Author Topic: Hydriodic Acid--Step by Step Write-Up  (Read 16176 times)

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Zen

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ref.
« Reply #60 on: November 01, 2004, 06:01:00 AM »
Correction H2S is pretty explosive.  ;)

"Hydriodic acid, HI, is formed by the direct union of its components in the presence of a catalytic agent; for this purpose platinum black is used, and the hydrogen and iodine vapour are passed over the heated substance. On shaking up iodine with a solution of sulphuretted hydrogen irf water, a solution of hydriodic acid is obtained, sulphur being at the same time predpitated. The acid cannot be prepared by the action of concentrated sulphuric acid on an iodide on account of secondary reactions taking place, which result in the formation of free iodine and sulphur dioxide. The usual method is to make a mixture of amorphous phosphorus and a large excess of iodine and then to allow water to drop slowly upon it; the reaction starts readily, and the gas obtained can be freed from any admixed iodine vapour by passing it through a tube containing some amorphous phosphorus. It is a colorless sharp-smelling gas which fumes strongly on exposure to air. It readily liquefies at 0 C. under a pressure of four atmospheres, the liquefied acid boiling at 34-14 C. (730-4 mm-); it can also be obtained as a solid melting at 50-8 C. It is readily soluble in water, one volume of water at io C. dissolving 425 volumes of the acid. The saturated aqueous solution is colorless and fumes strongly on exposure to air; after a time it darkens iii color owing to liberation of iodine. The gas is readily decomposed by heat into its constituent elements. It is a powerful reducing agent, and is frequently employed for this purpose in organic chemistry; thus hydroxy acids are readily reduced on heating with the concentrated acid, and nitro compounds are reduced to amino compounds, &c. It is preferable to use the acid in the presence of amorphous phosphorus, for the iodine liberated during the reduction is then utilized in forming more hydriodic acid, and consequently the original amount of acid goes much further. It forms addition compounds with unsaturated compounds."

"IODINE." LoveToKnow 1911 Online Encyclopedia. © 2003, 2004 LoveToKnow.

http://33.1911encyclopedia.org/I/IO/IODINE.htm


Lestat

  • Guest
Please don't consider leaving anything ...
« Reply #61 on: November 01, 2004, 09:16:00 AM »
Please don't consider leaving anything generating something as deadly as H2S for all to find, even if it is off the beaten track, a small child could open that, or for that matter the parents, and you would have been responsible for the death quite possible, of an innocent man, and child >:(


NMR

  • Guest
Yes, you are quite correct regarding the ...
« Reply #62 on: November 01, 2004, 09:50:00 AM »
Yes, you are quite correct regarding the preferred method of gas generation, that is, dropping acid upon sulfide rather than dropping chunked sulfide into weak acid.
   My purpose, however, was to tailor a procedure that required no special glassware.  Unfortunately, most do not have dropping funnels, Erlenmeyers, burets and separatory funnels with stopcocks, etc. for such fine control.
   An additional consideration that factored into my choice of gas generation technique was the fact that the crude ferrous sulfide thus generated was in the form of hard chunks semi-coated with un-reacted sulfur.  The experimenter will find that these chunks decompose in weak acid a very constant rate giving quite nice control of the rate of evolution of gas.  Should faster gas evolution be desired, this may be effectuated by simply adding more concentrated acid to the gas generator.  Once the desired rate is achieved, by  adjusting the concentration of the acid in the gas generator, gas will be evolved at a constant and controlled rate for many hours with no further adjustments being necessary until very near the end of the HI production, if at all.  It is almost automatic once it is going.
   However, since you are one of the lucky ones with all of the equipment, let me share a little secret with you.  I would guess that you are one of the ones who generates HCl gas for final conversion, instead of using pool acid like most everyone else does.  You probably drop H2SO4 on NaCl to generate your HCl gas.  The problem with that is that you generate wet HCl gas that must be dried first before introduction into your amine solvent solution.  Instead of using NaCl, use instead CaCL2.  Sulfuric on calcium chloride will generate very, very dry HCl gas, therefore no drying needed, greatly simplifies apparatus needed, cuts much time, and produces better product.

