662 LABORATORY HINTS 



Certificate of Analysis of a Sample of Water. 



Date received : 



From : 



Particulars on label : London tap water. Taken at Laboratory 



Physical characters : 



Colour in 2 ft. stratum : clear pale blue. 



Suspended matters : nil. 



Taste. 



Odour when warmed to 37° C. : nil. 



Reaction : alkaline. 

 Chemical characters : — 



Total solids dried at loo*^ C... 



Loss on ignition (after recarbonating) 



Chlorine... 



Chlorine x 1,647 — sodium chloride 



Nitrites (as N2O3) 



Nitrogen as nitrates ... 



Saline ammonia 



Albuminoid ammonia ... 



Oxygen absorbed in 3 hours at 37° C. 



Hardness — Total 



„ — Temporary 



,, — Permanent 

 Poisonous metals — lead 



!> —copper 



,, — iron 



TO EXAMINE SEWAGE AND SEWAGE EFFLUENTS. 



The same processes as for water with a few modifications. 

 The Ammonias. 



Dilute sewage five times when estimating the ammonias. 

 Make 100 c.c. up to 500 c.c. with ammonia-free water. 

 When distilling collect 200 c.c, mix well, Nesslerize, and multiply 

 the result by 4. 



It is best to collect 50 c.c. more to see that no more ammonia 

 remains. 



The Solids in Suspension. 

 The estimation of these is required. 



Filter 1,000 c.c. of the effluent through a weighed filter paper. 

 Wash and dry the residue and weigh again. 

 The Rate of O, Absorption after Filtration. 



Do this as for estimating the aeration of water, p. 661, but tested 

 at different times : — 



O, absorbed in four hours at 60° F. 



O, absorbed in twentv-four hours at 60° F. 



O2 absorbed in forty-eight hours at 60° F. 



O, absorbed in five days. 



