ASTM E223 Analysis of Sulfuric Acid

Scope:

ASTM E223 standard covers the test methods for the analysis of sulfuric acid. These test methods help in the classification of various grades of sulfuric acid and in the determination of various impurities. This standard includes analytical procedures for estimating total acidity, Baumé gravity, non-volatile matter, iron, sulfur dioxide, and arsenic. 

Test procedure:

The following procedures are described in ASTM E223:

Total acidity determination: The sample is weighed using the dely tube or the snake tube test methods. A weighed sample of acid is diluted in water and titrated with standard sodium hydroxide solution, using phenolphthalein as the indicator.

Baumé gravity determination: A glass hydrometer is used to determine the Baumé gravity of concentrated sulfuric acid. Baumé gravity is determined at 15.5 °C.

Non-volatile matter determination: A weighed sample of acid is evaporated, ignited, and the residue is weighed.

Iron content determination: The iron is reduced and determined calorimetrically with 1,10-phenanthroline (ortho-phenanthroline), which forms an orange-red complex with ferrous iron. The intensity of the color so formed is measured in a photometer calibrated with standard iron solutions.

Sulfur dioxide content determination: The sulfur dioxide is swept out of the sample of sulfuric acid by means of a current of nitrogen gas. The evolved sulfur dioxide is absorbed in an alkaline solution, treated with an excess of iodate-iodide solution and the excess is titrated with sodium thiosulfate.

Arsenic content determination: The arsenic is reduced to arsine gas, which is absorbed in a pyridine solution of silver diethyldithiocarbamate, forming a red-colored complex. The intensity of which is measured on a photometer.

Video 01: Titration of sulfuric acid

Specimen size:

The size of the sample used in ASTM E223 testing shall be sufficient to perform all analyses without the reuse of any portion of the sample.

Data:

The following equations are used for the ASTM E223 test methods,

V = corrected mL of NaOH solution required for titration of the sample, N = normality of the NaOH solution, W = grams of sample used

R = weight of evaporating dish and residue, D = weight of the evaporating dish, W = sample used

M = iron found from calibration curve, W = sample used

B = Na₂S₂O₃ solution required for the titration of the blank solution, A = Na₂S₂O₃ solution required for the titration of the sample solution, N = normality of the Na₂S₂O₃ solution, W = sample used

M = arsenic found from calibration curve, W = sample used

Conclusion:

ASTM E223 standard covers the test methods for the analysis of sulfuric acid.