At atmospheric pressure 100% sulphuric acid has a freezing point of 10.371⁰C and the hypothetical freezing point of the undissociated acid is 10.625⁰ . Sulphuric acid has a fairly large value of the cryoscopy constant (molal freezing point depression) K = 6.12 g mole^-1 kg. The high value for the cryoscopy constant and the concenient freezing point of 10.371⁰ make sulphuric acid an ideal solvent for cryoscopy. For such measurements. v, the number of moles of particles produced by one mole of solute may be obtained. The value of v, the total number of moles of particles (molecules or ions) formed by the reaction of one mole of the solute with sulphuric acid is calculated by using the expression.

V   =    θ
        6.12m

Where θ is the freezing point depression calculated form the hypothetical freezing point of the undissociated acid and m the molality of the solute.

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