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entropy51
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You're full of it, JohnWW, or maybe they don't let people in New Zealand have access to dangerous things like chemistry books.
When I click that link there's a button to download PDF, and I did that just now.
Off your meds again?
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S.C. Wack
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That problem and its solution have been discussed time and time again, even in this thread. Like it needs to crawl across the top of the screen in
flashing red or something.
Simple heating of ferrocyanide to just below red heat is wasteful of CN, since some nitrogen is lost. Needless to say, the ferrocyanide must be quite
white first.
It was just last night that I threw away a shelf near where I had ground dried ferrocyanide on years ago, the blue stains that eventually showed up
were still there.
So anyways as some have found, the distillation from H2SO4 is less than theoretical. The addition of CuCl has been recommended - CA 6, 2375 (1912):
A New Method for the Estimation of Ferrocyanides. H.E. WILLIAMS. J. Soc. Chem. Ind. 31, 468-71 [1912] The limitations and errors of the methods in
general use are discussed and the following method given: Dissolve 0.5 g. of the ferrocyanide in 100 ml. of water, transfer to a 250-300 ml.
distilling flask and add 0.05-0.1 g. of CuCl dissolved in a few drops of HCl, or a sat'd soln of NaCl or KCl; gently shake to mix contents add 25-30
ml. of 4N H2SO4 and distil through a condenser into absorption flasks containing NaOH or KOH. The ferrocyanide is completely decomposed and the HCN
distilled off in about 30 mins. gently boiling. The distillate is washed out and titrated in the usual manner with AgNO3 using a few drops of 10% KI
soln. as indicator. If desired 25-30 g. of ferrocyanide may be taken, only between 2-3% of its wt. of CuCl being required. Sufficient H2SO4 over that
required to form FeSO4 and NaHSO4 must be added. It is advisable to wash the CuCl with a little dil. H2SO4 before using to remove any CuCl2. Sol. or
insol. ferrocyanides or those of the heavy metals may be estd. Insol. compds. are finely powdered, transferred to flask and requisite amts. of
reagents added. In the case of ferric ferrocyanide Prussian blue etc., more CuCl than that already mentioned should be added. Results reported are
practically theoretical even on an experimental scale using 20-25 lbs.
[Edited on 30-9-2009 by S.C. Wack]
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JohnWW
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Using Mozilla Firefox 3.52, the latest version, when I load
http://books.google.com/books?id=qE4wAAAAMAAJ in the browser, I find that NO such button appears, inviting one to download the book as a PDF.
Perhaps Mozilla Firefox cannot load such download buttons? What sort of browser did you use?
I find that most, if not all, books (usually incomplete, even the clearly copyright-expired ones) that Google posts online can be only viewed online
as single OCRed pages, the images of which cannot be downloaded, except by screen-capture using something like ScreenThief.
[Edited on 30-9-09 by JohnWW]
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entropy51
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Quote: Originally posted by JohnWW  | Using Mozilla Firefox 3.52, the latest version, when I load http://books.google.com/books?id=qE4wAAAAMAAJ in the browser, I find that NO such button appears, inviting one to download the book as a PDF.
Perhaps Mozilla Firefox cannot load such download buttons? What sort of browser did you use?
I find that most, if not all, books (usually incomplete, even the clearly copyright-expired ones) that Google posts online can be only viewed online
as single OCRed pages, the images of which cannot be downloaded, except by screen-capture using something like ScreenThief.
|
Your browser may be the problem. I'm using the lame old IE 6.0 something or other. Google won't let you
download PDF for anything after 1920 or so, even if copyright is expired, but these old books are available, at least to me. What can I say? Except
that I try to always check the links that I post?
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entropy51
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| Quote: Originally posted by S.C. Wack | | That problem and its solution have been discussed time and time again, even in this thread. Like it needs to crawl across the top of the screen in
flashing red or something. |
Those who ignore history.......
That's what happen when threads exceed a few pages.
Thanks for posting the other prep!
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crazyboy
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I am considering a synthesis which may employ small amounts of HCN. Obviously this is an incredibly dangerous and hazardous compound and before I even
think of generating such a compound I would like to know if anyone has ever dealt with it and exactly what precautions should be taken.
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kmno4
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Adding some Cu salt as catalyst of decomposition of ferrocyanide sounds very promissing.
I have a few grams of CuCN so I am going to try it.
I think I will try 25g of K4[Fe(CN)6] and 1g of CuCN.
I have read about decomposition of ferrocyanide with Hg or Mg salts, but Cu is something new for me 
BTW.
Sometimes Google Books try cheating by not allowing some books to be downloaded by some IP numbers.
Then you try cheating by changing IP (proxy). In most cases even "useless" Codeen proxies are good for this purpose.
