1839.J 



On Chemical Teste. 



313 



metallic solution must be concentrated, and then very strong alcohol 

 must be added so thai the liquid may contain 60 per cent of it in vo- 

 lume. The, precipitate will be chloride of iridium and the alkaline 

 matter, boih of which av« insoluble in alcohol. The solution should 

 contain a small excess of chloride of potassium the precipitate may 

 he washed with spirits of wine. 



a. The muriate of iridium is iridescent having a brown or green 

 tinge; yields a red solution with water, which is rendered colourless 

 by alkalies, sulphuretted hydrogen, ferrocyante of potash, ?.nd infusion 

 of galls. No precipitate is produced by carbonate of soda. 



65. IRON is detected ly tincture of g alio, which produces a purple 

 colour, see 55 : also by ferrocyanate of potash which produces a blue colour, 



a. Solut ions of protoxide of iron may le discriminated by their action 

 with hydrosulphuret of ammonia which gives a black precipitate, and ly 

 the red prwsiate of potash producing a dark blue precipitate ; and the 

 peroxide of iron by hydrosulphuret of ammonia, prussiale of potash, and 

 liquid sulphuretted hydrogen : by which the indications are respectively, 

 a black precipitate by the first, a dark blue precipitate insoluble in muri- 

 atic acid by the second; and a milky white precipitate of separated sul- 

 phur by the last. These tests discriminate iron f rom other bases. 



b. The neutral .solutions of iron redden litmus paper. 



c. When carbonate of lime, or carbonate of magnesia is boiled with a 

 solution of peroxide of iron, and protoxide of manganese, the iron is 

 completely precipitated, and the whole of the manganese remains held 

 in solution. See 29. 



d. When protosalts -nnd persalts of iron exist together in solution, 

 if the solution be boiled with carbonate of magnesia, the persalt is com- 

 pletely separated, and precipitates in the state of a sub-salt. See 36. 

 The carbonate of lime, of baryta, of strontian, or of magnesia, when ad- 

 ded to a cold solution of peroxide of iron, so completely separates it, 

 that no re-agents indicate a trace of it afterwards. The carbonates of 

 baryta and strontia are to be preferred. This is s;;id to be an excellent 

 process for procuring also oxide of cerium entirely free from peroxide 

 of iron. 



e. The following list shews the colours of the precipitates of the 

 protoxide and peroxide of iron, using the same test in both cases. 



