216 CHEMISTRY 



possessing a great affinity for oxygen. Absolutely pure, dry ethylether, 

 dissociation-point 550, contains a sufficient per cent of ethylidene 

 particles at ordinary temperatures to burn very slowly in dry oxygen ; 

 sodium ethylate, dissociation-point 250, on the other hand, being 

 dissociated to a far greater extent, burns with great violence in dry 

 air. Ethylalcohol, dissociation-point 650, is not capable of burning 

 in the air; if, however, we increase the per cent of ethylidene parti- 

 cles by means of catalytic agents, enzymes, platinum sponge, etc., 

 it, too, oxidizes readily, with incandescence with platinum sponge, 

 giving acetic acid. The aldehydes, RCH =0, as has long been known, 

 reduce Fehling's solution and silver solutions with great ease. This 



R 



is due to the presence of oxyalkylidene particles, /^\ which 



HO 



burn at the expense of the oxygen of the water. The discovery that 

 all primary and secondary alcohols reduce silver oxide to metallic- 

 silver in aqueous solution in the presence of caustic alkalies has only 

 very recently been made. The function of the alkali is obviously to 

 form first the metallic alcoholate, 



R H R H 



^C/ +MOH^ \C/ +H 2 0, 



R' OH R' OM 



which, having a far lower dissociation-point than the free alcohol, 

 causes a great increase in the per cent of alkylidene particles present ; 

 consequently the following reaction takes place, 



R R 



, etc., 



R' R' 



giving as the end result a fatty acid in the case of primary alcohols. 

 The most striking proof that ethylalcohol is dissociated only into 



H 



ethylidene and water, CH 3 CH <= CH 3 CH + H 2 0, i. e., contains 



OH 



no ethylene particles, is the following. Ethylalcohol, containing one 

 molecule of aqueous sodic hydrate, gives in the cold with potassium 

 permanganate solution practically acetic acid only. If any active 



ethylene particles were present, CH 3 CH 2 OH^CH 2 CH 2 + H 2 O, 

 these must necessarily, in view of the work of Wagner with olefines 

 and permanganate, be first converted by oxidation to ethyleneglycol, 



