I R O N. 



add a clear folution of the fiib-carbonat of potadi. Let it 

 boil for a little time, ar.d the oxyd of iron will fubfide. 

 AVafli it and dry it a'tabovT, afterward"^ weighing llie prodcO. 

 The quantity of oxygen in the oxyd of iron thi^s obtain- 

 ed, mav be known by the quantity of iron ob'ained 

 from it in theprocefsof alTaying, which \vc (lia!l afterwards 

 give. If the' ore'conliil of oxygen and iron only, it may, 

 without any previous treatment, be referred to the dry pro- 

 cefs. Wiien, however, earthy matter is combined with it, 

 the humid analyfis (hould be reforted to, which requires a 

 different mode of proceeding to that already given. 



Let lOo grains of the ore be reduced to a fine powder, as 

 above directed, obferving to weigh it afterwards, for the 

 purpofe of afcertaining whether any of the materials of 

 the mortar be mixed with it. The matter fo added, if 

 it be acquired from the agate mortar, may be deemed 

 pure files. 



To this powder add 300 grains of dry potafh, in a filver 

 crucible, capable of holding about fix or fcven ounces. 

 Pour to the mixture a very little water, jud fufficient to 

 moifte.i the whole. Apply a gentle heat in the firft inftance, 

 to prevent the mafs from fwelHrg too much, and gradually 

 increafe the temperature till the crucible is red-hot. The 

 mafs will now be in a ftate of fufion more or lefs perfect, ac- 

 cording to the quantity of filex contained in the ore. If, 

 from a great proportion of alumiiie being prefent, the fufion 

 fhould be very imperfedl, more potafh mud be added, and 

 the heat continued and raifedaahigh as the crucible will bear. 

 When the crucible, with its contents, are fufficiently cooled, 

 let both together be put into a capfule of porcelain, and 

 nearly filled with dillilled water. The whole Ihould then be 

 fet upon a faiid-bath, r.nd boiled for fome time, taking care 

 to ftir it very frequently. Tiiis will detach the matter ad- 

 luM-ing to the crucible, and if any filex remain una61ed upon, 

 it will be dilTolvcd by the potalh. 



Let the whole be now faturated with muriatic acid, and 

 even added a little in excefs ; and then gently boiled till all 

 the hquid is evaporated. During this, the mixture mud be 

 conftanlly ftirred ; and particularly at the time the mafs 

 is becoming dry. 



To this refiduum let a large quantity of diftilled water b^ 

 poured. All the fub (lances foluble in the acid will be now 

 taken up. If it contain filex that will be left at the bottom. 

 Let the whole be decanted into a narrow tall glafs vefiel, to 

 fuffer the filex to fubfide. Carefully pour off the clear 

 liquor, and then add freih hot diililled water, and continue 

 to do fo till the fluid does not caufe a precipitate with nitrat 

 of filver ; obferving to fave all tlie wafliirgs which are acted 

 upon by that tell. Tlie remaining water may now be evapo- 

 rated from the filex, and the powder, being heated red-hot 

 in a crucible of filver or platina, fhould be then weighed. 

 If it be pure, it will be of a delicate white colour, not adhering 

 to the fingers, as is the cafe with fome of the oilier earths. 



The folution containing the remaining fubftances fltould 

 be evaporated to as fmall a quantity as poffible, fo that the 

 fluid remain liquid and clear. To this let a faturated folu- 

 tion of the fubcarbonat of potafh be added, and afterwards 

 boiled a few minutes. By this means, the whole of the in- 

 gredients will be precipitated together, and when all of 

 them have perfectly fubfided, decant off the liquor, re- 

 peatedly wafhing it with hot water. The firft decanted li- 

 quor, with the wafhipgs, may be thrown away. Laftly, 

 evaporate the remaining water, till the fohd matter is ot a 

 pulpy confidence. To this, in a capfule of good porcelain, 

 add a folution of pure potafli. The aluniine will be thus 

 .diffolvcd, while all the other fubilances will remain un- 



touched. Let this fluid be poured off, and frefh water 

 mingled with it, to take away all the alumine. Then, to 

 the p.ixture containing the alumine, add not only as much 

 r i ■. : -■ will faturate the potafli, but alfo a quantity fufScient 

 • c'.i'lMvc ihe alumine, when the liquid will be quite cle?r, 

 li::..ily, to this pour in carbonat of ammonia, till no more pre- 

 cipi'.ate falls down. The precipitate, when wafhed and dried 

 as above direfied, and heated to rednefs in a filver crucible, 

 may be confidered as pure alumine. 