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Taoiseach
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| Quote: Originally posted by garage chemist | Ullmanns Encyclopedia says 0,57g/100g in 100% Ethanol at 19,5°C, and 4,91g/100g in Methanol at the same temperature. No other temperatures are given.
I've used Methanol with a Soxhlet extractor to extract KCN from the powdered residue of K4Fe(CN)6 fusion, and the residue from evaporating the MeOH on
a boiling water bath in vacuum came out as 85% KCN upon titration with 0,1M AgNO3. |
85% purity is less than satisfactory. Any idea what other crap has dissolved in your methanol?
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Jor
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| Quote: Originally posted by crazyboy | | I am considering a synthesis which may employ small amounts of HCN. Obviously this is an incredibly dangerous and hazardous compound and before I even
think of generating such a compound I would like to know if anyone has ever dealt with it and exactly what precautions should be taken.
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Fume hood and gloves (absorbed through skin!), or outside. It is dangerous, but not THAT dangerous. The compound is about 3 times as toxic as
chlorine, but has bad warning properties (some people cant smell it).
There are much more hazardous gasses like phosgene (10 times more toxic). I have generated quite a lot of HCN, and no problem at all.
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woelen
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I also once had an experiment, which went awry somewhat, the contents of a test tube was bubbling vigorously, giving off pure HCN gas. I lighted the
gas and it nicely burnt away, until the vigorous reaction stopped and evolution of gas became too slow to keep the flame. So, this also can be an
option if you have to deal with a stream of HCN gas. In the past, this was used as a fiarly safe way to get rid of the gas, which burns to CO2, H2O
and N2.
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kmno4
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I have just tested this "Cu method".
Effect is the same as without Cu 
Maybe is works on high dilutions and large excess of acid.
Volume ~130 ml, 0,5g K4..... and ~48-fold mole excess of H2SO4 is not interesting for me. On this proportions it woks also without any Cu salt, as it
is described in previously cited paper from JChemSoc.
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entropy51
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| Quote: Originally posted by kmno4 | I have just tested this "Cu method".
Effect is the same as without Cu
Maybe is works on high dilutions and large excess of acid.
Volume ~130 ml, 0,5g K4..... and ~48-fold mole excess of H2SO4 is not interesting for me. On this proportions it woks also without any Cu salt, as it
is described in previously cited paper from JChemSoc. |
Without a catalyst only part of the ferrocyanide is converted to HCN. A few percent by weight of CuCl increases the yield of HCN considerably for me.
How did you determine that the effect was the same as without Cu? It doesn't require a huge excess of H2SO4. See the patent I posted in the
References Wanted thread about a week ago.
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kmno4
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| Quote: Originally posted by entropy51 | | A few percent by weight of CuCl increases the yield of HCN considerably for me. How did you determine that the effect was the same as without Cu?
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I determined it by weight, comparing (by amount of prepared NaCN) with no-Cu methode described earlier by me.
But what you mean by "considerably" ?
How much of KCN or NaCN can you get from, for example, 100g of anhydrous K4[Fe(CN)6] ? Just recalculate it accordingly to amount of K4... used by you.
BTW. I have found paper about cyanate/cyanide conversion:
J. Am. Chem. Soc., 1918, 40 (3), pp 482–489.
The most important conclusion from reading it: cyanides are really powerfull reductants 
ps. I read mentioned patent but I cannot find amounts of chemicals needed to convert given amount of K4.. to HCN. Some amounts are given but with no
sense for me.
ps2
Funny thing. I discovered that CuCN I put in flask (with H2SO4, K4.. and H2O) reminded undissolved  .
Maybe CuCN is not catalyst, but some chloride salts ?
I will try with CuCl, but I have to prepare it first
[Edited on 1-10-2009 by kmno4]
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entropy51
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Did you use enough H2SO4? Without Cu you need 1.5 mol H2SO4 per mol of ferrocyanide. With Cu catalyst you need 5 mol H2SO4 per mol of Ferrocyanide.
If the H2SO4 is your limiting reagent, adding catalyst won't increase the yield. That's the reason for the stoichiometry used in the patent.
Have you ever tried to titrate your NaCN product? Just to see how pure it is?
Seems like the Cu would need to be in solution to work, doesn't it?
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kmno4
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Patents are very bad source of knowledge, in most cases.
I took 25g of K4[Fe(CN)6], 52g of 96% H2SO4, ~160g of H2O and 0,7g of CuCN (small granules, 1-2 mm).
After 5-hours heating (boiling) I still had lots of light green shit in a flask.
After cooling I removed green slury from flask and then noticed granules of CuCN on the bottom. It seem that CuCN is not soluble in this mixture on
boliling. It would be good if someone else confirmed (or not) this observation.
Yield of NaCN: ~6g. A few grams remain in ethanolic/water solution (~200 ml) . So it is close to 50% recovery of cyanide from ferrocyanide.
