Young — Vapour-Pressures^ ifc, of Thirty Fure Substances. 391 



cotton-wool; and the lower extremity of the glass tube is drawn out and 

 bent round so that the narrow end just touches the cotton-wool. 



The liquid to be investigated is placed in the reservoir ; and the apparatus 

 is exhausted. A little liquid is then admitted so as to moisten the cotton- 



wool. The condensing bulb is then cooled ; and the vertical tube is heated by 

 means of a water- or oil-bath, which sliould always be kept at a temperature 

 at least 20*^ higher than that registered by the thermometer. 



The liquid on the cotton- wool evaporates rapidly, and displaces the air in 

 the lower part of the vertical tube, so that the remaining liquid is soon 



3b2 



