November 18, 1922] 



NA TURE 



671 



tion to the large increase in the German capacity to 

 produce synthetic nitrogen compounds, and the 

 erection of new plants in that country. At the end of 

 this year Germany will be independent of all importa- 

 tion of nitrates, while the large munition works in this 

 country are being dismantled. The subject, there- 

 fore, has political importance as well as scientific and 

 commercial interest. 



Mr. J. H. West's paper dealt with the manufacture 

 of the nitrogen and hydrogen required for synthetic 

 ammonia processes. Three volumes of hydrogen being 

 required for one of nitrogen, and the former being the 

 more expensive gas, the cost of the process depends 

 mainly on that of the hydrogen. The electrolytic 

 process is convenient, and yields pure hydrogen, but 

 the capital cost of the plant is high, and the method is 

 only practicable where cheap hydro-electric power is 

 available. Coke oven gas may be used, the method 

 employed being that of liquefying all the gases present 

 except hydrogen, but in this case the small quantity 

 of carbon monoxide which always remains mixed with 

 it must be removed by chemical washing or by con- 

 version into methane, the gas being a poison to the 

 catalvst in the subsequent ammonia synthesis. Water 

 gas may be used, a reaction with steam being brought 

 about in presence of a catalyst : CO + H 2 = C0 2 + H 2 . 

 In a modified process, due to the author and A. Jacques, 

 the coal is treated by a process of complete gasification, 

 and the gaseous products treated in the same apparatus 

 to yield carbon dioxide and hydrogen with a catalyst. 

 Nitrogen is made by the liquid air process, or by mixing 

 air and hydrogen in such proportions that on passing 

 over a suitable catalyst the oxygen is converted to 

 water, and a mixture of nitrogen and hydrogen in the 

 required proportions remains. In the Haber process, 

 water gas and producer gas are mixed in such pro- 

 portions that a correct mixture is left after removal of 

 the carbon monoxide. 



Both this paper, and the succeeding one. by Mr. ('. 

 J. Goodwin, were presented in the absence of their 

 authors, so that they suffered in the discussion. Mr. 

 Goodwin described the Hausser process for the pro- 

 duction of nitric acid by exploding nitrogen and oxygen 

 with a fuel gas in a bomb. Although the plant has 

 hitherto been on an experimental scale, it is expected 

 that the new bombs of 1200-1500 litres capacity 

 will give commercial yields, and the use of stainless 

 steel has overcome much of the corrosion difficulty. 

 The absorption towers have been greatly reduced in 

 size by employing nickel-chromium steel or silicon- 

 iron for the vessels, under a pressure of 2-5-4 atmo- 

 spheres. The suggestion has been made that a special 



gas engine or Humphrey pump might be used in place 

 of a bomb, in order to utilise the heat energy of the fuel 

 more economically, but it remains to be seen whether 

 such a change would prove advantageous on the whole. 

 The main advantage of the process is its compactness, 

 the size of the plant being small, especially when gases 

 of high calorific value are used. 



Dr. E. B. Maxted's contribution concerned the 

 question whether nitrogen fixation, based on water 

 power, could be economically undertaken in this 

 country. Under present conditions, there are several 

 sites in these islands where it should be possible to 

 produce hydro-electric energy for 4Z.-5Z. per kilowatt- 

 year, the greater part of this sum representing interest 

 on the capital cost. This would allow of the produc- 

 tion of electrolytic hydrogen at a cost of is. "jd. per 

 1000 cubic feet, which does not compare unfavourably 

 with the cost of hydrogen from fuel. Greater economy 

 would be effected if uses for large supplies of oxygen 

 in the chemical industries could be found. Comparing 

 together the ammonia and cyanamide processes, it 

 appears that a given amount of power, say 10,000 

 kilowatts, being available, either process would result 

 in the fixation of about the same quantity of nitrogen, 

 but the ammonia process would yield large quantities 

 of oxygen as a by-product, while the cyanamide 

 process would require the bringing of anthracite and 

 lime to the site. There would be some compensating 

 conditions, such as the greater simplicity of the cyana- 

 mide process, and the necessity of fixing ammonia by 

 means of an acid. 



Mr. E. Kilburn Scott denied the contention that the 

 arc process is uneconomical. It has been stated that 

 in Norway nitric acid could be made profitably where 

 electric energy costs 10/. per kilowatt-year, while the 

 Scottish schemes can provide the same quantity for 

 4I. The arc process is the only one capable of utilising 

 off-peak power, and where large generating stations 

 are set up it is quite economical. Moreover, calcium 

 nitrate is the best of all artificial fertilisers. Little else 

 emerged in the discussion. It is clear that processes 

 which promised well during the exceptional conditions 

 of the war have to be re-examined very carefully in 

 regard to their practicability under ordinary conditions 

 of competition, and it has yet to be demonstrated that 

 synthetic processes can be established successfully 

 where power has to be obtained from the combustion 

 of coal. Whatever may prove to be the future of these 

 processes, Dr. Harker's review of the present position 

 of the question will be of value, as an addition to the 

 important memoirs already published from official 



The Thermal Basis of Gas Supply. 

 By Prof. John W. Cobb. 



THE amount of attention which has been given in 

 the Press during the past few months to the 

 new basis of charge for gas introduced by the Gas 

 Regulation Act of 1920, is at first sight somewhat 

 surprising and unexpected. To the scientific mind 

 there seems to be so little in it that calls for mental 



NO. 2768, VOL. I io] 



strain in its comprehension, or for criticism in its 

 introduction. 



Gas is now to be sold at so much per therm, and 

 the therm is simply 100,000 British Thermal Units — 

 i.e. a convenient multiple of what is the most widely 

 known and generally accepted unit of heat. A 



