ETHERS AND ESTERS. 521 



with a tube, leading through a suitable cooler, in order to condense 

 the highly volatile product of the distillation. 



Experiment 60. Mix 100 grammes of alcohol with 180 grammes of ordinary 

 sulphuric acid, allow to stand and pour the cooled mixture into a flask which 

 is provided with a perforated cork through which pass a thermometer and a 

 bent glass tube leading to a Liebig's condenser. Apply heat and notice that 

 the liquid commences to boil at about 140 C. (284 F.). Distil about 50 c.c., 

 pour this liquid into a stoppered bottle and add an equal volume of water. 

 Ethyl ether will separate into a distinct layer over the water, and may be 

 removed by means of a pipette. Eepeat the washing with water, add to the 

 ether thus freed from alcohol a little calcium chloride and distil it from a dry 

 flask, standing in a water-bath. The greatest care should be exercised and the 

 neighborhood of flames avoided in working with ether, on account of its 

 volatility and the inflammability of its vapors. 



The apparatus described above for etherification can be constructed so as to 

 make the process continuous. This may be done by using with the boiling- 

 flask a cork with a third aperture through which a glass tube passes into the 

 liquid. The other end of the tube is connected by means of rubber tubing 

 with a vessel filled with alcohol and standing somewhat above the flask. As 

 soon as distillation commences alcohol is allowed to flow into the flask at a 

 rate equal to that of the distillation, keeping the temperature at about 140 C. 

 (284 F.). The flow of alcohol is regulated by a stop-cock. 



The action of sulphuric acid upon alcohol is not quite so simple as 

 described above in connection with the general methods for obtaining 

 ethers, where the final result only was given An intermediate pro- 

 duct, known as ethyl sulphuric acid or sulpho-vinic acid, is formed, 

 which, by acting upon another molecule of alcohol, forms sulphuric 

 acid and ether, which latter is volatilized as soon as formed. The 

 decomposition is shown by the equations : 



C 2 H 5 OH 



Su 

 acid. 



C 2 H 5 OH = (C 2 H 5 ) 2 



Alcohol. Sulphuric Ethyl-sulphuric 



acid. 



Ethyl-sulphuric Alcohol. Ether. Sulphuric 



acid. acid. 



The liberated sulphuric acid at once attacks another molecule of alcohol, 

 again forming ethyl-sulphuric acid, which is again decomposed, etc. Theo- 

 retically, a given quantity of sulphuric acid should be capable, therefore, of 

 converting any quantity of alcohol into ether ; practically, however, this is not 

 the case, because secondary reactions take place simultaneously, and because the 

 water which is constantly formed does not all distil with the ether, and there- 

 fore dilutes the acid to such an extent that it no longer acts upon the alcohol. 



Ether thus obtained is not pure, but contains water, alcohol, sulphurous and 

 sulphuric acids, etc. ; it is purified by mixing it with chloride and oxide of 

 calcium, pouring off the clear liquid and distilling it. 