Purity: unknown, probably very high because it works as it should work. I have to buy at last some standard sol. of AgNO3 to confirm this purity.
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entropy51
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| Quote: | | It seem that CuCN is not soluble in this mixture on boliling. |
CuCN is not soluble in most aqueous, not even acids (up to a point). It dissoves in aqueous NaCN.
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kmno4
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So maybe CuCN is not a catalyst (as patent states) in this reaction. Besides it is hard to imagine how any Cu salt can act for ferrocyanide
decomposition in H2SO4.
But if CuCl really works catalytically, then real catalyst can be HCl. It sounds stupid, but....
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Jor
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I wonder if dilute HCl also works in place of H2SO4, as some H2SO4 tends to oxidise the cyanide. Indeed you wouldn't want the HCl to run in your
EtOH/KOH, but at low concentration, water evaporates and not HCl, until the azeotrope is reached.
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entropy51
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| Quote: Originally posted by kmno4 | So maybe CuCN is not a catalyst (as patent states) in this reaction. Besides it is hard to imagine how any Cu salt can act for ferrocyanide
decomposition in H2SO4.
But if CuCl really works catalytically, then real catalyst can be HCl. It sounds stupid, but.... |
I think the Cu salt needs to be in solution. I dissolved the CuCl in a minimal amount of HCl before adding it, which is what Williams describes in
the article quoted by S.C. Wack above. For me, CuCl gave over a 50% increase in HCN, determined by titration. I did not try to isolate the NaCN - I
have enough of that for the time being.
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kmno4
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It is interesting, but I would be more interested in absolute amounts and conditions.
50% increase from 30% gives 45%... etc
Has your ferrocyanide dissolved completely ?
I am afraid that Cu cannot exist in any soluble form in such mixtures, because it will be converted to unreactive CuCN in these conditions at once.
However, I will try this. But first I will try simple NaCl as "catalyst" to exclude/confirm any "HCl mechanism".
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S.C. Wack
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Maybe you should read Williams' book?
http://books.google.com/books?id=vW86AAAAMAAJ&pg=PA361
Whether it's practical compared to other methods is debatable, but as far as actual results when done properly, it's completely non-bullshit.
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JohnWW
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Its details are:
The Chemistry Of Cyanogen Compounds And Their Manufacture And Estimation (1915)
Author: Williams, Herbert E
Subject: Cyanogen compounds
Publisher: London : J. & A. Churchill.
You can download it through this page:
http://www.archive.org/details/chemistryofcyano00willrich
The URLs for downloading it directly are:
http://ia331413.us.archive.org/2/items/chemistryofcyano00wil... 42.5 Mb and
http://ia331413.us.archive.org/2/items/chemistryofcyano00wil... 11.7 Mb
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kmno4
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Williams' book says about patent (in case of use CuCl), not about practical method
This is reality, not patented :
25g K4[Fe(CN)6], 52g H2SO4, 100g H2O and ~0,5g CuCl dissolved in conc. NaCl solution(~10 cm3).
Reaction goes smoothly, boiling mixture is a little pinky, in the end of reaction it turns white and HCN stops to go off. After cooling colour is
quickly getting blue. Of course flask is full of suspension, as usually....
Amount of distillate: 5,5 g
It corresponds to ~50% of total cyanide from K4[Fe(CN)6] and ~100% yield of HCN in this conditions.
Another patent, another bullshit....
[Edited on 4-10-2009 by kmno4]
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Taoiseach
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Ammonium cyanide from K4FeCN6 and NH4Cl is confirmed by "the chemistry of cyanogen compounds" p. 39, available from archive.org:
"It is prepared in the dry state by gently heating(sic!) finely powdered potassium cyanide or ferrocyanide with ammonium chloride: K4FeCN6 + 6NH4Cl
---> 4KCl + FeCl2 + 6NH4CN, and condensing the vapour in a receiver cooled with a freezing mixture"
Heating an intimate mixture of 37g ferrocyanide and 25g salmiac to 100°C should give 24g ammonium cyanide. Adding 20grams KOH in ethanol should lead
to precipation of pure KCN.
NH4CN is slightly less volatile than HCN (bp 36°C vs 26°C) and might be more convenient to work with.
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entropy51
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| Quote: Originally posted by kmno4 | Amount of distillate: 5,5 g
It corresponds to ~50% of total cyanide from K4[Fe(CN)6] and ~100% yield of HCN in this conditions.
Another patent, another bullshit.... |
How you figure 5.5 gm of distillate is 50% without titrating the CN?
Not bullshit, with CuCl I can get 80% of the CN from ferrocyanide. That's by titration.
S.C. Wack seems quite capable of detecting bullshit, and he said it ain't.
It didn't work for you because your CuCN wasn't dissolved.
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