In chemistry, Hill order is a method for writing molecular formulas, according to which C appears first, H second (if present), and then the other element symbols in alphabetical order. [1]

In 1900, the so-called Hill order of element ordering in molecular formulas was introduced by American chemist Edwin Hill and used by the classification division of the US Patent Office in 1907.

In 1936, American plant physiologist Frank Thone, employed Hill order to described plants, pictured as "CHNOPS plus" systems.

In the 2000s, with the publication of human molecular formulas, wherein mass composition ordering dominance began to talk precedence, over that of alphabetical ordering, a dual usage compromise approach began to be employed, according to which a human is defined as powered CHNOPS+22 molecular form, using classical Hill order, but when the exact molecular formula is written out, mass percent tends to take precedence in elemental ordering.

1. Lind, David R. (1994). Handbook of Organic Solvents (MF, pg. #). CRC Press.

External links
‚óŹ Hill system – Wikipedia.

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