Figure 2

Raman spectra of vapour bubbles (a) before and (b) after re-heating. (a) Raman spectrum before re-heating of the bubble shown in the inset (Brhm-33). The two phases present are CO₂ gas and anhydrite solids. (b) Raman spectrum of the same bubble after re-heating. The volume of the bubble increases, as well as the mass of CO₂ within the bubble (see Table 1 and Supplementary Table S2). However, the total density of CO₂ decreases. Anhydrite present before re-heating hydrates to gypsum. Additional S enters the bubble from the glass and forms pyrite, marcasite and SO₂ gas.