ABSTRACT
CONTENTS 12.1 Introduction ..................................................................................................................... 313 12.2 Analytical Methods ........................................................................................................ 314
12.2.1 Spectrophotometric Technique and Methods .............................................. 314 12.2.1.1 American Public Health Association, APHA
Standard Method ............................................................................. 314 12.2.1.2 Application of the Molybdate Method and Other
Spectrophotometric Methods......................................................... 316 12.2.1.3 Flow Injection Analysis Technique and
Spectrophotometric Methods......................................................... 319 12.2.1.4 Sequential Injection Analysis Technique and
Spectrophotometric Methods......................................................... 324 12.2.2 Other Techniques and Methods ..................................................................... 329
12.2.2.1 Infrared Methods ............................................................................. 329 12.2.2.2 Titrimetry and Gravimetry............................................................. 329 12.2.2.3 Thermogravimetry........................................................................... 330 12.2.2.4 Chromatography.............................................................................. 331 12.2.2.5 Electroanalytical ............................................................................... 332 12.2.2.6 Sound Velocity and Density Method ........................................... 332
References ................................................................................................................................... 333
Several methods have been employed for quantitative determination of silica in different water samples. This involves spectrophotometry, titrimetry, gravimetry, electroanalytical, or chromatography techniques. The demand for routine rapid analysis resulted in the introduction of the flow injection analysis (FIA) technique. FIA has proven to be adding a lot to the development of water analysis at large. The determination of silica in water samples is considered very important in the industry because silica deposits on stream turbine blades at high pressure and temperature. This lowers the efficiency of heat transfer, leading to costly downtime for cleaning and may result in total failure of the boiler system. Phosphate is usually added to the boiler feed water to ensure that it is in the alkaline range, and this serves as an anticorrosion measure. Phosphates react similarly with reagents used for silica determination to give the same colored product; this poses a
serious interference problem for the colorimetric determination of silica in the presence of phosphate. This interference problem is especially challenging when analyzing very low concentration of silica.
