W. J. V. OSTERHOUT 423 



constants of these reactions we can approximate the observed results. 

 The velocity constants thus found are given in Table 11. An inspec- 

 tion of the table shows that all these velocity constants behave like 

 K^ and K^ in that as the per cent of CaCl2 in the mixture increases 

 (beginning with 1.41 per cent CaCl2) the value of the velocity con- 

 stant first falls and then rises, and that this value in every case reaches 

 its minimum in the mixture containing 97.56 NaCl -f 2.44 CaCl2. 

 It would therefore appear that the reactions N -^ —^ P and R — > 

 S —^ T are inhibited by Na4XCa in the same manner as the reactions 

 A -^ M —^ B. This is borne out by an inspection of Fig. 2. in which 

 the decrease^ of the velocity constants is plotted, together with the 

 increase of Na4XCa. 



We have seen that the value of Kj^ -^ Kj^ increases as the per cent 

 of CaCl2 increases and we interpreted this to mean that the reaction 

 A -^ M h catalyzed by CaCl2. In the same manner we infer that 

 the reaction i? -^ 5 is catalyzed by CaCl2, since we find that the 

 value of Kji -f- Ks increases with increasing percentage of CaCl2, as 

 shown in Fig. 3. It is not certain that the curve does not reach a 

 minimum in the mixture of 97.56 NaCl + 2.44 CaCl2 but for prac- 

 tical purposes we may, for the present, regard it as a straight Hne.^ 



^ By the decrease in the velocity constant is meant the decrease which we 

 observe as we pass from the solution containing the highest per cent of calcium 

 (38.0 per cent NaCl + 62.0 per cent CaCy to mixtures containing smaller per 

 cents of calcium. Thus the decrease of Km = 0.009 — Km', the decrease of 

 Kjs; = 0.00134 — K;^; the decrease of Kq = 0.0013266 — Kq; and the decrease 

 of Ks = 0.00319 — Ks- In the same manner we find that the increase in the 

 amount of Na4XCa = amount of Na4XCa — 0.000047. 



The decrease of the amount of Ka and Kr is not shown in the figure because 

 it depends not only on Na4XCa but also on the per cent of CaCl2. 



The fact that even in the presence of the maximum amount of Na4XCa these 

 velocity constants are greater than in sea water is of course to be attributed to the 

 other substances present in sea water. 



® Since in pure NaCl or CaCl2 the salt compound Na4XCa is not formed, we 

 should expect that in these solutions all the reactions would be more rapid than 

 in the mixtures. That this expectation is fully realized is evident from Table II. 



The velocity constants are somewhat higher in NaCl than in CaCl2; this is 

 not explained by the assumptions already made but it does not seem desirable at 

 present to make additional assumptions for this purpose. We might expect the 

 values of Ka -^ Km and Kr -f- Ks to reach a maximum in CaCl2. This is actually 

 the case. It might perhaps be expected that these values would fall to a minimum 

 in NaCl. This is the case with Ka -^ Km but not for Kr 4- Ks- 



