Hydrogen compounds are only required to contain carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond which gives this class of compounds most of its particular chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known, and they are usually formed by complicated synthetic pathways that seldom involve elementary hydrogen. Compounds of hydrogen are often called hydrides, a term that is used fairly loosely. The term "hydride" suggests that the H atom has acquired a negative or anionic character, denoted H, and is used when
Law of reciprocal proportions of multiple proportions. The law of definite proportions refers to the fixed composition of any compound formed between element A and element B. The law of multiple proportions describes the stoichiometric relationship between two or more different compounds formed between element A and element B. The law of reciprocal proportions was proposed in essence by Richter, following his determination of neutralisation ratios of metals with acids. In the early 19th century it was investigated by Berzelius, who formulated it as follows: Later Jean Stas showed that within experimental error the stoichiometric laws were correct. Law of reciprocal proportions The law