290 MR. V. H. VELET ON THE CONDITIONS OF THE 



The relation between the values for r and T is expressible by the general formula 



in which t is the interval of time elapsing from the moment at which, the conditions 

 remaining the same, r = oo and 6 O l = 0, and the actual commencement of the 

 observations ; C is a constant. In the above series the value for t is taken as 378', 

 and in the following Table are given the values for log (T + t), log r, and the sum of 

 their values : 



The values for the third column are as concordant as could be desired ; taking the 

 mean as 3'781, the observed and calculated values for T will be as follows : 



The greatest error between the observed and calculated values does not exceed 

 2 per cent., and is within the limits of experimental error. The curve representing the 

 intervals of time from the commencement of the set, in terms of the residues at each 

 of the several observations, is a portion of a hyperbola. It is apparently illustrative 



of the law 



dr_ r* 



dT = " C ' 



which expresses the rate at which equivalent masses react upon each other ; in each 

 experiment 1/C is the amount of each unit mass, which reacts with the other per 

 unit time, when an unit mass of each substance is present. It would thus seem 

 probable that in the system of formic and sulphuric acids with water the chemical 

 change taking place does not merely consist in the removal of the elements of water 



