Researches respecting the radical of Benzoic Acid. 



265 



filled with chloride of calcium, c, Fig. 2. is a glass tube about thir- 

 ty inches in length fastened above to the pump by a short and broad 

 piece of a tube, and dipping below in mercury. It has no other 



object than to prove by the rise of the mercury that all the con- 

 nections of cork and caoutchouc are tightly closed, and it is removed as 

 soon as the pump is put in operation. Indeed it may be dispensed 



