Professor Thomas Thomson <m the Oxides of Bismuth. 



3d November y 1841, — Dr. Thomas Thomson, President, in the Chair 



The Librarian reported the state of the Library funds, and pre- 

 sented a list of the Scientific Periodicals, proposed to be ordered for, 

 the ensuing year; consisting of 11 English and American, 8 Fren 

 and 5 German works. 



The Vice-President having taken the Chair, the following com- 

 munication was read: — 



L On the Oxides of Bismuth. Bj Thomas Thomson, M.D., F.R.S., 

 &c., Regius Professor of Chemistry, University of Glasgow. 



Bismuth is rather a rare metal ; but in consequence of the lowness of 

 its melting point, and the few purposes to which it is applied, it sells 

 at a comparatively small price. It occurs in nature almost always 

 in the metallic state ; and most of the bismuth of commerce comes 

 from Saxony, where it is found mixed with the ores of cobalt. It is 

 obtained by simply exposing these ores to heat in a crucible, — the 

 bismuth melts at a low heat, and is collected at the bottom of the 

 crucible. Bismuth as it occurs in commerce, is a somewhat brittle 

 metal, having a reddish white colour, and is composed of broad plates 

 adhering to each other. 



It is not quite pure, for it contains iron, arsenic, sulphur, copper, 

 and nickel, and probably other foreign bodies, though not in any con- 

 siderable quantity. But it is easy to obtain it pure by the following 

 process : — 



Dissolve it in nitric acid, taking care that the excess of acid is not 

 too great. Pour the solution into a large quantity of pure water. A 

 fine white precipitate falls in scales, having a pearly or satiny lustre. 

 This precipitate is a nitrate of bismuth. It must be collected on a 

 filter, and washed with water ; but we must not persist in washing it 

 too long, because it is slightly soluble in water. Allow it to dry, and 

 then expose it to an incipient red heat, in a platinum or porcelain 

 crucible. The nitric acid is expelled, and an oxide of bismuth 

 remains, having a deep orange colour while hot, but assuming a fine 

 yellow colour on cooling. It is a pure oxide of bismuth. To 

 reduce this oxide to metallic bismuth, we have only to put it into a 

 bulb, blown in a green glass tube, and to pass through it a current of 

 dry hydrogen gas, while the bulb is kept hot by means of a spirit 

 lamp. If the heat be properly regulated, the reduced bismuth 

 remains in the state of powder, or rather of small grains about the 

 size of gunpowder, and may be easily taken out of the bulb. It was 

 bismuth purified in this manner, that I employed in the following 

 experiments : — 



1. 13-5 grains of metallic bismuth, were put into a platinum 