WizardX

  • Guest
Precautions !
« Reply #63 on: November 01, 2004, 10:13:00 AM »
I think I've covered the HI synthesis via H2S + I2 well enough in my X File, so if you take ALL the precautions as indicated, and use some common sense, you SHOULD be OK!

NMR

  • Guest
Reply to Scotty dog about water ratio
« Reply #64 on: November 01, 2004, 10:18:00 AM »
57% is the usual HI concentration made.  Percentage solutions usually are expressed in grams, not moles.  So, in this case, for example, a 57% aqueous solution of something would mean that if I had 100 grams of the solution, 57 grams would be the something and 43 grams would be water.  Here the "something" is HI.  Well, the weight of hydrogen is negligible, so we can just ignore it, therefore we need 57 grams of iodine.  Now, the weight of water is one gram /ml, so 43 grams of water is 43 mls.

   So, for every 57 grams of iodine in your flask add 43 mls of water to get 100 grams of a 57% solution.  Now remember, I said to get 100 grams of solution, not 100 mls.  Since iodine is very dense, HI will also be very dense, much more dense than water.  You will be shocked to see all of that iodine disappear into that little bit of water, but it will in an hour or so of slow bubbling with constant stirring or swirling.

   Also, be careful not to let the sulfur wad that forms on the end of your bubbling tube block the tube, which will easily happen if you stop stirring.  If it does become blocked, mechanically and quickly unblock it or your gas tube outlet will become completely blocked and can cause you gas generator rubber stopper to blow off.

Organikum

  • Guest
H2S produces not 57% HI
« Reply #65 on: November 01, 2004, 03:26:00 PM »
The reaction of H2S with iodine produces not constant boiling HI of 57% whats no "concentrated" HI anyways as HI comes as high as about 70% in concentration so called "fuming HI".
HI made by the reaction of H2S and iodine has to be redistilled to get the wanted 57%.

The reaction setup as published by WizardX in his X-file is inherently hazardous - dont do it this way. If you want how this is done right download the Vogel´s 3rd from Rhodiums page and look it up there.

Wiz, no offense, but I PM´d you about this times ago and I am astonished to see you recommend your dangerous setup here again. Whats up?

The best procedure for HI from H3PO4 was posted by SHORTY - search for it.
This ARGOX stuff is mostly boasting.
The production of HI from H3PO4 makes it possible to get HI stronger than 57% and thats preferred, the stronger the better as stronger HI allows the reaction to be run at lower temperatures and that supresses the formation of byproducts (azides).


Rhodium

  • Guest
azides & aziridines
« Reply #66 on: November 01, 2004, 07:42:00 PM »
stronger HI allows the reaction to be run at lower temperatures and that supresses the formation of byproducts (azides).

Azides are never formed as byproducts in the HI reduction, and I fail to see how the formation of aziridines could be suppressed by a lowered reaction temperature... Could you elaborate?

In my opinion aziridines are formed due to incomplete reduction, while excessive temperatures favor higher condensation products such as the several dozens of known dimers.


Organikum

  • Guest
uups
« Reply #67 on: November 01, 2004, 09:16:00 PM »
aziridines of course.

Wasnt it you Rhodium who posted that high temperatures and high HI concentration favor the formation of aziridines? I think yes. Will do a search when time is by hand.


Rhodium

  • Guest
aziridines are forged by impatience
« Reply #68 on: November 02, 2004, 01:13:00 AM »
Wasnt it you Rhodium who posted that high temperatures and high HI concentration favor the formation of aziridines? I think yes.

Now I catch your drift - the study you are referring to reviewed the infamous "short dry hot cook", in which insufficient water is used and the reaction is not allowed to go to completion. It is the ephemeral and arid aspects of that technique which is to blame, rather than its blazing fury, which merely result in a rather non-specific destruction of precursors and product through condensations, dimerizations and cyclizations.

The article you are referring to might be either the following one, or the one above it in the same thread:

Post 362724 (missing)

(Rhodium: "Methamphetamine impurity identity profiling", Stimulants)



WizardX

  • Guest
What?
« Reply #69 on: November 02, 2004, 11:36:00 AM »
Organikum: states...


