84 



VAPORIZATION. 



which the roots on the highest stage will part with, descends 

 and is still capable of abstracting a second quantity of moisture 

 from the roots on the next,, and so on, as it proceeds, till it 

 passes away into the chimney absolutely saturated with mois- 

 ture,, after having reached the bottom of the chamber. 



It is frequently an object to dry a small quantity of a sub- 

 stance most completely (such as an organic substance for analy- 

 sis) at some steady temperature,, such as 212. This is effected 

 by the following simple and elegant arrangement contrived by 

 M. Liebig. The substance to be dried is introduced,, (in the 

 state of a powder if possible) into a short glass cylinder #, 

 which may be three inches in length, and one and a half inch in 

 diameter, or any other convenient size, and of which the two 

 ends are terminated by open tubes, bent as represented in the 

 figure. The vessel a is immersed in a water-bath b, which may 



be kept boiling by a lamp below. One of the tubes from a is 

 connected by means of a short caoutchouc tube with the upper 

 stopcock s ? of a gas-holder ff, or any similar vessel, filled with 

 water. The lower opening h, of the gas-holder is left open, so 

 that water can escape by it in proportion as air is admitted by s, 

 which air must pass through a. The other tube from a is con- 

 nected with a wide glass tube c, of eight or ten inches in length, 

 containing fragments of fused chloride of calcium, in passing 

 through which the air is deprived of all moisture before it 

 reaches the substance in a. A regulated current of absolutely 

 dry air at 212 may thus be conducted over the substance to be 

 dried. 



