Currently. arsenic is removed from blister copper by soda and calcium hydroxide injection into liquid metal. In consequence sodium and calcium arsenates are formed. These arsenaies could be converted to analogues of minerals, which naturally contain high concentration of arsenic and are known to be durable over geological time and slightly soluble in water. The project attempted to show that sodium arsenate contained in slag could be convened into svabite Ca;(AsO4)3F which is being considered for safe disposal of arsenic. The thermal stability of the synthesised svabite under low oxygen pressure was also determined.