:Gasoline is not a pure substance, so it doesn't have a single molecular formula; it is a mixture of different hydrocarbons.
32.
For many purposes they are prepared in situ, not isolated, but many have been isolated as pure substances and thoroughly characterized.
33.
In nature, minerals are not pure substances, and are contaminated by whatever other elements are present in the given chemical system.
34.
If you mean specifically another rare metal or similar pure substance, I don't believe any nation employs such a standard at present.
35.
Natural sources contain only pure substances which are easily absorbed and expelled by the body and, therefore, have almost no side effects.
36.
Unlike most things in your kitchen, sugar is a very pure substance; something like 99.9 % sucrose is the estimate I've heard.
37.
For example, for pure substances, one can take the entropy of the solid at the melting point at 1 bar equal to zero.
38.
It's less obvious whether a pure substance would outperform a mixture when it comes to variables like efficiency of combustion and pollution control.
39.
Many mineral groups and species are composed of a solid solution; pure substances are not usually found because of contamination or chemical substitution.
40.
With a few exceptions, chemical feedstocks, none of which are pure substances, but each of which must be separated from the raw crude.
