produced by Catalytic Bodies. 213 



ficially increased, this compound is broken up, for distil- 

 lation drives off the water and concentrates the acid. Now 

 when starch is in the presence of this weak combination 

 of sulphuric acid and water, at a temperature at which the 

 latter is just able to exert its affinity and again have it de- 

 stroyed by heat, it is not at all extravagant to suppose that 

 the starch may seize the water in its nascent state at the mo- 

 ment of expulsion, or even that it may be able to unite with 

 the last atoms of the series of acid and water when presented 

 in that condensed state, although it cannot do so when the 

 water is free and not nascent. Any such union would explain 

 the transformation of starch into grape-sugar, the change 

 merely being in the acquisition of water, Cjg Hiq Oio + 4HO 

 = C,2 Hi4 O14. The action here is not the same, but the very 

 reverse of that which ensues in the preparation of aether. In 

 the one case the sulphuric acid abstracts water, in the other 

 it is the means of adding it, and the difference of the action 

 depends on the relative strength of the acids employed. 

 Without at all giving an opinion in favour of the necessity 

 for the formation of sulphovinic acid, as supposed by Liebig*, 

 or as to its not being an essential condition, as argued by 

 Mitscherlichf, the final result is simply of the order now 

 under consideration. In this decomposition the sulphuric or 

 phosphoric acid is so strong that it combines with the water 

 instead of yielding it, and the elevation of temperature essen- 

 tial to the change may either be due to the formation and 

 after decomposition of sulphovinic acid, or it may be simply 

 owing to the necessity of rendering the molecule of alcohol 

 tense by heat, the elasticity of the aether and water both 

 tending to break up the hydrate, the decomposition of which 

 is determined by the presence of the strong acid now also 

 aiding and abstracting the water. The final result is certainly 

 purely catalytic in whatever light it is considered, although 

 there may be more than one step in the process. 



In conclusion, facts have been brought forward to show 

 that there is at least as m\ich probability in the view that the 

 catalytic force is merely a modified form of chemical affinity 

 exerted under peculiar conditions, as there is in ascribing it 

 to an unknown power, or to the communication of an intes- 

 tine motion to the atoms of a complex molecule. Numerous 

 cases have been cited in which the action results when the 

 assisting or catalytic body is not in a state of change, and 

 attempts have been made to prove by new experiments that 

 the catalytic body exercises its peculiar power by acting in 



* Geiger's Pharmacie, vol. ii. p. 711 ei seq. 

 t Lehrbuch der Chemie, vol. i. p. 247 et seq. 



