A solution of 1 N sulfuric acid is prepared by obtaining 27.5 mL of concentrated sulfuric acid and diluting it up to 1 liter with distilled water. Ratio and proportion may be used to calculate the required mixture for a different solution volume requirement. For safety reasons, the acid must be added to the water to prevent rapid generation of heat that may otherwise cause an explosion.
To prepare one liter of 1 N sulfuric acid, roughly 500 mL of distilled water must be poured into a 1-liter volumetric flask. Then 27.5 mL of concentrated sulfuric acid is dispensed to the volumetric flask using a pipette. Dosing of the concentrated acid must be slow with constant swirling of the flask. Once the pipette is emptied, the volumetric flask contents are diluted further with distilled water until the level reaches the 1-liter mark. Finally, the exact normality of the prepared sulfuric acid is determined by titration with a standard solution.
The formula to calculate the grams of sulfuric acid needed to create a particular solution concentration is the desired normality multiplied by the equivalent mass and also by the desired volume of solution in liters. Equivalent mass may be calculated as the molecular or gram-formula weight divided by the number of hydrogen ions in the compound. For sulfuric acid, its molecular weight is 98 grams per mole, while it has two hydrogen atoms in its structure. Therefore, the equivalent mass of sulfuric acid is 49. The grams of sulfuric acid needed to prepare 1 N solution is therefore calculated as the product of 1 N, the equivalent mass of 49, and the volume required which is 1 liter. The result is 49 grams of sulfuric acid.
However, concentrated sulfuric acid exists in liquid form. To calculate the volume of concentrated sulfuric acid required to prepare 1 N solution, the grams of acid are divided by the product of percent concentration and the specific gravity of the substance. "Pure" sulfuric acid exists only as 97 percent purity with a specific gravity of 1.84. From these values, the volume of concentrated acid is calculated as 49 grams divided by the product of 0.97 and 1.84, resulting to a value of 27.5 mL of concentrated sulfuric acid.