Birendra Chandra Sinha

Volumetric Estimation of Silica

The limitations of the volumetric silico-fluoride methods were studied and a modified procedure has been worked out for rapid and accurate estimation of silica. Standard deviation of the results is 0.154 and one sample can be analysed in duplicate in 2 hours. The method has been used for analysis of quartz, clays and clay products, glass, alumino silicate refractories and felspar. Other silicate constituents, including boron, antimony and fluorine did not interfere.

Masking of manganese in relation to stepwise complexometric determination of calcium, magnesium and manganese.

A critical study has been made of the masking of manganese with potassium cyanide in alkaline medium for complexometric titration of calcium and magnesium. It has been found that there is incomplete oxidation to manganese(III) unless the solution is aged for a sufficient period or air is bubbled through the solution at 35 +/- 5 degrees for 10 min. The manganese(III) complex can be reduced with ascorbic acid for titration with EDTA. Procedures are given for stepwise titration of magnesium, manganese and calcium in silicate materials. Mixed indicators are used, to improve the end-points.

A Rapid Method for Determination of Silica in High Titanium and Zirconium Bearing Materials

Effects of titanium and zirconium on the volumetric estimation of silica have been critically studied. Based on the observations, a procedure has been described for rapid and accurate estimation of silica in rutile, ilmenite and zircon sand.

Rapid Analyses of Silicates

A general scheme has been worked out for rapid and accurate analysis of a wide variety of silicate material such as sand, felspar, clay, bauxite, glass, etc. Silica has been estimated by a modified silico-fluoride method, Al2O3, CaO and MgO by complexometry, Fe203 and TiO2 by polarography and the alkalies by flame photometry. The analytical methods have been described in detail and the advantages and limitations of the proposed scheme have been discussed.

Extraction spectrophotometric method for determination of aluminium in silicates

A simple, rapid and sensitive method has been worked out for spectrophotometric determination of macro and micro amounts of alumina in ceramic raw materials and finished products, including glasses. The method is based on the extraction of aluminum oxinate into chloroform after masking of titanium with chromotropic acid and of iron with ascorbic acid and 1,10-phenanthroline or ferrocyanide at pH 5.2. The absorbance is measured at 385 nm. Interference by Cu, Zn, Cd, Ni and Co, when present, is overcome by stripping them as cyanide complexes by shaking the chloroform extract with potassium cyanide solution. Zr is masked with quinalizarin sulphonic acid and fluoride with BeSO(4).

A study of the titrimetric potassium silicofluoride method for determination of silica in aluminosilicate materials

A critical study of the titrimetric potassium silicofluoride method for determination of silica reveals that quantitative precipitation of the sificofluoride is possible in 3.5-7.5N acid containing 1% sodium fluoride and >/ 12% potassium chloride. An aqueous wash solution (pH approximately 5.3) containing 0.1% sodium fluoride and 12% potassium chloride has been found ideal for washing the precipitate without significant hydrolysis even at 35 degrees C. The interference of large amounts of aluminium (up to 160 mg of Al(2)O(3)) is eliminated by precipitating the silicofluoride in 6-7.5N acid solution, the aluminium then forming practically no fluoro-complex, because of extensive protonation of fluoride. Interference by large amounts of boron (up to 160 mg of B(2)O(3)) is eliminated by precipitating silicofluoride with the minimum permissible potassium chloride concentration (12%) and washing with the aqueous wash solution at room temperature. Nitrazene Yellow has been used as a more sensitive indicator.

Separation of lead sulphate from barium sulphate in their determination in glass

The conventional method for separation of lead from a combined lead and barium sulphate precipitate by extraction with ammonium acetate has been critically studied. The results show that quantitative separation of lead is possible only when the molar concentration ratio of barium to lead is 4.2 or above, but at ratios below 4.2 the method fails because of the formation of a solid solution of lead and barium sulphates which is maximal at initial mole-ratio 0.42. The lead in the solid solution, however, forms a strong soluble complex with EDTA and can be quantitatively separated. Based on this, a gravimetric method has been worked out for determination of lead and barium in glass.

Stepwise Complexometric Determinations of Calcium and Magnesium in Lime and Magnesia Bearing Materials

A simple and rapid complexometric method for stepwise titration of calcium and magnesium, when present in unfavourable ratios, has been successfully worked out. The method is based on the direct titration of calcium of pH 12 with EDTA, using thymolphthaleincalcein indicator. The adsorption of metallochromic indicator and any Ca2+ has been prevented by the prior addition of titan yellow which masks magnesium by lake formation. Glycerine is also added as a protective colloid to stabilize the lake and to prevent coprecipitation of Ca(OH)2. After dissolution of the lake in HC1 acid, subsequent addition of ascorbic acid, then ammonia and ammonia buffer, for controlling the pH at 10, Mg is determined in the same aliquot by direct titration with EDTA using Eriochrome Black T indicator. The method has been successfully applied for the determination of calcium oxide and magnesium oxide in magnesite, dolomite, asbestos and other lime and magnesia bearing materials.

Stepwise complexometric determination of calcium and magnesium, and manganese in blast furnace slags and manganese minerals

A simple and rapid complexometric method for stepwise titration of Ca and Mg, and Mn in blast furnace slags and manganese minerals has been worked out without involving any separation of manganese. The method is based on the joint titration of Ca and Mg at pH 10 using naptholgreenorthocresolphthalein-ammonium chloride mixed indicator after masking manganese effectively with KCN and bubbling air through the solution (30° -40°C) for 10 minutes. Manganese is then titrated at the same pH in the presence of indicator solution containing eriochrome black T, titan yellow and triethanol amine after reducing the Mn (III) hexacyano complex to Mn (II) cyanide complex with ascorbic acid. Calcium is, however, determined from a separate aliquot by direct titration with EDTA using calcein-thymolphthalein indicator after masking Mn with TEA and K CN. © 1980 Taylor & Francis Group, LLC.

A Scheme for Rapid Analysis of Enamels and Frits

A scheme has been worked out for rapid and accurate analysis of enamels and frits. The scheme enables the determination of seventeen different constituents from a stock solution of single decomposition. The stock solution was prepared by decomposing the sample with hydrofluoric and sulphuric acids. Lead and barium were separated as sulphates prior to the determination of other constituents and then lead sulphate was separated from barium sulphate for the first time with EDTA at pH 4.3. Different aliquots were used for determination of sodium and potassium by flame photometry; cadmium and zinc by polarography and traces of iron, chromium, nickel, copper, cobalt and manganese by spectrophotometry. From another aliquot of the stock solution interfering elements were removed by mercury-cathode electrolysis and then zirconium, aluminium, calcium and magnesium were determined by complexometric methods and titanium by the spectrophotometric or polarographic method. Separate samples were decomposed for determinat...