44 Estimations occurring in Agricultural Analysis [66, 67 



only necessary to measure out 200 c.c. of the seminormal 

 solution into a litre flask and fill up to the mark with water. 

 Of course the new solution must be thoroughly mixed. The 

 seminormal solution of H 2 S0 4 is of very convenient strength 

 for nitrogen estimations, so that it must be remembered that 



50 c.c. potash solution correspond to 20 c.c. sulphuric 

 acid solution. 



ESTIMATION OF CHLORINE IN SOLUBLE 

 CHLORIDES 



66. Method. — A solution of silver nitrate is made of 

 known strength, and the volume required to precipitate the 

 whole of the chlorine as AgCl is noted. 



67. Preparation of Standard Silver Nitrate So- 

 lution. — Two watch glasses having ground edges and a clip 

 are weighed, and into one of them is introduced as nearly 

 as possible 17 grams of powdered pure silver nitrate. This 

 watch glass is then placed in the steam oven for half-an- 

 hour, allowed to cool in a desiccator, and then clipped to 

 the other watch glass. The two watch glasses, with clip 

 and dry nitrate of silver, are then weighed accurately. A 

 glass filter funnel is placed in the neck of a graduated litre 

 cylinder. The clip is taken off the watch glasses, and the 

 silver nitrate is washed with cold water down the funnel into 

 the cylinder. The glasses and funnels are well washed to free 

 them from any adhering silver nitrate, and the washings, which 

 should not exceed 300 c.c, allowed to run into the cylinder. 

 The solution is left standing until all the solid is dissolved. 

 The cylinder is then filled up to the 1000-c.c. mark with 

 distilled water. 



If exactly 1 7 grams have been taken, then the solution will 

 be decinormal ; but if it should be more or less, then a certain 



