THIS book is a new and amplified edition of the author's well-known treatise on “Fractional Distillation,” first published in 1903. Prof. Sydney Young is an acknowledged authority on the subject on which he writes, and for many years prior to the appearance of the first edition of his work, the principles underlying the separation of substances by distillation had been investigated by him and the results communicated to various scientific societies. But his book embodied not only his own experience. Everything that was known at that period concerning the science and art of distillation was duly recorded and discussed, and the relative merits of the various still-heads and other forms of apparatus employed in the processes of fractional distillation were carefully inquired into and compared. The rapid development of organic chemistry, pure and applied, during the latter half of the nineteenth century was the immediate cause of the attention which the subject then received. Distillation was practically the only means available for the isolation of the constituents of mixed liquids. The art of distillation is, of course, as old as any chemical process, but the principles upon which its efficient application as a method of separation of complex liquids depend, were very imperfectly understood. Prof. Young's book was the first systematic attempt to explain these principles and to illustrate their bearing upon laboratory and technical procedure. It has not only been of great use to operative chemistry, but it has served to indicate many points of theoretical interest concerning the thermal behaviour of substances which, although they may have no immediate utilitarian value, are certain to influence practice in the future.