299 
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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 ina platinum crucible, they sublime unaltered, emitting a 
strong aromatic odour ; their vapour does notaffect 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. 
‘TI 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 
