and of Carbonates by the Light of the Sun. 169 



and second of those experiments the volume of the oxygen is 

 to that of the nitrogen as two to one ; in the third as one to 

 one. In certain cases this apparent simplicity of proportion 

 is departed from ; but from its frequent occurrence in many 

 analyses I have made, it seems to demand attentive considera- 

 tion. Moreover, in other plants, as in experiments 4 and 5, 

 the amount of oxygen is relatively greater, and between it 

 and the nitrogen there does not appear any exact propor- 

 tion. 



In order to ascertain whether decompositions taking place 

 under absorbent media, as bichromate of potash, produce the 

 same results as indicated in the foregoing table, I made se- 

 veral analyses of gas collected under these circumstances. 

 The presence of the absorbent medium did not seem to exert 

 any influence whatever, the general results coming out as 

 though it had not been employed. 



It has long been a matter of popular observation that the 

 sunlight has the quality of extinguishing domestic fires. I do 

 not know whether there is in reality any ground for this opi- 

 nion ; or if so, whether the phenomenon is in any way con- 

 nected with the relations of light to carbon and oxygen. 

 Popular opinion ascribes the effect to the light and not the 

 heat of the ray. To determine whether radiant heat, unac- 

 companied by light, had the power of producing decomposi- 

 tion of carbonic acid through the agency of leaves, I placed 

 in the focus of a large brass concave mirror a vessel containing 

 some pine leaves in carbonated water. The mirror was set 

 before a wood fire, and after a little time the leaves began 

 evolving bubbles. The temperature of the water rose as high 

 as 140° Fahr., and when sufficient gas was collected, exami- 

 nation proved that nearly the whole of it was absorbed by 

 lime or potash water. From this it is evident that radiant 

 heat merely liberates the carbonic acid, and does not decom- 

 pose it. This corroborates therefore the result of pneumatic 

 analysis, that it is the light and not the heat which brings 

 about the change. 



Decomposition of Alkaline Salts. — The conditions under 

 which carbonic acid gas is decomposed being understood, I pass 

 now to the description of similar decompositions occurring in 

 the case of saline bodies. It has always been a subject of sur- 

 prise to chemists, that the powerful affinity by which carbon 

 and oxygen are held together should be so easily overcome at 

 common temperatures. Even potassium cannot decompose 

 carbonic acid in the cold. It might therefore be reasonably 

 expected that the energetic forces which bring about this 

 change ought also to effect other remarkable decompositions. 



