ANALYSIS. 



liiey are diffolved in muriatic acid, and ammonia is added in 

 ■xcefs. The oxyd of iron will be thus precipitated, and its 

 weight may be afcertained. The excefs of ammonia will 

 retam the oxyJ of nickel in folution, which may be laftly 

 obtained feparately by driving off the ammonia by heat. 



When the different conftituent principles of a foflil have 

 been thus obtained feparately, their united weight ought of 

 courfe to be equal to the original weight of the foffil itfelf. 

 If they correfpond, or differ only by .03 or .04 of a part, 

 we may conclude that the ar.alyfis has been properly per- 

 formed. But if the lofs of weight be confiderable, the ana- 

 lyfis muft be repeated ; and if the refult be ftill the fame, it 

 may be concluded that the ftone has contained feme principle 

 either volatile or foluble in water, which mutt, therefore, be 

 fought for. A proportion of the ftone being broken to 

 pieces, is firft. to be expofed to a ftrong heat in a retort of 

 porcelain, to which a receiver is adapted. If it contains 

 water, or any other volatile fubftance, this will be coUefted 

 in the receiver, and its nature and quantity may be afcer- 

 tained. But if it fuftain no lofs by this operation, or a lofs 

 not equivalent to the lofs indicated by the analyfis, it is pro- 

 bable that it contains fome fubftance foluble in water. 



To afcertain the quantity of potafh prefcnt in a mineral, 

 Vauquelin (from whom the above account of the analyfis of 

 Ilony bodies has been chiefly extrailed) recommends that 

 the ftone reduced to an impalpable powder (hould be cau- 

 tioudy heated with fulphuric acid, and the mafs digefted 

 vf ith water. The folution properly concentrated is fet afide 

 for fome days. If cryftals of alum make their appearance, 

 the ftone contains patafli. If no cryftals appear, the folution 

 is to be evaporated to drynefs, and the refidue expofed to a 

 moderate red heat. It is then to be digefted in water, and 

 the folution mixed with carbonate of ammonia, and filtered. 

 It muft be then again evaporated to drynefs, the refidue 

 expofed to a heat of 700°, and rediflblved. The folution 

 by proper concentration will yield cryftals, either of fulphate 

 of foda or of potafti, which may be readily diftinguiftied. 

 The prefence or abfence of potafh may be alfo afcertained 

 by means of the muriate of platina. 



The following method has been recommended by Rofe 

 for detefting and diftinguifhing the fixed alkalies in minerals, 

 and is eafier than the above. He fufed one part of the 

 mineral with four parts of nitrate of uarytes in a porcelain 

 crucible. A fpongy mafs of a light blue colour, and com- 

 pletely foluble in muriatic acid, was obtained. The yellow- 

 coloured folution formed was mixed with a fufficient quantity 

 of fulphuric acid, not only to precipitate the barytes, but to 

 expel the muriatic acid ; and the liquid was evaporated to 

 drynefs. The mafs was digefted in water, and thrown 

 upon a filtre. The fulphate of barytes and filica remained 

 behind. The folution was now faturated with carbonate of 

 ammonia, which feparated all the earthy and metallic bodies, 

 leaving in the folution only the fulphates of fixed alkali 

 and ammonia, the latter of which was then expelled by 

 heat. The fixed alkahne fulphate thus obtained was re- 

 difTolved in water, and decompofed by means of the acetate 

 of barytes. The fulphate of barytes formed was then fepa- 

 rated by the filtre, and the liquid evaporated to drynefs. 

 The other fait was acetate of a fixed alkali, which was 

 expofed to a red heat in a crucible, the charry refidue 

 diffolved in water, filtered, and cryftallized ; and thus a fixed 

 alkaline carbonate was obtained, eafily diftinguilhed by its 

 properties. 



