114 LIFE: ITS NATURE AND ORIGIN 



istry (1912) relative to the iron catalyst used in the first step of the 

 Haber process: 



"Extremely minute quantities of these bodies (impurities), which are 

 almost always present even in the purest commercial products or in 

 so-called pure gases, suffice to render the catalysts absolutely inactive 

 or at least to diminish their activity very seriously. Thus iron, for 

 example, prepared from ordinary iron oxide with a content of one per 

 thousand of sodium sulphate is, as a rule, inactive. Iron containing 

 0.1 per cent sulphur is generally quite useless, and even with 0.01 per 

 cent is of very little use, although in appearance and when examined 

 with the ordinary physical and chemical methods no difference at all 

 can be detected as compared with pure iron. 



"The recognition of these facts gave rise to two problems: (A) The 

 preparation of contact masses free from poisons or the removal of 

 poisons from them; and (B) freeing the gases to be acted upon 

 catalytically from all contact poisons. A trace of sulphur, one part per 

 million, in the gas mixture, can under certain conditions be injurious, 

 so that electrolytically prepared hydrogen must generally be further 

 specially purified." 



Since a small amount of a catalyst may, if given sufficient time, direct 

 an enormous amount of chemical change, we can understand how 

 minute may be the quantity of promotor or modifier needed to pro- 

 duce a great change in the final output. 



Experimenting with the catalytic production of methanol from 

 carbon monoxide and hydrogen, Sir G. T. Morgan 31 observed that 

 while catalysts made by calcining equimolecular mixtures of manganese 

 and chromium nitrates gave methanol containing only traces of higher 

 alcohols, catalysts prepared by precipitating a mixed solution of oxides 

 of manganese and chromium in caustic potash gave a product con- 

 taining appreciable percentages of higher alcohols. This led him to try 

 the effect of regulated additions of alkali metals to the catalyst. To 

 quote one outstanding case, when the catalyst contained 15 per cent of 

 rubidium hydroxide, the carbon in the gases passing over the catalyst 

 was distributed as follows: (with equimolecular proportions of the 

 pure Mn and Cr oxides the yield of methanol was 80.5 per cent). 



Methanol 41.5% 



Ethanol 1.6 



Higher alcohols 36.7 



Aldehydes, acetals, ketones 15.5 



Methane 2.0 



Carbon dioxide 2.0 



The higher alcohols in this case consisted chiefly of isobutanol, but 

 contained besides normal propanol, 2-methylbutanol, 2-methyl- 

 pentanol, and 2, 4-dimethylpentanol. 



