pressure cycling without danger of structural fatigue. It also provides greater strength, structural rigidity and safety with hazardous fluids. Another feature of this special design is that welds are kept to a minimum. In a standard 4 × 4 module, there are only 6 stainless steel welds. The vapourizers are manufactured in standard pressure ratings of 3 000, 6 000, and 10 000 lb/in z, all of which are standard 4 × 4 modules measuring 38 in. by 32 in. by 90 in. high. Their rated capacity is 5 000 std ft3/h of nitrogen at 3 000 lb/in z, 70 F ambient and 70 ~ relative humidity. The pressure drop is nominal; 1 lb/in 2 per 4 x 4 module, and the temperature of the discharge gas is within 20 F of ambient.
Variable temperature cryostat A variable temperature cryostat based on research carried out at the Weizmann Institute of Science, Israel, has been developed by High Voltage Engineering, Burlington, Massachusetts 01803, USA. This cryostat was essentially developed for MiSssbauer effect measurements but can easily be modified for other nuclear appli-
cations, optical experiments, magnetic studies, etc. In operation, the cryostat is stored on top of a dewar and cryogenic liquid is pumped through it. Varying temperatures are achieved by regulating the cryogenic liquid flow through the heat exchanger. In order to achieve this the cryostat must operate in conjunction with a temperature controller, TC-4. This is a sensitive closed loop instrument which activates a solenoid valve placed in the outlet of the cryostat. The special advantages of this cryostat are that its thermal capacity is low and the refrigerant volume negligible. The dead time between experiments is very short; warm up, sample change, pumping, and cool down is performed within 20 to 30 minutes. Also it is easy to operate since installation and sample changing can be performed without the use of tools. There are negligible cool down and warm up losses, the consumption of cryogenic liquid is very low; using liquid helium 0.25 1/h at 20 K, and 0.12 1/h at 40 K, and with liquid nitrogen less than 0"05 I/h. Temperature stability of better than 0.02 K can be achieved using temperature controller TC-4 up to 300 K, above 300 K a power supply is required.
BOOKREVIEWS Proceedings of the Fourth International Vacuum Congress THIS BOOK contains more than 150 papers presented at the congress held at the University of Manchester Institute of Science and Technology in April 1968. It gives a survey of the possibilities, problems and applications of modern vacuum science and technology. The section 'Sorption pumps and cryopumps', comprising papers on the pumping properties of molecular sieves at low temperatures, the application of titanium cryosublimation pumping, the design of cryopumps and continuous cooling methods as well as the automatic control, information processing, and analysis of cryopumping experiments, will possibly be of most interest to the reader working in the cryogenic field. However, as there are strong connexions between cryogenics and Published in 2 parts by the Institute of Physics and the Physical Society as Conference Series No. 5 (1969).
Lehrbuch der K ltetechnik (Handbook of refrigeration) Printed in 2 volumes with sections by H. Stettner, G. K6rner, H. Brauer, d. Gutschmidt, H. Weimer, and W. Hodapp.
THIS BOOK contributes to the professional education of refrigeration plant fitters. Consequently, no basic knowledge is required. The book conveys mostly information which the fitter needs to help him assemble Published by C. F. Muller, Verlag, Karlsruhe, West Germany (1968); 995 pages, DM72. CRYOGENICS • OCTOBER 1969
vacuum techniques, physicists and engineers will also find much useful information among the great number of papers on topics ranging from vacuum standards, units, and terminology over constructional design and operating behaviour of the various types of pumps, measurement of total pressure and partial pressure, mass spectrometers, gas kinetics, applications such as freeze drying, space simulation, and vacuum deposition of thin films, up to design features of different vacuum systems as well as materials and components. The partition of the rather vast material into almost twenty sections enables the readers to find easily sections of special interest. The first section of Part 1 contains three reviews on physical processes in vacuum in the pressure range below 10-3 torr (125 references), principles and methods of mass spectroscopy (32 references), and high voltage electron microscopy which is being introduced extensively into these fields of science, and will be most valuable for many readers. G. KLIPPING with understanding a refrigeration plant and to carry out simple calculations. Following an introduction in the elements of technical calculation and physics, the main processes of refrigeration are described in an easily understandable manner. Whereas only three pages are dedicated to the techniques of low temperatures, the book deals comparatively extensively with condensators, evaporators, valves, and fittings. Over-all this book presents an introduction to electrical engineering, mechanical isolation, and the preservation of foodstuffs by refrigeration. P. GRASSMANN 407