lOO 
Therefore the amount of hydrogen that must be present 
in nitrogen in order that the green band in its spectrum 
may be observed in the spectroscope is ’25 per cent. 
(c) Nitrogen in oxygen. 
The oxygen was made by decomposing potassium chlorate, 
passing the gas through NnOH and H2SO4 and collecting 
over mercury, as usual. 
To 153 c.c. oxygen 2'9 c.c. nitrogen were added, and the 
nitrogen green line wave length 5001 was visible. 
To 132 c.c. oxygen 2 c.c. nitrogen were added, and the 
nitrogen line was again seen. The gas was not dried in the 
above two experiments at all. 
To 130 c.c. oxygen 1 c.c. nitrogen was added, and the 
nitrogen line was seen, but it was very faint. This gives 
*78 per cent. 
To 128 c.c. oxygen -6 c.c. nitrogen was added, and the 
nitrogen line was not seen; on adding *8 c.c. more nitrogen 
the green nitrogen line wave length 5004 was visible, and 
on addition of ‘3 c.c. more nitrogen it could easily be seen. 
Therefore the smallest amount of nitrogen that must be 
present in oxygen in order to be detected in the spectroscope 
is *8 per cent. 
{d) Oxygen in nitrogen. 
To 127 c.c. nitrogen 30 c.c. air had to be added before the 
oxygen blue line wave length 4648 became visible; this 
gives 4-7 per cent. 
To 108 c.c. nitrogen 22 -6 c.c. air were added before the 
oxygen line became visible ; this gives 4*5 per cent. 
To 104 c.c. nitrogen 5 c.c. oxygen were added and the 
oxygen line was seen very easily. 
To 138 c.c. nitrogen 4 c.c. oxygen were added and the 
oxygen line was not visible, but on adding 3 c.c. more 
oxygen it could be seen easily ; this gives 4*4. 
In the last two experiments the gas was not dried at all. 
