XB/T 601.5-2008Chemical analysis methods of lanthanum boride - Determination of acid dissolving silicon content - Silicon molybdenum blue spectral luminosity method (English PDF)

Foreword

This standard is divided into the following 5 parts.

XB/T 601.1-2008 Methods for chemical analysis of lanthanum hexaboride. Determination of boron content. Acid-base titration XB/T 601.2-2008 Methods for chemical analysis of lanthanum hexaboride Determination of iron, calcium, magnesium, chromium, manganese, and copper content inductively coupled plasma Emission spectroscopy XB/T 601.3-2008 Methods for chemical analysis of lanthanum hexaboride-Determination of tungsten content-Inductively coupled plasma emission spectrometry XB/T 601.4-2008 Methods for chemical analysis of lanthanum hexaboride. Determination of carbon content. High frequency induction combustion infrared absorption method XB/T 601.5-2008 Methods for chemical analysis of lanthanum hexaboride-Determination of acid-soluble silicon content-Silicon molybdenum blue spectrophotometric method this part is part 5.This part is a reference to XB/T 601.6-1993 "Methods for chemical analysis of lanthanum hexaboride, silicon molybdenum blue spectrophotometric method Revision of "Determination of Acid Soluble Silicon Amount". Compared with XB/T 601.6-1993, the main changes are as follows.

---Edited the standard text;

--- Added precision (repeatability) clause.

This part was proposed and managed by the National Rare Earth Standardization Technical Committee.

1 Scope

This section specifies the method for determining the acid-soluble silicon content in lanthanum hexaboride.

This section applies to the determination of acid-soluble silicon content in lanthanum hexaboride. Measurement range. 0.0020%~0.10%.

2 Principles of the method

The sample is decomposed by dilute nitric acid. In a 0.1mol/L sulfuric acid medium, orthosilicic acid and ammonium molybdate generate yellow silicomolybdenum heteropoly acid, which improves sulfuric acid.

Concentration to 1.2mol/L to eliminate the interference of phosphorus and arsenic, use ascorbic acid to reduce silicomolybdenum yellow to silicomolybdenum blue, with a spectrophotometer wavelength of 660nm Measure the absorbance at the place. Use the working curve to find the silicon content.

3 Reagents

3.1 Nitric acid (1+1), pure superior grade.

3.2 Hydrochloric acid (1+1), excellent grade pure.

3.3 Sulfuric acid (1+1), pure superior grade.

3.4 Sulfuric acid (1 + 17), pure superior grade, stored in plastic bottles.

3.5 Ammonia (1+1), ultra-pure, stored in a plastic bottle.

3.6 Ammonium molybdate [(NH4)6Mo7O24·4H2O] solution (50g/L), stored in a plastic bottle.

3.7 Ascorbic acid solution (30g/L), prepared when used.

3.8 Silicon standard stock solution. Weigh 0.2139g of spectrally pure dioxygen that has been pre-fired at 950°C for 2h and cooled to room temperature in a desiccator Add 5g of anhydrous sodium carbonate (superior grade) to the silicide in a platinum crucible, and melt it at 1000°C until it becomes transparent. After cooling, it is leached with hot water and heated to dissolve it.

Cool to room temperature, transfer to a 1000mL volumetric flask, dilute to the mark with water, and mix. Store in a plastic bottle, this solution is 1mL Contains 100µg silicon.

3.9 Silicon standard solution. Pipette 50.0mL silicon standard stock solution (3.8) into a 1000mL volumetric flask, dilute to the mark with water, and mix Evenly, store in a plastic bottle. This solution 1mL contains 5µg silicon.

3.10 p-nitrophenol solution (1g/L).

4 Instruments and utensils

4.1 Spectrophotometer.

4.2 Teflon beaker with a capacity of 100 mL.

5 Sample

The sample is mixed and dried at 105°C to 110°C for 1 h, then cooled to room temperature in a desiccator and weighed immediately.

6 Analysis steps