Spectrophotometric Studies of Strontium Oxide in Portland Cement

As given by the current ASTM Standard Test Methods for chemical analysis of hydraulic cement(C114), strontium, usually present in Portland cement as a minor constituent,was precipitated with calcium as the oxalate and was subsequently titrated and calculated as CaO, or alternatively correction of CaO for SrO was made,if the SrO content is known. Many analysts and ASTM members have expressed the opinion that(C 114) does not make the distinction between CaO and SrO and this may direct the analyst to not correct the CaO for SrO.Accordingly, the development of a new, sensitive and accurate method for the determination of Sr as a minor constituent in cement is of upmost importance.The main problem faced in the determination of SrO and/or MgO content of cement is the interference from excessive amounts of CaO.Derivative spectrophotometry opens up possibilities for the determination of metal ions in their binary and ternary mixtures, through their complexes with the same organic ligands.In the present work,new spectrophotometric procedures for simultaneous determination of SrO, MgO and CaO content of Portland cement, using derivative ratio spectra-zero crossing technique, are developed.