Testing method for industrial grade sulfuric acid products:

1. Determination of sulfuric acid content and determination of free sulfur trioxide content in fuming sulfuric acid [1]

① This method is GB11198.1-89 "Determination of sulfuric acid content in industrial sulfuric acid and calculation of free sulfur trioxide content in fuming sulfuric acid titrimetric method". This standard refers to the international standard ISO910-1977 "Industrial sulfuric acid and oleic acid - Determination of total acidity and calculation of free sulfur trioxide content in oleic acid - Titration method".

1.1 Method principle

Using methyl red methylene blue as the indicator, neutralize and titrate with sodium hydroxide standard solution to determine the sulfuric acid content. Or convert the measured sulfuric acid content into free sulfur trioxide content.

1.2 Reagents and Solutions

Sodium hydroxide (GB629) standard solution: c (NaOH)=0.5mol/L; Methyl red methylene blue mixed indicator.

1.3 Instruments

Glass ampoule ball (diameter approximately 15mm, capillary end length approximately 60mm).

1.4 Preparation of sample and test solution

1.4.1 Special sulfuric acid and concentrated sulfuric acid

Using a weighed small weighing bottle with a ground cap, weigh approximately 0.7g of the sample (accurate to 0.0001g) and carefully transfer it into a 250ml conical flask containing 50ml of water. Cool to room temperature and set aside.

1.4.2 Fuming sulfuric acid

Weigh the ampoule ball (accurately to 0.0001g), then heat the ball on a low fire, quickly insert the capillary of the ball into the sample, inhale about 0.7g of the sample, immediately sinter and seal the top of the capillary with flame, and dry the acid solution on the outer wall of the capillary with a low fire, and weigh again.

Place the weighed ampoule ball into a 50ml conical bottle with a ground stopper containing 100ml of water, tighten the bottle stopper, shake vigorously to crush the ampoule ball, continue shaking until the misty sulfur trioxide gas disappears, open the bottle stopper, gently crush the capillary of the ampoule ball with a glass rod, and rinse the bottle stopper, bottleneck, and glass rod with water for later use.

1.5 Measurement steps

1.5.1 Concentrated sulfuric acid of special sulfuric acid

Add 2-3 drops of mixed indicator to the test solution (1.4.1) and titrate with sodium hydroxide standard solution until the solution turns grayish green as the endpoint.

1.5.2 Fuming sulfuric acid

In the test solution (1.4.2), titrate according to the method in 1.5.1.

1.6 Calculation

1.6.1 Special sulfuric acid and concentrated sulfuric acid

Calculate the content X (%) of sulfuric acid according to equation (1):

X=(V * c * 0.04904)/m * 100 (1)

In the formula, V - Volume of sodium hydroxide standard solution consumed for titration, ml;

C - Concentration of sodium hydroxide standard solution, mol/L;

0.04904- The mass of sulfuric acid expressed in grams, which is equivalent to 1.00ml1.000mol/L sodium hydroxide standard solution.

1.6.2 Fuming sulfuric acid

The content of free sulfur trioxide X1 (%) in fuming sulfuric acid shall be calculated according to equation (2) or obtained from Table A1 in Appendix A.

X1=4.444 * (X-100) (2)

In the formula, X - the mass percentage content of sulfuric acid in fuming sulfuric acid calculated according to equation (1) in 1.6.1;

4.444- Conversion coefficient of free sulfur trioxide.

1.7 Allowable Error

The measurement results are reported as the arithmetic mean.

The allowable absolute deviation for parallel determination of sulfuric acid content in special sulfuric acid and concentrated sulfuric acid is 0.2%.

The allowable absolute deviation for the parallel determination of free sulfur trioxide content in oleic acid in 1.7.2 is 0.6%.

2. Determination of gray content (according to GB11198.2-89 "Gravimetric method for the determination of ash content in industrial sulfuric acid")

3. Determination of iron content [in accordance with GB11198.3-89 "Determination of iron sulfate content for industrial use - Phenanthroline spectrophotometric method" (arbitration method) or GB11198.4-89 "Determination of iron sulfate content for industrial use - Atomic absorption spectrophotometric method"]

4. Determination of arsenic content [in accordance with GB11198.5-89 "Determination of arsenic content in industrial sulfuric acid - Silver diethyldithiocarbamate photometric method" (arbitration method) or GB11198.6-89 "Determination of arsenic content in industrial sulfuric acid - Gucai method"]

5. Determination of lead content [according to GB11198.7-89 "Determination of lead content in industrial sulfuric acid - Dithizone photometric method" (arbitration method) or GB11198.8-89 "Determination of lead content in industrial sulfuric acid - Atomic absorption spectrophotometric method"]

6. Determination of mercury content [in accordance with GB11198.9-89 "Determination of mercury content in industrial sulfuric acid - The thiohydrazone photometric method" (arbitration method) or GB11198.10-89 "Determination of mercury content in industrial sulfuric acid - Cold atomic absorption spectrophotometric method"]

7. Determination of nitrogen oxide content (according to GB11198.11-89 "Industrial sulfuric acid - Determination of nitrogen oxide -2,4-xylenol spectrophotometric method")

8. Determination of sulfur dioxide content (according to GB11198.12-89 "Determination of sulfur dioxide content in industrial sulfuric acid - Iodometric method")

9. Determination of chlorine content (according to GB11198.13-89 "Determination of chlorine content in industrial sulfuric acid - Potentiometric titration method")

10. Determination of transparency (according to G11198.14-89 "Determination of Transparency of Industrial Sulfuric Acid")

11. Determination of chromaticity (according to G11198.15-89 "Determination of chromaticity of industrial sulfuric acid")

Industrial grade sulfuric acid