PRESENT PROBLEMS 265 



but there appears to be little doubt that if looked for, the same or 

 similar phenomena would be discoverable in compounds with much 

 simpler formulae. The two forms of S0 3 , sulphuric anhydride, are 

 an instance in point. No doubt formation under different conditions 

 of temperature and pressure might result in the greater stability of 

 some forms which under our ordinary conditions are changeable and 

 unstable. The fact that under higher pressures than are generally at 

 our disposal different forms of ice have been proved to exist, and the 

 application of the phase rule to such cases will greatly enlarge our 

 knowledge of molecular isomerism. 



The phenomena of catalysis have been extensively studied of recent 

 years, and have obviously an important bearing on such problems. 

 A catalytic agent is one which accelerates or retards the velocity of 

 reaction. Without inquiring into the mechanism of catalysis, its ex- 

 istence may be made to influence the rate of chemical change, and to 

 render bodies stable which under ordinary conditions are unstable. 

 For if it is possible to accelerate a chemical change in such a way that 

 the usually slow and possibly unrecognizable rate of isomeric change 

 may be made apparent and measurable, a substance the existence of 

 which could not be recognized under ordinary circumstances, owing 

 to its infinitesimal amount, may be induced to exist in weighable quan- 

 tity, if the velocity of its formation from an isomeride can be greatly 

 accelerated by the presence of an appropriate catalytic agent. I am 

 not aware that attempts have been made in this direction. The dis- 

 covery of catalytic agents is, as a rule, the result of accident. I do not 

 think that any guide exists which would enable us to predict that any 

 particular substance would cause an acceleration or a retardation of 

 any particular reaction. But catalytic agents are generally those 

 which themselves, by their power of combining with or parting with 

 oxygen, or some other element, cause the transfer of that element to 

 other compounds to take place with increased or diminished velocity. 

 It is possible, therefore, to cause ordinary reactions to take place in 

 presence of a third body, choosing the third body with a view to its 

 catalytic action, and to examine carefully the products of the main 

 reaction as regards their nature and their quantity. Attempts have 

 been made in this direction with marked success; the rate of change 

 of hydrogen dioxide, for example, has been fairly well studied. But 

 what has been done for that compound may be extended indefinitely 

 to others, and doubtless with analogous results. Indications of the 

 existence of as yet undiscovered compounds may be derived from 

 a study of physical, and particularly of electrical, changes. There 

 appears to be sufficient evidence of an oxide of hydrogen containing 

 more oxygen than hydrogen dioxide, from a study of the electro- 

 motive force of a cell containing hydrogen dioxide; yet the higher 

 oxide still awaits discovery. 



