OF GASES AT HIGH EXHAUSTIONS. 
419 
a vacuum of about 40 M, nothing is visible but the two lines X 519 and X 560. At 
higher exhaustions these lines disappear, and the phenomena of “ radiant matter” 
commence. 
VISCOSITY OF CARBONIC OXIDE. 
682. This gas was prepared by heating oxalate of ammonia and strong sulphuric 
acid, and collecting the mixed carbonic oxide and carbonic anhydride over solution of 
caustic potash in the bell-jar shown in fig. 12 (666). Previous to entering the appa¬ 
ratus the gases are slowly passed through long tubes containing powdered caustic 
potash. 
Carbonic oxide was also prepared by heating ferrocyanide of potassium with strong 
sulphuric acid, and passing the resulting gas through potash tubes as before. This is 
the preferable way to prepare the gas, for it is difficult to remove the last traces of 
carbonic anhydride when the oxalic acid process is used. 
The gas is passed into the well-exhausted apparatus through the tap in the manner 
already described, and the exhaustion and filling are repeated a sufficient number of 
times. All usual precautions are taken, as described in the case of gases previously 
examined. 
The following table gives the experimental results obtained :— 
683. Table V.— Log. dec. of carbonic oxide, between pressures of 760 millims. 
and 0'76 millim. Temp. 15° C. 
Pressure. 
Millims. 
760 
687 
517 
426 
353 
266 
219 
125 
89 
79 
32 
18 
12 
10 
2-6 
1-4 
1-2 
0-76 
Log. 
decrement. 
0-1092 
0-1073 
0-1031 
0-1012 
0-1000 
0-0983 
0-0979 
0-0972 
0-0971 
0-0970 
0-0971 
0-0968 
0-0968 
0-0967 
0-0969 
0-0957 
0-0958 
0*0947 
3 i 
MDCCCLXXXI. 
