1880.] On the Spectra of the Compounds of Carbon, fyc. 501 



A bulb was then blown in the middle of a piece of narrow glass 

 tubing, and platinum wires sealed into it ; some carbon tetrachloride 

 was introduced into the bulb, and a current of hydrogen passed through 

 the tube at atmospheric pressure ; when the air was judged to be 

 expelled sparks were passed by means of the wires in the bulb, but no 

 nitrocarbon bands could be detected. In this case the rapid deposit 

 of carbon soon brought the observations to a close, but the result was 

 the same as before. 



Solid trichloride was next tried. It was introduced into a tube 

 similar to that described above in the first experiment with tetra- 

 chloride, and treated as the tetrachloride had been, the trichloride 

 being mostly sublimed over into the small bulb shown in fig. 4, b. 

 The trichloride was found to behave as far as the spectrum is con- 

 cerned very much as the tetrachloride had done. It gave no nitro- 

 carbon bands at all. 



Having satisfied ourselves by repeated trials that pure carbon 

 chloride if free from nitrogen does not give any of the bands we 

 ascribe to nitrocarbon compounds, our next step was to determine 

 whether the addition of nitrogen would bring them out, and if so what 

 quantity of nitrogen would make them visible. For this purpose we 

 first loosened the binding of the rubber tube connecting to the pump a 

 sparking tube containing tetrachloride, and found to give no nitro- 

 carbon bands, and, after letting in very little air, immediately closed 

 it again. On now passing the spark the six violet bands at once ap- 

 peared, and soon became quite bright, the seven blue bands were not 

 seen immediately the air was admitted, but they too were in a short 

 time well seen. 



After trying some other experiments of a similar kind which indi- 

 cated that a very small quantity of nitrogen was sufficient to develope 

 the nitrocarbon bands in one of these tubes, we introduced a minute 

 fragment of bichromate of ammonia, carefully weighed, and wrapped 

 in platinum foil, into the neck of one of the sparking tubes containing 

 carbon tetrachloride, connected the tube to the Sprengel pump, and 

 removed the air as before. On examination of the spark with the 

 spectroscope no trace of any nitrocarbon band could be detected. A 

 pinch-cock was now put on the rubber tube, and the bichromate was 

 heated by a spirit lamp to decomposition (whereby it is resolved into 

 nitrogen, water, and oxide of chromium). On now passing the spark 

 the six violet bands were well seen. There was no change in the condi- 

 tion of the coil or rheotome, so that the spark was of the same character 

 as it had been before when no nitrocarbon bands were visible, and the 

 change in the spectrum cannot be attributed to any change in the 

 spark. The weight of the bichromate was between '0005 and "0006 

 grm. ; and the nitrogen this would evolve would fill just about of a 

 xjubic centimeter at atmospheric pressure. The tube held 30 cub. 



2n2 



