624 SEC. 13. CHEMISTRY. 



into the tube K, through the cup and stop-cock. The lower end of the tube 

 is now firmly closed by the thumb, and the contents violently agitated by a 

 simultaneous vertical and lateral movement, in such a manner as always* to 

 leave an unbroken column of mercury, at least an inch long, between the acid 

 liquid and the thumb. In about a minute from the commencement of the 

 agitation a strong pressure begins to be felt against the thumb of the operator, 

 and mercury spurts out in minute streams as nitric oxicle gas is evolved. In 

 from three to five minutes the re-action is completed, and th nitric oxide 

 evolved must then be transferred for measurement to the apparatus No. 2 I. 

 The volume of the nitric oxide so measured is exactly equal to that of the 

 nitrogen as nitrates and nitrites contained in one litre of the water. 



2455. Apparatus for the Analysis of Gases. 



E. Franktand, F.R.S. 



Several of the mechanical arrangements of this apparatus were first cm- 

 ployed in an instrument invented by Messrs, llcgnault and Keiset, but the 

 principles involved in the determination of the gaseous volumes are different 

 in the two instruments. 



The apparatus, which is represented by the accompanying figure, consists 

 of the tripod A furnished with the usual levelling screws, and carrying the 

 vertical pillar 15, B, to which is attached, on the one side, the movable 

 mercury trough C, of gutta percha, with its rack and pinion a, a, and on the 

 other, the glass cylinder 1), D, with its contents. This cylinder is 36 inches 

 long and 3 inches in diameter, its lower extremity is cemented into an iron 

 collar, c, the under surface of which can be screwed perfectly water-tight 

 upon the bracket-plate, d, "by the interposition of a vulcanised caoutchouc 

 ring. The circular iron plate d is perforated with two large apertures for the 

 passage of the tubes E and F, besides a smaller one into which the brass 

 cock b is screwed. E is a glass tube of uniform bore, and about 18 mm. 

 internal diameter, and marked with 10 divisions equidistant from each other. 

 It serves to contain the gas during measurement. Its upper extremity 

 terminates in the capillary tube e, which carries a glass stop-cock, and is 

 cemented into the steel cap /in such a way as to exclude any air space. For 

 the passage of the electric spark, two platinum wires are fused into E at g 

 At its lower extremity the tube E, after passing water-tight through a 

 caoutchouc cork in the plate d, is connected with the junction piece h. 



F is a second glass tube only 5 mm. internal diameter, graduated with a 

 millimeti'e scale throughout its entire length, and reaching to a height of 

 about 8 inches above the glass cylinder. It is furnished at top with a small 

 funnel, i, into the neck of which a glass stopper, about 2 mm. in ditimeter is 

 carefully ground. In this tube the pressure of the gas in E is measured. 

 Like E, it also passes water-tight through the plate d, and is connected with 

 the junction piece h, which is furnished with a stop-cock, and is continued to 

 the floor, where it is connected by a long caoutchouc tube with the glass 

 mercury reservoir G. The caoutchouc tube is 3 mm. internal diameter, and 

 is strengthened by a jacket of tape to enable it to withstand the pressure of 

 mercury] The reservoir G can be raised or lowered by the cord and pulley 

 /e, /. H is an absorption tube, in which the gases are brought into contact 

 with various liquid or solid re-agents. It is supported on the clamp o, and 

 connected with the capillary tube e, by the cap and junction clamp p. 



The tubes E, F, are held firmly in position by the clamp m, which is screwed 

 to the under side of the plate d. 



Before using the apparatus, the cylinder D, D is filled with Avater through 

 the cock b, and a slow stream is afterwards established through the syphon 

 n, one leg of which encloses the upper part of the tube F. The internal walls 



