In reducing these observations the following corrections were in- volved : a correction of 0-0015 gramme, due to imperfect exhaustion of the flask A while being weighed as empty ; the correction due to the neck of the flask between the mark and the stopcock was negligible ; the volume of the flask when corrected for temperature was 315-973 c.c., and when it was necessary to correct further for excess of external over internal pressure, the values were as given in Column V in the last four experiments this correction varied from about 0*059 to 0-073 c.c.
The first three experiments give a mean value of 1*260 grammes, at standard temperature and pressure, as the weight of a litre of nitrogen. This is about a quarter per cent, higher than the accepted value of 1-257. The extreme variation in the individual experiments is about half a per cent. The average value of the results under about one-third of an atmosphere is 1*266 grammes the tendency under the low pressures being to make the density half a per cent, higher. Considering that in the actual low-temperature experiments the mass of gas to be weighed would be at least three times greater, it was inferred that in spite of difficulties of manipulation and corrections the results might be anticipated to lie within a half per cent, of the true value.
The following table gives the results of six experiments made on the density of the vapour of oxygen at its boiling-point taken as 90 -5
Table II. Density of Oxygen Vapour at its Boiling-point.
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No.
P = Pi-
T,. a. b.
d.
p.
mm.
gramme. gramme.
1
775-5
15-5 0-388 1-0225
0-004402
227 -15
2
770-3
16 -5 -3865 1 -015
-004403
227 -07
3
771-0
17-5
-3875 1 -0245
-004432
225 -60
4
771-8
17-5
-3875 1 -0260
-004432
225 -59
5
775-Q
16-0 0-388 1-028
0-004422
226 -12
6
774-2
16-5
-3875 1 -028
-004425
225 -97
absolute, and under atmospheric pressure, where p, p\, T lt a, I, are the same symbols as used in the previous table, d is the calculated density at 90-5 absolute and 760 mm., and v is the specific volume l/'rf.
In the above reductions the following corrections were involved : 0-002 gramme due to imperfect exhaustion of A flask while being weighed as empty 0-0002 gramme due to the contents of the neck of the flask between the mark and the stopcock not being at 90 -5 -. the volume of the flask up to the mark contracted at 90 *5 to 314-398 c.c. no correction was necessary for compression.
Thus the mean weight of one litre of oxygen vapour at 760 mm. and 90 -5 absolute is 4-420 grammes, and the specific volume is