Sir H. Davy adopted ftill a different method. He fufed 

 one part of the mineral with two parts of boracic acid, 

 diffolved the fufed mafs in diluted nitric acid, and con- 

 centrated the folution to feparate the filica. The liquid was 



then mixed with carbonate of ammonia in excefs, and 

 boiled and filtered ; by which means all the earthy and metal- 

 lic ingredients were feparated. The liquid was then mixed 

 with a fufficient quantity of nitric acid, and evaporated till 

 the whole of the boracic acid feparated. Nothing now 

 remained but the nitric acid, combined with the alkaline 

 conftituents of the mineral, and with ammonia. The 

 nitrate of ammonia was diffipated by heat, and the nature of 

 the alkaline nitrate left was eafily diftinguifhed by its 

 properties. 



When the mineral contains _y?!/or:<r acid, Klaproth afcer- 

 tained its prefence by heating the mineral with fulphuric 

 acid in a glafs retort. The corrofion of the retort, and the 

 filiceous depofit in the water of the receiver, fuf&ciently de- 

 monftrate the prefence of that principle. To determine its 

 quantity, the mineral was fufed with potafh, and the fdica 

 feparated as ufual. The remaining liquid was precipitated by 

 means of the carbonate of potafh ; and the liquid being 

 neutralized was mixed with lime-water. The precipitate 

 of fluate of lime thus obtained was heated to rcdnefs, 

 and from its weight the quantity of fluoric acid prefent 

 in the mineral was eftimated. 



Thofe foffds in which earths are combined with acids, 

 forming compounds not foluble in water, require different 

 modes of analyfis. The earthy carbonates are analyfed by 

 calcination by heat, with or without charcoal, or by folu- 

 tion in dilute nitric or muriatic acid ; eftimating the 

 quantity of carbonic acid difengaged, by coUefting it, and 

 difcovering the bafe by the nature of the fait obtained by 

 evaporation ; or by precipitation by re -agents, and eftimating 

 by the fame modes their quantities. Y^sxthy fulphates may 

 be decompofed by boiling with carbonate of potafh for a 

 confiderable time : the fulphuric acid unites with the potafh, 

 and its quantity may be eftimated by precipitating \vith 

 barytes : the carbonic acid is attradled by the earthy bafe, 

 and the carbonate thus obtained may be decompoftjj in the 

 fame manner as a native carbonate, or the quantity of earth 

 v/hich it contains may be eftimated by its weight. Phof- 

 phate of lime, which is the only earthy phofphate that has 

 been difcovered, may be diffolved in diluted nitric acid by 

 the afTiftance of heat ; the lime may be then precipitated by 

 fulphuric or oxalic acid ; the phofphoric acid remaining in 

 folution may be obtained concrete by evaporation ; or its 

 quantity may be eftimated by combining it with lead, a 

 folution of acetate of lead being added for the purpofe. 



Anal^Ju of Ores. — Metallic minerals, in general, admit 

 more eafily of analyfis in the humid way than the earthy 

 foflils, from their being lefs hard. In the dry way alfo, their 

 compofition may be fometimes afcertained by expelling tlie 

 mineralizing fubftance by heat, and reducing the metal to 

 its metallic ilate. 



Proper fpecimens of the ore, free from all foreign mat- 

 ters, ftiould be chofen ; and if the objeft be to afcertain the 

 quantity of metal it may contain, different fpecimens taken 

 from different parts of the metallic vein ftiould be exa- 

 mined, as it often happens that different parts of the fame 

 vein vary much in richnefs. The ore being powdered, the 

 general procefs, in the dry way, confifts in calcining it at a 

 low red heat in an earthen veffel loofely covered, to expel the 

 fulphur or other volatile matter. Or this operation may be 

 performed in an earthen retort and receiver, when the objeift 

 is to afcertain the nature and quantity of the fubftance ex- 

 peUed. Therefidual matter in cither cafe bemg weighed, 

 to afcertain the lofs of wciglit it has fuffored, is mixed with 

 three rimes its weight of black flux, and expofea in a cru- 

 cible, to a heat fufficienlly intenfe for its reduaion :-id fu- 

 fion. Sometimes borax, pounded glafs, or hmc, arc i-.led 



