Bleaching earths

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BOOK REVIEWS

volving seismic body waves. It is a minor chapter of the book but interesting the point of view of its being a well-defined exercise in seismic theory.

from

After going through the contents of Bath’s book, admittedly in a cursory manner, for it is not a book to be read at one sitting, one may justifiably ask whether the expectations raised by the title are fulfilled. The answer, I think, must be “only in part”. One searches in vain for a thorough discussion of topics like phase and group velocities (basic concepts of all wave motion and stumbling blocks to many a student), the derivation of the wave equation, diffraction, anisotropy, propagation through the real earth, damped wave motion or the extraction of seismic signal from noise. The last topic leads naturally to power spectrum analysis and its omission is surprising since Bath is world-famous for his researches on microseisms and his work on the detection of underground nuclear explosions. In the preface he simply refers to the monograph of BLACKMAN and TUKEY (1958) on the measurement of power spectra with the plea that “such material has not been included which is either more directly concerned with observational seismology or which can be more easily grasped even with a simple mathematical background”. The implication in the last part of the quotation is somewhat misleading. One needs considerably more than a simple mathematical background to follow the monograph of Blackman and Tukey. Besides, it is written from the point of view of communicawould by no means have been untions engineering and a “seismic translation” welcome. To summarize, Prof. Bath’s book is a good one and will be a handy companion to many, but considering the proportions allotted to mathematics and seismology, I would have been happier in reviewing it if it had been entitled “Applied Mathematics for Seismology Students” rather than “Mathematical Aspects of Seismology”. D. S. PARASNIS (Boliden,

Sweden)

REFERENCE BLACKMAN, R. B. and TUKEY J. W., 1958, The Measurement N. Y., 190 pp.

Bfeachirzg

Earths.

M. K. HASNUDDIN

of Power Spectra,‘Dover,

SIDDIQUI. Pergamon,

Oxford,

New York,

1968, 86 pp.,

42 s.

This little book deals with the application of bleaching earths, i.e., fuller’s earths and bentonites, to the bleaching of vegetable and mineral oils, and to petroleum refining. It commences with a review of the classification and composition of bleaching earths, which are mainly clays of the sepiolite-attapulgite family or Geoexploration,

I (1969) 189-196

195

BOOK REVIEWS montmorillonites,

their mode

of formation,

their structure,

and the nature

and

origin of the absorption properties of clays. The book continues with a brief discussion of the various techniques for the determination of clay minerals, with greatest emphasis being placed on differential thermal analysis. Methods for the production of bleaching earths, and their activation where necessary, are then described, followed by a discussion of the mechanism of bleaching of vegetable and mineral oils and a description of the industrial processes in which clays are used for bleaching. The differential thermal analysis curves of some commercial bleaching earths from Germany and the United States are then given, and the nature of the clay minerals present and the pre-treatments which they have undergone are deduced from these. The final section of the book discusses the occurrences of clay deposits in India and gives differential thermal analysis and electron microscopic evidence of the mineralogy of these deposits. It is difficult to see for what type of reader the book is intended. The treatment of the subject, although factually correct, is very brief and the sources quoted are not always the most recent. For this reason the book is likely to be misleading to anyone expecting a review of this type to take cognisance of the most recent information available. The only material not readily available in other reference books on similar subjects are the discussion concerning the activation of bleaching earths, especially the interpretation of differential thermal analysis patterns of clays that have been activated to varying extents, and the discussion of the occurrence of clays suitable for industrial use in India. The book would have most appeal to a clay technologist interested in the clay resources of India, and pai titularly in their industrial application as bleaching earths. G. G. C. CLARIDGE (Lower Hutt)

Transformation of Petroleum in Nature. P. F. ANDREEV, A. I. BOGOMOLOV,A. F. DOBRYANSKII and A. A. KARTSEV. Pergamon, Oxford, 1968, 466 pp., 53 tables, 55 fig., f7. “One of the defects in many hypotheses about the origin of petroleum is the p. 447 of Transformation of illusory completeness of the picture.” Dobryanskii, Petroleum in Nature. This statement provides a meaningful summary of the very comprehensive study of the topic put together by four respected Russian scientists, recently translated and published by the Geochemical Society. This is an outstanding publication in the sense that it attempts to cover all aspects of petroleum formation for which there were pertinent data, and the approach involves both chemists and geologists. The fundamental assumption is that the components of petroleum undergo continual transformation, and the indicated Geoexploration,

7 (1969)

189-196