Silica Test Kits
Visual Kits
| Range | MDL | Method | Type | Test Kit | Refill |
|---|---|---|---|---|---|
| 0.00 - 0.20 ppm | 0.02 ppm | Heteropoly Blue | ULR CHEMets | K-9011 | R-9011 |
| 0.0 - 1.0 & 1 - 10 ppm | 0.05 ppm | Heteropoly Blue | CHEMets | K-9010 | R-9010 |
Photometric Kits
| Range | Method | Type | Test Kit |
|---|---|---|---|
| 0 - 10.00 ppm (0 - 4.00 ppm Spectrophotometer) | Heteropoly Blue | Vacu-vials | K-9003 |
CHEMetrics offers test kits for the determination of Silica in aqueous solutions employing the well-known Heteropoly Blue method, delivering sensitivity and accuracy within two minutes or less.
CHEMetrics patented Self-Filling Reagent Ampoule technology reduces the user’s exposure to chemicals and creates a test with fewer steps, saving time. Premixed. Premeasured. Precise. Each kit contains 30 tests. Visual and instrumental ammonia testing kit formats span all required measurement ranges. With the Heteropoly Blue method, a blue colour develops in the presence of silica.
CHEMets® and ULR CHEMets® visual test kits use colour comparators for analysis. The K-9010 CHEMets kit employs two colour comparators, for low and high range measurements. The K-9011 Ultra Low Range (ULR) CHEMets kit uses extended ampoules to provide a longer path length to show more colour that allows measurements at lower concentrations. Vacu-vials® instrumental kits rely on CHEMetrics direct-readout photometers or spectrophotometers capable of accepting a 13-mm diameter round cell.
Heteropoly Blue Method
CHEMetrics' test method determines molybdate reactive silica. The heteropoly blue chemistry is employed. Silica reacts with ammonium molybdate under acidic conditions to produce heteropoly acids, which are then reduced to form a blue colour. Phosphate interferences are masked with the addition of citric acid. Results are expressed as ppm (mg/l) SiO2.
References:
APHA Standard Methods, 22nd ed., Method 4500-SiO2 D - 1997.
ASTM D 859-05, Silica in Water.
USEPA Methods for Chemical Analysis of Water and Wastes, Method 370.1 (1983).
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Technical Data Sheet |
Applications
Silica is found in natural waters in the form of silicate, with typical concentrations between 1 and 30 mg/l, in granular, colloidal and reactive forms. Silica in water can form a harmful scale on equipment and heat transfer surfaces, particularly steam turbine blades. Silica will also foul reverse osmosis (RO) membranes, severely reducing efficiency. Commercial water treatment to remove silica is typically employed for boiler water, cooling tower water, semi-conductor manufacture, car washes, and membrane treatment processes including wastewater treatment.
The initial step in water treatment for silica often involves removal of granular silica, which has a large particle size, by physical and chemical separation, e.g. lime softening. Colloidal silica particules are finer, and can be removed by flocculation as well as ultra filtration (UF), after larger suspended solids have first been removed. Reactive silica, consisting of silica anions, are mildly acidic, and can be removed by ion exchange. Electrocoagulation (EC), also known as electroprecipitation or electrochemical precipitation (EP), is an increasingly popular treatment approach in wastewater treatment for removing hardness, silica and other suspended solids.
Regular testing of silica ensures sufficient pretreatment is being conducted to ensure system performance and longevity. Silica testing is crucial for boiler water, cooling water, natural water, wastewater, and high purity water environments.
The vast majority of commercial use of silica is in the construction industry as sand used in cement production, but also for sand casting for moulding metal parts. Silica is the primary constituent in glass. Fumed (pyrogenic) silica is a low density, high surface area powder that is used as an additive to high performance concrete, as well as thickening agent and anti-caking agent for other applications. Silica is used in food, cosmetic and pharmaceutical industries as an anti-caking agent in powdered foods or tablet, an abrasive agent in toothpaste, a fining agent in beverages and a light-diffuser and absorbant in cosmetics. It also has applications in the microelectronics industry in passivation and dielectrics.
What is Silica?
Silica is the common term for silicon dioxide (SiO2). It is a relatively inert, white or colourless solid with a high melting point of 1713°C. It exists in mineral and synthetic forms, either crystalline or amorphous. Silica is insoluble in water except for silicate mineral salts, which are the form found in most natural waters. Higher concentrations may exist in brackish waters and brines. Silicates can be found in solution in water or as colloids. Silica in tap water does not constitute a health concern but may cause scaling.
Silica is most commonly found as the hard, crystalline mineral Quartz, a framework silicate mineral. Quartz is the second most abundant element in the earth's crust, with feldspar, another silicon containing mineral, being the most abundant. Silica is a component of sand. When inhaled, crystalline silica can cause inflammation and scarring of the lungs known as silicosis, an occupational lung disease, and can be fatal.