a pale-green solution in produced. Tais is 

 used as a sympathetic ink, and fur the pur|Miso of 

 I'aintiug*, which, by beim; heated, change from a wii 

 to a summer-like appearance, by the production oi 

 jreen colour which -Ives. Tho sub-chl 



may be prepared from the chloride, by heating the chli >ndc 

 with copper filings in a crucible. 



The di.sulphido of copper is found naturally, and is 

 one of the ores of copper, as wo have already stated. It 

 may be produced artificially, by heating sulphur and 

 copper in a crucible. The ore is largely employed in 

 Glasgow and other places, as a source of sulphur for tho 

 manufacture of sulphuric acid. The proto-sulphide is 

 readily produced by passing sulphuretted hydrogen 

 through a solution of a copper salt, when a black p< > 

 is thrown down. With cyanogen, copper forms tho 

 cyanide, which is chiefly used for the purposes of electro- 

 typing. 



The most important salt of copper is the sulphate, 

 which may be obtained by boiling copper in sulphuric- 

 acid. It is a product of many copper mines ; and when 

 crystallised, ull'ords large blue crystals, -vhich are known 

 in commerce as blue vitriol This salt has become of 

 great importance since the discovery of the electrotype 

 process; and by means of this ingenious application of 

 science, copies of expensive works of art, such as statues, 

 engraved plates, etc., art; lined, at a trifling 



cost compared with that of the original. 



The nitrate of copper is readily procured by dissolving 

 the metal in nitric acid. Its chief use is that of affording 

 the oxide of copper used in organic analysis, to which 

 we have already referred. 



Tho native carbonate of copper, called nvJachite, lias 

 been named previously. It is often fashioned into vari< ma 

 ornamental articles, owing to the beautiful appearances 

 which it presents. A compound of carbonic acid, copper, 

 and water is readily produced on adding carbonate of 

 soda to the sulphate of the metal, both being in solution, 

 when a light-green powder is precipitated. Native car- 

 bonates are very common in the specimens of ores 

 obtained from the copper mines. 



( in adding ammonia to a solution of a cupreous salt, a 

 deep-blue colour is produced, which is a combination of 

 the metal with the alkali, often termed by old writers the 

 iimmoniurot of copper. 



One of the most valuable salts of the metal is tho 

 acetate, which is familiarly known as "verdigris." and 

 extensively employed as a pigment. The pure ac 

 is readily obtained by dissolving oxide of copper in acetic 

 acid. The ordinary commercial product is obtaiie-d by 

 means of the waste of the vineyards and metal'. 

 the external surface of the metal beimr converted into 

 an impure acetate. This is removed, and the process 

 is repeated until the plate is completely used up. 

 " Scheele's green" is acompouud of arsenic and cupper, 

 and is also used as a pigment. 



IRON. 



Tins metal is so well known, and used in such a variety 

 of ways in civilised life, as to require no -n on 



our part. It in universally distributed, and is one of 

 the most abundant I in nature. Its sp 



is 7-6 ; symbol, Fo ; and tho equivalent = 2.S. 

 Its ores are chiefly the carbonate, oxide, and sulphide; 

 tho latter Iming a compound of the met... with sulphur, 



1 iron pyrites : this, with the copper p 

 been used by sulphuric acid-makers as a source of 

 sulphur.* 



The iron district of this country embraces a very ex- 

 tended area. In Scotland, a band of ironstone is found, 

 Sec ante, p. 368. 



