44 PUBLIC HEALTH CHEMISTRY 



flask. This gets rid of any free or saline or albuminoid 

 ammonia in this added fluid. 



PROCESS. Take the residue from the estimation of 

 free and saline ammonia, and keeping it still in the flask, 

 add to it 50 c.c. of freshly-boiled permanganate solution, 

 and about 100 c.c. of ammonia-free distilled water, to 

 incfease the bulk. Some fragments of pumice stone, which 

 have been heated to redness in a Bunsen flame and cooled, 

 are also added. The apparatus is now fixed together 

 and distillation resumed, the distillate being collected as 

 before in 50 c.c. Nessler glasses. The determination of 

 the amount of ammonia is made in precisely the same 

 way as for free and saline ammonia. The number of lots 

 of 50 c.c. to be collected cannot be approximately stated, 

 as the splitting up of the organic matter occurs irregularly, 

 and in this way more ammonia may be found in the second 

 or third lot than in the first. The process should be 

 continued until no reaction with Nessler is got. In some 

 cases it may be necessary to stop the. process and allow 

 the apparatus to cool, then add more distilled water, 

 and then resume the distillation. The amount of ammonia 

 found is of course derived from the original 500 c.c., and 

 must be calculated accordingly. 



Free and saline ammonia represents the ammonia 

 combined with carbonic, nitric, or other acids, and also 

 what may be derived from urea, or other easily decom- 

 posable substances, if present. The limit in pure waters 

 is 0-002 mgr. per 100 c.c., and in a usable water it should 

 not exceed 0-005 m g r - P er I0 c.c. 



Albuminoid ammonia in drinking waters of good 

 quality should not exceed o-oi parts per 100,000. Much 

 albuminoid ammonia with a small amount of free ammonia 

 usually indicates vegetable contamination, particularly if 

 the chlorides and nitrates are low. Peaty waters yield 

 large quantities of albuminoid ammonia, which is slowly 

 evolved ; whereas badly polluted waters as a rule yield 

 their high proportion more rapidly. 



Oxygen Absorption or Consuming Power. Tidy's 

 process is based on the fact that much of the organic 

 matter in a water is capable of oxidation, and especially 

 by permanganate in acid solution. Unfortunately, different 



