Question

The density of an aqueous solution increases as solutes such as salts are added. What bearing might this have on predicting whether the aqueous solution will be on the top or on the bottom for an extraction?

Answer 1

In a liquid-liquid extraction which consists of one organic and one aqueous layer, sometimes the density of the layers is too close. This difference in the density is the basis of separation of the two layers. In the mixture when solutes are added, the density of the aqueous layer increases as more salt dissolves into the layer. Hence the density difference between the two layers increases and the more dense layer, now the aqueous layer settles as the bottom layer of the extraction.