Determination of silica in boiler water - Database & Sql Blog Articles

Determination of silica in boiler water

Determination of Silica in Boiler Water: KeyWord: spectrophotometry; silica; analysis instrument; UV-1200 silicon molybdenum blue spectrophotometry 1. Range and determination of acidity at pH 1.2-1.3 The soluble silica in water reacts with ammonium molybdate to form silicon molybdenum yellow H4[Si(Mo3O10)4], which is then reduced with zinc chloride to form silicon molybdenum blue H6[Si(Mo12O40)]. The blue color It is related to the soluble silicon content in the water sample. The interference of phosphate with this method can be eliminated by adjusting the acidity or adding oxalic acid or tartaric acid. This method is applicable to the test of SiO2 content of less than 10mg / L. 2. Safety 2.1 Ammonium molybdate 2.2 Stannous chloride 2.3 Sulfuric acid 2.4 Silica 2.5 Sodium carbonate 3. Reagent 3.1 50g/L ammonium molybdate solution: Prepared with high purity water, the solution should be clear and transparent after preparation. Store in plastic bottles. 3.2 1% stannous chloride solution: Weigh 1.5g of pure grade stannous chloride in a beaker, add 20mL hydrochloric acid solution (1+1), heat and dissolve, add 80mL of pure glycerin (glycerol), stir After mixing, transfer the solution to a plastic bottle for later use. It is easy to fail, and it is stored at a low temperature. 3.3 C (1/2H2SO4) = 10 mol / L sulfuric acid solution: 280 mL of concentrated solution was slowly added to 720 mL of high purity water. 3.4 superior grade pure sodium silicate Na2SiO3·9H2O3.5 anhydrous sodium carbonate 3.6 deionized water 4. Instrument 4.1 Spectrophotometer UV-1200, 720nm; cuvette, 2cm4.2 Platinum 坩埚 4.3 High temperature furnace: 100 °C 5. Test 5.1 Silica stock solution (1mL is equivalent to 1.0mg silica): accurately weigh 4.730g of pure grade sodium silicate, dissolve in 200mL of high-purity water, dilute to 1L, and store in plastic bottle. 5.2 Silica stock solution (1 mL corresponds to 0.01 mg of silica): Pipette 105.1 mL of silica standard solution (5.1) and dilute to 1 L with high purity water. 5.3 Standard curve drawing: Take 5 50 mL colorimetric tubes, add 0, 1.0, 2.0, 3.0, 4.0 mL silica solution (1 mL equivalent to 0.01 mg silica) with pipette, dilute with water to about 25 mL at high 0.2 mL of H2SO4 (3.3) was sequentially added to each tube at 20 ° C, and shaken. Add 1.0 mL of 50 g/L ammonium molybdate and shake well. After standing for 5 minutes, 5.0 mL of H2SO4 (3.3) was added, shaken, and allowed to stand for 1 minute. Add 2 drops of 1% SnCl2 glycerin solution, shake well, and let stand for 5 minutes. The absorbance was measured at a wavelength of 720 nm using a 2 cm cuvette with a blank solution as a control. Using the absorbance as the ordinate, the milligrams of silica (milligrams or micrograms in a 50 mL colorimetric tube) is plotted on the abscissa and a standard curve is drawn. 5.4 Determination of water sample: Take 50 mL of colorimetric tube, add 25 ml of water sample and 25 ml of deionized water, respectively. The latter is blank. Then, it is carried out in the above step 5.3, "Adding to the respective tubes at a temperature higher than 20 ° C, and measuring the absorbance with a 2 cm cuvette". 6 Calculate the silica content in the water sample X (mg / L) = (a ÷ v) × 1000 where: a - the number of mg of silica found in the standard curve v - water sample volume, mL. Note: The abscissa of the standard curve is the absolute amount of silica (or ug) in a 50 mL colorimetric tube. If expressed in ug, the formula should be: X(ug/L)=a÷v because: mg/L=1000ug/L7. Note 7.1 The colorimetric tube should be thoroughly washed with silicomolybdic acid waste liquid and subjected to a blank test to check the cleanliness. 7.2 Due to the influence of temperature on the growth and reduction of silicon molybdenum yellow, the temperature of the water sample shall not be lower than 20 °C, and the temperature difference between the water sample and the standard solution shall not exceed ±5 °C. 7.3 Preparation of Ammonium Molybdate Solution If dissolution is difficult, 0.3-1 mL of concentrated ammonia water may be added per liter of solution to promote dissolution, and the solution thus prepared is less likely to precipitate when stored. 7.4 Stannous chloride-glycerol solution can also be prepared entirely with glycerol. In order to accelerate the dissolution of stannous chloride, glycerin can also be heated to about 50 °C. The solution thus formulated is more stable. Key words: spectrophotometry; silica; aesthetic instrument; UV-1200