Odidizable Variety of JSitrogen. 413 



The chief interest of the work consisted in a comparison 

 of the gases obtained from the ozonizer and spark-gaps 

 separately with the " combined " gas obtained by using both 

 forms of discharge, in accordance with a process devised by 

 Mr. Sydney Leetham, of York, in 1903. At the time when 

 the experiments were made the bleaching gases manufactured, 

 by this process were usually obtained by blowing air at the 

 rate of about 70 c.f.m. through one of the ozonizers and then 

 through a box in which 3 spark-gaps were energized in series 

 with the ozonizer by an alternating current of O'l ampere 

 at 9000 volts. Other arrangements were, however, described, 

 and some of these were tested by the spectroscopic method. 



The spectroscopic apparatus consisted of three parts : 



(1) A wooden trunk 64 feet in length and 3 in. x 3 in. 

 in section, the volume being thus about 4 cubic feet. The 

 trunk was provided with glass windows at each end, and 

 inlet and outlet pipes were provided for the gases under 

 examination. The effective length of the trunk could also 

 be reduced to 16 feet by inserting a glass slide and using an 

 additional " blow-off" hole so that the gas was confined to 

 the earlier portion of the trunk. 



(2) A Nernst lamp with filament vertical served as a 

 source of light. It was placed in the focus of a condensing 

 lens of 3^ in. focal length, fixed immediately in front of one 

 of the glass windows. At the other end of the trunk the 

 light was picked up again by a condensing lens of 11 in. focus, 

 but on account of the great length of the trunk the image 

 formed by the second lens was circular in form, all the light 

 from the upper and lower portions of the filament being lost 

 against the sides of the trunk, so that the effective illumi- 

 nation was derived only from a minute portion in the centre 

 of the filament. 



(3) The spectroscope was provided with achromatic quartz- 

 calcite lenses of 13 in. focus, but when it was desired to photo- 

 graph the spectrum a camera with a lens of 22 in. focus was 

 used. W ratten and Wainwright's "panchromatic plates" 

 were used with six minutes' exposure and two minutes' 

 development in the dark. 



The exposures shown in Plate VIII. at once revealed the fact 

 that, whilst the ozonizer and spark-gaps separately produced 

 no visible absorption, the flutings characteristic of nitrogen 

 peroxide could be recognized clearly in the spectrum which 

 had been photographed through the " combined " gas. The 

 copper spectrum shown at the bottom of the plate served for 

 calibration, the two yellow and three green lines being 

 clearly seen at one end and two violet lines at the other end 

 of the spectrum. 



