CHEMICAL DATA NOTEBOOK SERIES #92: SULFUR MONOCHLORIDE
HAZARDOUS MATERIALS
Sulfur monochloride is a corrosive, toxc, water-reactive, combustible, reactive, irritating, fuming, amber-to-yellowish oily liquid with a penetrating, nauseating odor. It is used to manufacture dyes, insecticides, pharmaceuticals, poison gases, and rubber substitutes, among various other chemicals. It is also used as a vulcanizing agent for rubber, an extractant of gold from its ore, and a hardener for soft ^voods.
PROPERTIES
Sulfur monochloride is a combustible liquid with a flash point of 245°F, a flammable range that has not been determined, and an ignition temperature of 453°F. Its specific gravity is 1.69, its molecular weight is 135, and its vapor density’s 4.65. Its boiling point is 280°F, its freezing point is — 105°F, and it reacts violently with water. Sulfur monochloride’s molecular formula is
HAZARDS
Sulfur monochloride has several hazards, and it is difficult to select the worst one. Water-reactivity is a hazard that surprises most emergency responders, especially when the Department of Transportation (DOT) placarding identities its major hazard as corrosivity. When sulfur monochloride contacts water, heat is evolved, in addition to several hazardous materials. These hazardous reaction products include hydrochloric acid, hydrogen sulfide (see Fire Engineering, July 1991), sulfur, and sulfurous acid. Hydrochloricacid is generated as hydrogen chloride (see Fire Engineering, February 1988), which immediately dissolves in water to form the acid.
Hydrogen sulfide is extremely hazardous if inhaled. It has the classic odor of rotten eggs, but it quickly will paralyze the olfactory nerve (the nerve responsible for the sense of smell). It is extremely toxic and can kill anyone exposed to any appreciable amount.
The solution created by the reaction of sulfur monochloride with water will be acidic, due to the presence of hydrochloric acid, or HC1, and sulfurous acid, or H2SO3 (the formula for sulfuric acid is H1SO4). Any contact this solution has with many metals will cause the evolution of explosive hydrogen gas (see Fire Engineering, November 1993). Protecting emergency responders from contact with this solution may require different protective suits than those required for sulfur monochloride.
Any sulfur produced by the reaction of sulfur monochloride with water will rise to and float on the surface of the solution as a yellow powder or a brown molten mass that solidifies into a brownish-yellow “blob.” Sulfur is not a hazardous material, but when it burns it liberates sulfur dioxide, which is toxic in high concentrations (see Fire Engineering, July 1990).
Sulfur monochloride is a very corrosive material. It will attack most common metals, corroding them severely and releasing explosive hydrogen gas in the process. Contact with structural metals over a long period of time, even from a minor leak, could cause the metal to collapse. It is also corrosive to human tissue and will produce severe burns if not removed from the skin immediately.
Sulfur monochloride is a toxic material. Its TLV-TWA (threshold limit value-time weighted average) is one ppm (part per million of air), and it has a STEL (shortterm exposure limit) of three ppm for 15 minutes. Inhaling sulfur monochloride vapors will cause severe coughing spells. Inhaling high concentrations of the vapors will cause breathing difficulties and can produce pulmonary edema or chemical pneumonia. All symptoms may be delayed for some period of time.
Exposure to the vapors also will severely irritate the eyes, producing tearing and burning. Continued exposure could cause permanent damage.
If the liquid contacts the skin, it will cause severe irritation and chemical burns. Exposing the skin to high concentrations of the vapors also will burn and irritate the skin.
Sulfur monochloride is one of a group of chemicals described as “fuming.” This means that under normal temperatures and pressures, the product will produce a visible fume or mist, caused by the reaction of the evaporated sulfur monochloride with the moisture in the air. This means that the air around any release or downwind will be contaminated with the vapors of hydrochloric acid, hydrogen sulfide, sulfurous acid, and any unreacted vapors of sulfur monochloride.
