GB/T 8152.14-2019Methods for chemical analysis of lead concentrates - Part 14: Determination of silicon dioxide content - Molybdenum blue spectrophotometry (English PDF)

3.1 Mixing flux

Mix two parts of anhydrous sodium carbonate with one part of boric acid.

3.2

Potassium hydroxide.

3.3

Ammonium ferrous sulfate.

3.4

Oxalic acid.

3.5

Ascorbic acid.

3.6

Sulfuric acid (rho=1.84g/mL).

3.7

Hydrochloric acid (rho = 1.19 g/mL).

3.8

Hydrochloric acid (1 1).

3.9

Hydrochloric acid (1 6).

3.10

Hydrochloric acid (8 92).

3.11

Potassium hydroxide solution (200g/L).

3.12 Ammonium molybdate solution (100g/L)

Weigh 50g of ammonium molybdate in a 500mL beaker, add 400mL of boiling water, stir until dissolved

Whole, diluted to 500mL.

3.13 Phenolphthalein indicator (10g/L)

Weigh 1g of phenolphthalein in 100mL of ethanol.

3.14 Reducing solution

Weigh 8.4g ammonium ferrous sulfate (3.3), 10.9g oxalic acid (3.4), 0.68g ascorbic acid (3.5) in 1000mL beaker

Add.200 mL of water, slowly add 45.5 mL of sulfuric acid (3.6), stir while stirring, and dilute to 500 mL after the dissolution is complete.

3.15 Silica standard storage solution

Weigh 0.2500g of superior pure silica (pre-fired at 950 °C for 30min, placed in the dryer

In the middle of cooling to room temperature) in a platinum crucible containing 5g of mixed flux (3.1), mix, and then cover 2g of mixed flux (3.1), placed at 900 ° C ~

Melt in a high temperature furnace at 950 ° C for 1 h, take out, slightly cold, rinse the bottom of the crucible with water, place in a 300 mL Teflon beaker, add

Immerse in 150 mL of hot water, wash it, cool to room temperature, transfer to a 500 mL volumetric flask, dilute to the mark with water, and mix. Immediately transfer to plastic

Store in the bottle. 1 mL of this solution contained 500 µg of silica.

3.16 Silica standard solution

Pipette 5.00mL of silica standard storage solution (3.15), place in a 100mL volumetric flask, dilute with water

Release to the scale and mix. Immediately transfer to a plastic bottle for storage. 1 mL of this solution contained 25 µg of silica.