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  1. #1
    Michel Hardy-Vallée's Avatar
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    Photography is a matter of Taste: a lesson by Sir John Herschel

    There's nothing I hate more than lore.

    Lore is stuff that's well-known, but untraceable. Examples of photographic lore are "simple table salt can be used to clear fixer," or "John Herschel was the first to notice the fixating action of thiosulfates upon silver salts."

    But from every idiot with a blog on the internet, to the greatest minds of photographic writing, very few people ever bother to cite properly, and merely parrot. The problem is often that they never read the primary material to begin with.

    Well, I did my homework, and I finally traced the most important paper in the birth of photography: the discovery of fixer by John Herschel in his paper "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. (available from archive.org)

    The paper begins thus (my emphasis):

    Quote Originally Posted by Sir John Herschel (1819)
    The experiments about to be described, were occasioned by the following accident. Having set aside, for a few days, a solution of hydroguretted sulphuret of lime, I was struck by observing a bitterness in the liquid, when almost wholly decomposed and colourless, similar to that of sulphate of magnesia, which I could not account for.
    This bitterness is the triggering factor: not being able to account for the sudden appearance of bitterness in a compound he already knew, Herschel sought to figure out what chemical transformations had happened in his solution, and how he could characterize it. After a quick trip to the library, our man found some clues as to the possible composition of his solution. His compound could not be "sulphuric" or "sulphurous" (the two forms of sulfur compounds he knew), and he found the excluded third in an experiment on the decomposition by atmospheric exposure of his original solution. "Hyposulphurous Acid" had been created in the solution, and while this acid is not available alone, it can readily be found attached to a base in the form of "hyposulphites". However, the literature already available was rather bad, vague, or incomplete with respect to the properties of these compounds.

    Thus began the quest to study the properties of "hyposulphites". In the paper, Herschel decribes their taste ("intensely sweet or intensely bitter"), what precipitates they form, etc. But must importantly, one notable property of all "hyposulphites" is their ability to dissolve "muriate of silver" or silver salts (not sure if he means strictly AgCl or all AgX, here).

    On page 19, the first clear mention of this property is thus given:
    Quote Originally Posted by Sir John Herschel (1819)
    One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution.
    I merely glanced over this part the first time I read the paper because I had no idea what "muriate" was. Although Herschel, in another paper, kept referring to this article as his discovery of hypo, I couldn't connect it with the birth of photography, and was looking for other papers, until an internet search finally helped me connect "muriate" with "halide" or "salts".

    Later in the paper, Herschel describes thus the impact of dissolved silver salts on hypo:
    Quote Originally Posted by Sir John Herschel (1819)
    Muriate of silver newly precipitated is soluble in all the liquid hyposulphites, and, as has been before observed, in that of soda, with great ease and in large quantity. This solution is not accomplished without mutual decomposition, as its intense sweetness proves,—a sweetness surpassing even that of honey, and diffusing itself over the whole mouth and fauces, without any disagreeable or metallic flavour.
    There you have it: Herschel's test to know if your fixer is fresh or exhausted. Bitter = fresh ; sweet = exhausted. Easy!

    The 1819 paper makes no mention of photography, but it is well known that afterwards the word got out, and people like Talbot and Daguerre added 2+2: silver salts, reducing to silver after exposure to light, soluble in hypo = fixed photos!

    Thanks to printing, we have a record of the development of knowledge, and we can also witness that earlier scientists still used their bodies as fundamental measuring instruments. If you're into the study of smell, the Luca Turin saga on the vibrational nose also begins with the quest to figure out what two different chemical compounds smell like, even the toxic, dangerous ones (cf. The Emperor of Scent for a general public version and The Secret of Scent for the heavier version).

    In photography, we are indebted to a man's taste buds and their ability to transform all sorts of chemical information into subjective impressions, triggering a revolution with a lasting legacy.
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

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  2. #2
    Photo Engineer's Avatar
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    Muriatic Acid = HCl and therefore Silver Muriate or Muriate of Silver = AgCl using old terminology common in the days of Phlogiston.

    You can still buy Muriatic Acid at Hardware stores in the US.

    PE

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    Isn’t phlogiston an essential ingredient of pyro developers?

  4. #4

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    Does this mean I can use exhausted fixer as a zero-calorie sweetener?
    "Panic not my child, the Great Yellow Father has your hand"--Larry Dressler

  5. #5
    holmburgers's Avatar
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    Great work Michel! You've done a service to the analog world by finding the original text and reproducing it here. Not many people know the excitement of finding original texts, but they should and easily could!
    If you are the big tree, we are the small axe

  6. #6
    Klainmeister's Avatar
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    This should be moved to the article section!
    K.S. Klain

  7. #7
    Michel Hardy-Vallée's Avatar
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    The first early text on photography I read was Talbot's The Pencil of Nature. It is truly remarkable, not just for its scope, but also for its form, alternating images with explanations, using a methodical, organized approach to all aspects of photography. In many respects, I find that all how-to books of photography that we have access to are merely recapitulating the fundamental concerns of Talbot's book. It's still available as a reprint, and I read it from a facsimile available at my university.

    If you read French, another good text to read is François Arago's report to the French Académie des Sciences on the daguerreotype.: http://mapage.noos.fr/paltman/daguerreotype.html

    I once bought it as a small letterpress book, and it's a joy to read. Like Talbot's book, this speech encompasses so many issues we have not yet escaped.

    Finally, there's another great Herschel article on photography, "On the Chemical Action of the Rays of the Solar Spectrum on Preparations of Silver and Other Substances, Both Metallic and Non-Metallic, and on Some Photographic Processes" published in issue 130 of the Philosophical Transactions of the Royal Society (1840), pp.1-59. It's about silver halides response to various part of the light spectrum (Arago's speech, cited above, references his pre-publication work on the matter), but the first part is also a recapitulation of Herschel's discoveries pertaining to photography, including his work on optics (1821 on aberrations of compound lenses, published by the Royal Society) and things like direct positives, bleaching/redeveloping, contact printing, glass plates, platinum printing, bromide v. iodide v. chloride salts, etc. It's where I got the lead to find Herschel's article on hypo, since he cites himself, but incorrectly (1821 instead of 1819!).

    That article is available directly from the Royal Society: http://rstl.royalsocietypublishing.o...d-2d04485dfcc6 but you need either a subscription or a university access to read it for free.

    Thanks for all the kind words. When knowledge is so readily available as it is nowadays, there are no excuses for being lazy!
    Last edited by Michel Hardy-Vallée; 04-15-2011 at 12:50 PM. Click to view previous post history.
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

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  8. #8
    Photo Engineer's Avatar
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    Many early chemists described the taste of every new compound that they made, and there was quite a "dictionary" of types of flavors. I used to enjoy reading some of them, especially the German articles in Berichte and Beilstein trying to figure out the flavors that they were describing.

    Some of those chemists died early, I have been told, but some lived to ripe old ages.

    Unfortunately, you can use old hypo as no-cal sweetener, but only once. You probably would not survive. (just kidding but it will make you very ill, especially those containing Ammonia - enough could kill)

    PE

  9. #9
    holmburgers's Avatar
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    Hmm... can we use ants to test our fixer? (half serious though... now that'd be an old school test method!)
    If you are the big tree, we are the small axe

  10. #10
    Michel Hardy-Vallée's Avatar
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    Wikipedia page on Herschel now updated!
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

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