MacLKOI). — l'(it< of Oriddt 11)11 of An idhit Injih to Arclir Arid. 49 



atoms present is pi'opoi'tional to tlie square root of the oxygen-pressure, 

 and that the action goes on only between the aldehyde molecules and the 

 oxygen atoms. Now, according to the kinetic theory of gases, these oxygen 

 atoms, if present, would be formed during the collision of two oxygen 

 molecules, and the number formed would be proportional to the number 

 of these collisions. At the same time, the number of molecules re-formed 

 would increase as the number of atoms present increased, until a state 

 of equilibrium would be reached. The value of K' then, thus worked out, 

 does not take into account the possibility of an oxygen molecule being 

 split up on coming in contact with an aldehyde molecule, and perhaps, 

 in some cases at least, oxidizing the aldehyde molecule at the same time. 

 If this went on to any great extent, then the greater the percentage of 

 aldehyde molecules to oxygen molecules present, the greater would be the 

 •excess of oxygen atoms present, caused by contact of aldehyde and oxygen 

 molecules, over the calculated number. The effect, then, if this be a deter- 

 mining factor, of raising the oxygen-pressure and keeping the aldehyde 

 constant would be to lower the value of K' ; but on raising the aldehyde- 

 pressure to something nearer to that of the oxygen the value of K' would 

 again rise. In other words, the value of K' would be somewhat dependent 

 on the percentage pressures of aldehyde and oxygen. In most of the ex- 

 periments there seemed to be a more or less distinct lowering in the value 

 of K' as the proportion of aldehyde became less, on account of the more 

 rapid decrease in the pressure of aldehyde. 



At the same time, it must be remembered that at no time during the 

 ■experiment is a state of equilibrium reached either between the formation 

 of oxygen atoms from molecules and the re-formation of the oxygen mole- 

 cules, or between the oxygen atoms and aldehyde molecules. Now, if the 

 percentage pressure of aldehyde were great, then an aldehyde molecule 

 would seize upon an oxygen atom in many cases as soon as it was formed 

 — that is, before it had time to come in contact with another oxygen atom 

 — and thus count in the determination of the equilibrium. Thus the fact 

 that oxygen atoms are being removed continually from the sphere of action 

 would prevent a state of equilibrium being reached, and could cause, for 

 any particular pressure of oxygen, the number of oxygen atoms ready to 

 combine with aldehyde molecules to be greater than that calculated from 

 the assumption of a state of equilibrium. Also, the greater the pressure 

 of alf^ehyde in comparison with that of oxygen, the more would this be 

 felt. This, it seems to me, might be a very considerable factor, and it is 

 hard to see why it should not have at least some effect. 



There is another factor which might have some effect, though it would 

 in all probability be slight, if noticeable at all. With higher pressures of 

 oxygen the proportion of oxygen atoms to oxygen molecules would be less 

 than with lower pressures of oxygen. For instance, suppose the pressure 

 of oxygen molecules to be A millimetres in one case and B in another, the 

 value of B being greater than that of A. The number of oxygen atoms 

 in the two cases would be KAi and KBi respectively, and the proportion of 



oxygen atoms to oxygen molecules in the two cases would be , and ^ 



respectively — that is, in the second case, where B is greater than A, the 

 oxygen atoms are more diluted with the oxygen molecules, which are for 

 the purposes of the reaction inert. This diluting of the reacting sub- 

 stances — namely, the aldehyde molecules and the oxygen atoms — by inert 

 oxygen molecules might have the effect of retarding the action. Unless, 

 however, we assume that time is taken up on collision — and the assumption 



