Testing silica content in quartz sand
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This post was last edited by Yuèěr Dòngtīng on 2020-11-12 at 15:08. Recently, the company has been developing new products and needs to determine the silica content in quartz sand; however, this value remains within the range of 65%–69%. The parallel samples also give similar results each time, but the laboratory staff claim that the actual content is much lower than this. It’s not clear what the reason for this is. I would be extremely grateful if the experts here could give me some advice! The potassium fluosilicate titration method is used: a small amount of quartz sand that has been dried at 105°C until a constant weight is achieved is taken, ground fine in an agate mortar, and then a small amount of the resulting powder is dried again until a constant weight is obtained for use. About 1 gram of potassium hydroxide is added as a base in a dry nickel crucible. 0.1 g of quartz sand powder is then placed in the crucible, and an additional 1–2 grams of potassium hydroxide is added to cover the sample. The mixture is heated in an electric furnace; once it has melted, it is gently stirred, and heating continues for another fifteen minutes. After that, the mixture is removed and allowed to cool. After cooling to room temperature, the nickel crucible was washed several times with small amounts of distilled water, then washed with 1 milliliter of 1+1 hydrochloric acid, and finally washed again with a small amount of distilled water (the amount of distilled water used being kept under 60 milliliters). All the washing solutions were poured into a 500-milliliter plastic beaker. Add another 15 milliliters of nitric acid to the plastic beaker, stir well, and cool to room temperature. Potassium chloride is added to achieve a supersaturation level corresponding to about the size of a 1-cent coin. 10 milliliters of 15% potassium fluoride solution is then added, the mixture is stirred, left to stand for 10 minutes, and then filtered. After filtration, the beaker is washed three times with 10% potassium chloride solution, and the filter paper is washed once. Add 1 drop of phenolphthalein and 10 milliliters of 5% potassium chloride ethanol solution to a 500-milliliter plastic beaker; place the filter paper in the beaker and unfold it. Neutralize the residual acid with a 0.15 mol/L sodium hydroxide standard solution, then squeeze and crush the filter paper until it turns slightly red. Add 200 milliliters of boiling water to the beaker (boiling water that has been neutralized with 0.15 mol/L sodium hydroxide until phenolphthalein turns slightly red). Finally, it is titrated to a faint pink color using 0.15 mol/L sodium hydroxide standard titrant.
First, have your company’s laboratory provide the testing methods, so that our experts can analyze whether there are any issues with them. If the method is correct and the replicates are done properly, then it’s a problem with the content of the product itself.
The potassium fluosilicate titration method is used: a small amount of quartz sand that has been dried at 105°C until a constant weight is achieved is taken, ground fine in an agate mortar, and then a small amount of the resulting powder is dried again until a constant weight is obtained for use. About 1 gram of potassium hydroxide is added as a base in a dry nickel crucible. 0.1 g of quartz sand powder is then placed in the crucible, and an additional 1–2 grams of potassium hydroxide is added to cover the sample. The mixture is heated in an electric furnace; once it has melted, it is gently stirred, and heating continues for another fifteen minutes. After that, the mixture is removed and allowed to cool. After cooling to room temperature, the nickel crucible was washed several times with small amounts of distilled water, then washed with 1 milliliter of 1+1 hydrochloric acid, and finally washed again with a small amount of distilled water (the amount of distilled water used being kept under 60 milliliters). All the washing solutions were poured into a 500-milliliter plastic beaker. Add another 15 milliliters of nitric acid to the plastic beaker, stir well, and cool to room temperature. Potassium chloride is added to achieve a supersaturation level corresponding to about the size of a 1-cent coin. 10 milliliters of 15% potassium fluoride solution is then added, the mixture is stirred, left to stand for 10 minutes, and then filtered. After filtration, the beaker is washed three times with 10% potassium chloride solution, and the filter paper is washed once. Add 1 drop of phenolphthalein and 10 milliliters of 5% potassium chloride ethanol solution to a 500-milliliter plastic beaker; place the filter paper in the beaker and unfold it. Neutralize the residual acid with a 0.15 mol/L sodium hydroxide standard solution, then squeeze and crush the filter paper until it turns slightly red. Add 200 milliliters of boiling water to the beaker (boiling water that has been neutralized with 0.15 mol/L sodium hydroxide until phenolphthalein turns slightly red). Finally, it is titrated to a faint pink color using 0.15 mol/L sodium hydroxide standard titrant.
The potassium fluosilicate titration method is used: a small amount of quartz sand that has been dried at 105°C until a constant weight is achieved is taken, ground fine in an agate mortar, and then a small amount of the resulting powder is dried again until a constant weight is obtained for use. About 1 gram of potassium hydroxide is added as a base in a dry nickel crucible. 0.1 g of quartz sand powder is then placed in the crucible, and an additional 1–2 grams of potassium hydroxide is added to cover the sample. The mixture is heated in an electric furnace; once it has melted, it is gently stirred, and heating continues for another fifteen minutes. After that, the mixture is removed and allowed to cool. After cooling to room temperature, the nickel crucible was washed several times with small amounts of distilled water, then washed with 1 milliliter of 1+1 hydrochloric acid, and finally washed again with a small amount of distilled water (the amount of distilled water used being kept under 60 milliliters). All the washing solutions were poured into a 500-milliliter plastic beaker. Add another 15 milliliters of nitric acid to the plastic beaker, stir well, and cool to room temperature. Potassium chloride is added to achieve a supersaturation level corresponding to about the size of a 1-cent coin. 10 milliliters of 15% potassium fluoride solution is then added, the mixture is stirred, left to stand for 10 minutes, and then filtered. After filtration, the beaker is washed three times with 10% potassium chloride solution, and the filter paper is washed once. Add 1 drop of phenolphthalein and 10 milliliters of 5% potassium chloride ethanol solution to a 500-milliliter plastic beaker; place the filter paper in the beaker and unfold it. Neutralize the residual acid with a 0.15 mol/L sodium hydroxide standard solution, then squeeze and crush the filter paper until it turns slightly red. Add 200 milliliters of boiling water to the beaker (boiling water that has been neutralized with 0.15 mol/L sodium hydroxide until phenolphthalein turns slightly red). Finally, it is titrated to a faint pink color using 0.15 mol/L sodium hydroxide standard titrant.
This post was last edited by Yang Qing on 2020-11-12 at 16:19. I think it should be possible to determine the properties of your sample using the potassium fluosilicate titration method; after reviewing the details of the procedure, I don’t see anything problematic with it. I’m not sure what the required quality standard for silica content is for your products. If there are no issues with the fineness of the sample or the calibration concentration of the standard solution, and if the testing is carried out strictly in accordance with the steps outlined in the method, it can be assumed that this is indeed the content of the product. Alternatively, the sample can be sent to a qualified third-party laboratory for comparison (using the same testing methods). I’m curious to hear what other friends have to suggest or add regarding the original poster’s method. The original poster can also search for details regarding the use of this method for detecting silica. Overall, it seems that if certain details are not given too much attention, it won’t lead to serious discrepancies; moreover, according to you, the parallelism in sample testing is acceptable.