Paul Walden. Chemie der freien Radikale. Vol. II of “Chemie und Technik der Gegenwart,” edited by Walter Roth, pp. X + 351. S. Hirzel. Leipzig. 1924.

P. Walden. Chemistry of Free Radicals.

One of the most interesting problems of modern chemistry, one of the brilliant achievements of the first quarter of the twentieth century; a striking wealth of ideas, leading the reader far beyond the narrow subject of the book and compelling him to recall the development of chemical ideas throughout the nineteenth century; the author’s remarkable knowledge of the entire literature (down to the most ancient); an engaging exposition—all this compels one to recognize in this book an outstanding literary phenomenon.

It is of particular interest to compare the work of Academician P. I. Walden with Schmidlin’s work on triphenylmethyl, which appeared in 1914. Against the background of that, in its day, very useful survey, there stands out still more vividly all the abundance of ideas with which P. I. Walden’s newest work shines.

The first part of it is devoted to the history of the development of the doctrine of free radicals; the following chapters are devoted to triphenylmethyl and its homologues, to free organic radicals with four-, two-, and monatomic nitrogen, to derivatives of monatomic oxygen, to organometallic compounds, to inorganic free radicals, to free radicals as intermediate stages in chemical reactions, to analogies with metals, and to many other questions. Especially valuable are the author’s own calculations of the dissociation constants of individual hydrocarbons and the idea of “ultradissociation.”

The book may be recommended to everyone interested in the development of chemical thought.

M. Blok.