GB622113A - Improved apparatus for growing crystals - Google Patents

Abstract

An apparatus for growing crystals, Fig. 1, particularly of ammonium dihydrogen phosphate, comprises a container 8 for the nutrient solution with a rotating shaft 12, whose direction of rotation is periodically reversed, carrying supports 10 for the crystals. The crystal may also turn about an axis to assist even flow of solution over it. The container may be lagged and the bottom may be heated as by element 50 and by elements 44, 46 controlled through <PICT:0622113/III/1> <PICT:0622113/III/2> relay 38 by regulator 30. Extraneous crystals are bunched at the centre of the bottom by the vortex caused by rotation, and redissolved in the thin layer of unsaturated solution produced by the heating elements. The bottom of the container may be dished to assist this bunching, Fig. 2 (not shown), and may be provided with a central inlet for the introduction of solution, which overflows at 74. Various types of crystal support are illustrated in one of which, Fig. 7, a single large crystal bar 4, as for instance 15 inches long and 4 or more inches wide, is grown from a seed crystal 2 mounted on radial supports 10H attached to the central rotating shaft 12. The seed crystal may be of various types. Ammonium sulphate (4 grams per litre) or ferric nitrate or phosphate or aluminium nitrate (0.001 mol. per litre) may be added to the solution of primary ammonium phosphate to affect crystal growth in specified ways, or the pH value may be varied. The Specification as open to inspection under Sect. 91 refers also to the use of the apparatus to grow crystals such as of Rochelle salt or other tartrates, sodium chlorate or sodium bromate; to the addition of chromium, tin, or barium selenate, lithium, alkali, pyridine, trimethylamine or secondary ammonium phosphate to the solution; to methods of growing initial seed stock; to growing crystals in stages; and to the optical inspection of crystals. This subject-matter does not appear in the Specification as accepted.