236 On the Effect of the Quantity of Matter in 



But does not this substance, in the common process for 

 obtaining oxygen, afford a striking instance of the effect of a 

 relative increase in the quantity of matter, in modifying the 

 force of attraction, even beyond those limits at which definite 

 proportions are formed ? It is not necessary for us to attend 

 at all to what remains after the operation is finished, or to 

 enquire whether it be a pure deutoxide or a mixture of that 

 and the protoxide. It is sufficient to observe that a low red 

 heat determines the separation of the oxygen — that a con- 

 tinual elevation of the temperature is necessary to maintain 

 a regular and uniform flow of the gas — and that the process 

 is stopped when the gas-bottle is heated to whiteness, and 

 the gas still continues to come over, though but slowly.* 

 The carbonate of lime affords corresponding results. Alow 

 red heat drives oft' the carbonic acid but for its entire sepa- 

 ration, a violent heat is required, even when the carbonate 

 has been procured from the muriate, by means of a carbo- 

 nated alkali, and is therefore in the state of an impalpable 

 powder. 



These examples are valuable on account of their simplici- 

 ty, and because they are not embarrassed by the question 

 about sub-salts and super-salts, and the state in which the 

 chemical elements exist in a solution. Why is it that the 

 low red heat which decomposes one particle of the carbo- 

 nate, does not decompose every particle 1 The fact may be 

 explained, (and the explanation extended, mutatis mutandis, 

 to other chemical combinations,) upon either of two suppo- 

 sitions. 



1. The improbable one that between different atoms of 

 lime and carbonic acid, there is a difference in the strength 

 of their affinities, so that there may be a separation of the 

 component atoms of one particle of carbonate of lime, by a 

 force that is altogether inadequate to the decomposition of 

 any other particle. 



2. That the force of affinity reaches beyond the distance 

 at which atoms combine, and compounds definite in their 

 proportions are formed, so as to exert an influence upon 

 atoms between which there is no proper chemical combina- 

 tion, and enable a large number to compensate by the 

 strength of their united action for the feebleness of the force 



* Lorsque I'oxide sera pres de la chaleur rouge il commencera a se degager 

 du gaz oxig^ne. Vous pourrez regarder I'operation comme faite lorsque le 

 fourneau etant plein de feu il ne se d6gagera presque plusde gaz. — Thenard, 