The refiduum from wl'.ich the alumine vras lad taken 

 is now to be difTolved in fulphnric acid, diluted with a large 

 quantity of water, the acid being flightly in excefs. This 

 folution may contain magnefia, iron, and probably manga- 

 nefe. If iime were prefent, it will be left infoluble at 

 the bottom of the vefTej, in the ftate of fulphat of lime. 

 The fmall portion of this fubliance difTolved by the Huid, 

 may be precipitated by the addition of alcohol. The pow- 

 der, when coUefted and dried at a dull red heat, mu(t 

 be weighed; allowing for every 100 parts 42 of pure 

 lime. The fohition from which the lime wss feparated, 

 mud next be faturated with a folution of the neutral carbonat 

 of potafh. In a few minutes the iron will be precipitated 

 in the ftate of oxyd, while the magnefia and mangancfe will 

 be difTolved by the carbonic acid. The iron niuil be fe.. 

 parated, dried, and weighed. If with the folution containing 

 the magnefia and manganefe a folution of hydrofulphuret of 

 potafh be mingled, the latter will be precipitated in the form 

 of a fulphuret ; and this being waflied and heated till the 

 fulphur is driven off, the oxyd of manganefe will be left in 

 fufficient purity. 



Tlie magnefia ftill held in folution maybe precipitated br 

 adding a fufficient quantity of pure potafli. Tiie produtt 

 muft h< heated to rednefs, and weighed. The weights of the 

 different fubftances being added together, will, if great care 

 has been ufed, be within one or two per cent, of the quan- 

 tity originally fubmitted to experiment. If the deficiency 

 be confiderable, fome miftake mud have been made, and it 

 will be neceffary to repeat the analyfis. 



In the examination of falts of iron, nothing more is re- 

 quifite than to difengagethe acid with which the iron is com- 

 bined. The arfeniat of iron, for example, muft be boiled 

 with potafh, which will feparate the arfcnlc acid, and leave 

 the oxyd of iron but very little acted upon. The arfenic 

 acid may be afterwards precipitated by nitrat of lead ; allow- 

 ing for every 100 parts of the arfeniat of lead, when dried, 

 33 parts of arfenic acid. 



If the ore be a pure carbonat, to ico grains in powder, 

 add an equal quantity of fulphuric acid, in a glafs vefTel 

 which can be placed over a lamp. Heat the mixture for 

 fome time, ftirring it with a glafs rod. The carbonic acid 

 will be thus expelled, and its quantity will be indicated by 

 the lofs of weight fufiained. Care fhould, of courfe, be 

 taken that the heat be not too great, otherwife the evaporation 

 of fluid matter may create error in the experiment. The iron 

 may be afterwards treated as in the analylis of the earthy ores, 

 and its quantity afcertained, by the methods there defcribed. 

 Having learned the exaft proportions of the ingredients 

 united in the ore, we may, with fome degree of certainty, 

 proceed to the afTay by the crucible and fluxes. If the ore 

 confid of oxyd of iron fimplv, nothing more is neceflary 

 than to introduce it into a crucible with about half its weight 

 of charcoal powder, and any fubdance fufceptible of vitri- 

 fication, fo as to keep off the air. This may be either 

 pounded glafs, or equal parts of lime and clay. But perhaps 

 the bed fubftance that can be employed, is the mod fufible 

 part of the blaft furnace cinder, which is the leaft coloured 

 with oxyd of iron. This may be employed in quantity 



amounting 



