CHEMISTRY. 11 
its own abundance. As soon as the action of the acid on the soda is 
supposed to be completed, the opening of B is closed by means of the valve 
at b, and the apparatus taken apart. On opening the valve at 0, the 
liquified carbonic acid will flow out as soon as the cylinder B is inverted. 
The walls of the vessel must be strong enough to resist a pressure of sixty 
atmospheres, and the entire experiment is at all times dangerous. In an 
experiment of the kind, instituted in Paris by Thilorier, the apparatus burst 
and killed one person, and severely wounded several others. The liquified 
carbonic acid evaporates so rapidly when the pressure is removed, that a 
great part of it becomes solid, the part converted into gas rendering so much 
of the heat latent as to freeze the rest. In the condensation of carbonic 
acid gas, we have, therefore, an example of a gas condensed to a liquid by 
pressure, and, at the same time, the condensation of a liquid by cold into a 
solid body, the acid being actually frozen by the rapid abstraction of the 
heat required by the evaporation of the gas. Thilorier obtained solid 
carbonic acid in a white mass, similar to a ball of snow. By combining 
solid carbonic acid and ether, the acid becomes at first liquid, and then 
evaporates along with the ether; a cold of such intensity is thus produced 
as causes the thermometer to sink to 180° below the freezing point of water. 
Faraday has obtained a still lower temperature of 175° below the zero of 
Fahrenheit, or 207° below the freezing point of water, by the action of 
solidified carbonic acid in a vacuum. By the use of carbonic acid, Faraday 
succeeded in liquifying many other gases which until then had resisted 
every effort. Oxygen, hydrogen, and nitrogen, however, resisted every 
attempt of the kind, even when combined with enormous pressure. 
Liquified nitrous oxyde boiled on the application of the carbonic 
acid. 
Many gases may be liquified on a small scale in bent tubes 
(pl. 30, fig. 48), at one of whose extremities a strong glass bulb is blown. 
Supposing the bi-carbonate of soda to be introduced into the bulb, and the 
sulphuric acid kept in the angle of the bend until the open end of the tube 
is melted together; on bringing the two in contact a rapid evolution 
of gas ensues, which results as before. One end, of course, must be 
placed in a freezing mixture. 
Il. Evementary Conpition or Marrer, or THE ELEMENTS. 
Only a small amount of the matter surrounding us is in its elementary 
condition. Of the gaseous elements, two, oxygen and nitrogen, mixed in 
proportions of twenty-one to seventy-nine, form atmospheric air. Of liquid 
elementary substances, mercury is the only one which occurs in nature. 
On the other hand, many of the solid elements occur uncombined, as gold, 
silver, iron, platinum, &c. All these substances, however, occur more 
frequently in a compound state, or united together, and by far the greater 
number of these chemical combinations consist of one element, combined 
with one or more others in a definite proportion. The material composing 
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