A NEW TYPE OF ENTOMOLOGICAL KILLING-BOTTLE. 285 



pour out the surplus chloroform from the upper surface of the cork. None of the 

 chloroform in the space below will escape, owing to the air pressure at the upper 

 open end of the glass tubing. Gently warm the sides of the tube above the cork 

 to drive off any remnants of liquid chloroform, and when an ordinary cork has 

 been fitted, we have an apparatus similar to that shown in fig. 1. 



Although pure rubber is soluble in chloroform, it will be found that the compound 

 from which the rubber corks (red variety) are made, swells when in contact with 

 chloroform but will not dissolve. 



The following are the advantages of the apparatus : — (1) A high concentration 

 of chloroform vapour is always available ; (2) if the tube is accidentally broken 

 there is no danger of poisoning ; (3) 5 cc. of chloroform is sufficient for a week's 

 continuous use, and the tube is therefore exceedingly economical. 



Care should, however, be taken that the lower end of the tube containing the 

 chloroform be not unduly heated by the hand, otherwise gaseous pressure will 

 force the liquid up the central glass tubing. Should this occur at any time it is only 

 necessary to shake out the few drops of liquid at the upper end of the cork, and 

 blow into the tube to dry the cork surface. If the tube is inverted, no amount 

 of overheating will do more harm than to dissipate the chloroform to some extent, 

 and for this reason it should be carried in this position. The open lower end of 

 the glass tubing then stands above the surface of the liquid chloroform, and the 

 apparatus is " sealed." 



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