Reply to Comment on "Refractive Index and Density Variations in Pure Liquids. A New Theoretical Relation"

Abstract

The experimental data presented by Niedrich do not invalidate our theoretical equation.' Indeed, we noticed in 75 liquids that the mean relative deviation between experiment and theory was 6.6% while in his set of data M = 4.7%. Our A values are +1.3, -3.1, -5.0, -6.9, and -7% for carbon disulfide, benzene, n-hexadecane, n-octane, and isooctane, respectively. His other nine compounds were treated in our paper1 and compared to the same set of experimental values, except for carbon tetrachloride.The agreement between experiment and theory (A < 1%)presented by Niedrich seems fortuitous; otherwise, it would imply extreme accuracies in measured values of (dn/dT),, (dd/dT),, (dn/dP)T, and ( 3~ (at less 0.5%), while assuming that calculated values are not questionable. In the case of @T, the examination of literature data2 shows a mean deviation close to 5%. In the case of the other three quantities, a 1% mean accuracy is very optimistic. In some cases the choice made by Niedrich among several experimental values may lead to doubtful values. For instance, in carbon disulfided(dn2/dd), = 2.08 from ref 3, instead of 2.24. In our work we adopted values, all collected in the same well-known reference of the current literature3 which usually come from a critical analysis of different sources.