Re. Bruns et al., IS STATISTICAL LACK OF FIT A RELIABLE CRITERION FOR CHEMICAL COMPLEXITY, Chemometrics and intelligent laboratory systems, 33(2), 1996, pp. 159-166
Complexations of Fe-III and Co-II ions with thiocyanate in water-aceto
ne-ethanol ternary mixtures are investigated using multivariate statis
tical techniques. Simplex lattice and hexagonal mixture designs lead t
o model equations resulting in similar conclusions. The Fe-III thiocya
nate complex exhibits a very simple dependence (quadratic) on the tern
ary mixture composition. On the other hand this dependence is much mor
e complex for the Co-II thiocyanate complex since even a full cubic mi
xture model shows a significant lack of fit at the 95% confidence leve
l. These results indicate that the different possible symmetries of th
e Co-II complexes are more sensitive to the ternary mixture compositio
n than are the multistep Fe-III complex equilibria.