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XX. On the Composition of Blende. By THOMAS THOMSON, M. D. 

 F. R. S. L. & E., Professor of Chemistry, Glasgow. 



(Read 2d February 1829.) 



IT is nearly a century since chemists began to suspect the nature 

 of the well known mineral usually distinguished by the name of 

 Bknde or Pseudo-Galena. BRANDT, in 1735, showed that zinc 

 was one of its constituents*. In 1744, FUNCK demonstrated 

 that it was an ore of zinc f. MARGRAAFF soon after actually ex- 

 tracted zinc from it J. It was impossible to subject it to heat in 

 an open vessel, without perceiving that it contained sulphur. But 

 chemists did not succeed in their attempts to combine zinc and 

 sulphur together. This led them to conclude, that in blende 

 the zinc and sulphur were united together by the intervention 

 of iron. This opinion was stated by CRONSTEDT in the first edi- 

 tion of his Mineralogy. In 1779 BERGMAN attempted an ana- 

 lysis of blende, and drew, as a conclusion from his experiments, 



* BERGMAN. Opusc. ii. 313. 



t KONGL. Vet. Acad. Handl. 1744, p. 57. 



+ Opuscul. de MARGRAAFF, i. 190. 