Sulfur monochloride is a combustible liquid by virtue of its flash point of 245°F. It produces dangerous products when it reacts with water and when it burns. Hazardous combustion products include sulfur dioxide, chlorine (see Fire Engineering, July 1986), and hydrogen chloride. Its relatively high flash point means that at least some portion of the liquid must be heated to 245°F before vapors sufficient to form an ignitable mixture near the surface of the release are generated. However, once the vapors have entered the flammable range, the material’s relatively low ignition temperature of 453°F easily can be reached by any common ignition source. It also means that heated metal parts that can reach that temperature also will ignite the vapors. An ignition of any accumulation of vapors will cause an explosion.
The vapors of sulfur monochloride at concentrations below those that would cause major damage to the lungs and/or eyes still will be very irritating to eye tissue. They also will react with any moisture on the skin in the same manner as with any other water, producing a solution that will irritate the skin if not removed.
NONFIRE RELEASE
A release of any appreciable quantity of sulfur monochloride will cause hazards sufficient to require the implementation of the community’s emergency response plan. Experts needed on the scene will be firefighters, environmentalists, toxicologists, emergency medical personnel, and all the support staff needed to protect the exposed citizenry and the environment.
Approach to and management of the scene must be compatible with all hazards presented by the material. Approach from upwind and uphill, if at all possible. Secure the immediate area of the spill and keep all unauthorized and unprotected persons out of the danger zone. Responders entering the immediate area of the release must wear the appropriate personal protective equipment, and even they should avoid contact with the product as much as possible.
Toxic fumes will endanger all areas downwind of the release. Depending on the configuration and amount of the release, the strength of the wind, the population exposed, and the resources present, immediate evacuation of the area surrounding the release and downwind of it must be the first consideration.
Immediately make every attempt to prevent the product from contacting water or moisture present in other materials. If sulfur monochloride enters a sewer opening, toxic, corrosive, and flammable vapors immediately will be generated. These vapors will be forced throughout the entire sewer system; and although they are 1.69 times heavier than air, they may be forced uphill through the pipes as well as downhill. This will spread the toxic and corrosive hazards throughout the system.
Immediately advise all endangered areas throughout the sewer system and sewage treatment facilities to which the contaminated water might flow of the danger of the spreading vapors.
The farther the vapors are carried from their liquid source, the less the chance that sulfur monochloride vapors will explode, since more and more moisture will be contacted, converting more of the sulfur monochloride vapors to hydrogen chloride, sulfurous acid, and hydrogen sulfide. Hydrogen sulfide is a deadly poison gas and must be avoided by everyone, without the proper respiratory protection.
Immediately diking the spill by pushing soil, sand, and other dry materials around the spill area will keep the product from spreading and entering a sewer system or a waterway. Additional dams may be built in front of catch basins and manhole entries. Wet diking materials will immediately react with the sulfur monochloride, producing toxic and corrosive vapors. As these vapors contact wet metal or dissolve in water that then contacts metals, explosive hydrogen gas may be generated.
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
10025-67-9
STCC
(Standard Transportation Commodity Code)
4932380
RTECS
(Registry of Toxic Effects of Chemical Substances)
WS4300000
UN/NA
(United Nations/North America)
1828
CHRIS
(Chemical Hazard Response Information System)
SFM
DOT
(U.S. Department of Transportation)
Corrosive, Class 8
NFPA 704 Rating 1-2-2-W
IMO
(International Maritime Organization)
8.0, corrosive
If any of the liquid reaches a stream, river, pond, lake, or other waterway, it will react instantly on contact with the water. Although no sulfur monochloride would be in the water after the reaction, the water will contain the reaction products. The water will be contaminated by the presence of hydrochloric acid (the result of hydrogen chloride dissolving in the water), sulfurous acid, metallic sulfites, and other by-products. The concentration of contaminants depends on the amount of sulfur monochloride that reaches the water; the amount of water into which the sulfur monochloride flows; and the speed, if any, of the water’s movement.
If the water into which the sulfur monochloride flows is moving, notify all downstream users (including sewage treatment plants) immediately. If the contaminated water enters any industrial operation where it may be used to cool equipment or processes, any equipment it may contact could become severely corroded. Try to divert the contaminated water into lowlying areas, where attempts may be made to decontaminate it by neutralization and other techniques.
