By THOMAS C. VAN NUYS and BENJAMIN F. ADAMS, JR.
During the month of April, 1886, we made eighteen estimations of
carbonic acid in the air, employing Van Nuys' apparatus,[1] recently
described in this journal. These estimations were made in the
University Park, one-half mile from the town of Bloomington. The park
is hilly, thinly shaded, and higher than the surrounding country. The
formation is sub-carboniferous and altitude 228 meters. There are no
lowlands or swamps near. The estimations were made at 10 A.M.
[Footnote 1: See SCI. AM. SUPPLEMENT No. 577.]
The air was obtained one-half meter from the ground and about 100
meters from any of the university buildings. The number of volumes of
carbonic acid is calculated at zero C. and normal pressure 760 mm.
--------+----------+--------------+------------------------
| | Vols. CO_{2} |
Date. | Bar. | in 100,000 | State of Weather.
| Pressure | Vols. Air. |
--------+----------+--------------+------------------------
April 2 | 743.5 | 28.86 | Cloudy, snow on ground.
" 5 | 743.5 | 28.97 | " " " "
" 6 | 735 | 28.61 | Snowing.
" 7 | 744.5 | 28.63 | Clear, snow on ground.
" 8 | 748 | 27.59 | " thawing.
" 9 | 747.5 | 28.10 | " "
" 12 | 744 | 28.04 | Cloudy.
" 13 | 744 | 28.10 | Clear.
" 14 | 743.5 | 28.98 | "
" 15 | 750.5 | 28.17 | Raining.
" 19 | 748 | 28.09 | Clear.
" 20 | 746 | 27.72 | "
" 21 | 746 | 28.16 | "
" 22 | 741.5 | 27.92 | "
" 23 | 740 | 28.12 | "
" 24 | 738.5 | 28.15 | "
" 25 | 738.5 | 27.46 | "
" 28 | 738 | 27.34 | "
--------+----------+--------------+------------------------
The average number of volumes of carbonic acid in 100,000 volumes of
air is 28.16, the maximum number is 28.98, and the minimum 27.34.
These results agree with estimations made within the last ten or
fifteen years. Reiset[2] made a great number of estimations from
September 9, 1872, to August 20, 1873, the average of which is 29.42.
Six years later[3] he made many estimations from June to November, the
average of which is 29.78. The average of Schultze's[4] estimations is
29 2. The results of estimations of carbonic acid in the air, made
under the supervision of Munz and Aubin[5] in October, November, and
December, 1882, at the stations where observations were made of the
transit of Venus by astronomers sent out by the French government,
yield the average, for all stations north of the equator to latitude
29° 54' in Florida, 28.2 volumes carbonic acid in 100,000 volumes air,
and for all stations south of the equator 27.1 volumes. The average of
Claesson's[6] estimations is 27.9 volumes, his maximum number is 32.7,
and his minimum is 23.7. It is apparent, from the results of
estimations of carbonic acid of the air of various parts of the globe,
by the employment of apparatus with which errors are avoided, that the
quantity of carbonic acid is subject to slight variation, and not, as
stated in nearly all text books of science, from 4 to 6 volumes in
10,000 volumes of air; and it is further apparent that the law of
Schloesing[7] holds good. By this law the carbonic acid of an
atmosphere in contact with water containing calcium or magnesium
carbonate in solution is dissolved according to the tension of the
carbonic acid; that is, by an increased quantity its tension
increases, and more would pass in solution in the form of
bicarbonates. On the other hand, by diminishing the quantity of
carbonic acid in the atmosphere, some of the bicarbonates would
decompose and carbonic acid pass into the atmosphere.
[Footnote 2: Comptes Rendus, 88, 1007.]
[Footnote 3: Comptes Rendus, 90, 1144.]
[Footnote 4: Chem. Centralblatt, 1872 and 1875.]
[Footnote 5: Comptes Rendus, 96, 1793.]
[Footnote 6: Berichte der deutsch chem. Gesellschaft, 9, 174.]
[Footnote 7: Comptes Rendus, 74, 1552, and 75, 70.]
Schloesing's law has been verified by R. Engel[8].
[Footnote 8: Comptes Rendus, 101, 949.]
The results of estimations of bases and carbonic acid in the water of
the English Channel lead Schloesing[9] to conclude that the carbonic
acid combined with normal carbonates, forming bicarbonates, dissolved
in the water of the globe is ten times greater in quantity than that
of the atmosphere, and on account of this available carbonic acid, if
the atmosphere should be deprived of some of its carbonic acid, the
loss would soon be supplied.
[Footnote 9: Comptes Rendus, 90, 1410.]
As, in nearly all of the methods which were employed for estimating
carbonic acid in the air, provision is not made for the exclusion of
air not measured containing carbonic acid from the alkaline fluid
before titrating or weighing, the results are generally too high and
show a far greater variation than is found by more exact methods. For
example, Gilm[10] found from 36 to 48 volumes; Levy's[11] average is
34 volumes; De Luna's[12] 50 volumes; and Fodor's,[13] 38.9 volumes.
Admitting that the quantity of carbonic acid in the air is subject to
variation, yet the results of Reiset's and Schultze's estimations go
to prove that the variation is within narrow limits.
[Footnote 10: Sitzungsher. d. Wien. Akad. d. Wissenschaften, 34, 257.]
[Footnote 11: Ann. d. l'Observ. d. Mountsouris, 1878 and 1879.]
[Footnote 12: Estudios quimicos sobre el aire atmosferico, Madrid, 1860.]
[Footnote 13: Hygien. Untersuch., 1, 10.]
Indiana University Chemical Laboratory,
Bloomington, Indiana.
--_Amer. Chem. Journal._
* * * * *