Modifying the force of Chemical Attraction. 235 



of a small portion of its acid, and on treating oxalate of lime 

 with nitric acid, some nitrate of lime is generated. As these 

 partial decompositions are contrary to the supposed order of 

 elective affinity, it was conceived that they were produced 

 by quantity of matter acting in opposition to force of attrac- 

 tion. But they by no means justify such a conclusion. In 

 the decomposition of sulphate of baryta by potash, no care 

 was taken to exclude the atmospheric air during the opera- 

 tion : the alkali must consequently have absorbed carbonic 

 acid, and it is an established fact, that carbonate of potash, 

 decomposes partially the sulphate of baryta. A similar omis- 

 sion appears to have been made in the other experiments, 

 where decomposition was attempted by pure potash or soda. 

 In many instances, the result may fairly be attributed to oth- 

 er causes." " On the whole, therefore, we may infer that 



BerthoUet has given no satisfactory case, in which quantity 

 of matter is proved to compensate for a weaker affinity.''''^ 



To the experiments of BerthoUet, we shall presently have 

 occasion to return. In the mean time, we may remark that 

 the influence of quantity of matter in modifying the force of 

 chemical attraction, in some particular cases, is universally 

 admitted. 



1. In the case of solution. It is well known and acknowl- 

 edged, that a given weight of any salt thrown into so much 

 water as is barely sufficient to effect its solution, will not dis- 

 appear as rapidly as when the quantity of water is considera- 

 bly greater. 



2. In those cases where an element A. enters into combi- 

 nation with another element B, in two, three or more differ- 

 ent proportions ; each additional dose of A, appears to op- 

 pose a feebler resistance to any force that may be employed 

 to separate it from B. A familiar example is furnished by 

 the black oxide of manganese, which from a tritoxide, is con- 

 verted into a deutoxide, by the application of a low red heat, 

 whilst no elevation of temperature to which it can be sub- 

 jected, effects a perfect decomposition and the separation of 

 all the oxygen. 



* Turner's Chemistry, p. 87.— See also, Davy's Elements of Chem. Philo- 

 sophy, Div. 1, Chap. 6, Sect. 13—18. Paris's Med. Chem. Sect. 237. Ure's 

 Dictionary, Art. Attraction. Brande has neglected this subject while he has 

 introduced a minute account ot such obscure subjects as uranium, tungsten 

 and molybdenum into a work intended for persons obtaining a knowledge of 

 Chemical Philosophy, and " tYie principal facts of the science." 



