Chemistry of Chemical Agents
Kirstin F. Warner Ph.D.; Department of Defense Explosives Safety Board; Program Evaluation
Division; Alexandria VA, USA
Keywords: chemical warfare agents, sulfur mustard, nitrogen mustard, bis-(2-chloroethyl) sulfide, tris-(2-
chloroethyl) amine, H/HD, HN-3
ABSTRACT
The Department of Defense Explosives Safety Board (DDESB) oversees the Demilitarization and Disposal of
Chemical Warfare Agents. One such group of agents of interest, that have been stockpiled and are still being uncovered
in buried munitions, are bis-(2-chloroethyl) sulfide (sulfur mustard, H/HD) and tris-(2-chloroethyl) amine (nitrogen
mustard, HN-3). Although H/HD was originally used in World War I, it has reemerged as a major threat around the
world due to its ease of manufacture and can be a first choice if a country were to undertake chemical warfare
development. Sulfur mustards were first developed in the early-to-mid-1800s and were introduced as chemical warfare
agents in 1917 during World War I. Nitrogen mustards were first developed in the late 1920s and the early 1930s.
This class of chemical warfare agents are vesicants. The term mustard has been used interchangeably whereas “H” is
not distilled with 20-30% impurities; “HD” is distilled or purified form; and “HN-3” is nitrogen mustard. An overview
of the chemistry of bis-(2-chloroethyl) sulfide (H/HD) and tris-(2-chloroethyl) amine (HN-3) and related physical
properties will be discussed.
INTRODUCTION
The chemical warfare agents bis-(2-chloroethyl) sulfide (sulfur mustard, H/HD) and tris-(2-
chloroethyl) amine (nitrogen mustard, HN-3) are very reactive vesicants that damage the skin,
eyes, respiratory and the immune system. Sulfur mustard was first developed in 1822 and nitrogen
mustards were developed in the late 1920s and the early 1930s. Sulfur mustard is a colorless oily
liquid at 25
o
C and odorless in its pure form. HN-3 nitrogen mustard is one of three nitrogen
blistering agents that include bis-(2-chloroethyl) ethylamine (HN-1) and bis-(2-chloroethyl)
methylamine (HN-2). HN-3 is a colorless to pale yellow oily liquid at 25
o
C, has a faint almond
odor and is the most stable of the nitrogen mustard agents. Their physical properties are shown in
Table 1.
1,2.
Table 1. Physical Properties of Chemical Agents
Bis-(2-chloroethyl) sulfide
(H/HD)
Tris-(2-chloroethyl) amine
(HN-3)
Decomposition Temperature
-4 to-3.7
o
C
(24.8 to 25.3
o
F)
Colorless to pale oily liquid
