Equipment for single crystal growth from aqueous solution

Abstract

Tho I!;ro\\"ing of large single crystals of hi gh quality from solution requ ires t he p~• e cise control of s upersat uration a nd t he avoida ncc of t hermal and m echal1lcal shock. Ul1Iform arowth conditions a nd cleanliness need to be maintained. Good seed crystals a re necessary ~lld the accidental int rodu ction or generation of new nuelei should be prevent.ed insofar as possible. In the apparatus and eq uipment assembli es here describcd , t he cr ystal-growth bath is d esigned for uniform growth conditions a nd the exclusion of co ntam ination. The s upport [or t he cr ystals provides for convenient mo unting of t he secds, h olds Lhe cr ystals firml y, an d allows their easy rcmoval with min imum damage. A I~CW rever sin g rotat. ion m echa nism promotes equal wash ing of t he crystal s ur faces and ach lcves unIform te mperatu re and composition of the solu tion without, at t h e same t im e,. prod ucin g .significant mechanical stresses in the crystals. The te mperature controller gi ves r eg ulallOn of the temperature an order of mag ni t ud e more sensitive than those hitherto used and provides for s tepl eR'> cha nge of temperature. The crystals are t hus fr ee. fr om li q uid in clL!s!ons found to rcs ul t from s udden acceleration of growth. The electrolytIC conductanee of lo mc solut ions may be used as a precise and sens iti\•e measure of solution co ncC'ntration and supersat uration. The crystal-growt h procedures whi ch are reported have res ul ted in t he p rodu ctio n of very good single crystals of a cons ide rable variety of chemi cal phases.

A phase study of the system: Oxalic acid/acetic acid/water; its significance in oxalic acid crystal growth

“…Attempts have been made to purify oxalic acid by growth of anhydrous single crystals from its solution in acetic acid. Even when using equipment [1]2 with precise control of solution temperture, good crystals only up to 1 cm in length could be grown from glacial acetic acid. Larger crystals became cloudy owing to the inclusion of mother liquor.…”