180 Dr. J. P. Kuenen on the Condensation and Critical 



Andrews's critical constants are 30 O- 9 and about 73 atmo- 

 spheres. The deviations .are in the same direction, only 

 much more pronounced. Andrews's carbonic acid contained 

 about -4- of air. 



Preparation of Acetylene. 



- - 13. This gas was prepared in the same apparatus as car- 

 bonic acid, from calcium carbide and water. The water had 

 been previously saturated with carbonic acid. The gas was 

 washed in silver nitrate to absorb the phosphoretted hydrogen 

 and sulphuretted hydrogen which it contained. It was freed 

 from carbonic acid by soda-lime and dried in sulphuric acid 

 and phosphorus pentoxide. Two samples were obtained. 

 The first probably contained some air and also some phos- 

 phoretted hydrogen. In preparing the gas for the second 

 time, a second washbottle with silver nitrate was introduced, 

 and this bottle was only just beginning to get blackened, 

 when the acetylene was collected. The only possible im- 

 purity of this sample is therefore a trace of air. 



Some of this sample was used in making the mixture with 

 C0 2 , the results for which are communicated below. Some 

 mixtures of the first sample with C0 3 gave, however, similar 

 results. The results obtained with the purer sample are 

 contained in Table V. 





Table V. 







Acetylene. 





t. 



Pb- 



Pe- 



14-95 



38-09 



38 66 



2015 



4318 



43-75 



26-8 



5029 



50-85 



271 



50-55 



51-12 



30-8 



55 05 





35-25 



61 



02C 



14. Evidently the gas contained an admixture of some 

 other substance. If this admixture is air, the vapour-pressures 

 are slightly higher than for pure acetylene, and the critical 

 temperature a few tenths of a degree too low. In this case 

 .also the p^s were used in drawing the vapour-pressure 

 curves in the diagrams. 



The pressures agree very well with those given by Villard *, 



* Ann. de Chimie et Physique, March 1897. 