The reaction setup as published by WizardX in his X-file is inherently hazardous - dont do it this way. If you want how this is done right download the Vogel´s 3rd from Rhodiums page and look it up there.




The X-file procedure is a merge of references from (1) Vogel´s 3rd Ed, (2) Vogel´s 5th Ed, (3) Journal of Inorganic Chemistry, and two other sites that I can't be bothed right now to look up.


Wiz, no offense, but I PM´d you about this times ago and I am astonished to see you recommend your dangerous setup here again. Whats up?




Post me AGAIN ABOUT YOUR CONCERNS? PLEASE!


Organikum

  • Guest
I will see if I have the PM exchange on disk...
« Reply #70 on: November 02, 2004, 06:27:00 PM »
I will see if I have the PM exchange on disk somewhere Wiz, where I uttered my critics and YOU advised me to use the method as described in Vogel´s 3rd instead.


WizardX

  • Guest
Compare Procedures.
« Reply #71 on: November 03, 2004, 01:33:00 AM »
Organikum: Lets for argument sake I responded, "where I uttered my critics and YOU advised me to use the method as described in Vogel´s 3rd instead."

This is to give you a reference to read and compare both procedures.

Organikum

  • Guest
Two points: - H2S + I will not produce 57% HI...
« Reply #72 on: November 03, 2004, 03:12:00 PM »
Two points:
- H2S + I will not produce 57% HI without redistillation
- magnetic stirring the vessel where the HI is formed and sulfur precipitates is impossible, the stirrbar WILL clog. Thats why Vogel advises a STRONG OVERHEAD stirrer.

My advises:
- use pitch to seal the vessels and connections
- do this under a fumehood, outsides or at a window with a fan blowing out
- dissolve the iodine in a solution of KI or NaI and dont stirr at all
- redistill (preferred), or alternativly use the KI/NaI-HI solution produced together with anhydrous H3PO4 directly for reduction.
- go slowly

The setup is:
H2S generator - into - KI/NaI-iodine in water solution - over - water - into - soda crystals.
Avoid any more schickmick in the setup it WILL cause trouble and will NOT provide more safety.


WizardX

  • Guest
HI
« Reply #73 on: November 04, 2004, 03:18:00 AM »


From X-File 9

57% HI SOLUTION (HYDRIODIC ACID) : B.p 125.5-126.5 deg C/760mm Hg ;
Density 1.70 gr/ml ;  55-57%  w/w HI is 0.936 to 0.99  grams of HI per ml.

H2S + I2 ===>> 2HI + S

In a fume cupboard a 1.5 three neck flask is added a mixture of 480 grams of
iodine and 600 mls of distilled water. The centre neck is added a sealed stirring unit which leads almost to the bottom of the flask. The left neck is fitted and sealed with a glass tube which extends almost to the bottom of the flask but does not touch the stirrer. This is connected to the hydrogen sulphide (H2S) generator.  The right neck is fitted and sealed with a short glass tube connected with a plastic tube to the bottom of an inverted   funnel in a 5% sodium hydroxide solution.

The mixture is vigorously stirred and a stream of hydrogen sulphide (H2S) gas is passed rapidly in the iodine/water mixture as rapidly as it reacts with the iodine. After several hours, 2-3 hours, the iodine disappears and the liquid assumes a yellow colour (sometimes almost colourless) and most of the precipitated sulphur sticks together in the form of a hard lump.[NOTE 1]
This liquid contains a mixture of HI, H2S and S. The liquid is now filtered through a large funnel plugged with glass wool to  remove the sulphur S. No need removing the dissolved H2S as this enhances the reductive power. Add a few crystals of iodine to this HI/H2S solution and store at 0-5 deg C.

[NOTE 1] The sulphur lump in the flask can be removed by refluxing with concentrated nitric acid.


From X-File 11

FLASK C: H2S GAS ABSORBION TRAP and HYDRIODIC ACID SYNTHESIS

57% HI SOLUTION (HYDRIODIC ACID) : B.p 125.5-126.5 deg C/760mm Hg ;
Density 1.70 gr/ml ;  55-57%  w/w HI is 0.936 to 0.99  grams of HI per ml.

