218 CHEMICAL TRANSFORMATIONS. 



elements of water), which unite with the sulphuric 

 acid,, and its cause is the superior affinity of the 

 acting body (the sulphuric acid) for water. In 

 consequence of the removal of the component 

 parts of water, the remaining elements enter into 

 a new form ; in place of oxalic acid, we have its 

 elements in the form of carbonic acid and carbonic 

 oxide. 



This form of decomposition, in which the change 

 is effected by the agency of a body which unites 

 with one or more of the constituents of a com- 

 pound, is quite analogous to the decomposition of 

 inorganic substances. When we bring sulphuric 

 acid and nitrate of potash together, nitric acid is 

 separated in consequence of the affinity of sulphuric 

 acid for potash ; in consequence, therefore, of the 

 formation of a new compound (sulphate of potash). 



In the second form of these decompositions, 

 the chemical affinity of the acting body causes 

 the component parts of the body which is decom- 

 posed to combine so as to form new compounds, 

 of which either both, or only one, combine with the 

 acting body. Let us take dry wood, for example, and 

 moisten it with sulphuric acid ; after a short time 

 the wood is carbonised, while the sulphuric acid 

 remains unchanged, with the exception of its being 

 united with more water than it possessed before. 

 Now this water did not exist as such in the wood, 

 although its elements, oxygen and hydrogen, were 

 present ; but by the chemical attraction of sul- 



