212 



Mr. G. Ansdell. 



[June 19, 



rises. The curves, however, have no appearance of actually crossing 

 at a higher temperature. 



The critical point of acetylene, or that temperature at which no 

 appearance of liquefaction takes place, however great a pressure is 

 exerted on the gas, was found after many careful experiments to be 

 37°-05C. 



For determining the density and compressibility of the liquid at 

 different temperatures, a tube of much smaller dimensions was used, 

 having a capillary bore of about "8 mm. in diameter, the whole of the 

 tube having a capacity of 36*3708 cub. centims. This gave a column 

 of liquid about 15 centims. long when the upper part of the tube was 

 entirely full at 15° C. 



The density at any particular temperature was taken by forcing the 

 liquid up the capillary tube at that temperature, until the upper part 

 was completely filled ; the length of the column of liquid was then read 

 off, its volume calculated, and this observed volume divided into the 

 calculated weight of the gas at zero. They are as follows : — 



Temp. Density. 



- 7° -460 



-3 -456 



-451 



-4*4 -441 



9-0 '432 



16-4 -420 



20-6 -413 



26-25 '404 



30-0 -397 



34- -381 



35- 8 -364 



It has, therefore, about half the density of liquid carbonic acid, and 

 if we take the actual volume of the liquid at — 7 as unity, it becomes 

 1*264 at + 35*8, which gives '00489 as its coefficient of expansion per 

 degree, for the total range of pressure ; it is, therefore, only about 

 half as expansible as carbonic acid, whose coefficient is "010, and is 

 not much more expansible than a gas. Comparing the density of 

 liquid acetylene with that of liquid benzene, the latter is found to be 

 almost exactly three times as great as the former at the same tempera- 

 ture ; as for instance, at 0°C. the density of the acetylene is "456, 

 whereas that of the benzene is '899 ; the vapour density, however, of 

 the benzene is three times as great, viz., 2" 704. 



The apparent compressibility in glass was determined by direct 

 observation, the liquid being forced up in the capillary tube until the 

 latter was completely full, and then the pressure gradually increased, 



