Now we formulate a least squares function in the constants (now variables) k1 and k2 using the data from ALL the chemicals.

Input := 


SS[k1_,k2_] = SSa[k1,k2] + SSb[k1,k2] + SSc[k1,k2];

Input := 


solk = FindMinimum[SS[k1,k2],{k1,.1},{k2,.2}]

Output =


{1.00038, {k1 -> 0.0629595, k2 -> 0.0211523}}