48o 
F. L. PICKETT 
(B) leading into C determines the volume of air available. In the 
present work D = i m., B = 2.5 m., and two of the latter were 
used to keep three sets of apparatus running. Tubes of the number 
Fig. I. Desiccation apparatus. A BCD, pump for securing positive air- 
pressure. W, inlet from water main, PS, pump to furnish negative pressure. 
E, first drier filled with filter paper saturated with glycerine. H, O, checks filled 
with fused calcium chloride. F-G, glycerine desiccator and tubes. I-K, sulphuric 
acid desiccator and tubes with cooling jar about Winkler's tube. L-0, calcium 
chloride desiccator and tubes. (X 1/12.) 
and dimensions given furnish abundant pressure and volume for easy 
control. Negative pressure was secured by using the pump PS 
