58 



PROXIMATE CONSTITUENTS OF SOILS 



tion may conveniently be carried out in Schrotter's 

 apparatus (Fig. ii), which consists essentially of a 

 flask with three openings. A is closed with a glass 

 stopper and is used for introducing the material. B is 

 in reality a tap-funnel, used for running in the dilute 



acid, the delivery tube 

 being extended and bent 

 round to prevent splash- 

 ing. The outlet tube C 

 is half-filled with con- 

 centrated sulphuric acid, 

 which thoroughly dries 

 the liberated carbon di- 

 oxide before allowing it 

 to escape. 



Procedure. — The 

 dropping funnel B is 

 filled with dilute nitric 

 acid and the apparatus 

 weighed. About i gram 

 of the carbonate is in- 

 troduced into the flask, 

 the stoppers are inserted, 

 and the apparatus again 

 weighed. Acid from the 

 funnel is now slowly 

 admitted, so that the 

 liberated COg escapes in single bubbles, which pass 

 through the drying tube at a rate of about two per 

 second. When the evolution of the carbon dioxide 

 has ceased, the remainder of the acid is run in, the 

 tap left open,* and the tube of the drying apparatus 

 connected to an aspirator of some sort, or simply sucked 

 carefully with the mouth. During aspiration, which 

 must not be too long continued, the apparatus and its 



Fig. II. — Schrotter's apparatus for 

 estimating carbonates. 



