I R O N. 



»-liic!i are without luftre. Fragments indeterminate ; foils ; 

 is foft, and very fofr. Sometimes friable. Meagre to the 

 touch. Eafily frangible, and moderately heavy. 



Siihfp. 2. Cohfren! gnat iron eiuth. — Co\mit rather darker 

 than the laft fubfpecics. Occurs maffivc, and corroded. 

 Irile;nally dull. Fracture fine earthy, palTing into even, 

 and fometimes into fplintery. Fragments indeterminate; 

 foft. Rather brittle, and inclining to heavy. 



Before tlic blow-pipe, it becomes firil red, and then of a 

 dark brown ; but does not melt. It tinges borax of a. yel- 

 low colovir, inclining to olive-green. No exaft analyfss has 

 been made of thi:. fpecics ; but it i<; fuppofed by Werner to 

 have iron and phufphoric acid for its principal ingredients. 



It is a rare mineral, and has hitherto been only found at 

 Brauiifdorf and Schneibcrg, in Saxony, where it occnrs in 

 veins : in the former place, accompanied with quartz and 

 pyrites ; and in the latter, with quartz and native bif- 

 mnth. 



Sp. I). Cubi-orc. JVurfcler'::: Per arfmiiate. 



Colour olive-green, of difTerent degrees of intenfity. 

 Occurs maffive, difleminated, and cryftallized in fmall and 

 very fmall cubes, which are fometimes flattened and trun- 

 cated at the angles. Planes of the cry (lals fmoofh and fplen- 

 dent. Internally it is gliltening, and its lullre between 

 pearly and adamantine. Fradure imperfect foliated. Frag- 

 ments indeterminate. Occurs in granular dilUnft concre- 

 tions. It is tranflucent ; foft ; brittle, and gives a llreak of 

 a ftraw-yellow colour. Sp. gr. 3.000. It appears fome- 

 times m the form of a reddilh-yellow powder, which is thinly 

 diilributed over the furface. 



, Before the biow-pipe it fwells up, and emits an arfenical 

 odour ; melting afterwards into a grey metallic globule, 

 fliglitly tinged with yellow. From the analylis of Ciiene- 

 fix, it appears to be compofed of 



Arfenic acid - - 31. 



Oxyd of iron - 45.,- 



Oxvd of copper . - y. 



Rile'x - . - 4. 



Water of cryllallization 10.5' 



It occ'jrs in veins, accompanied with fome ores of copper, 

 quartz, mica, and fcldfpar. 



The only places that have, hitherto, afforded it, arc the 

 mines of Carraiach and Muttrell, in Cornwall. 



Until the account pubUdied of this mineral by the count 

 de Bournon, and Mr. Clu-nevix, in the Pliilofoplilcal 

 TraiifaClions for iSci, it was niillaken for an arfeniat of 

 copper. 



§ 2. AJfay and Analyfis. 



Since the metal contained in every ore is of fo much 

 greater fpecific gravity than any other of its accompanying 

 ingredients, it will be eafy to form a tolerable idea of tiie 

 value of an iron-ore by the weight of a given l)ulk. 



Previoufly to working any iron-ore it tliould be very mi- 

 iiiitciy analyfed, both in the humid and dry way. By the 

 humid procefs we flud afecrtain the exact proportions of its 

 conilituents, without which it would be a mere work of 

 chai ce to attempt to cxtra£l the iron in the metallic form. 



When we are acquainted with the nature of the earthy 

 matter in combination with the ore, we know with the 

 grcatefl certainty what fubilances we ought to add in tlie 

 crucible, for the purpofc of eliminating the metal. All fiicli 

 fubilances are coiled fluxes, merely becaufc they form fullblc 



compounds with the earthy mat^r of the mificral. It is to 

 this treatment of a fmall quantity of the ere that we give the 

 name of affaying. 



The procefs by which the component parts are afcertained, 

 confills in fubjecting a fmall quantity of the ore in line pow- 

 der to the action of an acid, and fometimes to an alkali. 

