400 



STATE BOARD OF AGRICULTURE 



APPARATUS 



The electrometric titration apparatus used for this work consisted 

 of the following named units connected as illustrated in Fig. 1. 



Go,. 



.^ 



vwww 



7? 



Fig. 1. — Diagram showing arrangement of apparatus. 



Fig. 1 — P — Leeds and Northrup Students' Potentiometer 

 R — Plug Resistance, 11, 110 ohms capacity 

 Ba — 2 Columbia Dry Cells 

 G — Galvanometer, D'Arsonval, wall type 

 S. C. — Weston Standard Cell 

 C. E. — Wendt's Calomel Electrode Vessel 

 H. E. — ^Wendt's Hydrogen Electrode 



Jelly tumblers were used for containers for hydrogen ion concentra- 

 tion determinations on the materials under investigation. Covers of 

 these containers were coated with parafin and used to prevent evapora- 

 tion and contamination of the solutions during the time of standing. 

 Stirring was accomplished by means of a bent glass rod actuated by a 

 Cenco Friction Drive, Variable Speed, Motor Stirrer with a flexible 

 shaft. Hydrogen was generated from C. P. stick zinc and hydrochloric 

 acid and washed through a solution of potassium hydroxid and pyro- 

 gallic acid and finally through distilled water. The flow of hydrogen 

 was regulated with a Hofl'man pinch cock. An elevated bottled con- 



