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Letter 2974

Darwin, C. R. to Cresy, Edward, Jr

2 Nov [1860]

    Summary Add

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    Discusses pamphlet by A. S. Taylor

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    and note by A. W. v. Hofmann concerning iodine solution.


15 Marine Parade, Eastbourne

Nov: 2nd.

Dear Cresy

I return by this post Dr. Taylor's pamphlet which is very interesting.—

This morning I vowed to myself that I would give you no more trouble; this evening I break my vow! Do read over Hofman's note, it seems to me clear that he asserts that he has easily distinguished 0.002 of milligram of iodine and this equals, as I make out, 3/100,000 of a grain! Whereas Taylor, in your copy, speaks of only 11400 of a grain. Can you understand this? Pray do not trouble Hofman again, for I shall see him in course of early winter. Now I am on weights, can you assist me in another point. I have used ordinary apothecary measures (which I shall state in my paper), viz, fluid oz. divided into 8 drachms and each drachm into 60 minims,—so that each oz. contains 480 minims. But when I looked into such books as I possessed I found the most ridiculous discrepancies and misprints of weight of one such oz. of distilled water. I applied to good and clever druggist and he says positively one such oz. weighs 437.5 grains and this agreed with one of my printed authorities; so I have provisionally used it in calculating proportions. Can you anyhow aid me in telling me whether this is correct?

God forgive me for being so troublesome, and believe me, | Yours very sincerely | C. Darwin

Please return Hofman's note.

    Footnotes Add

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    f1 2974.f1
    The letter was written in the evening, after the preceding letter was posted.
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    f2 2974.f2
    Taylor 1860. See preceding letter.
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    f3 2974.f3
    Letter from A. W. von Hofmann to Edward Cresy, 27 October 1860. See preceding letter.
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    f4 2974.f4
    Taylor 1860. There is a note on this pamphlet in DAR 60.1: 69 listing the amounts of arsenic and antimony that could be detected.
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    f5 2974.f5
    A note giving these calculations and apparently subsequent emendations is in DAR 60.1: 70.
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    f6 2974.f6
    See letter from Edward Cresy, 10 November 1860.
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