Being curious about the true difference between the efficiency of simple versus fractional distillation, I elected to perform a small research experiment to determine the results for myself. The density of a standard solution of 70% isopropyl alcohol was measured and compared to the densities of the two distillates.

The density of the 70% standard isopropanol solution was measured to be 0.863g/mL, giving a concentration by weight of 68.3% and a concentration by volume of 75.0%

The density of the simple distillate solution was measured to be 0.820g/mL, giving a concentration by weight of 85.8% and a concentration by volume of 89.5%

The density of the fractional distillate solution was measured to be 0.807g/mL, giving a concentration by weight of 91.1% and a concentration by volume of 93.6%