| 摘要 |
<p>Aluminium fluoride is prepd. by treating aq. acid aluminium chloride with stoichiometric quantity of hydrofluosilicic acid at 100-105 degrees C: 2AlCl3 + H2SiF6 + 2H2O right arrow SiO2 + 2AlF3 + 6HCl Silicic acis is in easily filtered form and hence completely removed. Filtrate-soln. is either concd. to deposit AlF3 or cooled to 20-30 degrees C and treated with NaF to produce sodium aluminium fluorides. Exact compsn. of complex depends on Na:Al ratio e.g., if 3, cpd. is cryolite 3NaF . AlF3. Very pure fluorides are formed in excellent yield. The SiO2 and HCl produced in process can be used to form further AlCl3 for a highly efficient cyclic operation.</p> |
