E.F.G. Herington's 1963 text Zone Melting Of Organic Compounds mentions on page 44 that for the purifying of organic compounds ( such as DMSO,) the melt zone should move at a rate of 0.3 to 5 centimeters per hour.
This might be accomplished by lowering a tube (made of thick glass, stainless steel or inert plastic) of DMSO into an insulated bottle of ice-water, using clockwork. An axle with two drum-like radii could speed up or slow down the clockwork, using cords wrapped around the two drums. A cuckoo clock powered by falling weight might accomplish a useable descent rate even without such an intermediating axle. Matthew
