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Darwin Correspondence Project

From Leonard Darwin to W. de W. Abney   [before 27 June 1874]1

Brompton Barracks, | Chatham.

Dear Abney

The following are the questions.

“Carbonate of ammonia, sold as purified by druggists in large solid lumps.

Nitrate of ammonia in acicular crystals.

Phosphate of Ammonia in white dry powder sold by a good chemist.—

(1) Proportion of water of water of crystallization in each per cent.

(2) Proportion of nitrogen either in the anhydrous of crystalline state.2

I hope the above wont give you any bother.

Yours very sincerely | Leonard Darwin


The date is established by the subject matter, which relates to CD’s research for Insectivorous plants, published in 1875, and by Leonard’s departure on the transit of Venus expedition on 27 June 1874 (see G. B. Airy ed. 1881, p. 483).
Water of crystallisation is the water that is incorporated into the crystal lattice structure of many compounds. In Insectivorous plants, p. 155, CD noted that the crystallised phosphate of ammonia that he used contained 35.33 per cent of water of crystallisation. He did not give figures for carbonate of ammonia or nitrate of ammonia, but did note the percentage of nitrogen in all three substances (ibid., p. 168).


Insectivorous plants. By Charles Darwin. London: John Murray. 1875.


Asks for proportion of water and of nitrogen in various ammonium salts.

[WWA’s replies are with the letter.]

Letter details

Letter no.
Leonard Darwin
William de Wiveleslie Abney
Sent from
Source of text
DAR 58.1: 147
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9202,” accessed on 22 October 2020,

Also published in The Correspondence of Charles Darwin, vol. 22