CHEMICAL SCIENCE. 227 



tions of manganese ores in fine powder, and the author's son, Dr. E. W. Davy, 

 readily detected manganese in a single drop of a solution containg one grain 

 of solid sulphate in ten thousand grains of water. The presence of other 

 oxyds does not appear to impair the efficacy of this test A strong solution 

 of hydrate of soda in water, used in a similar manner, affords an excellent 

 test for manganese, little inferior in delicacy to potash, but the latter is shown 

 to be preferable. Carbonate of soda has long -been regarded as one of the 

 most delicate tests of manganese, especially if aided by a little nitrate or 

 chlorate of potash ; but that carbonate is much inferior as a test for manga- 

 nese to potash or soda, requiring a far higher temperature to form the manga- 

 nate of soda, and the aid of oxydizing substances, as niter and chlorate of 

 potash, which are quite unnecessary with those alkalies. Borax, too, in point 

 of delicacy is not to be compared with the fixed alkalies as a test for manga- 

 nese. The author is of opinion that the fixed alkalies in solution and silver 

 foil will form a valuable addition to the agents employed by the mineralogist and 

 chemist in the examination of minerals, ores, &c. 2. Sulphur. If a little 

 flower of sulphur be mixed with about its own bulk of the common peroxide 

 of manganese, and exposed on a slip of platina foil to a red heat, sesqui- 

 oxyd, sulphuret, and sulphate of manganese will be formed, and by continu- 

 ing the heat for a short time, an additional quantity of the sulphate will be 

 produced from the sulphuret. On treating the mass with water and filtering 

 the fluid, a solution of sulphate of manganese will be obtained, which will 

 yield a white precipitate with the ferro-cyanide of potassium, without a trace 

 of iron. Similar experiments may be made with any manganese ores, or with 

 substances known or suspected to contain manganese. The quantity of ma- 

 terials operated on may be increased or diminished at pleasure ; but if in- 

 creased, the heat should be continued a little longer, to decompose any re- 

 maining sulphuret, and thus add to the quantity of sulphate formed. In the 

 same way manganese was detected in some minerals in which it was known 

 to exist, and in others in which it had not been previously found ; likewise in 

 soils and subsoils, in the ashes of coal and peat, in a number of pigments, and 

 also in the ashes of different fabrics partially dyed brown by manganese. 

 Sulphate of manganese is formed, with sulphuret, when sulphurous acid gas 

 is made by heating a mixture of peroxide of manganese and flowers of sul- 

 phur, even in close vessels. The sulphate may also be more readily obtained, 

 in quantity, by simply boiling a solution of common green vitriol in water for 

 about a quarter of an hour or upward, in contact with an excess of sesqui- 

 oxide of manganese in fine powder, till the solution affords a white precipitate 

 with ferrocyanide of potassium. Chloride of manganese may also be formed 

 in a similar manner by boiling an aqueous solution of protochloride of iron 

 with an excess of sesquioxyd, or it may be made with greater facility by dis- 

 solving this oxyd in the common muriatic acid of commerce, taking care that 

 the oxyd be present in excess. The brown sesquioxyd of magnesia may be 

 made, not only by means of sulphur, but more readily and better by mixing 

 the common peroxyd with about one third of its weight of peat-mold, saw- 

 dust, or starch, and exposure to a red heat in an open crucible, with occa- 

 sional stirring for about a quarter of an hour, or until the oxyd acquires a 



