EINSTEIN, Albert. Zur allgemeinen molekularen Theorie der Wärme.
Leipzig: Johann Ambrosius Barth, 1904. First edition.

In: Annalen der Physik, Vol. 14, pp. 354-362. The complete volume offered ( VIII,1040 pp. and 3 plates) bound in recent half morocco with gilt spine lettering. 8vo: 219x152 mm. Ex-library stamp on titlepage. A very good copy. Collected Papers: 1904. Weil: 5.

"It was in this last of his early series of papers, before the announcement of the theory of relativity in 1905, that Einstein introduced a new theme. Einstein asked for the physical significance of the constant now known as Boltzmann's constant k. It was already well known from the theory of the ideal gas that k was simply related to the gas constant 'R' and to Avogadro’s number, the number of molecules in a gram-molecular weight of any substance. Einstein showed that k entered into still another basic equation of the statistical theory, the expression for the mean square fluctuation of the energy about its average value. This meant that k determines the thermal stability of a system ... the paper contains the seeds of much of his later work …” (Walter Alicke).