crucible a cylinder of gas containing 1 2 mole cf 3 cl is connected through teflon plumbing to the inlet of the crucible which is also fitted with an outlet leading to a scrubber the temperature of the crucible is raised to 1000 u00b0 c at which point the bacl 2 powder becomes molten the flow of the rap mixture is maintained at 1 ml sec through the whole process this process consists of a preliminary scrubbing of the molten charge and interior surfaces of the crucible followed by the crystal growth operation with a pull rate of 4 mm hr until the entire crystal is outside of the hot zone of the furnace the vaporous phase about the crystal is still in the hot zone and remains chemically reactive the furnace temperature is allowed to drop linearly to 200 u00b0 c within a four hour period subsequently the crystal is allowed to cool to room temperature and removed from the crucible bacl 2 crystals prepared in accordance with the above procedure exhibit a higher environmental stability than crystals prepared by prior art processes and do not show the solid solid transition behavior characteristics of crystals prepared by prior art processes the above process is applicable to srcl 2 and bacl 2 when the temperatures are adjusted to match the respective melting points of the materials table i______________________________________rap agents for alkaline earth chloridesingle crystal growthalkaline earth rap pyrolyticchloride agent decay constant k sec sup 1______________________________________bacl sub 2 cf sub 3 cl 0 044 ch sub 3 cl 0 12 ch sub 3 cl.