抄録
In previous paper, it was stated that the scale of quadruple effect evaporator at saltworks was converted into dihydrate of calcium sulfate by treating with sodium chloride solution readily, of which that of No.1 evaporator was hydrated readily by adding seed crystal of the dihydrate ot the solution.
In this study, the growth of crystal of gypsum produced was taken into consideration at the time of treatment of the scale with salt solutions (Nacl-, HCl-solution, bittern and desulfated bittern), namely, the scale of No.2 and 3 evaporator was considered to be in almost all hemihydrate and was added successively into the salt solutions suspending the seed crystals of calcium sulfate dihydrate, which was maintained at a proper supersaturation without nucleation, and the scale of No.1 evaporator was considered to be a mixture of hemihydrate and anhydrite of calcium sulfate, of which the hemihydrate was treated as above mentioned and the anhydrite was stirred with the dihydrate produced in the solution. Addition rate of the scale and the form of gypsum produced was shown.
