Prof. Johnston on the Iodide of a new Carbo-hydrogen. 3 



yellow by the action of chlorine. In hot solutions of carbo- 

 nated alkalies it is partly decomposed, iodine being separated, 

 but its colour remains unchanged. Heated to 212° Fahr., 

 it slowly but sensibly loses weight, evolving the odour of 

 naphtha and a little iodine. At a higher temperature it gives 

 off a volatile combustible liquid resembling naphtha, which 

 burns with much smoke, and if the heat be still increased, 

 iodine vapour appears in large quantity colouring the naph- 

 tha (?) dark brown, and a bulky shining charcoal remains be- 

 hind. It is not unlikely that hydriodic acid may also be 

 among the products. 



Burned with oxide of copper this substance gave the fol- 

 lowing results : 



1. 8*77 grs. gave C = 18-56 and H = 4*94 grs. 



2. 8-77 grs. gave C = 18*15 and H = 4-855 grs. 



3. 6-137 grs. gave C = 12-316 and H = 3-505 grs. 

 These are equivalent, per cent., to 





1. 



2. 



3. 



Carbon 



Hydrogen 

 Iodine 



= 58-203 

 = 6-258 

 = 35-539 



57-225 



6-151 



36-624 



55*490 



6-346 



38-164 



100 100 100 



It was not till I observed the discrepancy between the first 

 and second analyses that I studied the action of a tempera- 

 ture of 212° Fahr. on this compound, and found that it was 

 slowly decomposed, and iodine expelled from it by this de- 

 gree of heat. The third analysis therefore was made with 

 more precaution, and care was taken to avoid decomposition 

 by the application of heat while pumping out the moisture 

 from the oxide of copper. In this analysis therefore the 

 chances of error were least, and the result agrees very closely 



th the formula CgQ H 20 Ij since 







Calculated. 



Experiment. 



30 carbon... = 2293-110 



55'667 



55-490 



20 hydrogen = 249*592 



6-059 



6-346 



1 iodine.... = 1578-290 



38-274 



38-164 



4120*992 100 100 



The excess of hydrogen is due to the more imperfect man- 

 ner in which it was necessary to pump out the water in order 

 to avoid the separation of iodine, as had probably been the 



B2 



