VAPORIZATION. 



the condensing tube of Professor Liebig, (Figure 2). This is 

 a plain glass tube, 1 1 about eighteen inches in length, and two- 



FIG. 2. 



thirds of an inch internal diameter, which is enclosed in a larger 

 tube b, of brass or tin-plate, about twelve inches long and two 

 inches in diameter, the ends of which are closed by perfor- 

 ated corks. A constant supply of cold condensing water from 

 a vessel a is introduced into the space between the two tubes, 

 being conveyed to the lower part of the instrument by the fun- 

 nel and tube /, and flowing out from the upper part by the 

 tube g. The condensed liquid drops quite cool from the lower 

 extremity of the glass tube, where a vessel is placed to re- 

 ceive it. This is an admirable apparatus, and ought to super- 

 sede all other means of condensation in the laboratory. The 

 spiral copper tube or worm which is used for condensing in 

 the common still, is commonly made longer than is necessary, 

 and from its form cannot be examined and cleaned like a straight 

 tube. Much vapour may be condensed by a small extent of surface, 

 provided it is kept cold by an ample supply of condensing 

 water. 



FIG. 3. Both the outer and in- 



ner tube may be of glass 

 in the condensing appa- 

 ratus which has been 

 described, and then the 

 small tubes to bring and 



