On some of the combinations of mercury

Abstract

In this paper, Mr Reid presents a systematic examination of the various chemical combinations of mercury, particularly its oxides and nitrates, as studied through controlled reactions with nitric acid and related compounds. The study distinguishes between the protoxide (blue oxide) and peroxide (red oxide) of mercury, detailing their respective affinities for oxygen and their ability to form metallic salts when combined with nitric acid.

Reid describes the formation of pernitrate and pronitrate of mercury under different conditions of acidity, temperature, and dilution. He identifies several crystallised forms of pronitrate—hexagonal, acicular, and rhombic—each distinguished by its solubility and behaviour under heat and water. The paper also records the transformations among these compounds through heating, precipitation, and decomposition, showing the progressive oxidation of mercury and the derivation of the red precipitate (nitroxide of mercury).

Furthermore, Reid provides refined preparation methods for pure calomel (the protochloride of mercury) and red oxide of mercury, arguing that the pronitrate process yields products of higher purity and finer mechanical division than traditional methods. His experimental observations challenge prevailing chemical theories of the period—particularly regarding the composition of calomel and red precipitate—and suggest that many older assumptions about mercury’s combinations require revision.

This detailed chemical treatise demonstrates early nineteenth-century experimentation and analysis in inorganic chemistry, exemplifying the precision and empirical reasoning characteristic of the scientific work presented at the South African Institution.