Minerals analysis
Two grams of sample was digested in a digestion flask containing concentrated hydrochloric acid
and nitric acid, then 5 mL of hydrochloric acid 4 N was added into the solution, adjusted until 100 mL with distilled water in measuring flask. Calcium, Potassium and Sodium contents were measured by using a flame photometer (BWB XP, UK) after 2 mL of lanthanum chloride 10% was added to the solution. Determination of Fe content was done according to Riganakos and Veltsistas (2003), by measuring the complex of FeSCN. The complex was formed by oxidation of Fe2+ in the solution to Fe3+ using saturated K2S2O3 and added by KSCN. An UV-Vis spectrophotometer (Shimadzu UV 1800, Japan) was used to measure the complex formed. K4Fe(CN)6 was
used as a standard.