M. Calvin, C. Heidelberger, J. Reid, B. Tolbert, P. Yankwich. Isotopic Carbon. Techniques in its Measurement and Chemical Manipulation, John Wiley and Sons, Inc., New York. Chapman and Hall Limited, London, 1949.

M. Calvin, C. Heidelberger, J. Reid, B. Tolbert, and P. Yankwich. Isotopic Carbon.

The appearance of a book devoted to the technique of working with isotopes of a single element is vivid evidence of the broad application that isotopes have received in recent times. The exceptional importance of carbon in biology and chemistry explains, to a considerable degree, the special attention paid to carbon isotopes. Nevertheless, it may be asserted that only after the discovery and practical realization of the slow-neutron reaction, which makes it possible to produce the radioactive isotope \(C^{14}\) in sufficient quantities, did work with labeled carbon acquire a truly broad scope. At the same time a whole series of purely experimental problems arose, and this book is to a large extent devoted to their consideration.

Unlike other monographs devoted to the tracer-atom method, the present book does not examine cases of the use of isotopes for solving particular concrete problems. The book is an experimental manual on the technique of working with carbon isotopes. The physical characteristics of the practically important carbon isotopes are such that each of these isotopes requires the use of special working methods. Thus, \(C^{11}\) is short-lived \((\tau = 20.5\) min.), \(C^{13}\) is stable, and \(C^{14}\) emits soft \(\beta\)-radiation. Such a varied set of carbon isotopes makes the book useful not only for investigators working specifically with labeled carbon, but also for investigators dealing with isotopes of other elements.

The first five chapters of the book constitute the purely physical part. They discuss methods for obtaining isotopes (chap. 1), the characteristics of their radiation (chap. 3), and methods of recording it (chaps. 4, 5). Questions relating to the passage of \(\beta\)-rays through matter and, in particular, the question of self-absorption of \(\beta\)-rays, are set forth in comparatively great detail. Various instruments for measuring \(C^{14}\) are described in detail (down to design details).

Chapter 2, written in concise form, is devoted to the measurement of the stable isotope \(C^{13}\), but its excessive brevity deprives this chapter of practical interest.

Two chapters, 6 and 7, important from a practical standpoint and well written, are devoted to the question of preparing radioactive samples, a matter of special importance for obtaining quantitative results with \(C^{14}\).

The eighth chapter sets forth certain questions concerning the use of vacuum technique in organic chemistry.

The remaining chapters (9–12) deal with purely chemical questions. These include methods for the synthesis of compounds containing labeled carbon in definite positions, methods for determining the position of car—

of carbon in a given compound, and methods for the biological synthesis of complex organic compounds containing labeled carbon.

The book is provided with a substantial appendix. It sets forth the fundamentals of the isotope-separation method, the method of statistical processing of data obtained with Geiger–Müller counters, ways of introducing corrections for the dead time of the counting apparatus, the determination of the geometrical efficiency of the counting apparatus, the determination of the dependence of counting efficiency on backscattering, and the absorption and self-absorption of \(\beta\)-rays.

As can be seen, the book reflects the principal methodological questions that arise when carbon isotopes are used as labeled atoms. It must be noted, however, that the question of isotope effects is not touched upon. Only in the introduction do the authors mention in passing that, owing to the comparatively small difference in the atomic weights of carbon isotopes, the difference in their chemical behavior should be negligible. The validity of this assertion for biological systems, however, cannot be regarded as obvious. Vernadsky long ago pointed out that, in living organisms, the possibility is not excluded of a special selectivity with respect to isotopes not found in purely physicochemical systems. This important question undoubtedly deserves closer attention from investigators working with labeled atoms, and in this respect the broad range of carbon isotopes offers considerable possibilities.

L. Bell