/ 



341] Analysis of Water for Drinking Purposes 203 



Alkaline Permanganate Solution. Boil together in a large 

 basin 200 grams of caustic potash, 8 grams of potassic per- 

 manganate, and a litre of water until the solids are completely 

 dissolved. This should be kept in a well-stoppered Winchester 

 quart bottle. 



Standard Ammonium Chloride Solutions. Two solutions 

 are usually prepared, one ten times as strong as the other. 

 Dissolve -117 (really -11688) gram of pure crystallised NH 4 C1 

 in a little water, and make up to 500 c.c. with ammonia- 

 free water. Label the bottle containing this ' Strong NH 4 C1 

 solution.' One c.c. will contain -000074 gram of NH 3 , or, 

 when the ammonia is estimated in 500 c.c. of water, 1 c.c. 

 = -oi grain of NH 3 per gallon. For the ' weak solution ' 

 take 50 c.c. of this strong one, and dilute to 500 c.c. The 

 NH 4 C1 should be tested by estimating the nitrogen therein. 



Water Free from Ammonia. It may happen that the ordi- 

 nary distilled water supplied in the laboratory is free from am- 

 monia. This may be tested by nearly filling a testing cylinder 

 with the water, adding 2 c.c. of Nessler's solution, and stir- 

 ring. If, after standing for five minutes, no yellow colouration 

 appears in the water, it is sufficiently pure for use. Should the 

 slightest pink, brown, or yellow appear, the water must be 

 re-distilled as follows : 



Place as much of the water as can conveniently be boiled 

 in a large flask. Add about a gram of recently ignited soda 

 crystals. Connect with a condenser, and distil. Test 20 c.c, 

 of the distillate from time to time for ammonia. As soon as 

 no further ammonia comes over, collect the water in a clean 

 Winchester and keep it very carefully stoppered. In this 

 operation it is very necessary to use soda crystals ; as the 

 bicarbonate always contains ammonia, often in considerable 

 quantities. 



341. Free Ammonia. — Place 50 c.c. of the water 



