1880.] On the Solubility of Solids in Gases. 



183 



version into a sulphide, and the subsequent solution of the sulphide 

 formed. 



Carbon tetrachloride was also tried as a solvent, but as the number 

 of substances soluble in this fluid is very small, we can only record a 

 few negative experiments. Cupric chloride did not dissolve, but 

 appeared to be acted on chemically above the critical point, its colour 

 changing to brown. Chromic chloride showed no sign of solution. 

 Zinc oxide did not dissolve, but at a temperature 20° or 30° above the 

 critical point a sudden chemical change occurred, and as a result the 

 critical point was found to be lowered from 280° C. to about 200°. On 

 cooling some transparent globules were seen, and on opening the tube 

 there was an outrush of gas. The transparent globules dissolved in 

 water, and were found to be chloride of zinc. 



The use of water as a solvent was quite out of the question, both on 

 account of its high critical point and the corrosion of the glass tubes, 

 so that we were debarred from the use of the liquid whose examination 

 promised most. 



The mixture of light paraffins known as paraffin spirit was tried as 

 a solvent for some organic substances. A solution of resin in this 

 liquid remained perfectly bright and without sign of separation at a 

 temperature of 350° to 360°, almost 100° above the critical point. 



The examination of liquids to determine their critical temperature 

 and pressure was not exactly in the line of our research, but as 

 Cagniard de la Tour's numbers, so far as we are aware, are the only 

 ones on record, we have made a number of experiments in this direc- 

 tion. To obtain accurate measurements of pressure is a matter of 

 very great difficulty, and as for our purpose these were not required, 

 it would have made our research unnecessarily tedious to attempt it. 

 Our numbers are as follows : — 





Alcohol. 



Carbon 

 disulpbide. 



Carbon 

 tetrachloride. 





234°- 6 



272°-96 



277°-9 





47 



12 



4 



Probable error of a single experiment 



2°06 



l°-34 



0°-69 





65 atmos. 



77'9 atmos. 



58 - l atmos. 





14 



12 



4 



Probable error of a single experiment 



1"0 atmos. 



15 atmos. 



"55 atmos. 



The alcohol used had a specific gravity of "7949 at 15 0, 5 C. In the 

 carbon tetrachloride experiments the mercury was attacked, but our 

 numbers were taken as quickly as possible, and before chemical action 

 had taken place to any great extent. 



Cagniard de la Tour gives the following results for alcohol and 

 carbon disulphide : — 



vol. xxx. o 