 By this means the whole is dilTolved, and the difierent mate- 

 rials of which it is compofed are feparately precipitated by 

 different chemical re-agents. The procefs, however, varies 

 confiderably with the nature of the ore to be examined. 



Iron ores, as fubjecls of analyfis, are divided into three 

 heads ; namely, fulphurets, oxyds, and falls. 



The firll are diilingiiillied b"y tlieir gen. ;;:,:. . ' -.r, 

 but more particularly by the fuffocating ti. 1 ; 



acid gas, vv-hicli they afford by being heatL J o 



open a;r. The fecond confift of iron uiiitid \win o>.\ j;(_ii, 

 and are by f^u- the moll common of all. Nearly the wliole 

 of the iron-ores in ufe are of this kind, contaimng alfo dif- 

 ferent proportions of earthy matter in their compoiition. 



The third divilion comprehends fuch as conllli: of the oxyd 

 of iron combined witli fome acid, and hence are called I'alts. 

 The principal varieties of thefe are the phofphats, fulphats, 

 arlVniats, and carbonats. 



The apparatus em])loyed in the humid analyfis will be a 

 lamp fitted up with different-fized (liding-bearers, a filver cru- 

 cible, and fmall portable furnace, with a fand-bath, and one 

 of water, for drying precipitates ; capfules of glafs and 

 porcelain ; precipitating glaffes, funnels, and filtering paper. 

 For reducing the ore to powder, a mortar of hardened lleel 

 will be lirfl neceffary, and afterwards one of agate, to grind- 

 it very fine. Accurate weights and fcales will be highly 

 requifite, witli cups of filver or platina. 



The re-agents wanted \\\\\ be fwlphuric, muriatic, and 

 nitric acids. Pure potadi, foda, and borax, in the folid 

 f)rm. Solutions of the lame, and alfo the pure aqua ammo- 

 nia. The fully latui.itcd carbonats of all the alkalis, and the 

 fubc.irbonats of the fame. The triple prufl'.at of potafh 

 and iron ; and, when mt rely ufcd as a tell, prufTiat of lime' 

 wi;l anfw.jr. The anal vll fliould, alfo, have in his poflefiiou 

 po ..,.•)■- IT l.l.iuonsof all the feparate fubllanees of which" 

 t;,e ii iii.i-.l :, fuppofed to eonfilt, for the purpole of com- 

 paring real rcfults with tliofe obtained in Ins experiments. 



If the ore to be analyfed be a pure fulphuret, 100 grains, 

 or any other given weight, may be reduced to powder, ob- 

 Icrving to weigh it after the operation, to fee if any of the 

 mortar has been abraded, which, wiien the ore is very hard, 

 is to be expefted ; and the inereafed weight mufl in that 

 cafe be noted down. 



Let this powder be boiled with nitric acid in a long narrow- 

 beaked glafs vcffel, which Ih.ould be very thin at the bottom, 

 to avoid cracking. By tiii. n.eihod the fulphnr of the ore 

 will be converted lit - i: 1 ,> ij ; part of the nitric acid 

 v.-ill be dccompo! . . - • i,- remainder fly off, I'o that 



the refulting flui-i v . . ; , ,, ...; eonfilt of the iron diffolved 

 in fulphuric acid. 



To this folution add the muriat of barytes, till a precipii 

 tation ceafes to take place. When the precipitate has fub- 

 fided, and the fluid is become perfedly clear, gently pour olT 

 the liquor, which is a folution now of iron in the muriatic acid. 

 Let the precipitate, confuting of fulphat of baryies, be re- 

 peatedly wafhed with hot dilliiled water, till the liquid gives 

 no precipitate with intrat of filver, and afterwards add the 

 wafhings to the fluid firlt poured off. After this white 

 powder has been dried on the Iteam-bath, which is an appa- 

 ratus conllructed for this particular ufe, let it be weighed, 

 and for every 100 grains of the fiibflance allow 21.3 ot ful- 

 phur. To the liquid parts wluch contain the oxyd of iron, 



add 



