In the seventeenth century the Honourable Robert Boyle made some shrewd observations, bearing on toxicology, in his work on “The usefulness of Natural Philosophy,” &c.: Oxford, 1664. Nicolas L’Emery also wrote a Cours de Chimie,—quite an epitome of the chemical science of the time.[19]
[19] Cours de Chimie, contenant la manière de faire les opérations qui sont en usage dans la Médecine. Paris, 1675.
In the eighteenth century still further advances were made. Richard Mead published his ingenious Mechanical Theory of Poisons. Great chemists arose—Stahl, Marggraf, Brandt, Bergmann, Scheele, Berthollet, Priestley, and lastly, Lavoisier—and chemistry, as a science, was born. Of the chemists quoted, Scheele, in relation to toxicology, stands chief. It was Scheele who discovered prussic acid,[20] without, however, noting its poisonous properties; the same chemist separated oxalic acid from sorrel,[21] and made the important discovery that arsenic united with hydrogen, forming a fœtid gas, and, moreover, that this gas could be decomposed by heat.[22] From this observation, a delicate test for arsenic was afterwards elaborated, which for the first time rendered the most tasteless and easily administered poison in the whole world at once the easiest of detection. The further history of what is now called “Marsh’s Test” is as follows:—
[20] Opuscula Chemica, vol. ii. pp. 148-174.
[21] De Terra Rhubarbi et Acido Acetosellæ. Nova Acta Acad. Veg. Sued. Anni, 1784. Opuscula Chemica, vol. ii. pp. 187-195.
Bergmann first described oxalic acid as obtained by the oxidation of saccharine bodies; but Scheele recognised its identity with the acid contained in sorrel.
[22] Mémoires de Scheele, t. i., 1775.