Discusses letter from A. W. v. Hofmann concerning solution of iodine in water.
15 Marine Parade, Eastbourne
My dear Sir
I have received Hofman's letter which is extremely interesting to me. It is a great shame to trouble you, but I should be very much obliged for a line here, of explanation, if you can give it.
Does Hofman mean that for instance
Pray forgive me, and believe me | Yours very truly | C. Darwin
At present I fully believe after endless experiments that
- f1 2950.f1Dated by the relationship to the preceding letter.
- f2 2950.f2See the preceding letter.
- f3 2950.f3The copyist originally wrote `
1/64,800', which has been corrected in an unidentified hand.
- f4 2950.f4CD only resolved the point to his own satisfaction by performing further experiments on the sensitivity of Drosera leaves to chemical substances. His notes on these experiments are in DAR 60.1. His results were given in Insectivorous plants, chapters 7--9. With respect to ordinary chemical tests for salts, he reported that about
1/4,000of a grain of arsenic could be detected, `but the power of detection depends much on the solutions under trial not being extremely weak' (Insectivorous plants, p. 170 n.).
- f5 2950.f5The figure given by CD is repeated in Insectivorous plants, p. 146, where CD described immersing four Drosera leaves in a weak solution of carbonate of ammonia for some hours. To find the amount of salt that each gland received, he divided the absolute quantity of ammonia in solution by the total number of glands. See also the first letter to Edward Cresy, 2 November .