299 



The Secretary of Council read the following notice of a 

 Compound of Fluorine and Carbon, by George J. Knox, Esq. ; 

 communicated in a letter to Dr. Apjohn. 



" When a current of dry chlorine gas is passed over 

 fluoride of silver fused in a platinum tube, the extremity of 

 which fits into a platinum receiver immersed in a freezing 

 mixture, the fluoride of silver is decomposed, being converted 

 into chloride of silver, and no solid or liquid substance is 

 found in the receiver. When, however, in place of chlorine, 

 the vapour of liquid chloride of carbon (serrulas) is substi- 

 tuted, the fluoride of silver is decomposed, and the receiver 

 is found to contain acicular crystals, which are insoluble in 

 water, acids, and alkalies, sparingly soluble in alcohol and 

 ether, but very soluble in spirits of turpentine. When heat- 

 ed in a platinum crucible, they sublime unaltered, emitting a 

 strong aromatic odour ; their vapour does not affect the colour 

 of litmus paper. When a cold glass plate is placed over the 

 mouth of the platinum crucible, the crystals subliming con- 

 dense upon the 'glass, and acting upon it, engrave upon its 

 surface a beautiful outline of their form. Ignited in a closed 

 platinum vessel, they are decomposed, depositing charcoal. 



" When the vapour of chloride of carbon is passed over 

 iodide and bromide of silver fused in glass tubes, analogous 

 compounds are formed ; the one in the form of long needles, 

 the other of feathery crystals. Both sublime unaltered when 

 heated ; are insoluble in water, acids, alkalies, alcohol, and 

 ether ; but soluble in warm spirits of turpentine and chloride 

 of carbon. 



" I have failed twice in obtaining a sufficient quantity of 

 the crystals for analysis, and so send you the paper as it is. 

 The first time I obtained 20 grs. which would have been 

 enough, but I lavished it in determining its qualities. I had 

 intended analyzing it by burning it with deutoxide of cop- 

 per in a leaden tube, estimating the carbonic acid by the in- 

 creased weight of potash, and throwing down the fluorine 



