1880.] 



on Investigations at High Temperatures. 



263 



Pure dry air gave no hydrocyanic acid or acetylene ; moist air, on 

 the contrary, giving abundance of the former, but only a trace of the 

 latter. 



The yield in all these experiments altered considerably with the 

 rate at which the gases were passed, a quick stream always producing 

 more than a slow one, unless when oxygen was present. 



Formation of Nitrites in the Arc, 



In these experiments the annular vessel was made use of, in which 

 the lamp was allowed to work automatically, often for an hour or 

 two. A continuous stream of dry air was kept circulating through 

 the interior, being afterwards passed through a series of wash bottles 

 containing dilute caustic soda, or directly through strong sulphuric 

 acid, to absorb the oxides of nitrogen. The nitrous acid was esti- 

 mated in the former case by titration with permanganate of potash, 

 and the total combined nitrogen by the mercury process. 



In this way many experiments were made with a Siemens lamp, 

 both with a long and short arc; Jablochkofif's candles without any 

 insulating material between the poles were also employed with the 

 highest intensity current of a De Meritens machine, in order to have 

 the greatest variety in the character of the discharge. 



The stream of dry air was forced through the vessel at varying 

 degrees of speed, and was found to have a decided effect on the 

 quantity of nitrites produced, the more rapid stream giving the largest 

 yield of nitrites. 



The following table gives the amount of the nitrous acid produced 

 in a number of different experiments. 



The nitrites are calculated as nitrous acid. 



1. Siemens' machine and lamj^. 2. Jablochkoff's candles. 



