skip to content

Darwin Correspondence Project

From Edward Frankland   16 October 1873

14 Lancaster Gate | Hyde Park W.

Oct. 16/73

My dear Sir,

The litmus paper possesses what chemists call a neutral tint.1 It is very sensitive to acids & still more so to alkalies. The longer piece which I return has been half immersed in a mixture of 1 part of sulphuric acid and 100,000 parts of water. I know not in what condition it may reach you but, as I write, the difference of tint (bright red & port wine red) is so strong, that, it can scarcely be doubted, a very much smaller proportion of acid could be detected.

You will find that the paper will most distinctly indicate the alkalinity of any chalk-spring or well water that you may have in your neighbourhood.

If you would like some bluer but less delicate, I shall have great pleasure in sending you some & would do so now but do not happen to have any at hand as I write.

Believe me | Yours sincerely | E. Frankland.


CD had questioned whether the sensitive litmus paper that Frankland had sent him should be pink (letter to Edward Frankland, 13 October 1873).


Sends some litmus paper for CD.

Letter details

Letter no.
Edward Frankland
Charles Robert Darwin
Sent from
London, Lancaster Gate, 14
Source of text
DAR 164: 209
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9098,” accessed on 18 January 2020,

Also published in The Correspondence of Charles Darwin, vol. 21