212 BULLETIN OF THE BUSSEY INSTITUTION. 
composed to a certain extent; 7.e., the gas is removed from the first 
portions of the liquid, either by being absorbed from it directly by the 
earth, or by being made to escape from the water through the me- 
chanical action of the earth.* In the cases where carbonic-acid water 
was poured upon earth that had been kept dry for a long while, the 
first portions of the liquid evidently acted as mere water to dissolve 
and push out the carbonated lime-compound that already existed in 
the earth, or was ready to be formed there on the arrival of the 
water. 
Some important facts first observed by BineauTt are to be remem- 
bered in this connection. He found, for example, that the carbonic 
acid contained in dilute solutions of supercarbonate of lime is much 
less readily expelled than carbonic acid that is simply dissolved in 
water. In a word, he found that dilute solutions of the acid carbonate 
of lime are not easily decomposed, and that they retain the excess of 
carbonic acid, over and above that contained in the normal carbonate, 
much more forcibly than pure water can retain it. Very dilute solu- 
tions of the acid carbonate may even be heated to the temperature of 
boiling, or left to stand in the exhausted receiver of an air pump with- 
out losing the excess of carbonic acid, or depositing carbonate of lime. 
He found that solutions of the acid carbonate which contain y5}55 OF 
less of normal carbonate of lime are in so far permanent that they do 
not give off carbonic acid at the ordinary temperature of the air. 
Such solutions are decomposed only by actual evaporation of their 
water, or by reacting chemically upon some other substance. But it is 
precisely these highly dilute solutions of the acid lime-carbonate that 
occur naturally in the soil. It is probable, indeed, that the solutions 
must, of necessity, be dilute, for the simple reason that they are in con- 
tact with the earth, which, like any other porous body, must tend to 
remove carbonic acid from its solution. Just as bubbles of gas are 
seen to adhere to the sides of a glass in which drinking water has been 
left standing for some time, or as a lively evolution of carbonic acid is 
caused when any rough or porous substance such as a bit of bread or 
* The results of experiments made by Mulder to determine the amounts of 
carbonic acid expelled from carbonic-acid water, on the addition thereto of 
moist earth, will be found in his ‘‘ Chemie der Ackerkrume,” Berlin, 1868, 2. 
pp. 24, 25. 
+ “ Annales de Chimie et de Physique,” 1857, 51. 290. 
