Method of distilling dimethyl sulfoxide and multistage distillation tower

A method of distilling a liquid containing dimethyl sulfoxide using a distillation system, comprising:

• (1) mixing sodium carbonate with a liquid containing dimethyl sulfoxide at a bottom of the distillation system such that sodium carbonate accounts for 0.005% to 25% by weight relative to 100% by weight of the liquid containing dimethyl sulfoxide and sodium carbonate in total at the bottom of the distillation system and heating the bottom;
• and
• (2) obtaining a distillate containing dimethyl sulfoxide at a position lower than a position at which the liquid containing dimethyl sulfoxide is introduced and higher than a position of the heating portion.

A multistage distillation tower that distills a liquid containing dimethyl sulfoxide, comprising:

• an apparatus that adds sodium carbonate at a tower bottom of the distillation tower, and
• a device that mixes sodium carbonate with a liquid containing dimethyl sulfoxide at the tower bottom of the distillation tower and heating the bottom, while controlling the concentration of sodium carbonate to 0.005% to 25% by weight relative to 100% by weight of the liquid containing dimethyl sulfoxide and sodium carbonate in total at the tower bottom of the distillation tower, and
• a side cut that allows a distillate containing dimethyl sulfoxide to flow out at a position lower than a position of a supply stage that supplies a liquid containing dimethyl sulfoxide and higher than a position of the heating portion.