From Alfred Swaine Taylor to Edward Cresy1 10 December 1860
St James’s Terrace | Regents Park
Dec 10 1860
Dear Mr Cresy
I saw a passage in the Chemical News of Nov 24th,2 which I think will interest your friend Mr Darwin as to the recognition of saline matter in an almost infinitesimal state of division
At p 281 of that number (published by Mitchell Red Lion Court Fleet Street)3 you will find it stated that by a peculiar optical property 1/3000,000 of a milligramme (th grain) of chloride of sodium or common table-salt may be discovered! This is equal to 1/195,000,000th of a grain!
A dilution to the extent of 1/500,000th grain admits of detection by the ordinary test,—nitrate of silver. The facts which you mention in your note regarding the Drosera serving to detect nitrogen by its sensitiveness, are very remarkable.4 The nitrogen in a salt of ammonia and the nitrogen in gun-cotton5 gutta percha—India rubber or Indigo are in very different states. It would be curious to try these substances—also ferrocyanide of potassium and ivory shavings
I am glad you think that Herapath has undergone a proper rasping in my paper6
I am | Your’s very truly | Alfred S Taylor
E Cresy Esqr
CD may be interested in a reference to a method of detecting 1/195000 of a grain of sodium chloride.
Also, on Drosera, suggests it would be interesting to try substances such as gun-cotton, in which nitrogen is in very different states from a salt of ammonia.
Please cite as
Darwin Correspondence Project, “Letter no. 3015,” accessed on 28 July 2016, http://www.darwinproject.ac.uk/DCP-LETT-3015