192 SCIENCE PROGRESS 



ORGANIC CHEMISTRY. By P. Haas, D.Sc. Ph.D., University 

 College, London. 



Under the general heading of " Catalytic Actions at Solid Sur- 

 faces," Armstrong & Hilditch {Proc. Roy. Soc, 191 9, A, 96, 

 137 and 322) have been studying the hydrogenation of un- 

 saturated fatty oils by finely divided nickel. By measuring 

 the volume of hydrogen entering and leaving the system by 

 means of water-meters and plotting time-absorption curves, 

 it was found that these were not of the logarithmic type re- 

 quired for a monomolecular reaction, but were composed of 

 two linear portions, representing changes in which the active 

 mass is constant, and it is concluded that this is evidence of 

 the interaction between the catalyst and the unsaturated 

 compound, similar to the combination between enzyme and 

 substrate observed in enzyme hydrolysis. In the second of 

 the two papers the question is raised whether this catalytic 

 action, like that of enzymes, is not reversible ; evidence in 

 support of such reversibility is offered by the observation that, 

 when equimolecular proportions of cyclohexanol and methyl 

 cinnamate are heated with nickel at 180° C, 10 per cent, of 

 the latter compound is reduced to methyl-phenylpropionate, 

 while the former is oxidised to cyclohexanone, which 

 implies a transference of hydrogen from a saturated to an 

 unsaturated compound. While this change may be due to 

 the production of hydrides of nickel, the authors prefer to 

 regard it as a case of catalytic equilibria represented by the 

 following scheme : 



Saturated compound + Ni ;t [Saturated compound, Ni] ^ 

 [Unsaturated compound, Ni, Ha] ^ Unsaturated compound + Ni + Ha. 



The reversibility of this catalytic hydrogenation is called 

 upon to explain the observation of Moore (/. Soc. Chem. Ind., 



1 91 9, 38, 320, T), that during the hydrogenation of ethyl oleate 

 to ethyl stearate some isomerisation to oleate is produced ; the 

 latter compound is, according to Armstrong and Hilditch, 

 formed by dehydrogenation of some of the freshly produced 

 ethyl stearate. 



In an earlier review (Science Progress, 191 8, No. 48, 564), 

 mention was made of a paper by Woker on the diastatic pro- 

 perties of formaldehyde ; since that time a considerable 

 amount of controversy has arisen over this question. Accord- 

 ing to Jacoby, von Kaufmann, Lewite and Sallinger [Berichte, 



1920, 53, 681), the supposed diastatic property of formaldehyde 

 may be explained by the fact that this compound forms a loose 

 addition compound with starch, whereby the physical pro- 

 perties of the latter are much altered, and it no longer gives 

 a blue colour with iodine ; the starch does not thereby undergo 



