The phase rule

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1897 Excerpt: ...points which have yet been studied. As the position of the curve shows, the vapor always contains a greater percentage of the more volatile component than the liquid. Through fractional distillation, if carried on long enough, the two liquids will §nally be separated completely, the more volatile being found in the distillate while the less volatile remains in the boiling flask. The Hempel column is merely an apparatus by which a large series of distillations is carried out in what seems to be a single operation. The vapor is partially condensed on the first set of beads, the uncondensed part becoming richer in the more volatile component, and this process is repeated through the whole length of the column. The condensed liquid flowiilg down through the tube washes off the beads so that the lower end of the column contains a liquid having a relatively large amount of the more volatile component and this takes yet more of the less volatile component out of the vapor. Other things being equal the column is more effective when in full action than when the distillation is first begun. The ease of separation depends on the difference between the percentage compositions of the vapor and the solution. If there is a large difference the two liquids can be separated easily; otherwise not. This can not be tola from the boiling point curve alone, and it is not correct to state, as Ostwald1 has done, that the ease of separation depends on the pitch of the curve. It is conceivable that there might be found a pair of consolute liquids which would give an almost straight boiling curve and yet have the composition of the two phases nearly identical at each temperature. On the other hand, it is to be noticed that when the boiling points of the two pure components lie v...