1880.] On the Spectra of the Compounds of Carbon, fyc. 503 



we have made a series of careful experiments with carbonic oxide 

 at atmospheric pressures. 



In our first experiments with this substance the gas was made by 

 the action of sulphuric acid on dried formiate of sodium. The dried 

 formiate was placed in a flask (fig. t>) fitted with a rubber stopper, 

 through which passed the tube of a globe funnel, with a stop- cock for 

 the admission of the sulphuric acid, and an exit tube for the gas. The 

 latter was plugged with asbestos to catch any liquid drops which 

 might be thrown up, and was connected by a thick rubber tube to a 

 tube of the form shown in fig. 6. That part of this tube marked a 

 was filled, one-half with soda-lime to catch acids, and the other half 

 with phosphoric anhydride to catch moisture ; the gas, after passing 

 through this tube, was burnt as it issued from the narrow opening at b. 



The spectrum of the spark was observed through the small bulb blown 

 on the end. The sulphuric acid was introduced gradually through the 

 funnel, and the stream of gas allowed to pass through the tube for 

 a long time. Sparks were passed between the wires, and the spectrum 

 observed from time to time. At first the six violet bands were well 

 seen, and the seven blue bands faintly ; but gradually, as the air 

 became more completely expelled, the blue bands disappeared entirely, 

 and then the violet bands so far died out that it was only by manipu- 

 lating the coil that they could be made visible, and then only very 

 faintly indeed. A bubble of air, estimated by the length of the tube 

 it filled to be about T ^ of the volume of gas in the flask and tube, 

 was now introduced through the funnel, and almost immediately the 

 bands reappeared brightly. As the stream of gas however continued, 

 they again gradually died away until they were represented only by a 

 faint haze. It was subsequently found that each introduction of fresh 



