1024 IRON 



soda, the fused mass is dissolved in hydrochloric acid, evaporated to drynoss, mois- 

 tened -with strong acid, diluted and filtered ; from the filtrate the sulphuric acid is 

 precipitated as sulphate of baryta, every 100 parts of which indicate 13748 parts of 

 sulphur, and 25'48 parts of bisulphide of iron. 



In the analysis of haematites it is necessary to bear in mind that perchloride of iron 

 is partially reduced when boiled with finely-divided iron pyrites and hydrochloric acid, 

 Bulphuric acid being formed. Dick. 



3. Phosphoric acid. From 60 to 75 grains of the ore are digested with hydrochloric 

 acid and filtered ; the clear solution, which should not be too acid, is boiled with 

 sulphite of ammonia, added gradually in small quantities till it either becomes colour- 

 less or acquires a pale green colour, indicating that the peroxide of iron originally 

 present has been reduced to protoxide ; the solution is nearly neutralised with car- 

 bonate of ammonia, excess of acetate of ammonia added, and the liquid boiled ; strong 

 solution of perchloride of iron is then added drop by drop, until the precipitate which 

 forms has a distinct red colour; this precipitate, which contains all the phosphoric acid 

 originally present in the ore, is collected on a filter, washed, and redissolved in hydro- 

 chloric acid, tartaric acid added, and then ammonia. From this ammoniacal solution, 

 the phosphoric acid is finally precipitated as ammonio-phosphate of magnesia, by the 

 addition of chloride of ammonium, sulphate of magnesia, and ammonia. The pre- 

 cipitate is allowed 24 hours to subside ; it is then collected on a filter, and if it has 

 a yellow colour, which is almost invariably the case, it is redissolved in hydrochloric 

 acid, and more tartaric acid being added, it is again precipitated by ammonia : 100 

 parts of the ignited pyrophosphate of magnesia correspond to 64*3 parts of phosphoric 

 acid. 



Alkalis^ It was ascertained by Mr. Dick, that nearly the whole of the alkali 

 present in an iron ore is contained in that portion which is insoluble in hydro- 

 chloric acid. The residue from about 50 grains of the ore is placed in a platinum 

 capsule, moistened with ammonia, and exposed for several hours to the action of 

 hydrofluoric acid gas in a closed leaden dish ; it may be necessary to repeat the ope- 

 ration if much silica is present ; it is then slowly heated to dull redness, and dis- 

 solved in dilute hydrochloric acid ; the solution is mixed with excess of baryta-watei 

 and filtered ; the excess of baryta is removed by carbonate of ammonia, and the so- 

 lution is evaporated to dryness and ignited ; the residue is redissolved in a little hot 

 water, and a few drops of oxalate of ammonia added. If no precipitate or cloudiness 

 occurs, it may be once more evaporated to dryness and gently ignited : the residue 

 is chloride of potassium, 100 parts of which indicate 63 parts of potash. Should 

 oxalate of ammonia have occasioned a precipitate, it must be filtered off, and the 

 clear liquid evaporated. The search for potash is troublesome and lengthy; it .may 

 be altogether omitted in a technical analysis. 



Determination of the remaining constituents. 25 or 30 grains of the finely -powdered 

 ore are digested for about half an hour with strong hydrochloric acid, diluted with 

 boiling distilled water and filtered. The residue on the filter being thoroughly washed, 

 the solution is peroxidised, if necessary, by the addition of chlorate of potash, nearly 

 neutralised by ammonia, boiled with excess of acetate of ammonia, and rapidly 

 filtered while hot; the filtrate (which should be colourless) together with the wash- 

 ings, is received in a flask, ammonia is added, and then a few drops of bromine, and 

 the flask closed with a cork. In a few minutes, if manganese be present, the liquid 

 acquires a dark colour ; it is allowed to remain at rest for 24 hours, then warmed, 

 and rapidly filtered and washed ; the brown substance on the filter is hydrated oxide 

 of manganese : it loses its water by ignition, and then becomes Mn 8 O 4 , 100 parts of 

 which correspond to 93 parts of protoxide. 



The liquid filtered from the manganese contains the lime and magnesia ; the former 

 is precipitated by oxalate of ammonia, and the oxalate of lime formed converted by 

 ignition into carbonate, in which state it is either weighed, having been previously 

 evaporated with carbonate of ammonia, or it is converted into sulphate by the ad- 

 dition of a few drops of sulphuric acid, evaporation and ignition. The lime being 

 separated, the magnesia is thrown down as ammonio-magnesian phosphate by phos- 

 phate of soda and ammonia, and after standing for 24 hours it is collected on a filter, 

 washed with cold ammonia-water, dried, ignited, and weighed; 100 parts of car- 

 bonate of lime correspond to 56 f O of lime ; 100 parts of sulphate of lime to 40'1 of 

 lime, and 100 parts of pyrophosphate of magnesia to 357 of magnesia. 



The red precipitate collected on the filter after the boiling with acetate of am- 

 monia, consists of the basic acetates of iron and alumina, together with the phosphoric 

 acid. It is dissolved in a small quantity of hydrochloric acid, and then boiled in a 

 silver or platinum basin with considerable excess of pure caustic potash ; the alumina 

 (with the phosphoric acid) is hereby dissolved, the insoluble portion is allowed to 

 subside, and the clearer liquor is then decanted, after which the residue is thrown on a 



