From Edward Frankland   [before 6 June 1876]1

—— Burnt Soil ——
Moisture at 100o 0.50 per cent
Loss on Ignition 1.20
Silica 89.09
Ferric Oxide 3.88
Alumina 3.41
Lime 0.84
Magnesia 0.49
Potash 0.15
Soda 0.04
Phosphoric Anhydride 0.092
99.69
Natural Soil
Moisture at 100o 2.22 per cent
Loss on ignition 4.26
Silica 77.72
Ferric oxide 5.52
Alumina 8.79
Lime 0.48
Magnesia 0.51
Potash 0.33
Soda 0.26
Phosphoric Anhydride 0.04
Sulphuric do traces
100.133

Contemporary Copy incomplete4

1
The date is established by the relationship between this letter and the letter to Edward Frankland, 6 June [1876].
2
Phosphoric anhydride is more commonly known today as phosphorus pentoxide; alumina is synthetically produced aluminum oxide. ‘Loss on ignition’ is a test used in analytical chemistry in which a sample is heated and then weighed until the mass is stable; for organic matter the temperature is high enough to burn organic matter but not so high as to decompose carbonates.
3
CD had sent Frankland samples of burnt and unburnt soils to analyse; see letter to Edward Frankland, [before 6 June 1876].
4
Francis Darwin quoted from Frankland’s letter in his letter to J. H. Gilbert, 8 June 1876.

Please cite as “DCP-LETT-10533F,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10533F