4-IO AGRICULTURAL ANALYSIS 



delivery tube with mercury. 44 The apparatus is arranged as 

 shown in Fig. 25. The flask in which the decomposition takes 

 place is provided with a long neck, into which a side tube is 

 sealed and bent upwards, carrying a small funnel attached to it 

 by rubber tubing. The piece of rubber tubing carries a pinch- 

 cock, by means of which the solution containing the nitrate and 

 hydrochloric acid can be introduced into the flask. The small 

 gas delivery tube is arranged as shown in the figure, and carries 

 at the end next the burette a device shown in Fig. 26. The cork 

 represented in this device has radial notches cut in it, so as to 

 permit of a free communication between the water in the burette 

 and in the pneumatic trough. The open end of the burette, when 

 the apparatus is mounted ready for use, rests on the notched sur- 



Fig. 26. End of Delivery Tube. 



face of the cork, and the end of the delivery tube is placed in the 

 crystallizing dish resting on the bottom of the pneumatic trough. 



The end of the delivery tube, as indicated, has fused to it a 

 vertical tube, open at both ends and from six to seven centimeters 

 in length, and carrying the notched cork already described. The 

 crystallizing dish in the bottom of the pneumatic trough is filled 

 with mercury until the point of union of the delivery tube with 

 the vertical end is sealed to the depth of a few millimeters. As 

 the gas is evolved it bubbles up through the mercury into the 

 measuring tube and the displaced water passes out through the 

 notches in the cork. Should any back pressure supervene, the 

 mercury at once rises in the delivery tube, which is of such a 

 length as to prevent its entrance into the flask. The operation 

 can then be carried on with absolute safety. 



To make an estimation, there are placed in the flask about 

 44 Zeitschrift fur analytische Chemie, 1894, 33 : 200. 



