Thermodynamische Begründung des photochemischen Äquivalentgesetzes. [With:] Nachtrag zu meiner Arbeit: Thermodynamische Begründung des photochemischen Äquivalentgesetzes.

Leipzig: Johann Ambrosius Barth, 1912.

First edition, extremely rare author’s presentation offprints (with ‘Überreicht vom Verfasser’ (Presented by the Author) printed on front wrappers), and the copies of Einstein’s son Hans Albert, of Einstein’s formulation of the photochemical equivalence law. This is a fundamental principle relating to chemical reactions induced by light, which states that for every quantum of radiation (photon) absorbed, one molecule of the affected substance reacts. Einstein’s formulation, founded on thermodynamics, marks the first application of quantum theory to photochemistry; it was one of his last significant contributions to quantum theory. The photochemical equivalence law is also known as the Einstein-Stark law: the German experimental physicist Johannes Stark had published his own derivation of it in 1908, but at that time Stark did not agree with Einstein’s views on the corpuscular nature of radiation, writing: “In my opinion it is not necessary to postulate a discontinuous structure of the radiation energy, which flows with the velocity of light in ether” (quoted in Mehra & Rechenberg, p. 103). OCLC lists only two locations (King’s College London and Swiss National Library for the main work, the latter only for the ‘Nachtrag’); no other copy in auction records (neither of these papers were in Einstein’s own reference collection of offprints in the Richard Green Library).

Provenance: Hans Albert Einstein (1904-1973), Swiss-American engineer and educator, and the second child and first son of Albert Einstein and Mileva Mari (ownership stamp on front wrapper). He moved to the US in 1938, and spent most of his career at the University of California, Berkeley, where he was a professor of hydraulic engineering.

Einstein’s work on the photochemical equivalence law came at a time of crisis in his attitude to the quantum theory of radiation. Einstein had first put forward the idea of light quanta in 1905, but in later years he came to doubt the validity of the idea, despite its earlier success in explaining the photoelectric effect. In May 1911, “Einstein confided to [Michel] Besso his doubts on the existence of quanta in general: “I no longer ask myself if these quanta really exist. And I do not try any more to construct them because I now know that my brain is unable to do it. But I still explore the consequences as carefully as I can to learn the range of validity of this idea.” In February 1912 he wrote to Hopf: “Quanta certainly do what they ought to, but they do not exist, like the immovable ether. At the moment, the latter is turning diligently in its grave intending to come to life again — poor fellow” … [Einstein] no longer sought to “construct” quanta and instead tried to see how far quantum results could be obtained without quantum discontinuity: “After many fruitless attempts,” he wrote in the same letter [to Wien in May 1912], “I too have come to the conclusion that one will not be able to put the theory of radiation on its feet merely by constructing models. This is why I tried to formulate new questions through pure thermodynamics, without making use of a picture.” The first yield of this new strategy was a derivation of an obvious consequence of the light quantum hypothesis, the law of photochemical equivalence, without light quanta [the first offered paper]” (Cambridge Companion to Einstein, pp. 131-2). Einstein derived the photochemical equivalence law using thermodynamics; the fact that this law is consistent with the conclusion one would derive from the light quantum hypothesis lends support to that hypothesis.

Einstein’s paper on the photochemical equivalence law led to a deterioration in his relations with Stark. “Several years later Albert Einstein gave a treatment of the photochemical laws on the basis of quantum theory [the two offered papers]. Johannes Stark, in a subsequent note, then drew attention to his earlier treatment, to which Einstein replied by stating: ‘J. Stark has written a note concerning a paper of mine, published recently [the first offered paper], with the purpose of defending his intellectual property. I do not wish to comment on the question of priority implied in it, for it would hardly interest anyone, especially since the photochemical equivalence law must be regarded as a completely obvious consequence of the quantum hypothesis’. He further remarked that his new derivation was different and founded on thermodynamic arguments. Stark pointed out in a second note that he agreed with the last statement; but he still claimed that he had obtained the photochemical laws on arguments different from Einstein's in his paper on the light-quantum … In 1912 the relations between Einstein and Stark had already become less cooperative than they had been in previous years, and they would deteriorate further in the future. Einstein’s harsh answer in the question concerning the priority of the formulation of photochemical laws may have triggered Stark’s unhappiness” (Mehra & Rechenberg, p. 104).

Mehra & Rechenberg, The Historical Development of Quantum Theory, 1, pp. 103-104. Weil, Albert Einstein Bibliography, 46.

Together two offprints from Annalen der Physik, 4. Folge, 37 & 38 Band, 1912. 8vo (220 x 144 mm), pp. 832-838 & 881-884. Original printed wrappers with ownership stamp of Hans Albert Einstein on front wrappers. Very fine condition.

Item #4034

Price: $12,000.00