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XXIII. —ON A NEW FORM OF APPARATUS FOR ESTI- 

 MATING AMMONIA IN POTABLE WATERS, by C. R 

 TICHBORNE, ll.d., f.c.s. &c. 



[Read, February 20th, 1882.] 



According to the generally accepted method of examining 

 potable waters, the estimation of minute traces of ammonia 

 existing as such, and the ammonia which results from the 

 oxidation of nitrogenous organic matter, are looked upon as 

 being of the greatest importance in arriving at a conclusion as 

 regards the quality of the water. The process maj" be concisely 

 described as distilling off a third of the water, and estimat- 

 ing tlie ammonia in the distillate by Nessler's delicate process, 

 which leaves nothing to be desired as regards its accuracy. 



As the amount to be determined does not much exceed one 

 part in ten million parts, it is evident that it is necessary to 

 avoid any accidental contamination from atmospheric ammonia. 

 This is particularly the case in chemical laboratories, where 

 ammoniacal solutions are constantly undergoing evaporation, 

 and the air is contaminated with that volatile base. 



The fact is, of course, well recognised by all expert analysts, 

 and is generally guarded against by the use of a special cup- 

 board or chamber, in which the whole operation can be per- 

 formed. Such a method is more or less imperfect, because the 

 gas-burner used will itself, under certain conditions, become a 

 source of ammonia. Also, it is evident that a general ammoniacal 

 atmosphere in the adjacent laboratory will find its way into the 

 chamber by the ordinary laws of diffusion. 



The capacity of the vapour of water (when in the act of con- 

 densing) of absorbing traces of ammonia is something extraor- 

 dinarj", and can only be appreciated by the practical worker. 



In distilling potable waters, I was accustomed to work with 

 an ordinary retort and receiver — the latter being provided with 

 a specially-contrived mercurial valve. Now, although this was 

 satisfactory in closing the interior of the retort and receiver from 

 general contact with atmospheric impurities, occasionally a 

 regurgitation would take place, and admitted a little of the 

 laboratory air. 



