32 Estimations occurring in Agricultural Analysis [51 



Fig. 



understood from fig. 20. A wide-mouthed 4-oz. flask is 



fitted with an india-rubber stopper, through which are bored 



two holes. Through one is fitted a 



tube, a a, reaching close to the 



bottom of the flask ; through the 



other is placed another tube, b b, 



which terminates at one end just 



inside the stopper and at the other* 



after being bent three times at right 



angles, inside a calcium chloride 



tube, c. The outer ends of these 



two tubes are closed by pieces of 



india-rubber tubing, into which fit 



stoppers of glass rod. 



The apparatus is completed by placing a portion of a test 

 tube, e, inside the flask. This must be just so long that it 

 cannot lie down in the flask, but so short that the india-rubber 

 stopper may be inserted without 

 touching it. 



The tube c is filled with small 

 pieces of fused calcium chloride, 

 and the test tube, e, is filled three- 

 quarters full of hydrochloric acid, 1 

 part strong acid and 1 part distilled 

 water, and the apparatus is ready 

 for use. 



51. Schroeder's Apparatus. 

 — 2. Should this form be used, the 

 cistern d, fig. 21, is filled with hydro- 

 chloric acid 1 to 1, and the cis- 

 tern c is half filled with strong sulphuric acid, which dries the 

 effluent gas just as the calcium chloride does in the first 

 apparatus. The apparatus, whichever of the two it may be, 



Fig. 21. 