H2S + I2 ===>> 2HI + S

In a fume cupboard a 1.5 three neck flask is added a mixture of 480 grams of
iodine and 600 mls of distilled water. The centre neck is added a sealed stirring unit which leads almost to the bottom of the flask. The left neck is fitted and sealed with a glass tube which extends almost to the bottom of the flask but does not touch the stirrer. This is connected to the hydrogen sulphide (H2S) generator.  The right neck is fitted and sealed with a short glass tube connected with a plastic tube to the bottom of an inverted   funnel in a 5% sodium hydroxide solution.

The mixture is vigorously stirred and a stream of hydrogen sulphide (H2S) gas is passed rapidly in the iodine/water mixture as rapidly as it reacts with the iodine. After several hours, 2-3 hours, the iodine disappears and the liquid assumes a yellow colour (sometimes almost colourless) and most of the precipitated sulphur sticks together in the form of a hard lump.[NOTE 1]
This liquid contains a mixture of HI, H2S and S. The liquid is now filtered through a large funnel plugged with glass wool to  remove the sulphur S. No need removing the dissolved H2S as this enhances the reductive power. Add a few crystals of iodine to this HI/H2S solution and store at 0-5 deg C.

[NOTE 1] The sulphur lump in the flask can be removed by refluxing with concentrated nitric acid.



I suggested the magnetic stirring if you want to contain the entire reaction in the glass fish tank. There are magnetic stirring units that have good torque with a large stirring magnet.

Azeotropic distillation (57% HI SOLUTION (HYDRIODIC ACID) : B.p 125.5-126.5 deg C/760mm Hg) will ONLY give 57% HI at 760mmHg. Increase pressure, increase HI concentration.

A 57% HI SOLUTION (HYDRIODIC ACID) cooled to 0-5 deg C, will increase in HI concentration IF you bubble HI gas into it. Approx 60-61% HI SOLUTION (HYDRIODIC ACID) at 0-5 deg C.


NMR

  • Guest
Reply to WizardX regarding your numbers
« Reply #74 on: November 04, 2004, 07:25:00 AM »
Dear WizardX:

     I have had a chance to read some of your Xfiles; they are very well done and you have quite a flare for making clear write-ups.
     But, it appears that you may have accidently mis-transcribed some numbers from your notebooks in your posting above:
     Your figures above do not appear to be correct.  You call for 480 g Iodine and 600 mililiters of water; these amounts do not make a 57% solution:

     480 g Iodine/(480 g Iodine + 600 ml's of Water)X100=(480/1080)X100=44.44% solution

For 480 g Iodine, the calculation is as follows:

     Let y=grams of solvent=grams H2O:
                                                  
                                                    480 g Iodine/(480 g Iodine + y) X 100 = 57
                                                    480 X 100                                      = 57(480 + y)
                                                                                             48,000 = 27,360 + 57y
                                                                                                  57y= 20,640
                                                                                                     y= 362.11 ml's

So, for 480 grams Iodine, you add only 362.11 ml's of water and gas with hydrogen sulfide to get a 57% solution.

WizardX

  • Guest
HI
« Reply #75 on: November 04, 2004, 12:59:00 PM »
I2     +   H2S  ==>  2HI     +  S

253.8  +  34.1  ==>  2x127.9 + 32.1

287.9           ==>  287.9

Reaction is balanced.

Now, 1 mol of I = 126.9 grams/mol.   So, 480/126.9 = 3.78 moles of I.

OR

Now, 1 mol of I2 = 253.8 grams/mol.   So, 480/253.8 = 1.89 moles of I2, equivalent to 3.78 moles of I.

Ratio of I2:HI is 1:2  Therefore, 2 x 1.89 moles of I2 = 3.78 moles of HI.

Concentration = moles/volume (Lt)

Concentration of HI = 3.78/(600/1000) = 3.78/0.6

Concentration of HI = 6.3 mol/Lt

OR

6.3 x 127.9 = 805.77 grams of HI per Lt. This is a 47% w/w HI.

Since, 55-57%  w/w HI is 0.936 to 0.97 grams of HI per ml. Therefore, 0.99 x 1000mls  = 990 grams of HI per 1Lt (1Lt = 1000mls)

When you azeotropic distill at B.P 125.5-126.5 deg C/760mm Hg you get 57% HI with is 0.97 grams of HI per ml, (7.58 mol HI/Lt) = (7.58 x 127.9 = 969.5 grams of HI per Lt)

NOTE The Vogel reference states a 57% w/w HI as 0.99 grams of HI per ml.

