1835.] Decolourizing Comhinations of Chlorine, 351 



tion from the action of chlorous acid, but with the deutoxide 

 a violent detonation takes place. This is accompanied with 

 the production of nitrous gas, which new bubbles of chlo- 

 rous acid may transform into nitric acid. Dry sulphurous 

 acid gas is freely acted on by chlorous acid. In a few hours, 

 however, the gaseous mixture placed over the mercury has 

 disappeared, and the sulphurous acid is changed into sul- 

 phuric acid. 



When blotting paper is brought in contact with chlorous 

 acid gas a detonation takes place, and in the vessel are found 

 oxygen and chlorine, nearly in the proportion to form chlo- 

 rous acid, which shews that the gas has detonated princi- 

 pally by the heat disengaged in its action upon the paper. 



Indigo decomposes chlorous acid without detonation, and 

 forms a yellow coloured compound. A volume of carbonic 

 acid is formed, much inferior to that of the oxygen which 

 the acid employed contained ; and the chlorine extricated, 

 is partly absorbed by the mercury and partly retained in 

 the pores of the vegetable matter, in consequence of which 

 acid vapours are disengaged when heat is applied. 



The facts detailed prove that chlorous acid, in the gaseous 

 state, acts nearly as when liquid. It might at first be 

 thought, that the free chlorine found in the vessel, proceeds 

 from the decomposition of a portion of the gas, induced by 

 the rise of temperature, which is produced by the action of 

 the compound combustible ; but only a portion of the chlo- 

 rine can be ascribed to this source. Because the quantity 

 of oxygen with which it is mixed, is almost always inferior 

 to that which in chlorous acid is united with the volume of 

 chlorine which is obtained. Hence, it is probable, that in 

 these cases the two combustible elements of the compound 

 are principally combined with the oxygen. 

 (To he continued.) 



Article III. 



On the number and character of the Colours that enter into 

 the Composition of White Light. By P. C. 



( Continued from p. 179. J 



If we suffer the direct light of the sun to fall on a prism, 

 and receive the spectrum upon a screen in the usual manner, 



