History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c17.s4.t2.17

v1.c17.s4.t2.17

It is evident from the data that a small part of sphalerite was not converted into oxide and remained in the retort as ZnS and ZnSO4. The presence of goslarite or ZnSO4, 7H2O (hydrated at later stage) was confirmed by the endothermic DTA peaks apart from X-ray and electron diffraction studies. Some ZnO was converted to complex silicates during roasting and some underwent atmospheric conversion at a later stage to the basic carbonates (vide Table 6). Trace element detection in the zinc residue/slag by the Energy Dispersive X-ray Micro-Analysis or EDAX in the Scanning Electron Microscope showed the existence of elements such as Na, K, S, Ti etc., which must have originated from the ore-body charged into the retort.