58 Mi. 11. B. Dixon. [May 29, 



carbonic oxide and oxygen ; he considers that the inflammability of 

 the mixture depends only upon pressure, and that in my experiments 

 the mixture was tested under a less pressure when dry than when 

 wet. This explanation of Dr. Botsch's does not account for the 

 facts observed. Under a pressure of 760 millims. the dry gases 

 do not unite, while the wet mixture is explosive. The addition of 

 a small quantity of nitrogen, carbonic acid, cyanogen, nitrons 

 oxide, or carbon bisulphide, does not render the dry mixture inflam- 

 mable. 



The part played by the steam in the ordinary explosion of carbonic 

 oxide and oxygen is similar to that of the nitric oxide in the 

 sulphuric acid chamber. By suffering a succession of alternate 

 reductions and oxidations the steam converts the carbonic oxide into 

 carbonic acid. With very little steam this conversion is compara- 

 tively slow, so that in a nearly dry mixture there is no explosion, but 

 the disk of flame is seen to travel slowly down the tube. With 

 increasing quantities of aqueous vapour the rapidity of inflammation 

 increases. An attempt* was made to measure this increase in tha 

 velocity of explosion by observing the pressures produced in the 

 eudiometer when equal masses of carbonic oxide and oxygen 

 were fired under nearly identical conditions of temperature, 

 pressure, and cooling surface, but with different proportions of 

 steam. These experiments showed that the velocity of explosion 

 increased with increasing quantities of steam, but they gave no 

 absolute value for the rates of explosion. To obtain absolute rates 

 direct measurements were made, with a chronograph, of the time 

 which elapsed between the passage of the spark through the mixture, 

 and the breaking of a thin silver bridge at the other end of the 

 explosion tube about 1 metre from the firing point. The explosion 

 tube of 13 millims. diameter was soldered into a metal trough, so that 

 each end projected a short distance from the end of the trough. The 

 trough was filled with water at the desired temperature. To 

 determine the rate of explosion of the nearly dry gases, the mixture 

 was forced slowly into the explosion tube (1) through two sulphuric 

 acid drying tubes, and (2) through two long tubes containing anhydrous 

 phosphoric acid. By removing the phosphoric acid tubes the gases 

 were tested in a less dry state. By making the gases bubble slowly 

 through a wash-bottle containing water at different temperatures 

 below the temperature of the explosion tube, the quantity of steam 

 added to the mixture could be approximately measured. 



The following table gives the results of these velocity experi- 

 ments: 



" British As*oc. Report," 1882. 



