Messrs. Knox on the Insulation oj^ Fluorine. 131 



had been formed ; but in moving the vessels over each other some air may have 

 got in, which would account for the detonation. This was repeated frequently ; 

 but, from the nature of the manipulation, the result could not be depended on. 

 On collecting and examining the gas that remained on one occasion, after deto- 

 nation, there was no hydrogen found. 



On placing many receivers filled with the gas in succession over water, 

 whether hot or cold, the solution, if such, had all the properties of hydro-fluoric 

 acid in acting on glass, reddening litmus, and giving precipitates with lime and 

 barytes. 



We passed some through hot water into a graduated glass tube. There was a 

 considerable absorption, and a deposit of flakes of silica. The remaining gas, on 

 examination, proved to be atmospheric air, with some oxygen. The admission of 

 some atmospheric air in the transference is, from the nature of the vessels, almost 

 unavoidable, for which reason the results must be received with caution. 



When a receiver of the gas is placed over dry litmus and Brazil wood-papers, 

 the former is reddened, the latter turned yellow, and in no instance were they 

 ever bleached* When a receiver was placed over wet glass it was strongly acted 

 upon. When the glass was carefully dried there was less action than before. 

 From which circumstance, supposing that if the glass were perfectly dry, there 

 would be no action upon it, we placed a small piece in a perforation in the inte- 

 rior of the receiver, and found it was still acted on, but not more so than when 

 fluoride of mercury alone was in the vessel. 



In trying the action on the metals we found it necessaiy to try the separate 

 action of hydro-fluoric acid and sublimed fluoride of mercury, in order to distin- 

 guish the action that might be due to fluorine alone, from that which might be 

 caused by their presence. Corrosive sublimate also, when in vapour, acts power- 

 fully in many cases, and these two last substances must necessarily be always 

 present. The hydro-fluoric acid was formed in the vessels themselves. 



The results given in the following table, in the column headed Fluorine, 

 are those which were produced on the various metals, over which a receiver, full 

 of the gas, obtained in the usual way, had been placed. 