If a large volume of rapidly moving water has been contaminated, the turbulence of the moving water may dilute the contaminants to a level that renders the water safe for use. This determination must be made by the environmental experts after testing.
If the water is stationary or if it has been diverted to a holding area, normal neutralization agents that work on common acids, such as calcium carbonate, sodium carbonate, and sodium bicarbonate, in addition to other basic materials, may neutralize the acidity of the water. The water may be further purified by sparging, air stripping, or aeration. Experts must determine the safety of the water.
If a small volume of water has been contaminated or the water is moving slowly, neutralization agents may be added to reduce the acidity of the water to a safe pH.
If the sulfur monochloride has been successfully contained, its vapors will be moving with a mild breeze or downhill if there is no breeze. A strong breeze will dissipate the vapors to a point where they should not present a problem. If they move downhill of their own accord, they will accumulate in low places or confined spaces. These areas pose a serious problem to anyone without proper respiratory protection.
Vapors may be knocked down as they are generated or prevented from moving downhill or downwind by the use of a high-pressure water spray or fog. No water should be allowed to contact the pool, and all runoff from the spraying should be contained, since it now will be contaminated with the reaction products created when sulfur monochloride contacted the spray.
Professional salvage firms should remove the product, if contained, as soon as possible. The liquid can be pumped or suctioned into secure containers and removed for reclamation. Any liquid remaining may be absorbed by using cement powder, clay, fly ash, sand, soil, or another dry sorbent. The resulting absorbed material must be handled as the original liquid and must be disposed of in accordance with all federal, state, and local regulations.
SYNONYMS
chloride of sulfur disulfur dichloride sulfur chloride sulfur subchloride sulphur chloride sulphur chlorides thiosulphurous dichloride trisulfurous chloride
FIRE SCENARIO
Should a container of sulfur monochloride be exposed to the radiant heat of a fire or flame impingement, cool the container with straight streams of water delivered from unmanned positions outside the danger area that would be produced if the container were to explode. Treat these containers as any container of combustible liquid being exposed to heat. Sulfur monochloride decomposes at its boiling point of 280°F, so an instantaneous pressure rise could occur at that temperaure as chlorine gas is generated from the jecomposition. This reaction could trigger a BLEVE (boiling-liquid, expandingvapor explosion).
Vapors released from the container as the result of the pressure rise will be sulfur monochloride vapors, as long as the boiling point hasn’t been reached. Those vapors will ignite (sulfur monochloride’s ignition temperature is very low, well within the range of all common ignition sources), producing highly toxic combustion products.
Carbon dioxide, dry chemical, or dry sand can be used to extinguish the burning sulfur monochloride, depending on the quantity of product burning, where the fire is located, the terrain, the weather, and the wind. The use of water is discouraged because of its violent reaction with sulfur monochloride. However, circumstances might demand that water be used. In this instance, a high-pressure water spray or fog may be required.
PROTECTIVE CLOTHING AND EQUIPMENT
Choose protective clothing and equipment that prevent any contact of the sulfur monochloride with the eyes or skin: rubber gloves, aprons, and boots for skin protection; splashproof chemical goggles for eye protection; and positive-pressure, self-contained breathing apparatus for respiratory protection against sulfur mono^chloride and its reaction products. Since the sulfur monochloride may be reacting and producing many different hazardous reaction products, contact individual manufacturers of total encapsulating suits and sulfur monochloride to determine the degree of safety offered by each recommended material.
FIRST AID
Inhalation. Move the victim to fresh air, and keep him calm and warm. If the victim’s breathing has stopped or becomes labored, administer artificial respiration, being aware that such action might expose the first-aid giver to the material in the victim’s lungs and/or vomit. Seek immediate medical attention.
Eye contact. Flush the eyes immediately for at least 20 minutes, lifting the eyelids occasionally. Seek immediate medical attention.
Skin contact. Wash affected body areas with large amounts of soap and water. If irritation continues alter washing, seek medical attention.
Ingestion. If conscious, have the victim drink large quantities of water immediately and then milk, milk of magnesia, or olive oil, if any of these are available. Do not induce vomiting. Never try to make an unconscious person drink anything or vomit. Seek immediate medical attention.
