140 SCIENCE PROGRESS 



from the initial, by giving heat to the gas or taking heat from it. The 

 system during the experiment must be thermally isolated. 



Nitrogen, free and combined, is given its due consideration. The rela- 

 tive costs of nitric acid, produced from Chili nitrate, by the arc process, by 

 the cyanamide process, and by the method of Haber, are found to be £10, 

 £i2, £17., and £j per ton respectively. If the last figure were increased by 

 £=)0 per cent, it would be a much more valuable estimate. The author's 

 low figure for nitric acid via Haber and ammonia oxidation may be ac- 

 counted for by the fact that in his section on Hydrogen he takes the price 

 of this gas at is. gd. per 1,000 cubic feet. This figure is believed to be too 

 low, and 2s. 6d. per thousand would be a nearer approximation. It is to be 

 remembered that the cost of production of hydrogen is a vital factor, and 

 every increase, or reduction, of 6d. per 1,000 cubic feet in the cost of the 

 gas affects the cost of synthetic ammonia to the extent of nearly £2 per 

 ton ; with a corresponding increase in the nitric acid derived therefrom. 



Sections are devoted to oxygen, argon and its allies, and ozone. The 

 oxides of carbon, sulphur dioxide, and nitrous oxide all form interesting 

 sections. The subject of asphyxiating gases is somewhat out of place in a 

 book of this nature ; and while all the sections are authoritative, this does 

 not apply when the author enters, to the extent of four pages, the domain 

 of organic chemistry. 



While much has been written in recent times on the subject of fuel 

 generally, the concise survey of the manufacture and applications of gaseous 

 fuels will amply repay attention. Nowadays we hear much of nationalisa- 

 tion ; and its advocates point to the uneconomic utilisation of our source of 

 power — coal. The author of Industrial Gases quotes facts and figures which 

 undoubtedly incline pne to the miner's point of view. Our sources of power 

 are not being developed ; particularly does this apply to coal-gas ; and 

 Industrial Gases quotes the work of Hocking as to the gain in efficiency, in 

 furnace operations, in changing from coke to a gas-fired system. 



The fixation of atmospheric nitrogen is no longer a problem, and Dr. 

 Greenwood has contributed largely to its solution. In Industrial Gases he 

 has placed much of his expert knowledge at the disposal of industry. 



G. J. Jones. 



The Use oJ Colloids in Health and Disease. By Alfred B. Searle. [Pp. 

 vii+ 120.] (London : Constable & Co., 1920. Price 85. net.) 



While there is much in this monograph that may be read with profit, it 

 is obvious that the physiological knowledge of the author is not up to the 

 standard of his chemical and physical knowledge. Those parts of the work 

 which deal with the properties and modes of preparation of colloidal solu- 

 tions of various kinds are well done. But the numerous errors with regard 

 to biological phenomena suggest that the author is insufficiently equipped 

 to arouse the reader's confidence in the correctness of his interpretations 

 of the effects of colloidal preparations on the living organism. He would 

 be well advised to study an elementary textbook of physiology before pub- 

 lishing a second edition. This being so, his conclusions must be received 

 with caution. Many instances might be quoted, but two or three will serve 

 to illustrate the point. The use of the word " isotonic " in several places is 

 not that universally understood and is indeed unintelligible. The process 

 of digestion as described on p. 42 conveys the impression that the products 

 are in the colloidal state, whereas in fact colloidal food materials are con- 

 verted into the diffusible crystalloidal form and their passage into the 

 blood-stream made easy. There is only very meagre reference to those 

 phenomena in which colloidal properties as such play an important part, 

 such as the formation of lymph, the secretion of urine, and the maintenance 



