ON MTROUS OXIDE IN' THE GASEOUS AND LIQUID STATES. 



Tabu; Y.— Nitrous Oxide at 4y°-8. 



21/ 



Comparing these results for nitrous oxide with those for carbonic acid found 

 by Dr. Andrews, we find the compressibility of the two gases nearly the same 

 at temperatures equidistant from their critical points. At the temperature of 

 25°-16, liquefaction begins under a pressure of r)7-83 atmospheres ; at 32°-2S, 

 the gas passes into the liquid state under a pressure of 67-45 atmospheres : at 

 this point a great diminution of volume occurs, but not abruptly as in the case 

 of carbonic acid ; this must be ascribed to the presence of a greater quantity 

 of a permanent gas in the nitrous oxide. 



In the li'iuid state, nitrous oxide yields as much to pressure as carbonic 

 acid ; the rate of expansion by heat wiU be therefore very great. This is a 

 confirmation of the results of Driou (Ann. de Chim. et de Phys. t. Ivi. p. 37), 

 that the coefficient of expansion of volatile liquids at a temperature still below 

 the critical point grows equal to the coefficient of expansion of gases and in- 

 creases further, tiU at the critical point it may attain to a value any number 

 of times greater than that of air. 



At temperatures above the critical point, the volume of nitrous oxide 

 diminishes with tolerable regularity with increase of pressure, though much 

 faster than according to the law of Boyle ; the higher the temperature the 

 more the compressibility approaches to that of a perfect gas. When the gas 

 is reduced to the volume at which it might be expected to liquefy, no trace 

 of liquid is to be seen, the whole mass of the gas remaining homogeneous ; " 

 but a rapid diminution of volume occurs from a small increase of pressure : 

 this diminution of volume is not abrupt as in the case of liquefaction, and 

 diminishes greatly at higher temperatures. 



The anomalies presented by nitrous oxide were : — 



1. Under a given pressure and temperature the volume of the compressed 

 gas is variable, or vice versa. This anomaly is very obvious in that condition 

 of matter where a rapid diminution of volume occurs at a small increase of 

 pressure ; under a given volume of the gas the difference of pressure can 

 amount here to 2 atmospheres, in the other cases this difference is very 

 slight, about 0-2 to 0*4 of an atmosphere. This appears from the folloAving 

 results : — 



