288 On the Estimation of Ammonia in Atmospheric Air, [Mar. 17, 



In the immediate vicinity of towns some of the ammonia must also be in 

 the form of sulphate, sulphite, or ammonium chloride. 



(1) Air taken from town. (Taken at a height of 2 metres from ground.) 



(XH 4 \ 2 C0 3 as grammes (^H 4 ) 2 C0 3 in parts 



Date of Experiment. per 100.000 litres of air by weight per 



at 0° C. and 760 mm. baroni. 100,000 of air. 



1S69. September 30 1*1294 -8732 



October 4 -62117 *480i 



6 -5251 -4059 



8 -62117 -4801 



November 26 1-0729 '8293 



28 1-1000 8503 



(2) Air from country. (Taken at a height of 2 metres.) 



C0 3 as grammes (XH 4 Y, C0 3 in parts 

 Date of Experiment. per 100,000 litres of air per "l 00, 000 of 



at 0 : C. and 780 mm. barom. air. 



1869. December 6 -7620 -5890 



8 -7826 -6085 



9 -6601 -5102 



11 -6635 -5121 



1870. February 12 -7639 -5904 



The direction of the wind doe3 not seem to have any influence on the 

 ammonia found ; immediately after heavy rain, however, the quantity falls 

 somewhat below the average, but the air is again restored to its normal 

 condition after a lapse of two or three hours. 



Attempts were made to make the method more delicate still by absorbing 

 the ammonia in pure water and then distilling, but the nitrogenous organic 

 matter suspended in the air was found to interfere with the results. 



"When the air is passed through cotton-wool before entering the absorp- 

 tion-tubes, it is found to be entirely deprived of its ammonia by the filter. 

 This is also the case with air artificially charged with ammonia to a targe 

 extent. This absorption is not due to the presence of hygroscopic mois- 

 ture, since cotton-wool, when absolutely dry, is capable of taking up 115 

 times its own bulk of dry ammonia (confined over mercury) at \0°'o C. 

 and 7 00' 7 millims. barom., the gas being again slowly evolved when the 

 wool is left in contact with the air at 100° C. 



All other porous substances that were tried for filtering agents were 

 found to possess this property more or less ; even freshly ignited pumice- 

 stone is not entirely without absorptive effect upon the gas. 



