TEST METHODS

[:ru]Катьял Н. К.[:en]Katyal N. K.[:] [:ru]Национальный совет по цементу и строительным материалам, Индия[:en]National Council For Cement And Building Materials, India[:]

[:ru]Дхаван А. К[:en]Dhawan A. K.[:] [:ru]Национальный совет по цементу и строительным материалам, Индия[:en]National Council For Cement And Building Materials, India[:]

[:ru]Али М. М.[:en]Ali, M. M.[:] [:ru]Национальный совет по цементам и строительным материалам, Баллабгар, Харьяна, Индия[:en]National Council for Cement and Building Materials, Ballabgarh, Haryana, India[:]

Alitinform №2 (14) 2010 г. 97-100 p.

Abstract

Calcium and magnesium oxides are important constituents controlling physical performance of Portland cement so their accurate estimation is very important to assess the quality of cement. In the present available complexometric methods, calcium and magnesium are estimated by titrating with complexing agents such as ethylenediamine tetra acetic acid (EDTA) using visual and photometric techniques making use of various indicators in the presence of masking agent such as triethanolamine to avoid the interferences of accompanying elements. Separate indicators are used for calcium and magnesium titrations. The visual detection of end points is complicated as the change in colour during titration is not very sharp. This leads to uncertainty of the results particularly for magnesium estimation.

In order to analyze cement and other allied materials with better accuracy, investigations have been carried out where calcium and magnesium are titrated with EDTA using one common indicator without any addition of any masking agent as the method developed is free from inter elemental inference. There is one-drop change at the end points in the titrations, hence the results for calcium and magnesium are very accurate.

The various standards of the world [1, 2, 3] for testing of cement have different methods of estimating calcium and magnesium by complexometry. As per the Indian Standard [1] calcium and magnesium in a cement/clinker sample are titrated using ethylenediaminetetra acetic acid disodium salt (EDTA). Calcium is first titrated at pH 12 using Patton and Reader’s reagent as indicator. Then magnesium is titrated at pH 10 using thymolphthalaxone indicator. Triethanolamine is used as masking agent in the titrations for masking the interference of accompanying iron and aluminum in the solution. The end point for magnesium is not very sharp as there is no one drop change in colour at the end point, hence the results may be doubtful.