description property "chemicalComposition" of "ChemicalSubstance" is misleading

[hujo91]

The description of the property chemicalComposition: "The chemical composition describes the identity and relative ratio of the chemical elements that make up the substance." is somewhat unclear/misleading and should be revised. Instead of "chemical elements", "molecular entities" should be used because according to the definition of ChemicalSubstance taken from ChEBI, a chemical substance is “composed of molecular entities”. Otherwise, it suggests that the sum formula (property molecularFormula, which is already defined in MolecularEntity) should be entered thereby mistakenly.

[tilfischer]

Dear all,

I would have expected to add the results of elemental analysis measurements here, as a molecular formula would not work for any chemical substance which is a mixture of two or many components, which might be individually described by their molecular (chemical) entities.

Changing this to, "The chemical composition describes the identity and relative ratio of the molecular entities that make up the substance." would be a way to go.

Another (more and clearly chemistry related) reference for the definition than ChEBI (of biological interest) would be provided by the IUPAC Goldbook: https://doi.org/10.1351/goldbook.C01039:

Matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of. Physical properties such as density, refractive index, electric conductivity, melting point etc. characterize the chemical substance. Best, Tillmann

[tilfischer]

Dear all,

I would have expected to add the results of elemental analysis measurements here, as a molecular formula would not work for any chemical substance which is a mixture of two or many components, which might be individually described by their molecular (chemical) entities.

Furthermore, I would like to add that I was mislead by the the definition telling "relative ratio" together with "chemical elements". If it is about the relative ration of chemical elements, then this should be headlined with "Empirical formula", but it is not.

Having, "The chemical composition describes the identity and relative ratio of the molecular entities that make up the substance." would raise the question what that "ratio" is. Is it mass ratio? Molar ratio? Volume ratio?

Lastly, I would only like to mention here, that if someone has a mixture of sodium chloride NaCl together with potassium bromide KBr and wants to describe that mixture with chemicalComposition, which is defined as some type of ratio of molecular entities, we end up describing these salts as molecules, but they are not molecules. However, this is a bigger discussion on inclusiveness.

Best, Tillmann