Volume is the three-dimensional space occupied by a given amount of matter. According to the SI international system of units, the unit of measurement used is the cubic meter, which is a cube with an edge length of one meter. In practice, however, the liter (L, l) is much more common, especially for liquids. One liter corresponds to a cube with an edge length of only 10 cm. For solids, on the other hand, the mass is more often, though not exclusively, given in kilograms (kg). An exception is, for example, manual hard capsule production, where the volume of the powders used is determined. If volume means a volume of space, the plural is also volume and not volumina, according to the Duden dictionary.
Liters and volumes
One liter (L) is equal to 10 deciliters (dl), 100 centiliters (cl), and 1000 milliliters (ml):
- 1 liter (L) = 10 dl = 100 cl = 1000 ml
- 1 deciliter (dl) = 10 cl = 100 ml
- 1 centiliter (cl) = 10 ml
- 1 milliliter (ml) = 1/1000 L (1 thousandth of a liter)
- 1 microliter (μL) = 1/1’000’000 L (1 millionth of a liter).
Furthermore, one milliliter is equal to one cubic centimeter.
Relationship to mass
The unit of density is kilograms per cubic meter. Alternatively, grams per cubic centimeter is also often used. The density is dependent on temperature and pressure. Because substances usually expand with increasing temperature, so the volume becomes larger, the density decreases with increasing temperature. The density of water at 3.98 °C (i.e., about 4 °C) and a pressure of one atmosphere is 1000 kilograms per cubic meter, or 1 gram per cubic centimeter. So, because the density of water is 1, its mass and volume are equal. 1 liter of water therefore has a mass of 1 kg. Whereby, as already mentioned, these figures are dependent on external influences. Ethanol 70% with camphor has a density of 0.88 grams per cubic centimeter. It is lower than that of water. Therefore, 100 grams have a larger volume of about 113 ml. The density of fatty oils is also lower than that of water. Because they do not dissolve in water, they float on top. At 19.3 grams per cubic centimeter, gold, for example, has an extremely high density and is correspondingly heavy.
Measuring a volume
A defined volume can be measured with various tools, for example for the production of pharmaceuticals or for dosage:
- Measuring cylinder
- Graduated pipette
- Solid pipette
- Dropping pipette
- Erlenmeyer flask
- Measuring cup
- Spoon: dosing spoon, teaspoon, soup spoon
See also under glassware in chemistry. These tools differ in their accuracy and areas of application. Also with drops, for example, with a dropper bottle, a volume can be measured. For example, 20 drops of purified water formed with a standard dropper is equal to one gram (1 g).
- Consequently, 1 drop of purified water (normal drop counter) = 0.05 g.
Due to the relationship between mass and volume, a volume can also be determined with a balance if the density is known (see above). The volume is also accessible to mathematical calculation, for example, if the vessel has a geometric shape. The volume of an object can be determined by displacement, for example in a measuring cylinder. For this purpose, the volume before and after immersion of the object is read. The difference corresponds to the volume of the object.
- 1 tea or coffee spoon = 5 ml
- 1 dessert or children’s spoon = 10 ml
- 1 tablespoon or soup spoon = 15 ml
Volume in pharmacy
In pharmacy, volume plays an important role in filling, for example, open goods. In this process, liquids such as surgical spirit or ethanol are transferred from a storage vessel into a container at the customer’s hand. Volumes also have to be measured in the production of liquid dosage forms such as solutions, suspensions and emulsions. Volumes are used in laboratory analyses and chemical syntheses. Finally, volumes are also important in the administration of medications, for example when taking cough syrups. They are taken with the aid of cups, spoons, syringes or dosing pipettes.