4-19. PHYSICAL/CHEMICAL CHARACTERISTICS (SECTION III)
Each MSDS must contain certain characteristics of the chemical.
a. Boiling Point. The boiling point is the temperature at which the product
changes from a liquid to a gas. If the boiling point is below normal room temperature,
which is about 68F, the product is a gas.
b. Specific Gravity. Specific gravity tells you whether a liquid is lighter than
water or heavier than water. Water has a specific gravity of 1. If the product is lighter
than water (less than 1) it will float on water if not soluble in water. If the product is
heavier than water (greater than 1) it will sink in the water if not soluble in water.
Vapor Pressure. Vapor forms above the liquid surface inside a closed
container. This vapor exerts a force in the walls of the container. The force is the vapor
pressure of the liquid. Vapor pressure is measured in millimeters of mercury (mm Hg).
Vapor pressure increases as the temperature of a liquid rises. Liquids with a high vapor
pressure at room temperature (greater than 100 mm Hg) present a special hazard. The
pressure inside a sealed container can make the container swell or burst open. This
releases a hazard and is most likely to happen if a sealed container is exposed to heat.
High vapor pressure will tell you how fast it gets into the air, as well.
Melting Point. This is the temperature at which a sold substance melts.
e. Vapor Density. Vapor density tells you whether a vapor is lighter than air
or heavier than air. Air has a density of 1. If the product is lighter than air (less than 1),
it will tend to rise and get out of your breathing zone. If it is heavier than air (greater
than 1), it tends to sink and will stay in your breathing zone. It will also accumulate in
Evaporation Rate. Evaporation rates are reported as comparisons. The
evaporation rate tells you how fast a liquid evaporates compared to water, which is 1.
Evaporation rates greater than 1 vaporize faster than water. Evaporation rates less
than 1 vaporize slower than water.
g. Solubility in Water. Solubility is the quantity of the chemical or product
that is capable of being dissolved in water.
h. Appearance and Odor. The appearance and odor block describes
physical form/appearance, color, and odor (if any).
4-20. FIRE AND EXPLOSION HAZARD DATA (SECTION IV)
Physical hazards include explosion hazards, fire hazards, and unstable or
reactive chemicals. The MSDS identifies these types of hazards and provides
information to help you control them.