Introduction
Higher Mathematics for Chemical Students (1911)
“The conservation of matter in a chemical change is represented in a balanced chemical equation for that process. The study of the relationships between the numbers of reactant and product molecules is called stoichiometry. Stoichiometry is fundamental to all aspects of chemistry.”
Principles of Modern Chemistry (7th ed., 2012), Ch. 2 : Chemical Formulas, Equations, and Reaction Yields
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David W. Oxtoby 13
President of Pomona college 1951Related quotes
“The nature of the chemical bond is the problem at the heart of all chemistry.”
New Chemistry (1957) by the editors of Scientific American, p. 65
Principles of Modern Chemistry (7th ed., 2012), Ch. 2 : Chemical Formulas, Equations, and Reaction Yields

A New System of Chemical Philosophy, Part I http://books.google.com/books?id=Wp7QAAAAMAAJ (1808) as quoted by Richard Reeves, A Force of Nature The Frontier Genius of Ernest Rutherford (2008)

"The Cause and Nature of Radioactivity" in Philosophical Magazine (September 1902)

attributed to Rudolph Virchow Coper, H., Herken, H., 1963. Dtsch. Med. Wochenschr. 88,2025– 2036. cited by 1. Gelman BB, Soukup VM, Schuenke KW, Keherly MJ, Holzer C, Richey FJ, et al. Acquired neuronal channelopathies in HIV-associated dementia. J Neuroimmunol. 2004;157(1–2 SPEC. ISS.):111–9.

Linus Pauling In His Own Words (1995) by Barbara Marinacci, p. 29.
1990s
Context: Just think of the differences today. A young person gets interested in chemistry and is given a chemical set. But it doesn't contain potassium cyanide. It doesn't even contain copper sulfate or anything else interesting because all the interesting chemicals are considered dangerous substances. Therefore, these budding young chemists don't get a chance to do anything engrossing with their chemistry sets. As I look back, I think it is pretty remarkable that Mr. Ziegler, this friend of the family, would have so easily turned over one-third of an ounce of potassium cyanide to me, an eleven-year-old boy.
Introduction
Higher Mathematics for Chemical Students (1911)

Grundrisse (1857-1858)
Source: Introduction, p. 10.