CNESSTSanté et sécurité du travailEnglishPreventionRépertoire toxicologiqueWHMIS 1988Material Safety Data Sheet User's GuideGuide - Physico-Chemical Properties
This section of the MSDS describes the physicochemical characteristics of a substance based on current scientific knowledge.
*Non-essential information for WHMIS purposes
The molecular formula describes, using their symbols, the elements that make up a substance, and indicates their proportion. Pure substances are the only ones with a definite molecular formula.
Toluene : C7H8
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This is the weight in grams of a fixed quantity of molecules of a chemical product. The molecular weight is defined only for pure chemical substances.
Toluene : 92.15 g
This is the form or state in which the product is present: gas, liquid or solid at ambient temperature (20°C) and at normal atmospheric pressure (760 mm Hg (101.32 kPa)).
Solid: limeLiquid: waterGas: oxygen
This subsection provides specific information on the product or presents additional information on the product’s physical state or appearance.
If the product is solid, it can be crystalline, granular, powdery, etc.If it is liquid, it can be viscous, gelatinous, oily, etc.
These are some of the product’s physical characteristics. A product can have a specific colour or be colourless. It may have a characteristic and distinctive odour or be odourless. The odour of some products may be detected, starting at a certain concentration, namely the odour threshold.
gray: copper sulfate
This is the minimum concentration of a substance likely to be detected in the air by human smell. It is usually expressed in parts per million (ppm).
Ammonia can be detected at 17 ppm.
Density is a physicochemical property related to the weight of a substance. It represents the weight of a substance per unit volume and is expressed in grams per millilitre (g/ml) at 20°C. Specific gravity is also a physicochemical property that is commonly used instead of density. However, it is a relative value that indicates how many times heavier than water the product is. If the density of a product that is rather insoluble in water is less than 1 g/ml, the product will float. However, if it is greater than 1 g/ml, the product will sink. This information is useful in predicting the behaviour of a product in the event of a leak or accident.
Toluene is not very soluble in water. Its density is 0.8661 g/ml, therefore less than 1, so it floats on water.
This is the temperature at which a substance goes from the liquid state to the solid state at normal atmospheric pressure (760 mm Hg (101.32 kPa)). The freezing point of a pure substance is the same as its melting point.
Water crystallizes at 0°C.
This is the temperature at which a substance goes from the solid state to the liquid state at normal atmospheric pressure (760 mm Hg (101.32 kPa)).
Ice melts at 0°C.
This is the temperature at which a substance goes from the liquid state to the gaseous state at normal atmospheric pressure (760 mm Hg (101.32 kPa)).
Water boils at 100°C.
When a substance evaporates, its vapours exert pressure in the ambient environment. Vapour pressure is expressed in millimetres of mercury (mm Hg) or in kilopascals (kPa) at 20°C and normal atmospheric pressure of 760 mm Hg (101.32 kPa). A vapour pressure greater than 760 mm Hg (101.32 kPa) indicates that the substance is in the gaseous state. The higher a substance’s vapour pressure, the more it tends to evaporate.
The vapour pressure of water is 17.5 mm Hg (2.33 kPa) and that of diethyl ether, 439.8 mm Hg (58.63 kPa). Therefore, diethyl ether evaporates faster than water.
This is the maximum concentration that a substance can reach in the air at equilibrium, 20°C and normal atmospheric pressure of 760 mm Hg (101.32 kPa).
Toluene has a concentration at saturation of 28,800 ppm.
This information indicates how many times the vapours of a substance are heavier or lighter than air (air = 1). This measurement is taken at the boiling point.
If the vapour density is greater than 1, a substance’s vapours will tend to remain near the ground.
Toluene has a vapour density of 3.18. Therefore, at its boiling point, its vapours will tend to remain at the ground.
Methyl alcohol has a vapour density of 1.1. Therefore at its boiling point, its vapours will mix easily with air, since its vapour density is close to 1.
The evaporation rate indicates the relationship between the time that a product takes to evaporate and the time that a reference product takes to evaporate. It indicates, at equal volume, how many times longer a product takes to evaporate than another. The rate varies with the type of product and the temperature. Diethyl ether, for example, is the reference product on which the most data is available.
Toluene’s evaporation rate is 4.5 in relation to that of diethyl ether. Therefore, toluene takes 4.5 times longer than diethyl ether to evaporate.
This is the ratio of the solubility of a product in oil to its solubility in water when they are brought into contact with the product.
A value below 1 indicates a better solubility of the product in oils and greases. The product is therefore likely to be absorbed by the skin. However, a value greater than 1 indicates a better solubility in water. This product could therefore be absorbed by the mucous membranes. This information can be useful in evaluating the first aid to be given and can facilitate the choice of protective equipment.
Toluene has a coefficient of water/oil distribution of 0.0026. Therefore, toluene is more soluble in oil than in water with a value of 0.0026 g in water to 1 g in oil.
The pH, expressed as a numerical value, indicates whether a solution is acidic or basic. Water is neutral and has a pH of 7. Acids have a pH below 7, and the lower the value, the stronger the acid. Bases have a pH greater than 7, and the higher the value, the stronger the base.
Vinegar (acid): pH = 2.127-30% Ammonium hydroxide (base): pH = 12.3
This is the maximum amount of a product that can be dissolved in water. It is expressed in grams per litre at a temperature of 20°C. If the solubility is not precisely known, the product is called, for example, “insoluble”, “slightly soluble” or “very soluble”. A liquid that mixes perfectly with water to form a single phase is called “miscible”.
The particle size indicates the size of the particles forming a powder, a dust, a mist, an aerosol or fumes. Particles smaller than 1µm* can penetrate deeply into the respiratory tract and deposit in the alveoli. Slightly larger particles (from 1 to 5 µm) reach the trachea, bronchi and bronchioles. Larger particles (from 5 to 30 µm) reach the nose and pharynx region. Even larger particles (larger than 30 µm) rarely penetrate the upper respiratory tract. Depending on the substance, they may dissolve and be absorbed by the body. Therefore, by knowing the size of the particles of a substance, one can decide on the corrective measures to adopt to reduce or eliminate the hazard at source (for example, by planning for local ventilation). If it is impossible to reduce or eliminate the hazard at source, knowledge of the particle size will make it easier to choose the respiratory protection device.
*1 µm (micron) represents 10-6 metres (0.000001 metre) or 10-3 millimetres (0.001 mm). For example, 1 µm is approximately 1,000 times smaller than a grain of sand.