223 Royal Society. 



are commonlj- mixed with those of iron, and though different methods 

 of separating them have been recommended, yet no very simple or 

 unobjectionable test for manganese seems to be known. Twd 

 methods for detecting manganese are recommended, viz. — 



1 . The pure hydrated fixed alkahes, potash and soda, and espe- 

 cially potash. 2. Sulphur. 



With regard to the first method. Though the compound Cha- 

 meleon mineral made by strongly heating nitre or potash and 

 peroxide of manganese together, has long been known, yet it 

 appears hitherto to have escaped obsen'ation, that potash seems 

 to be a more delicate test of manganese than any other known 

 substance. The use of potash in this way is simple and easy ; 

 it is emploj'ed in solution ; equal weights of the alkali and water 

 form a fluid well-adapted for the purpose ; different metals may 

 be used in the form of slips on which to make the experiments, 

 but a preference is given to silver foil, as it is less acted on by alka- 

 lies than platina, and is more readilj' cleaned. A slip of such foil, 

 about two or three inches in length and half an inch wide, answers 

 ■well. Solids, to be examined for manganese, are finely pulverized ; 

 fluids require no preparation ; the smallest portion of either is mixed 

 with a drop or part of a drop of the alkali on the foil and heated by 

 a spirit-lamp (for many experiments a candle affords sufficient heat), 

 when on boiling the alkali to dryness and raising the heat, the cha- 

 racteristic green manganate of potash will appear on the foil. The 

 delicacy of the alkali as a test thus applied, will be obvious on using 

 the most minute portions 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 containing one grain of solid sulphate in 

 ten thousand grains of water. The presence of other oxides do not 

 appear to impair the efficacy of this test. A strong solution of 

 hydrate of soda in water, used in a similar manner, aftords an ex- 

 cellent 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 

 manganese to potash or soda, requiring a far higher temperature to 

 form the manganate of soda, and the aid of oxidizing substances, 

 as nitre and chlorate of potash, which are quite unnecessary with 

 those alkalies. Borax, too, in point of delicacy is not to be com- 

 pared with the fixed alkalies as a test for manganese. 



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 flowers of sulphur be mixed with about its 

 own bulk of the common peroxide of manganese, and exposed on a 

 slip of platinum foil to a red heat, sesquioxide, sulphuret and sulj^hate 

 of manganese will be formed, and by continuing the heat for a short 

 time, an additional quantity of the sulphate will be produced from 



