Principle (chemistry)

Principle, in chemistry, refers to a historical concept of the constituents of a substance, specifically those that produce a certain quality or effect in the substance, such as a bitter principle, which is any one of the numerous compounds having a bitter taste. The idea of chemical principles developed out of the classical elements. Paracelsus identified the tria prima as principles in his approach to medicine. In his book The Sceptical Chymist of 1661, Robert Boyle criticized the traditional understanding of the composition of materials and initiated the modern understanding of chemical elements. Nevertheless, the concept of chemical principles continued to be used. Georg Ernst Stahl published Philosophical Principles of Universal Chemistry in 1730 as an early effort to distinguish between mixtures and compounds. He writes, "the simple are Principles, or the first material causes of Mixts; " To define a Principle, he wrote
A Principle is defined, à priori, that in a mix’d matter, which first existed; and a posteriori, that into which it is at last resolved. ( ) chemical Principles are called Salt, Sulfur and Mercury ( ) or Salt, Oil, and Spirit. Guillaume François Rouelle "attributed two functions to principles: that of forming mixts and that of being an agent or instrument of chemical principles." Thus the four principles, earth, air, fire, and water, were principles both of the chemist's operations and of the mixts they operated upon. As instruments they were, unlike specific chemical reagents, "natural and general," always at work in every chemical operation. As constituent elements, they did not contradict the chemistry of displacement but transcended it: the chemist could never isolate or characterize an element as he characterized a body; an element was not isolable, for it could not be separated from a mixt without re creating a new mixt in the process.