Boussingault, and later Stenhouse, determined the absorptive power of wood charcoal for ammonia to be 90 and 98 volumes respectively.
THE COMPOSITION OF GASES
ABSORBED FROM THE ATMOSPHERE
BY VARIOUS SOLIDS.
In 1864 and 1865 Reichardt and Blumtritt[99] investigated elaborately the composition of gases driven off by heat from various powders, including soils, exposed to the atmosphere. All the substances examined were therefore “air-dry,” therefore to a certain extent moist; and the presence of this aqueous vapor of course modifies in a measure the results that would have been obtained had the materials used been exposed to dry air only. They found that, as had already been stated by previous observers, the presence of capillary water diminishes materially the absorption of gases, especially of those not as easily absorbed by water as are carbonic gas and ammonia. Contrary to what might have been expected from the more ready condensation of oxygen by pressure or cold, in nearly all cases nitrogen is absorbed to a greater extent than oxygen, and sometimes exclusively so; so that in some cases the latter was found to be present only in traces, as will be perceived from the subjoined table:
COMPOSITION OF GASES ABSORBED FROM
THE ATMOSPHERE BY VARIOUS POWDERS
| Substance. | 100 Grms gave cc. Gas. | 100 Vol’s gave Vol’s. Gas. | 100 vol’s gas contained | |||
|---|---|---|---|---|---|---|
| Nitrogen | Oxygen | Carbonic Dioxid | Carbon Monoxid | |||
| Charcoal, coniferous, air dry | 16.21 | 100.00 | 0.0 | 0.0 | 0.0 | |
| “ moistened and air-dried | 140.11 | 59.0 | 85.60 | 2.12 | 9.15 | 3.13 |
| “ Lombardy Poplar | 466.95 | 195.4 | 83.60 | 0.0 | 16.50 | 0.0 |
| Peat | 162.58 | 44.44 | 4.60 | 50.96 | 0.0 | |
| Garden Earth, moist | 13.70 | 19.9 | 64.34 | 2.85 | 24.06 | 8.75 |
| ““ air-dried | 30.28 | 53.6 | 64.70 | 2.04 | 33.26 | 0.0 |
| River Silt, air-dried | 40.53 | 48.07 | 67.69 | 0.0 | 18.61 | 13.70 |
| “ “ slightly moistened | 24.12 | 29.2 | 67.34 | 0.0 | 30.56 | 2.10 |
| “ “ air-dried | 26.52 | 30.05 | 67.40 | 9.09 | 16.07 | 7.44 |
| Clay, long exposed | 25.58 | 39.05 | 70.17 | 4.71 | 25.12 | |
| “ slightly moistened | 28.62 | 35.08 | 59.59 | 6.39 | 34.02 | |
| Ferric Hydrate, commercial | 251.59 | 275.0 | 33.26 | 1.43 | 65.31 | 0.00 |
| ““freshly | 375.54 | 275.0 | 26.29 | 3.85 | 69.86 | 0.00 |
| precipitated, air-dried | ||||||
| Ferric Oxid, ignited | 39.4 | 52.4 | 82.87 | 13.41 | 3.72 | 0.00 |
| Aluminic Hydrate, air-dried | 69.02 | 82.0 | 40.60 | 0.00 | 59.40 | |
| “ “ dried at 100°C. | 10.83 | 13.6 | 83.09 | 16.91 | 0.00 | |
| Prepared Chalk, 1864-65 | 43.48 | 52.4 | 100.00 | 0.00 | 0.00 | |
| “ “ 1865 | 38.98 | 48.0 | 74.49 | 15.49 | 10.02 | |
| Calcic Carbonate, precipitated, 1864-65 | 65.09 | 80.81 | 19.19 | 0.00 | ||
| Calcic Carbonate, precipitated, 1865-66 | 51.53 | 52.0 | 77.37 | 15.09 | 7.54 | |
| Magnesic Carbonate | 729.21 | 124.9 | 63.92 | 6.72 | 29.36 | |
| Gypsum, finely powdered | 17.26 | 80.95 | 19.05 | 0.00 | ||
Discussion of the Table.—It will be observed that in this table, the largest amount of total gas given off by equal weights of any one substance was in the case of carbonate of magnesia; but it is quite probable that in part, at least, this large amount of gas was due to the evolution of carbonic gas from the easily decomposable carbonate; the more as the analysis of the gases shows over 29% of carbonic gas. But the highest absorption by equal volumes of any substance is shown by the ferric hydrate; next to this by the light poplar charcoal, and next by the carbonate of magnesia. The high absorptive power here shown by the ferric hydrate is of great interest in connection with the facts already stated regarding the absorption of moisture and ammonia by ferruginous soils ([see page 274, this chapter]); and the fact that the larger proportion of the gas—as much as 70% in one case—consisted of carbonic gas, is particularly interesting in the same connection. Both in the amount of gas contained, and in the proportion of carbonic gas therein, the ferric hydrate exceeds even peat, the representative of humus in soils. It will, however, be noted that in the garden soil, also, the proportion of carbonic gas is very large, while that of oxygen is very low. It is curious to note that in very few cases the proportion of oxygen to nitrogen is the same as in the atmosphere; in most cases the nitrogen predominates considerably beyond its normal proportion, and in two cases, that of charcoal and of calcic carbonate (whiting), the gas was found to consist of pure nitrogen.
We are forced to conclude that the substances here enumerated, as a rule, condense oxygen in smaller proportions than they do nitrogen, or carbonic gas. As regards the carbon monoxid mentioned in the table, it is doubtful that it was contained as such in the substance originally examined; it may readily have been formed under the influence of the heat required in expelling the gases from the substances containing organic matter. Among the important results shown in the table, is the comparative determination of the gases in moist, and in dry garden earth, showing that in the moist earth the amount of gas absorbed ranged from less than one-half down to almost one-fourth that absorbed by the dry. The importance of these differences in the case of the fallow can readily be appreciated.
The changes in the absorptive power brought about by wetting and drying, as shown in the above table, are very insignificant. In the case of the charcoal, soil and silt the diminution may fairly be assumed to be caused by the deposition of soluble salts on the surface, partly clogging the pores. In the case of the clay as well as in that of the river silt, the inevitable content of organic matter in process of decomposition has doubtless influenced the result, as is suggested by the increase of carbonic gas. That prepared chalk should in one case contain exclusively nitrogen gas, in the other case mixed gases, seems to indicate a difference in the air to which it is exposed, or in the water employed in its preparation; the latter case agreeing substantially with the results obtained from the precipitated carbonate. In both (as well as in the carbonates of barium and strontium), the absorption of carbonic gas is very small, or nil.
It thus appears that for the condensation of carbonic dioxid gas, ferric and aluminic hydrates are prepotent among mineral substances; while clays, river silts and soils may always be expected to contain relatively large proportions of this gas in absorption.