title: Stepwise complexometric determination of aluminium, titanium and iron concentrations in silica sand and allied materials.
abstract: BACKGROUND
  This study aimed at measuring the quantities of Al, Ti and Fe in silica sand and allied materials employing a complexometric method in the same analyte and a stepwise indirect titration with EDTA. The method involves the complexation of Al, Ti and Fe with excess EDTA and the selective de-complexation of TiO-EDTA and Al-EDTA complexes with tartaric acid and NaF respectively. In addition to its simplicity, rapidity and accuracy, the proposed method does not require the use of a separation technique or any sophisticated instrumentation.
  
  
  RESULTS
  Each of the test samples were analyzed five times using the proposed method. The method's accuracy was confirmed by analyzing the US National Institute of Standards and Technology's (NIST) Standard Reference Materials (SRM) 81a, 89 and IPT SRM 61 using the procedure proposed, in addition to analyzing Ti and Fe levels by spectrophotometry and that of Al by complexometry.
  
  
  CONCLUSIONS
  The study shows that there is good agreement between the proposed and existing methods. The standard deviations of the measurements were calculated by analyzing five replicates of each sample, and were found to be less than 1.5% in our method.
authors.affiliation: National Physical Laboratory, Dr K S Krishnan Marg, New Delhi, India. nijhuma@hotmail.com
authors.forename: Nijhuma
authors.initials: N
authors.lastname: Kayal
authors.forename: Nahar
authors.initials: N
authors.lastname: Singh