Sometimes, due to crystallographic voids, the formula of a compound varies. For example, FeO can become Fe0.95O. It doesn`t matter what the water source is (rainwater/tap water/seawater) or how the water was treated (ice melting/water vapor cooling) In 1779, French scientist Joseph Louis Proust first proposed the law of definite proportions. This is why the law is also called Proust`s law. French chemists Antoine Lavoisier and Joseph Priestley were the first to make the discoveries that led to this law. This law states that neither matter nor energy can be created or destroyed. In other words, the total mass, i.e. the sum of the mass of the reactive mixture and the mass of the products manufactured, remains constant. In 1789, Antoine Lavoisier published this law on the basis of data he had collected after observing various combustion processes. Pictorial representation of the law of constant proportions In non-stoichiometric compounds, the elementary ratio varies from sample to sample. Consequently, the law of constant proportions does not apply to these compounds. Since the masses of two different isotopes of an element differ, samples of elements with different isotopic compositions can also defy the law of certain proportions. Natural polymers have also been shown to defy proportional law.

In chemistry, the law of definite proportions, sometimes called Proust`s law or law of constant composition, states that a given chemical compound always contains its constituents in a fixed ratio (by mass) and does not depend on its source and method of production. For example, oxygen makes up about 8/9 of the mass of a pure water sample, while hydrogen makes up the remaining 1/9 of the mass: the mass of two elements in a compound is always in the same proportion. Together with the law of multiple proportions, the law of defined proportions forms the basis of stoichiometry. [1] The law of constant proportions is often called Proust`s law or the law of certain proportions. A figure describing the mass ratio of elements in some compounds is shown below. The ratio of the number of atoms of each element is given below the mass ratio. For example, in a molecule of nitrogen dioxide (NO2), the ratio of the number of nitrogen and oxygen atoms is 1:2, but the mass ratio is 14:32 (or 7:16). Proust`s law is another name for the law of certain proportions.

In some compounds, it refers to the mass ratio of the elements. Keep in mind that the number of nitrogen atoms and oxygen atoms in NO2 molecules is in a ratio of 1:2, but their mass ratio is 7:16. For it to form, the sodium and chlorine atoms must be in the same ratio. These 2 elements are present in a constant mass ratio, which is 1:8 Chemistry is an important topic on which our lives survive. Every fundamental thing in our body and in nature is based on the concept of chemistry. Chemistry is based on important fundamental laws. The law of conservation of mass, the law of constant proportion, the law of multiple proportions and the law of reciprocal proportions are these main pillars of chemistry. The law of constant proportion states that in any chemical compound, the elements are always present in a constant and defined mass ratio. This means that regardless of the source, the method of preparation of the compound or the amount of the compound, the same chemical compound always contains the same elements in the same proportion.

The law of constant composition states that in any chemical compound, the elements it contains always combine with each other in exactly the same proportions. Water molecules have combinations of hydrogen and oxygen atoms in a ratio of 2:1. Since they are present in a fixed mass ratio, water molecules obey the law of constant proportions. Another example of a chemical compound that obeys the law of constant proportions is methane. To form a methane molecule, 4 hydrogen atoms combine with 1 carbon atom. The law of certain proportions was first established in 1779 by the French chemist Joseph Louis Proust. This is why this law is also known as Proust`s law. The observations associated with this law were first made by the French chemists Antoine Lavoisier and Joseph Priestley. Since these natural polymers tend to vary in composition, several samples have different proportions by mass.

Some of the non-stoichiometric compounds tend to have different compositions of the elements between different samples. Therefore, they tend to follow the law of multiple proportions. The hydrogen and oxygen atoms in the water molecules are arranged in a ratio of 2:1. Water molecules follow the law of constant proportions because they have a fixed mass ratio. Methane is another chemical molecule that follows the law of constant proportions. Four hydrogen atoms combine with a carbon atom to form a methane molecule. The law of definite proportions is also called Proust`s law. Below is an image to explain the law of constant proportions. It describes the mass ratio of elements in some compounds. The ratio of atoms contained in an element is also given below. Consider, for example, that in NO2 molecules, the number of nitrogen atoms and the number of oxygen atoms are in a ratio of 1:2, but their mass ratio is 7:16.

The law of certain proportions may seem obvious to the modern chemist, as it is inherent in the definition of a chemical compound. By the end of the 18th century, however, when the concept of chemical compound was not yet fully developed, the law was new. In fact, when it was first proposed, it was a controversial statement and was rejected by other chemists, including Proust`s compatriot, Claude Louis Berthollet, who argued that the elements could combine in any report. [2] The existence of this debate shows that the distinction between pure chemical compounds and mixtures was not yet fully developed at that time. [3] In conclusion, I will deduce from these experiences the principle that I established at the beginning of these memoirs, namely.