444 
MR. GEORGE W. WALKER OK THE DEPENDENCE OF THE 
PliG WcivG-lGiigth for Na light may b© taken as 5890 X metre. 
1 he standard atmosphere as 7 6 centims. of mercury at 0° C. 
Hence we get for the refractive index of dry atmosjjheric air 
_ ^ , -0002928 db -000000^ 
^ {1 + ^ ( 00360 ± -00003)} 76 ■ 
Carhon Dioxide. 
The gas was made by warming a Indb containing sodium bicarbonate and dryino- 
by means of phosphoric pentoxide. The wliole apparatus was exhausted to under 
1 centum pressure by means of an oil-pump, and then the bulb containing the 
bicarbonate gently warmed until atmosplieric pressure was attained. This process of 
exhausting and refilling was repeated al^out six times, so that the apparatus might 
be considered filled with practically pure CO 3 . 
Obseiving foi neaily a week at about 10 C., I noticed a gradual diminution in the 
value of tlie refractive index, which was comparatively rapid at first and became very 
slow 111 a few days. The whole change was aliout 1 per cent. 1 consider that this 
was due to gas, proliably air, coming oft tlie walls slowly, and later results seem to 
support this view. 
I refilled with pure COo, and now there ajipeared no change. The results are given 
in the following table. Throughout the initial pressure was maintained as iiearl}’" as 
possible at atmos])]ieric pressure iiy adjusting tiie reservoir B. 
Carbon Dioxide, put in 28t]i February, 1902. 
1 Date. 
Temperature 
of 
Temperature 
of 
Ratio. 
Corrected 
Multiplied by 
tubes. 
manometer. 
ratio. 
1 + - 00375/. 
1+ -00380/. 
1 + -00385/. 
5tli March 
° C. 
9-7 
° c, 
15-8 
9-G87 
9-715 
10-070 
10-075 
10-080 
5th „ 
9-65 
lG-1 
9-G9S 
9-725 
10-075 
10-080 
10-085 
5th ,, 
9-6 
lG-4 
9 • G98 
9 - 725 
10-075 
10-080 
10-085 
5th ,, 
9-65 
17-1 
9-G98 
9-725 
10-075 
10-080 
10-085 
Gth „ 
GO-7 
18-9 
8-159 
8-175 
10-035 
lO-OGO 
10-085 
7th „ 
Gl-3 
18-1 
8-155 
8-180 
lO-OGO 
10-085 
10-110 
12 th „ 
84-1 
17-3 
7-G19 
7-G30 
10-040 
10-070 
10-100 
12th „ 
84-5 
17-4 
7-509 
7-G20 
10-040 
10-070 
10-100 
12 th „ 
84-G 
17-G 
7-G13 
7-G25 
10-045 
10-075 
10-105 
14th ,, 
77-1 
17-7 
7-773 
7-785 
10-035 
10-0G5 
10-095 
14 th „ 
7G-9 
17-8 
7-740 
7 - 755 
9 - 990 
10-020 
10-050 
Uth ,, 
18-5 
lG-8 
9-310 
9-335 
9-980 
9 - 990 
10-000 
17th ,, 
18-5 
17-1 
9-307 
9-330 
9 - 975 
9-985 
9-995 
17th „ 
18-G 
17-3 
9-280 
9-305 
9 - 955 
9 - 9G5 
9 - 975 
1 
Mean, excluding 14th and 17th 
. 
10-055 
10-075 
10-090 1 
Greatest variation . 
+ -020 
+ -010 
+ -02 
- -020 
- -015 
- -01 j 
