Abstract: It is necessary in many heat treatment processes conducted in open systems to maintain a given partial pressure of a volatile component of a material being treated, and it is desirable to conserve this volatile component, both on account of cost and in the case of components such as mercury, toxicity. A controlled unsaturated vapor pressure of a volatile liquid 28 may be produced in a tube 3 by passing a stream of a carrier gas through a vaporizer 4 containing the liquid 28 at a temperature T.sub.s, passing the mixture of the carrier gas and vapor of the liquid 28 through a tube 3 containing material 29 to be treated, which material 29 is at a temperature T.sub.t. The mixture of the carrier gas and vapor of the liquid 28 is then passed to a condenser 6 from which the carrier gas is vented to waste, and the vapor of the liquid 28 is condensed at a temperature T.sub.c in the condenser 6. T.sub.t >T.sub.s >T.sub.c.

Abstract: A method is set forth for simultaneously preparing a plurality of castings of a solution of an element, or compound, in a solvent, which solvent may also be an element and/or a compound. The solution is saturated at a temperature T.sub.s. A problem in liquid epitaxy growth processes is the simple preparation of growth charges of sufficient reproducible composition and size to produce epitaxial layers of reproducible composition and thickness. The present invention provides a melt consisting of the solvent, of the solvent together with at least one constituent of the solution, or of a solution which is unsaturated at the temperature T.sub.s, which melt is prepared in a boat body of a liquid-tight boat assembly. An equilibrium is established at T.sub.s between the melt and a solid body having an excess of any constituent in which the melt is deficient with respect to the saturated solution so as to form the saturated solution.