Automatic application of mobile phase for descending paper chromatography.

When volatile solvents are used for paper chromatography, as in the systems described by Bush (1952) for separation of steroids, it is usually necessary to hang the paper in the tank for several hours' equilibration before the addition of the mobile phase. If equilibration is allowed to proceed overnight much of the next day will be taken up with running the chromatogram. An apparatus has therefore been constructed which delivers the mobile phase into the upper trough at a pre-arranged time during the night, so that development of the chromatogram is completed by morning. The mobile phase is contained in a cylindrical glass chamber (Fig. I) constructed from a 250 ml. beaker or suitable length of wide-bore tubing. The chamber rests on the glass plate forming the roof of the chromatography tank, and is provided with (1) a filling tube, normally closed by a ground-glass stopper, and (2) a horizontal outlet tube, inserted a little above the floor of the chamber, so that any stationary phase which may have been added will not be carried over into the trough. This tube contains a 4 mm. two-way spring-loaded stopcock. Beyond the stopcock the tube turns downwards and passes through the roof of a small glass dome covering a