210 BULLETIN OF THE BUSSEY INSTITUTION. 
of carbonate of lime were immediately obtained, on adding ammonia 
water or lime water to the percolates. This result was obtained 
with fresh earth from the Plain-field that was operated upon 
directly, and with similar earth that had been rapidly dried upon 
a water bath. | 
Very different results from those just now described were obtained 
when the earths that had been kept dry for years in a store-room were 
percolated with carbonic-acid water. Thus, on charging a cylinder 
with 1,800 cc. of the Plain-field earth that had long been dry, and per- 
colating immediately with carbonic-acid water, 800 ce. of the liquid 
were absorbed by the earth, and the reactions of carbonic acid were 
obtained in the first 50 cc. of the percolate. As has been said already 
(p. 198), the reactions of carbonic acid were obtained in percolates 
from this earth when nothing but pure water was used. An almost 
precisely similar result was obtained in another trial: that is to say, 
825 cc. of carbonic-acid water were absorbed by the earth, and the 
reactions of carbonic acid were obtained immediately when the perco- 
late appeared. In one of these trials, the percolation with carbonic- 
acid water was continued until two litres of liquid had passed through 
the earth; but the percolate continued to react with ammonia from 
first to last, and the reaction for lime was obtained constantly with 
ammonium oxalate also. 
An effort was made to determine quantitatively the amounts of car- 
bonic acid that came through the earth in successive 50 ce. portions of 
the percolate, when 1,000 grms. of the dry store-room earth were percolated 
with carbonic-acid water. The filtrates were acidulated and boiled, and 
the carbonic acid was collected in a soda-lime tube, and weighed as such. 
50 cc. of the original carbonic-acid water contained 0.062 grm. of car- 
bonic acid, and there was found in the first 50 cc. fraction of the perco- 
late 0.004 grm. of CO,; in the second, 0.010 grm.; in the third, 0.011; in 
the fourth, 0.009; and in the fifth and sixth together, 0.019. 250 cc. of 
the percolate were then allowed to flow to waste, after which, 50 cc. of the 
liquid gave 0.027 grm. of CQ. 
In one experiment, where 1,800 cc. of dry earth from the store-room 
were percolated, first with 1,850 cc. of pure water, of which 850 cc. were 
required to saturate the earth, and then with carbonic-acid water, 900 ce. 
of liquid came through before a sufficiently decided reaction for carbonic 
acid to be attributed to the carbonic-acid water was obtained. On testing 
with ammonium oxalate, also, the reactions for lime were about as strong 
before the carbonic-acid water began to come through as afterward. 
1,000 ce. of carbonic-acid water were passed through the earth in this 
