Mustard gas or sulfur mustard is any of several chemical compounds that contain the chemical structure SCH₂CH₂Cl. In the wider sense, compounds with the substituent SCH₂CH₂X and NCH₂CH₂X are known as sulfur mustards and nitrogen mustards (X = Cl, Br), respectively. Such compounds are potent alkylating agents, which can interfere with several biological processes. Also known as mustard agents, this family of compounds are infamous cytotoxic and blister agents. The name mustard gas is technically incorrect: the substances, when dispersed, are often not gases but a fine mist of liquid droplets. Mustard gases form blisters on exposed skin and in the lungs, often resulting in prolonged illness ending in death. The typical mustard gas is the organosulfur compound called bis(2-chloroethyl) sulfide.