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  1. #41

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    Quote Originally Posted by Nikola Dulgiarov View Post
    . Mp is accurate, but the product seems to decompose at a lower temperature, presumably due to impurities.
    I don't know about glycin but there are some compounds that do start to decompose before reaching their melting point. This compound is know to decompose quickly at room temp so I would not be so quick as to say your product is not pure.

  2. #42
    Nikola Dulgiarov's Avatar
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    It is suggested that it browns at a temperature below mp and decomposes at bp, so I'd call the test valid, too
    I forgot to add that I tested the compound and it is a developing agent, but what should I look for when mixing a batch (i.e. activity in a carbonate alkali, relative induction time, image tone or papers) ?
    Thank you for your support and concern
    Nick

  3. #43
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    Nick;

    Good glycin is a pure white fine powder. It does brown up with keeping. I have no other guideline to suggest.

    PE

  4. #44

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    Quote Originally Posted by Nikola Dulgiarov View Post
    If you have ideas for any other test that can be carried out, I'd be glad to hear you out
    http://books.google.com.ua/books?id=...oluble&f=false
    To few milligram of compoind add FeCl3 solution. A blue coloured solition is obtained.
    PS I search any description or ideas for purification of old "brown" glycine
    Last edited by Relayer; 05-23-2013 at 04:23 AM. Click to view previous post history.

  5. #45
    Nikola Dulgiarov's Avatar
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    Yeah, the above test works for most aromatic compounds with a hydroxyl group, so in most cases it gives a "positive"
    As to purification, I can see two things working - a simple water recrystallization, but solubility in boiling water is still too low to make it viable. Secondly, dissolve the glycin in any mineral acid, preferably not a strong oxidizer, and neutralize. For example, warm 15% HCl will gladly dissolve all the glycin I try to put in it. Then, either via an indicator, pH meter, test paper, titrate to a neutral reaction with a base of your choice. Try to keep the amount of acid and base to a minimum so that there isn't a lot of salt to get rid of. Leave overnight in cold water, or icebath, or cooler at 5-10C. Filter and wash the precipitate with 2 parts water (you can wash as much as you like, but the minimal amount of salt remaining isn't fatal). Dry and either make up a stock solution in 1% Na2SO3 and 3%Na2CO3, or store in a vacuum-sealed envelope
    As to my progress. I feel that I have done what I wanted to, and my last test had a yield of 75% of the theoretical ( the remainder was left in the filtrate, as i hurried too much and shortened crystallization 4x.) The approach I took is analogous to the production of N-phenylglycine from aniline, whereby a derivative of MCA is used to prevent the formation of the pAP.HCl salt. Well, that is all there is to say. Case closed I'd like to thank all of you, who gave me reasonable advice and warning, and in particular to Rudi, who translated Vater's article and referenced me to the German patent I was looking for. Thank you

  6. #46
    Nikola Dulgiarov's Avatar
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    PS: Relayer, the above purification procedure is based on my experiences and may not prove useful for old, brown glycin. Try it on a quarter of a gram or so, as a proof of concept, before running a larger batch.

  7. #47

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    Nikola, thank you. Week ago I was try purification of glycin via dissolve in 20% H2SO4 and titration. Yes, it working, but result isn't have same activity as fresh glycin. I found that glycin soluble in EtOAc (Ethyl acetate). Maybe try this way later.

  8. #48
    Nikola Dulgiarov's Avatar
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    You can try the reverse, precipitating it from a basic solution with acetic acid, which doesn't dissolve as much glycin as the mineral acids. Activitywise, I am unable to make a claim.

  9. #49
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    Here is a thought for testing. Either IR (Infra Red) or NMR (Nuclear Magnetic Resonance) will do the trick. If a local school has either unit, a simple 10 minute test on either will reveal the nature (and possible purity including contaminants) of your material. I can't hurt to ask someone.

    There are huge textbooks of spectra out there that will also help.

    PE

  10. #50
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    Edit: Ours is $55/100g I think, I was thinking of catechol before, we have cheap catechol.
    Last edited by Athiril; 05-24-2013 at 04:33 AM. Click to view previous post history.

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