in different chemical Processes on Fluor Spar. 265 



taining many ingenious and original arguments in favour of 

 the analogy between the muriatic and fluoric compounds. 

 M. Ampere communicated his views to me in the most liberal 

 manner; they were formed in consequence of my ideas on 

 chlorine, and supported by reasonings drawn from the expe- 

 riments of M. M. Gay Lussac and Thenard. 



Before I enter upon the detail of the investigations which 

 promise to elucidate the nature of the fluoric compounds, it 

 will be right to describe those substances produced from fluor 

 spar, which have been the principal objects of my experi- 

 ments, and to mention the different hypothetical views that 

 may be formed respecting them. 



The first of these substances is the silicated fluoric acid gas,, 

 which was discovered by Scheele, and examined in its pure 

 state by Priestley. It is formed by heating a mixture of 

 fiuor spar, powdered glass, and sulphuric acid. It is a very 

 heavy elastic fluid, its specific gravity being nearly forty-eight 

 times as great as that of hydrogen. It produces, according to 

 my brother Mr. John Davy, a quantity of siHca equal to ^y^ 

 of its own weight by its action upon water, and a quantity 

 equal to -j^^ of its weight by its action upon solution of am- 

 Hionia. It condenses twice its own volume of ammonia, and 

 forms a solid salt, volatile when free from water without 

 decomposition. 



Liquid fluoric acid, the second of these substances, was 

 discovered by Scheele, but first obtained in its pure form by 

 M. M. Gay Lussac and Thenard. It is procured by heating 

 concentrated sulphuric acid and pure fluor spar, in retorts of 

 silver or lead, and receiving the product in receivers of the same 

 metals artificially cooled. It is a very active substance, and 



