54 
DR. T. ANDREWS ON THE PROPERTIES OF MATTER IN THE 
remove the pressure till the cloud appeared. In this way precise and concordant 
results were obtained. 
At the temperature of 6 0- 3, liquid first appeared when the pressure was raised to 
68'7 atmospheres, and, after being effaced by pressure, it reappeared at 113'2 
atmospheres. 
At 9°‘9, liquid appeared at a pressure of 77’6 atmospheres, and, after being effaced 
by pressure, it reappeared at 107’8 atmospheres. 
At 13 0, 2, liquid appeared at 91‘6 atmospheres, and, after being effaced by pressure, 
it reappeared at 103‘2 atmospheres. 
It is evident that, as we approach the critical point, the pressures at which the 
liquid first appears, and after being effaced reappears, will come almost exactly to 
coincide. This pressure, as already stated, for the mixture under examination was 
98 atmospheres. If we take the mean of the pressures at which the liquid appears 
and reappears after being effaced for the above temperatures, we shall have the 
following results :— 
o Atmospheres. 
6-3.90-9 
9-9.92*7 
13- 2.97-4 
14- 0.98-0 
The last numbers are the temperature and pressure for the critical state of the 
mixture. 
In making these experiments, it was found convenient to modify the form of the 
apparatus by bending the carbonic acid tube before introducing it into the apparatus, 
as shown in the annexed figure. On compressing the mixture below the critical 
Fig. 4. 
r- a 
v 
point, the liquid carbonic acid accumulated in the lower end of the tube, although a 
part of it was at first formed in contact with the mercury. But the latter portion 
soon fell down, and the whole of the liquid collected below. 
