The Tilted-Plate Molecular Still Charles K. Chiklis and William S. Port, Polymer Science laboratory, Avco/RAD, Lowell, Mass.
is designed t o heat sensitive compounds by appropriate geometric construction and the use of extremely low pressures. As a result, the mean free path of the distillate vapor is in the order of the distance between the heated and cooled (collecting) surfaces a t temperatures within the stability range of the material. Although the Hickman Still (1) is frequently used for this purpose because i t is an inexpensive and simple piece of equipment, it suffers from several limitations. It has a small capacity (about 40 to 50 ml.); i t has no provision for removal of the residue from the heating zone; and it has no positive means for creating a new liquid surface. The latter shortcoming may result in bumping and consequent contamination of the distilled product. A tilted-plate molecular still has now been made which corrects for these inadequacies without introducing a major cost increase. I n principle, the batch process-of the Hickman Still is replaced by a flow procedure. The material to be distilled is caused t o flow across a tilted heater-plate, and the residue is quickly and continuously removed from the heated zone. I n passing over the heated section, the liquid constantly presents a new surface, and this virtually eliminates any possible bumping. MOLECULAR STILL
A purify
DESCRIPTION OF APPARATUS
A description of the still components (Figure 1) and a brief operating procedure are given below: The feed flask (A), equipped with a pressure equalizing sidearm, is charged with the liquid to be distilled and the system evacuated to the desired pressure. The temperature of the ground-
Table I.
Epoxy resin As received First distillation Second distillation Theoretical
glass base plate (B) is regulated by a transformer-controlled brass heater (C) (which may be conveniently bonded in place with Sauereisen cement) and is monitored by a thermocouple which is embedded at the base plate/cement interface. A few drops of liquid from (
