322 



takes place, lies between 300 — 400°, dependent on I lie nature of 

 the catalysing substance; when the temperature is raised to about 

 400° and higher, the formation of aldehyde becomes prominent even 

 in the presence of substances like aluminium oxide and other catalysts 

 that split off water. 



It is well known that reaction (II) is reversible — aldehydes 

 can be smoothly reduced with molecular hydrogen over nickel — 

 but uothing is known about the reversibility of reaction (1). 



In the extensive literature on the splitting u|» of alcohols into 

 olefine and water, the (piestion whether direct addition of water to 

 the double bond in ethylene and propylene is actually possible, has 

 never been examined. We have carried out a number of experiments 

 to answer this question. A mixture of ethylene and water-vapour 

 was led over different contact-substances at a temperature between 

 300° and 400° C. On use of aluminiumhydroxyde or of aluminium 

 sulphate as catalysts, the reaction product contained acetaldehyde. 

 We have proved the presence of acetaldehyde by the usual reactions 

 (reduction of an ammouiacal solution of silver hydroxide); Schipf's 

 reaction; reaction with nitro-prussidsodium and piperidine according 

 to Levvin) and also isolated as p-nitrophenylhydrazone. The quantities 

 of acetaldehyde are very small; by far the greater part of the ethylene 

 remains unchanged during the experiment. The quantity of acetal- 

 dehyde amounted to from 0,2 to 0,4 '/o ^' 350° — 360°, calculated 

 to the quantity of ethylene. 



The presence of alcohol could not be verified "). 



In our opinion the formation of acetaldehyde must be explained 

 in this way that primarily ethylalcohol is formed through addition 

 of water to ethylene, and then acetaldehyde through splitting up of 

 hydrogen. If this .second reaction proceeds much more lapidly than 

 the addition of water to the double bond, no alcohol will be found 

 in the reaction product. As at 350° — 360° ethyl-alcohol is almost 

 quantitatively decomposed into ethylene and water (at this temperature, 

 however, a little hydrogen is also formed) it is clear that only 

 at a lower temperature the inverse reaction can take |)lace in a 

 considerable degree. We have, however, not succeeded in finding 

 a catalyst that causes the addition of water to ethylene below 300°. 



We have proved by means of a separate experiment that no acetal- 

 dehyde is formed from mixtures of dry ethylene with about lO'/, 

 of air at 360° over aluminiumoxide. It, therefore, appears from 



') The analytical particulars will be given later, as also the full description of 

 the arrangement of the experiments, 



