60] EXPERIMENTS ON WATER 2$ 



a rough indication of the * hardness ' or soap-destroying 

 power of the water. 



f. Ammonia in Water. — Take three test-tubes half 

 filled with the different kinds of water as before, and to each 

 add ten drops of Nessler's Solution. This is one of the most 

 delicate tests known to chemists, and should the smallest 

 trace of ammonia be present, the water to which the Ness- 

 ler's Solution (265) has been added will become coloured 

 yellow or brown, according to the amount of ammonia 

 present. So delicate is the test that distilled water, unless 

 it has been specially prepared, will contain sufficient ammo- 

 nia to show it. After the test-tubes have stood two or three 

 minutes notice their colour by holding them over a sheet 

 of white paper and looking down through the length of the 

 tube. The drainage water will be much more coloured 

 than the other two. As the most probable source of am- 

 monia in a natural water is decaying animal matter it will 

 be seen that it is very necessary that drinking water shall 

 contain as little of this substance as possible. 



