SCIENCE AND INDUSTRY. 
The history of nitrogen fixation dates back to the early years of the 
nineteenth century, when numerous attempts were made, both in this 
‘country and elsewhere, to manufacture cyanides and ferro-cyanides by 
fixing atmospheric nitrogen with the aid of mixtures of carbon and 
alkalies or alkaline earths heated to an elevated temperature. Although 
such cyanide processes have hitherto failed to attain to commercial 
success, important results have accrued from the researches undertaken 
in connexion with them, the study of the behaviour of metallic carbides 
towards nitrogen gas being directly responsible for the technical develop- 
ment of the calcium cyanamide process. In the meanwhile, the work 
of Sir William Crookes and Lord Ryleigh in Great Britain, some twenty 
years ago, had first directed attention to the possibility of utilizing the 
electric are for effecting the direct oxidation of atmospheric nitrogen 
on a technical scale for the production of nitric acid. As the result 
of the progress made in this field of investigation, the are process was 
the first of the modern nitrogen fixation processes to be established on 
a commercial basis, being followed a few years later by the calcium 
cyanamide process referred to above. The third of the estab- 
lished fixation processes resulted from the researches of Haber and 
others upon the synthesis of ammonia from hydrogen and nitrogen at 
elevated pressures and temperatures by the action of catalysts, and was 
brought into commercial operation in Germany in the year prior to the 
war. In addition to the three established processes just mentioned, 
many other methods of fixing atmospheric nitrogen have been tried, 
and the more important of these are dealt with in the report. 
The principal processes in operation or proposed for the manufac- 
ture of the more important nitrogenous products admit of a simple 
classification. The following table indicates the primary and 
secondary products :— . 
Processes. Primary Products. - ~ Secondary Products; 
Recovery Processes : 
By-product | Ammonia | Crude Ammonia Liquor or | Other Ammonium Salts 
processes Ammonium Sulphate (ac- 
; cording to the system of 
recovery adopted) 
Retort or Chile Nitrate | Nitric Acid, dilute (65 per | Nitrates, such as Ammonium 
process cent.) or concentrated Nitrate 
(90-96 per cent.) accord- 
- ing to method of opera- 
tion 
Fixation Processes 1 , : , 
(a) Are process .. | Oxides of Nitrogen, nor- | Concentrated (93-96 per 
; mally recovered as dilute cent.) Nitric Acid, or 
(80-40 per cent.) Nitric Nitrates such as Am- 
Acid monium or Calcium Ni- 
; ? trate 
(6) Calcium Cyanamide | Calcium Cyanamide -. | Ammonia or Ammonium 
process Sulphate ; Nitrate of 
Urea, Guanidine, and other 
: organic products 
(c) Haber process +. | Ammonia Liquor -. | Ammonium Sulphate or 
: other Ammonium Salts 
230 ; 
