OF ARKANSAS. 



191 



thus obtained is reduced to a small volume by evaporation, and an aliquot 

 part of the concentrated liquid evaporated to a syrupy consistency in a 

 porcelain crucible, over a water-bath. [It is nut possible to evaporate the 

 watery extract to dryness by means of the water-bath; the extract assumes 

 the consistency and appearance of honey, without solidifying]. 



Some pure, soft iron-wire is then dissolved in strong hydrochloric acid, 

 with the necessary precautions for the exclusion of atmospheric air, and 

 the crucible containing the extract thrown into the solution of protochloride 

 of iron; heat is applied to expel the nitric oxide, the liquid diluted with 

 water, and the amount of unoxidized protoxide of iron determined by 

 chamaileon mineral. 



Ox A L E N A. 



In the different specimens of galena which have been analyzed, the 

 amount of lead was not directly determined; but since it was proved by 

 the qualitative examination of these specimens, that no other impurities, 

 besides iron and silver, were present, the amount of lead can easily be 

 ascertained by subtracting from 100 the sum of these impurities plus the 

 amount of sulphur. 



For the determination of the silver, the following method was pursued: 

 50 grammes of the finely pulverized ore are intimately mixed with 50 

 grammes of carbonate of potassa, 25 grammes of cream of tartar, and 10 

 grammes of metallic iron (small iron tacks); the mixture is placed in an 

 iron crucible, covered with a layer of borax, the crucible closed with an 

 iron lid, and then exposed to a bright red heat until the mass flows quietly. 

 The contents of the crucible are then poured into a conical iron mould, 

 when the metallic lead falls to the bottom, forming a well-defined metal- 

 lic button which is easily separated from the slag by a blow with a ham- 

 mer. The weight of the button of lead varied from 39 to 40 grammes. 

 Of the metal thus obtained, about 5 grammes are subjected to cupellation, 

 and the button of silver is weighed on a very delicate balance. . 



The iron was determined in the following manner: The finely pulverized 

 galena is oxidized with strong nitric acid; to the mass a few drops of con- 

 centrated sulphuric acid are added, and heat applied until the excess of 

 nitric acid is completely removed. The dry mass is treated with water, 

 the insoluble sulphate of lead collected on a filter, and washed with dilute 

 sulphuric acid. To the filtrate a piece of metallic zinc is added, in order 

 to reduce the sesquioxide of iron to protoxide, and the amount of the lat- 

 ter determined by chamaileon mineral. 



