386 PRINCIPLES OF CHEMISTRY 



in connection with its considerable solubility in water, alcohol, and 

 other liquids. Its solubility in water has been already spoken of in 

 the first chapter. Carbonic anhydride is still more soluble in alcohol 

 than in water, namely at one volume of alcohol dissolves 4-3 volumes 

 of this gas, and at 20 2*9 volumes. 



Aqueous solutions of carbonic anhydride, under a pressure of several 

 atmospheres, are now prepared artificially, because water saturated 

 with this gas promotes digestion and quenches thirst. For this pur- 

 pose the carbonic anhydride is pumped by means of a force-pump into 

 a closed vessel containing the liquid, and then bottled off, taking 

 special means to ensure rapid and air-tight corking. Various etfer- 

 vescing drinks and artificially effervescing wines are thus prepared. 

 The presence of carbonic anhydride has an important significance 

 in nature, because by its means water acquires the property of 

 decomposing and dissolving many substances which are not acted On 

 by pure water ; for instance, calcium phosphates and carbonates are 

 soluble in water containing carbonic acid. If the water in the 

 interior of the earth is saturated with carbonic acid under pressure, 

 the quantity of calcium carbonate in solution may reach three grams 

 per litre, and on issuing at the surface, as the carbonic anhydride 

 escapes, the calcium carbonate will be deposited. 10 Water charged 

 with carbonic anhydride brings about the destruction of many rocky 

 formations by removing the lime, alkali, &c., from them. This process 

 has been going on and continues on an enormous scale. Rocks 



rapidity under the receiver of an air-pump, and consequently the refrigeration is more 

 intense. By this means many gases may be liquefied which resist other methods 

 namely, defiant gas, hydrochloric acid gas, and others. Liquid eai'bonic anhydride in 

 this case congeals in the tube into a glassy transparent mass. Pictet availed himself oi 

 this method for liquefying many permanent gases (see Chapter II.) 



Bleekrode, by compressing solid CO 2 in a cylinder by means of a piston, obtained a 

 eemi-transparent stick, which contained as much as 1*8 and even 1*6 gram of CO 2 per 

 cubic centimetre. In this form the CO 2 slowly evaporated, and could be kept for a long 

 time. 



10 If such water trickles through crevices and enters a cavern, the evaporation will 

 be slow, and therefore in those places from which the water drips growths of calcium 

 carbonate will be formed, just like the icicles formed on the roof-gutters in winter-time. 

 Similar conical and cylindrical stony growths form the so-called stalactites or pendants, 

 hanging from above and stalagmites formed on the bottom of caves. Sometimes these 

 two kinds meet together, forming entire columns filling the cave. Many of these caves 

 are remarkable for their picturesqueness ; for instance, 'the cave of Antiparos, in the 

 Grecian Archipelago. This same cause also forms spongy masses of calcium carbonate 

 in. those places where the springs come to the surface of the earth. It is therefore very 

 evident that a calcareous solution is sometimes capable of penetrating plants and filling 1 

 the whole of their mass with calcium carbonate. This is one of the forms of petrified 

 plants. Calcium phosphate in solution in water containing carbonic acid plays an im- 

 portant part in the nourishment of plants, because all plants contain both lime and 

 phosphoric acid. 



