t 



oj several Gases into Liquids. 419 



temperature of a tube containing some of it rose from 0° to 

 45°, part of the fluid rose in vapour, and its bulk diminished; 

 but there was no other change : it did not seem more adhe- 

 sive at 0° than at 45°. Its refractive power appeared to be 

 rather greater than that of water ; it decidedly surpassed that 

 of sulphurous acid. A small gauge being introduced into a 

 tube m which liquid sulphuretted hydrogen was afterwards 

 produced, it was found that the pressure of its vapour was 

 nearly equal to 1 7 atmospheres at the temperature of 50°. 



The gauges used were made by di'awing out some tubes at 

 the blow-pipe table until they were capillary, and of a trum- 

 pet form ; they were graduated by bringing a small portion of 

 mercurj' successively into their different parts ; they were then 

 sealed at the fine end, and a portion of mercury placed in the 

 broad end ; and in this state they were placed in the tubes, 

 so that none of the substances used, or produced, could get 

 to the mercury, or pass by it to the inside of the gauge. In 

 estimating the number of atmospheres, one has always been 

 subtracted for the air left in the tube. 



The specific gravity of sulphuretted hydrogen appeared to 

 be 0-9. 



Carbonic Acid. 

 The materials used in the production of carbonic acid, were 

 carbonate of ammonia and concentrated sulphuric acid ; the 

 manipulation was like that described for sulphuretted hydro- 

 gen. Much stronger tubes are however required for carbonic 

 acid than for any of the former substances, and there is none 

 which has produced so many or more powerful explosions. 

 Tubes which have held fluid carbonic acid well for two or 

 three weeks together, have, upon some increase in the warmth 

 of the weather, spontaneously exploded with great violence ; 

 and the precautions of glass masks, goggles, &c., which are at 

 all times necessary in pursuing these experiments, are parti- 

 cularly so with carbonic acid. 



Carbonic acid is a limpid colourless body, extremely fluid, 

 and floating upon the other contents of the tube. It distills 

 readily and rapidly at the difference of temperature between 

 32° and 0°. Its refractive power is much less than that of 

 water. No diminution of temperature to which I liave been 

 able to submit it, has altered its appearance. In endeavour- 

 ing to open the tubes at one end, they have uniformly burst 

 into fragments, with powerfid explosions. By inclosing a 

 gauge in a tube in which fluid carbonic acid was afterwards 

 jjroduced, it was found that its vapour exerted a i)ressure of 

 36 atmosplieres at a temperature of 32°. 



It may be questioned, perhaps, whether this and other si- 

 3 G 2 milar 



