D 09971 446 x 103 CHci 815 x 103 CFeCl2

where D is expressed in g/mL at 25 °C (77 °F) and the concentrations, C, of H2SO4, ferrous sulfate (FeSO4), HCl, and ferrous chloride (FeCl2) are expressed in g/100 mL.

Equipment for the analysis of pickling solutions should be installed near the pickling operation to monitor acid concentration and to test the solutions at regular intervals. Testing after each acid addition and once or twice during an 8 h shift might be sufficient for batch operations. For continuous operations, which often involve continuous additions of acid, more frequent testing is required, at least once every 2 h. Titration methods for acid and iron concentrations in solutions are widely used. The calculations follow from the stoichiometric relationships between the reactants and products.

With sulfuric acid solutions, add 75 to 100 mL of distilled water and two or three drops of methyl orange indicator to a 5 mL sample. A burette containing a 1.02 N sodium hydroxide solution is used to titrate until the red color changes to yellow. The sample solution should be agitated during the titration. Each milliliter of sodium hydroxide solution is equivalent to 1 g H2SO4 per 100 mL of pickling solution. The concentration of H2SO4 in g/100 mL is determined by:

0 0

Post a comment