New Observations on the Low Temperature Reaction between Hydrogen Sulphide and Sulphur Dioxide : A Novel Method for Analysing Milligram Quantities of Hydrogen Sulphide in the Presence of Carbon Dioxide

Abstract

When an anhydrous mixture of liquid hydrogen sulphide and liquid sulphur dioxide contained in a sealed tube at -78 °C is gently warmed, the liquid remains clear until the temperature reaches c. -40 °C, when sulphur is slowly deposited. Careful measurements reveal that the two compounds always react in the mole ratio, H₂S : SO₂ = 3 : 2, which contrasts with the stoichiometric equation 2H₂S + SO₂ =2H₂O + 3S, widely quoted for their reaction in the moist gaseous phase or in aqueous solution. This low temperature reaction forms the basis of a novel high vacuum method for estimating milligram quantities of hydrogen sulphide when in the presence of gases, such as carbon dioxide, whose volatilities are sufficiently similar to preclude the use of normal low-temperature vacuum fractionation methods.