1895.] Argon, a new Constituent of the Atmosphere. 275 



but this was partly compensated for by an improved vacuum. Two 

 experiments were made under the new conditions, in which the excess 

 was I, 0-0037 ; II, 0'0033. 



The excess being larger than before is doubtless due to the greater 

 efficiency of the atmolysing apparatus. It should be mentioned that 

 the above recorded experiments include all that have been tried, and 

 the conclusion seems inevitable that " atmospheric nitrogen " is a 

 mixture, and not a simple body. 



It was hoped that the concentration of the heavier constituent 

 would be sufficient to facilitate its preparation in a pure state by 

 the use of prepared air in substitution for ordinary air in the 

 oxygen apparatus. The advance of 3J milligrams on the 11 milli- 

 grams, by which atmospheric nitrogen is heavier than chemical 

 nitrogen, is indeed not to be despised, and the use of prepared air 

 would be convenient if the diffusion apparatus could be set up on 

 a large scale and be made thoroughly self-acting. 



VII. Negative Experiments to prove that Argon is not derived from 

 Nitrogen from Chemical Sources-. 



Although the evidence of the existence of argon in the atmosphere, 

 derived from the comparison of densities of atmospheric and chemical 

 nitrogen and from the diffusion experiments (. VI), appeared over- 

 whelming, we have thought it undesirable to shrink from any labonr 

 that would tend to complete the verification. With this object in 

 view, an experiment was undertaken and carried to a conclusion on 

 November 13, in which 3 litres of chemical nitrogen, prepared from 

 ammonium nitrite, were treated with oxygen in precisely the manner 

 in which atmospheric nitrogen had been found to yield a residue of 

 argon. The gas remaining at the close of the large scale opera- 

 tions was worked up as usual with battery and coil until the spec- 

 trum showed only slight traces of the nitrogen lines. When cold, 

 the residue measured 4 c.c. This was transferred, and after treat- 

 ment with alkaline pyrogallate to remove oxygen measured 3'3 c.c. 

 If atmospheric nitrogen had been employed, the final residue should 

 have been about 30 c.c. Of the 3'3 c.c. actually left, a part is 

 accounted for by an accident, and the result of the experiment is to 

 show that argon is not formed by sparking a mixture of oxygen 

 and chemical nitrogen. 



In a second experiment of the same kind 5660 c.c. of nitrogen 

 from ammonium nitrite was treated with oxygen. The final residue 

 was 3'5 c.c., and was found to consist mainly of argon. 



The source of the residual argon is to be sought in the water 

 used for the manipulation of the large quantities of gas (6 litres of 

 nitrogen and 11 litres of oxygen) employed. When carbonic acid 



