Identification of Organic Compounds. 29 



drying tube. During the process the copper oxide is 

 partially reduced to copper, which is reoxidized during 

 the passage of oxygen. 



This process consists essentially in the oxidation of all 

 the carbon to carbon dioxide, and of all the hydrogen to 

 water, and the amounts of these products formed from a 

 given weight of substance are weighed. 



In the more modern method due to Dennstedt, the 

 copper oxide is dispensed with, but the substance is burnt 

 in a current of oxygen instead of air, and the combustion 

 is promoted by the presence of a " contact substance " * 

 made from platinized quartz, or from platinum itself, 

 which promotes the oxidation of the volatile substances 

 produced when the organic substance is charred (see 

 Fig. 9). A form of furnace simpler than the older Liebig 



Fig. 9. 



apparatus can be employed when this process is used. 

 The method is illustrated by the accompanying figures. 

 The oxygen is passed from the gasholder B (Fig. 10) by 

 displacement of water contained in the bottle A, both of 

 which have a content of about five litres, through a 

 purifying tower, containing in the bottom concentrated 

 sulphuric acid, and in the upper part of the tower, first, a 

 layer of soda-lime, and above this a layer of calcium 

 chloride. In this way it can be completely freed from 

 moisture and carbon dioxide. Three special burners are 

 employed, one for heating the substance ; a second, for 

 the platinum star ; and a third, consisting of a number of 

 small jets, for the front part of the tube. The weighed 



* The action of substances which act catalytically will be discussed later. 



