several gases into liquids . 193 
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 
hydrogen. 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 experi- 
ments, are particularly so with carbonic acid. 
Carbonic acid is a limpid colourless body, extremely fluid, 
and floating upon the other contents of the tube. It distils 
readily and rapidly at the difference of temperature between 
32 0 and o®. Its refractive power is much less than that of 
water. No diminution of temperature to which I have 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 powerful explosions. By inclosing a 
gage in a tube in which fluid carbonic acid was afterwards 
produced, it was found that its vapour exerted a pressure of 
36 atmospheres at a temperature of 32°. 
It may be questioned, perhaps, whether this and other 
similar fluids obtained from materials containing water, do 
not contain a portion of that fluid ; in as much as its absence 
has not been proved, as it may be with chlorine, sulphurous 
mdcccxxiii. C c 
