204 Water Analysis [341 



under examination in a cylinder of clear glass standing on a 

 white tile, and add 2 c.c. of Nessler's solution. Allow it to stand 

 five minutes. Meanwhile, place in another similar cylinder 

 50 c.c. of ammonia-free water. Add from a burette *i c.c. of 

 'dilute' NH 4 C1 solution, and treat with Nessler as before. 

 Should the colouration in the two cylinders be about the same, 

 500 c.c. of water must be used for the determination. Should 

 it be darker in the first cylinder, less must be used. 



Fit up a flask and Liebig's condenser of the form ordinarily 

 used for distilling. The condenser is usually made with a 

 glass inner tube. In many laboratories a block tin tube is 

 preferred on account of the superior conductivity of the metal, 

 which allows of a much shorter condenser being used, and 

 thus economises space. Pour into the flask about 250 c.c. 

 of ammonia-free water, and add a gram of freshly ignited soda 

 crystals. Distil for a few minutes to wash the apparatus, 

 testing the distillate a little at a time with Nessler's solution, 

 until it is quite free from ammonia. Now pour 500 c.c. of the 

 water undergoing analysis into the flask, and distil, collecting 

 the distillate in a cylinder. When 50 c.c has collected, change 

 the cylinder for a fresh one, and estimate the ammonia in the 

 50 c.c. of distillate as follows : Add 2 c.c. of Nessler's solution, 

 and place on a white tile. Now make a comparison cylinder 

 by running '2 c.c. of 'weak' NH 4 C1 from a burette into 50 c.c. of 

 ammonia- free water in a clean cylinder. Add 2 c.c. of Nessler, 

 and stir. Place the two cylinders side by side, and compare. 

 Should the comparison cylinder show the fainter colour, a fresh 

 one must be made, using rather more NH 4 C1. On no account 

 must a further amount of NH 4 C1 be run into the liquid con- 

 taining Nessler's solution. By making up several comparison 

 cylinders one will be found of the same tint as the distillate. 

 The amount of NH 4 C1 solution in this is noted, as the two 

 cylinders will then contain equal quantities of ammonia. 



