342,343] Analysis of Water for Drinking Purposes 205 



By the time this test is finished another 50 c.c. will have 

 distilled over. The ammonia in this must be estimated in the 

 same way. The third 50 c.c. will probably contain no ammonia. 

 If it should, it must be estimated, and all the results added 

 together. 



342. Albuminoid Ammonia.— The solution of 'alkaline 

 permanganate ' whose preparation was described in paragraph 

 340 will act on organic matter, liberating the nitrogen, mostly 

 in the form of ammonia. This ammonia is known as ! albuminoid 

 ammonia.' 



To the liquid left in the flask after the last operation add 

 50 c.c. of the alkaline permanganate ; distil, and estimate the 

 ammonia in each 50 c.c. of the distillate, exactly as in para- 

 graph 341, until it ceases passing over. When the water is 

 being distilled with alkaline permanganate it shows a great 

 tendency to ' bump.' This can be lessened by putting a few 

 pieces of clean platinum wire in the flask. 



343- Estimation of Oxygen consumed by Organic 

 Matter. — In the absence of nitrites, sulphuretted hydrogen, or 

 other inorganic reducing agents, a very good idea of the 

 amount of organic matter in the water may be obtained by the 

 action of a standard solution of potassium permanganate on the 

 acidified water. 



Permanganate Solution. Weigh out accurately '395 gram 

 of pure permanganate of potash \ dissolve in water, and 

 make up to a litre. Each c.c. of this solution will contain 

 •0001 gram of available oxygen, or, as is very frequently 

 assumed in stating results, 1 c.c. of the solution corresponds to 

 •0008 gram of organic matter. 



Sodium Thiosulphate Solution. Dissolve 10 grams of sodium 

 thiosulphate in a litre of water. This solution alters in 

 strength when it is kept for some time, but as it is standardised 

 whenever it is used, the alteration is of no consequence. For 



