Physical Properties

The following physical properties are shown on chemical datasheets, when available:

• Chemical FormulaChemical Formula

  The molecular formula describing the exact number and type of atoms in a single molecule of a chemical.

• Flash PointFlash Point

  The lowest temperature at which a liquid gives off enough vaporThe gas given off by a substance that is liquid (or solid) at normal temperatures and pressures. to be ignited at its surface. See topic on Could it burn or explode?

• Lower Explosive Limit (LEL)Lower Explosive Limit (LEL)

  Also called lower flammabilityA substance's tendency to ignite or take flame. Flammability is closely related to the volatility of a substance (and is not its relative ability to burn in the presence of oxygen with the evolution of heat). limit. Lowest concentrationThe amount of a chemical present in a given weight or volume of air. Concentration of a gas in air may be expressed in units such as parts per million (by volume) or milligrams per cubic meter. of a flammableEasy to ignite and burns readily. vaporThe gas given off by a substance that is liquid (or solid) at normal temperatures and pressures. in air at which explosionA chemical or physical process in which the rate at which energy is being generated exceeds its ability to escape to its surrounding environment. The hazards of an explosion can include a shock wave (especially near the point of explosion) and projectiles generated by the shock wave. or combustionAlso burning. A chemical reaction between oxygen and another element or compound that is rapid and exothermic enough to generate heat and light. can occur. See topic on Could it burn or explode?

• Upper Explosive Limit (UEL)Upper Explosive Limit (UEL)

  Also called upper flammabilityA substance's tendency to ignite or take flame. Flammability is closely related to the volatility of a substance (and is not its relative ability to burn in the presence of oxygen with the evolution of heat). limit. Highest concentrationThe amount of a chemical present in a given weight or volume of air. Concentration of a gas in air may be expressed in units such as parts per million (by volume) or milligrams per cubic meter. of a flammableEasy to ignite and burns readily. vaporThe gas given off by a substance that is liquid (or solid) at normal temperatures and pressures. in air at which explosionA chemical or physical process in which the rate at which energy is being generated exceeds its ability to escape to its surrounding environment. The hazards of an explosion can include a shock wave (especially near the point of explosion) and projectiles generated by the shock wave. or combustionAlso burning. A chemical reaction between oxygen and another element or compound that is rapid and exothermic enough to generate heat and light. can occur. See topic on Could it burn or explode?

• Autoignition TemperatureAutoignition Temperature

  Minimum temperature at which a chemical ignites when no ignition source (such as a spark or flame) is present. See topic on Could it burn or explode?

• Melting PointMelting Point

  Also called freezing pointAlso called melting point. The temperature at which a chemical changes from a solid to a liquid. Depends on chemical composition and applied pressure.. The temperature at which the solid and liquid phases of a substance exist in equilibrium. Depends on chemical composition and applied pressure.

• Vapor PressureVapor Pressure

  A measure of a substance's tendency to evaporate; liquids with higher vapor pressures evaporate faster. See topic on Is its vapor dangerous?

• Vapor Density (Relative to Air)Vapor Density (Relative to Air)

  The ratio of the densityThe ratio of the mass (weight) of a substance to the volume it occupies. For example, if 1 cubic foot of a substance weighs 10 pounds, its density is 10 pounds per cubic foot. of a gas to the density of air at the same temperature. A gas with a vaporThe gas given off by a substance that is liquid (or solid) at normal temperatures and pressures. density greater than 1.0 is heavier than air and will sink in the atmosphere. Starting with CAMEO Chemicals 3.0.0, short phrases have been added to tell you if the chemical gas will likely sink or rise in air.

  Note: The vapor density comparisons are only valid when the gas escaping is at the same temperature as the surrounding air itself. If the chemical is escaping from a container where it was pressurized or refrigerated, it may first escape and behave as a heavy gas and sink in the air (even if it has a vapor density value less than 1).

• Specific GravitySpecific Gravity

  The ratio of the densityThe ratio of the mass (weight) of a substance to the volume it occupies. For example, if 1 cubic foot of a substance weighs 10 pounds, its density is 10 pounds per cubic foot. of a chemical to the density of water at the same temperature. A chemical with a specific gravity greater than 1.0 will sink rather than float in water. Starting with CAMEO Chemicals 3.0.0, short phrases have been added to tell you if the chemical will likely sink or float in water.

  Note: The specific gravity comparisons are for fresh water (density 1.0 g/mL). If your spill is in salt water (density about 1.027 g/mL), you need to adjust the point of comparison. There are some chemicals that will sink in fresh water and float in salt water. See topic on Would it float or sink?

• Boiling PointBoiling Point

  The maximum temperature at which the liquid phase of a substance exists in equilibrium with its vaporThe gas given off by a substance that is liquid (or solid) at normal temperatures and pressures. phase. Above the boiling point, a liquid vaporizes completely. At its boiling point, the vapor pressureA measure of a substance's tendency to evaporate; liquids with higher vapor pressures evaporate faster. of a liquid is equal to the atmospheric pressure on it.

• Molecular WeightMolecular Weight

  The sum of the weights of all the atoms in a moleculeA chemical entity composed of one or more elements in the form of atoms..

• Water SolubilityWater Solubility

  The highest amount of a particular material that can be mixed in water is its water solubilityA measure of a chemical's ability to dissolve in water. If a chemical is highly soluble, it will dissolve easily into water.. In CAMEO Chemicals, the water solubility ranges shown on chemical datasheets are as follows:

  • Water insoluble: <0.1% (<1 mg/mL)
  • Slightly water soluble: 0.1%-1% (1-10 mg/mL)
  • Water soluble: >1% (>10 mg/mL)

  See topic on Would it dissolve in water?

• Ionization Energy/PotentialIonization Energy/Potential

  The energy required to 'ionize' or remove an electron from an atom. The ions can be measured by a photoionization detector (PID), which measures the relative concentration of ionized compounds. The ionization energy identifies the minimum energy level of the PID lamp that is required to ionize an atom or molecule. Ionization energy may also be known as ionization potential.

• Levels of Concern (LOCs), such as IDLH, AEGLs, ERPGs, and PACsLevels of Concern (LOCs), such as IDLH, AEGLs, ERPGs, and PACs

  An LOCLevel of Concern. Threshold concentration of an airborne pollutant, usually the concentration above which a hazard to people is believed to exist. tells you what level of exposure to a chemical could hurt you or other people. See a guide to LOCs.

Here is an example of the Physical Properties portion of the chlorine datasheet: