312 Dr Smith on the Composition of the 



In this scheme, I have supposed the sulphuric acid to be 

 increased by -009 grain, in order to make it take up the 

 whole magnesia. The alkalies were determined together ; 

 but in the qualitative examination, potash was readily de- 

 tected in the residue of 1 gallon. 



The dry residue, obtained by evaporating the water, not 

 being deliquescent on exposure, the absence of earthy chlo- 

 rides was inferred. In the precipitate by ammonia from an 

 acid solution, the presence of lime and iron was detected, 

 but the proof of phosphoric acid was inconclusive. Operating 

 afterwards, however, on the solid contents of a much larger 

 quantity of water (about 15 gallons), this acid was shown 

 pretty distinctly. The dry residue of 1 gallon gave no in- 

 dication of nitric acid when tried with sulphuric acid and 

 sulphate of iron. Boiled with carbonate of soda, it gave 

 distinct proof of ammonia. 



The quantity of organic matter in specimen A was much 

 larger than the Dee water usually contains ; indeed the 

 brown tint caused by it was very well marked. A portion 

 kept in a glass bottle for some months, deposited a brownish 

 sediment, and became clearer. It was then found to contain 

 only 1 grain of matter volatile on ignition. A specimen (B) 

 taken from the same part of the river on the 15th of February 

 1851 — the river being of its usual size, and the water clear 

 and colourless — gave 3 grains per gallon of solid matter, of 

 which only r%tlis of a grain were volatilized by ignition. It 

 is in accordance with general experience that organic matter 

 in water is least abundant during the winter season. A 

 gallon (C) drawn from the laboratory pipe on the 26th of 

 September (the water being colourless), left the same quantity 

 of dry residue, and gave off about 0*8 grain on ignition. In 

 experiments at different times, I have thus found the solid 

 matter (dried at 212°) to vary from 3 to 4 grains per gallon ; 

 and the matter volatilized by a low red heat (generally 

 reckoned organic matter, though it probably always exceeds 

 the true organic matter in amount) to range from troths to 

 1| grains. 



