Equipment involx, ing the use of perforated (sieve) trays has met with great populari ty in extract ion operations, since perforated trays are s imple in design, show l i t t l e sensi t ivi ty to the presence of solid par t icu la te mat ter in the process fluids, and are compara t ive ly inexpensive. The effectiveness of extract ion in those equipments, as in other extract ion gear, is dependent in the first ins tance on the amount of surface ava i l ab le for phasecontac t between the liquids. It is, therefore, very important to know the mechanism governing the formation of that contact surface in the process of re la t ive fluid flow. This faci l i ta tes the study of the processes tak!ng p lace in bubb le -cap tray extract ion towers, and of ways for intensifying the processes. The amount of phase contact surface ava i lab le depends largely on the degree of dispersion of the liquids, which is in turn de te rmined by the relat ionship of the forces on a drop of l iquid during its continuous advance through the column. The dimensions of a l iquid drop are de termined by the equi l ibr ium prevai l ing between inert ia and surface forces. The iner t ia forces bring about a tomiza t ion of the drops as they col l ide with one another and with the trays, while the surface forces, charac te r ized by the value of surface tension, bring about coa lescence of the drops. The size of the droplets is therefore dependent on the extent to which inert ia forces a re capable of overcoming the surface tension of the l iquid phase. The qual i ty of the phase contact is charac te r ized by the relat ionship of forces determining the frequency at which l iquid is renewed in the tray orifices, s ince renewal of the contact surface occurs in the small layer of l iquid i m m e d i a t e l y ad jacen t to the orifices. The insufficient e f f ic iency of conventional perfora tedtray ext rac t ion towers owes to the fact that surface tension forces have a considerable edge over inert ia forces, s ince the value of the la t ter is de termined solely by the difference in the specif ic weights of the l iquid constituents. At the same t ime, theuse of s imi lar equipment in appl ica t ion to gas (vapor)l iquid systems, e.g. , in fract ional dis t i l la t ion, yields good results. The high ef f ic iency of f rac t iona l -d i s t i l l a t ion bubb le -cap tray equipment is due to the fact that iner t ia forces in the l a t t e r are proport ional to the difference in the specif ic weights of the vaporl iquid system, which is far in excess of the difference in the specif ic weights of two dropletphase liquids. A comparison of the operat ion of bubb le t r ay equipment in l i q u i d l i q u i d systems and gas (vapor) l iquid systems led m this concept : could not the energy of flow in an extract ion column be increased by introducing a system of gas into a bubblet ray extract ion tower through use of the forces act ing in fract ionat ing towers?