Method for detecting contents of calcium and magnesium in natural limestone

Abstract

The invention discloses a method for detecting contents of calcium and magnesium in natural limestone. The method for detecting contents of calcium and magnesium in natural limestone comprises the following steps: weighing 2g of a sample and placing the sample in a beaker, adding water for wetting, adding a hydrochloric acid solution for boiling, boiling for 15 minutes, carrying out a cooling to room temperature, adding a 1+1 ammonia-water solution for adjusting till floc generates, mixing the solution, filtering with filter paper, fetching 25.00ml of the filtered sample solution, adding 50mL of water, adding 5.0mL of triethanolamine solution, adding a drop of malachite green solution (1%), adding a sodium hydroxide solution (100g / L) for adjusting till the blue green color in the solution disappears, carrying out a heating for boiling, after boiling, carrying out a continuous heating with soft fire for about 5 minutes, after cooling, adding a few of calcium indicators, and carrying out a titration with an EDTA standard solution till the solution color changes into blue which is the terminal point from red; according to the invention, a malachite green solution is used for accurately controlling the pH value of magnesium deposition condition and the pH value of titration system terminal point, and the method provided by the invention is convenient, rapid and accurate; the step of heating, boiling and micro-boiling for 5 minutes is used for ensuring complete deposition of magnesium; the detection method is simple, rapid, and has stable determination results and good recovery rates.

Description

Technical field [0001] The invention relates to a method for measuring metal content in limestone, in particular to a method for detecting calcium and magnesium content in natural limestone. Background technique [0002] Calcium and magnesium in calcium carbonate have been detected by complexometric titration. The specific detection method is as follows: After the sample is processed by dissolving, adjust the pH of the solution to greater than 12.5 with lye, use calcium carboxylic acid as an indicator, and titrate calcium with EDTA standard titration solution; adjust the solution to pH=10 with lye. Chrome black T is used as an indicator, and the total amount of calcium and magnesium is titrated with EDTA standard titration solution. This detection step is more suitable for the determination of calcium carbonate with higher purity, but when the magnesium content is high or the impurity content is high, this detection method often fails to obtain satisfactory results. Especially ...

AI Technical Summary

Problems solved by technology

This detection step is more suitable for the determination of calcium carbonate with higher purity, but when the magnesium content is high or the impurity content is high, this detection method often does not give satisfactory results

Especially when the calcium carbonate background is complex (especially natural limestone is the most prominent), the traditional detection method, due to inaccurate pH control, insufficient precipitation of magnesium and other elements, shows unstable measurement results when titrating calcium, and the titration does not reach the end point, etc. phenomenon, resulting in inaccurate test results