130 Messrs. Knox on the Insulation 0/ Fluorine. 



on which it might be wished to try the effect of the gas ; one edge of the table 

 was straight, so that a receiver full of gas could be removed on a slab of fluor 

 without loss of the contents. The mode of using these vessels is as follows : — 

 after the vessel with its contents has been heated gradually, so as to raise the 

 temperature, and expel the water from the fluoride to be acted on, it is filled 

 with dry chlorine, and a receiver is fastened down upon it with a weight or clamp ; 

 then the apparatus being heated to any temperature required, when we wish to 

 examine the gas in the receiver, a second receiver, with a stopper in its cavity, 

 is placed beside the first, and is slid on the table, till it occupies the place of the 

 first ; its stopper then falls into the vessel, and its cavity is filled with gas. This 

 receiver, in like manner, is replaced by another, and so on till the vessel has 

 been choked up with stoppers. The contents of the receivers can then be 

 examined by being slid over various tests in the places made for that purpose 

 on the surface of the table. The entire apparatus is supported on a stand over a 

 lamp. 



In recommencing the experiments in these new vessels, adapted for showing 

 the colour of the gas in the manner above described, we found that when per- 

 fectly pure fluoride of mercury was used, the gas obtained was colourless ; and to 

 the upper part of the vessel inside, were suspended feathery crystals of corrosive 

 sublimate. The gas obtained in the receivers has a heavy smell, not pungent or 

 irritating, and thereby easily distinguishable from chlorine or hydro-fluoric acid. 

 When exposed to the air it does not fume, which would be the case were the 

 latter of these present. 



With regard to its power of supporting combustion, red-hot wire appeared to 

 become slightly brighter, but did not scintillate ; we tried it also with burning char- 

 coal and phosphorus, which latter was not extinguished ; but these effects were 

 very slight, and cannot be relied on as certain, as the atmospheric air must be 

 admitted in plunging in the heated wire. 



We attempted its detonation with hydrogen, thinking thereby to obtain 

 hydro-fluoric acid. For this purpose we inserted two platinum wires through the 

 opposite sides of a fluor-spar receiver, upon which, when filled with dry hydrogen, 

 we placed a receiver of the gas obtained in the vessels. On passing a spark from 

 a Leyden jar, detonation took place ; there was an absorption, and on separating 

 the vessels slight fumes appeared, frpm which we inferred that hydro-fluoric acid 



