ARGON, A NEW CONSTITUENT OF THE ATMOSPHERE. 9 



iiii[ir()bable that his residue was really of a ditt'ereiit ]<iiul iVoiii tiie main biillc of 

 the " plilogisticated air," and eoiitaiiied the gas now called argon. 



Cavendish gives data' from which it is possible to determine the rate of ab- 

 sorption of the mixed gases in his experiment. The electi-ical machine used "was 

 one of Ml'. Nairne's |)atent machines, the cylindei' of whi(di is 12-^ inches long, 

 and 7 in diameter. A conductor of 5 feet long and 6 inches in diameter was 

 adapted to it, and the ball which received the spaik was j)laced two or thi-ee inches 

 from another ball fixed to the end of the couductoi-. Now when the machine 

 worked well, Mr. Gil[)in supposes he got about two or tlii'ee hundred sparks a 

 minute, and the diminution of the aii; during the half houi' which he continued 

 working at a time, varied in general from -40 to 120 measures, but was usually 

 greatest when there was most air in the tube, provided the cpantity was not so 

 great as to prevent the spai'k from [lassing readily." The "measure" spoken of 

 represents the volume of one grain of quicksilvei', or 0.0048 c. c. ; so that an absoi'p- 

 tiou of one cubic centimetre of mixed gas per hour was about the most favorable, 

 rate. Of the mixed gas about two-fifths would be nitrogen. 



3. Methods of Causing Free Nitrogen to Combine. 



The concord between the determinations of density of nitrogen obtained from 

 sources other than the atmosphere having made it at least possible that some 

 heavier gas exists in the atmosphere, hitherto undetected, it became necessaiy to 

 submit atmospheric nitrogen to examination with the view of isolating, if possible, 

 the unknown and overlooked constituent, or it might be constituents. 



Nitrogen, however, is an element which does not easily enter into direct com- 

 bination with other elements ; but with certain elements, and under certain condi- 

 tions, combination may be induced. The elements which have been directly united 

 to nitrogen are (a) boron, (b) silicon, (c) titanium, (d) lithium, (e) strontium and 

 barium, (f) magnesium, (g) aluminum, (h) mercury, (i) hydrogen, and (k) oxygen, 

 the last two by help of an electrical discharge. 



(a) Nitride of horon was prepared by Wohler and Deville,^ by heating amor- 

 phous boron to a white heat in a current of nitrogen. Experiments were made to 

 test whether the i-eaction would take place in a tube of difficultly fusible glass ; 

 but it was found that the combination took place at a bright-red heat to only a 

 small extent, and that the boi'on, which had been })i'e[)aied by heating powdered 

 boron oxide with magnesium dust, was only superficially attacked. Boi'on is there- 

 fore not a convenient absorbent for nitrogen. 



' Philosophical Transactions, vol. LXXVIII, p. 271, 1788. ' Annaks de Chemie (3), 52, p. 82. 



