Processing alkali metal halide salts for growing into crystals in accordance with stockbarger process

Claim 2

IN THE GROWING OF ALKALI METAL HALIDE SALT CRYSTALS BY THE BRIDGEMAN-STOCKBARGER PROCESS, THE STEPS OF PURIFYING THE HALIDE SALT TO OBTAIN A HOT SLURRY, DRAWING OFF MOST OF THE MOTHER LIQUOR FROM THE PURIFIED HALIDE SALT SLURRY BY A VACUUM FILTRATION PROCESS TO LEAVE A HOT DAMP SALT, PLACING THE DAMP SALT IN CONTAMINATION-PROOF METAL TRAYS OF INDENTICAL BUT SLIGHTLY SMALLER CROSS-SECTIONAL SHAPE THAN THAT OF THE CRYSTAL-GROWING CRUCIBLE, PUTTING THE TRAYS IN AN OVEN AND HOLDING THEN THERE FOR AT LEAST 15 HOURS AT A TEMPERATURE IN EXCESS OF 212*F., LONG ENOUGH TO DRIVE OFF ALL OF THE WATER FROM THE SALT CAKES, LOWERING THE OVEN TEMPERATURE TO NOT LESS THAN 200*F. SO THAT THE SALT CAKES THUS FORMED CAN BE HANDLED, REMOVING THE CAKES FROM THE TRAYS, BREAKING UP INTO A POWDER SOME OF THE CAKES AND FILLING UP THE CONE PORTION OF THE CRUCIBLE, PLACING THE REMAINING HOT CAKES IN THE CRUCIBLE AND FILLING THE CRACKS AND INTERSTICES WITH THE REMAINING POWER TO OBTAIN AS MUCH SALT IN THE CRUCIBLE AS FEASIBLE, AND THEREAFTER GROWING THE CRYSTAL.

Claim 3

In the growing of alkali metal halide salt crystals by the Bridgeman-Stockbarger process, the steps of purifying the halide salt to obtain a hot slurry, drawing off most of the mother liquor from the purified halide salt slurry by a vacuum filtration process to leave a hot damp salt, placing the damp salt in contamination-proof metal trays of identical but slightly smaller cross-sectional shape than that of the crystal-growing crucible, putting the trays in an oven and holding them there for at least 15 hours at from 330* to 370*F., increasing the oven temperature to between 450* and 550*F. for at least 24 hours, lowering the oven temperature to not less than 200*F. so that the salt cakes thus formed can be handled, removing the cakes from the trays, breaking up into a powder some of the cakes and filling up the cone portion of the crucible, placing the remaining hot cakes in the crucible and filling the cracks and interstices with the remaining powder to obtain as much salt in the crucible as feasible, and thereafter growing the crystal.

Claim 4

In the growing of alkali metal halide salt crystals by the Bridgeman-Stockbarger process, the steps of purifying the halide salt to obtain a hot slurry, drawing off most of the mother liquor from the purified halide salt slurry by a vacuum filtration process to leave a hot damp salt, placing the damp salt in contamination-proof metal trays of identical but slightly smaller cross-sectional shape than that of the crystal-growing crucible, putting the trays in an oven and holding them there for at least 15 hours at from 330* to 370*F., increasing the oven temperature to between 450* and 550*F. for at least 24 hours, lowering the oven temperature to not less than 200*F. so that the salt cakes thus formed can be handled, removing the cakes from the trays, breaking up into a powder some of the cakes and filling up the cone portion of the crucible, placing the remaining hot cakes in the crucible and filling the cracks and interstices with the remaining powder to obtain as much salt in the crucible as feasible, and thereafter growing the crystal.

Claim 5

A process of drying and packing alkali halide salt crystals into a crucible for growing in accordance with the Bridgeman-Stockbarger process wherein the crystals are kept above at least 175*F. comprising the steps of a. purifying the alkali metal halide salt to form a slurry, b. separating the salt crystals from the mother liquor to obtain damp salt crystals, c. placing the damp salt crystals in contamination-proof trays with the same but slightly smaller cross-sectional shape than that of the crystal-growing crucible, d. putting such salt-filled trays in an oven at from 330* to 370*F. for at least 15 hours, e. increasing the oven temperature to from 450* to 550*F. for at least 24 hours, f. lowering the oven temperature to a temperature at which the salt crystal cakes thus formed in the trays can be handled, such temperature being at least 200*F., g. breaking up a small portion of the cakes into powder to fill the bottom of the crucible and the interstices between the cakes, h. placing most of the hot salt cakes in the crucible, and i. thereafter placing the crucible in a furnace and growing crystals in accordance with the Bridgeman-Stockbarger process.

Claim 6

A process of drying and packing alkali halide salt crystals into a crucible for growing in accordance with the Bridgeman-Stockbarger process wherein the crystals are kept above at least 175*F. comprising the steps of a. purifying the alkali metal halide salt to form a slurry, b. separating the salt crystals from the mother liquor to obtain damp salt crystals, c. placing the damp salt crystals in contamination-proof trays with the same but slightly smaller cross-sectional shape than that of the crystal-growing crucible, d. putting such salt-filled trays in an oven at from 330* to 370*F. for at least 15 hours, e. increasing the oven temperature to from 450* to 550*F. for at least 24 hours, f. lowering the oven temperature to a temperature at which the salt crystal cakes thus formed in the trays can be handled, such temperature being at least 200*F., g. breaking up a small portion of the cakes into powder to fill the bottom of the crucible and the interstices between the cakes, h. placing most of the hot salt cakes in the crucible, and i. thereafter placing the crucible in a furnace and growing crystals in accordance with the Bridgeman-Stockbarger process.

Claim 7

The process of claim 3 above in which the contamination-proof trays are made from a metal is selected from the group consisting of titanium, tantalum and platinum, the alkali metal halide salt is sodium iodide, adn the temperature of step (d) is about 350*F., the temperature of step (e) is about 500*F., and the temperature of step (f) is about 250*F.