NMR

  • Guest
Reply to WizardX re: HI route
« Reply #76 on: November 05, 2004, 02:35:00 AM »
Ok, so you agree with my figures for the most part, the difference between my 44.5% and your 47% being the result of the simplification I used in the calculation, that is, disregarding the hydrogen in HI and just calculating from the weight of the iodine only.

   So, what you are saying, then, is that the Vogel method uses the strategy of first getting a good rough acid strength approximation first, as in your example, say 47%, and then relies upon a distillation to get the final concentration.

   In other words, the initial H2S preparation is intentionally less that the desired end product, relying upon a separate process, azeotropic distillation in this case, to arrive at the final concentration.  OK, I see that.

   Now, the question naturally arises, is this two step process, as opposed to the single step process, with its attendant added difficulties and glassware requirement, of any demonstrable benefit if the HI is not being used for analytical purposes?

    That is, yes, of course, the two step process will give a purer product, a result necessary if the HI is to be used in quantitative analysis, but is that extra purity and precise control of concentration of any demonstrable benefit when the acid is to be used in a reduction reaction, especially when the recycling phosphorus is coming from matchbooks?

   My point is this: HI by the sulfide reaction affords the average user a quick, cheap, and unlimited access to strong HI and reduces the phosphorus requirement by 75%
    But that advantage to the average user vanishes if he is constrained to do a complex distillation with equipment that he likely does not have.  In other words, it appears to be an unnecessary and artificial roadblock to what should be seen, otherwise, as a holy grail route to the acid.
   In other words, it seems much like the pointlessness that I am guilty of above, that is, using a calculation simplification that introduces a 2% error and then reporting my result to two decimal places, silliness that is a result of pure habit.

   An additional minor point, if distillation is performed, any remaining H2 S is lost, dissolved H2S in the acid will actually reduce further the phosphorus need in the main reductive reaction, a minor point though.

Can anyone tell me how to work all of those buttons and choices on the posting page, any instructions around?

NMR

Organikum

  • Guest
Dear NMR, you dont get 57% HI from H2S and...
« Reply #77 on: November 07, 2004, 03:53:00 PM »
Dear NMR, you dont get 57% HI from H2S and iodine at all without redistillation. Thats the point. No matter how much iodine you throw into the mixture, there is something called "equilibrium".
Look it up.


Zen

  • Guest
H2S / I / E via Reflux
« Reply #78 on: November 08, 2004, 02:53:00 AM »
Reaction Mechanism:

1.  Fe(II) + S => FeS

2.  FeS + 2HCl => H2S + FeCl2
 
3.  H2S + I2 => 2HI + S

4.  2HI + E-OH => E-I + HI + H2O

5.  HI + E-I => M-H + I2

Summary:

1.  5.58 g Iron (II) plus 3.21 g Sulphur hydrated with 100 ml d:H2O then evaporated to dryness at 100 C to yield 8.79 g Grey Ferrous Sulphide.

2.  Iron Sulphide plus 7.29 g Hydrogen Chloride in acid solution is treated in a Kipp's Apparatus to produces 3.40 g (2.2 L) Sulphuretted Hydrogen Gas.  

3.  25.38 g Elemental Iodine reacts with Hydrogen Sulphide to yield 25.58 g Hydrogen Iodide in solution plus 3.20 g Sulphur precipitate.

4.  16.52 g Ephedrine Freebase in the presence of 12.79 g HI reduces to 1.80 g H2O.

5.  Remaining 12.79 g HI reduces Iodated Ephedrine to 14.92 g Methamphetamine and 25.38 g Iodine is returned.

Notes:

1.   Straight forward enough, glass vessel recommended because product sticks to stainless steel. Do not over evaporate.

2.   Kipp's apparatus is implemented for the production of a gas by interaction of a liquid and a solid.  It consists of three receptacles.  The top is a reservoir for the liquid and is connected to the bottom.  The middle contains the solid and a tap for the gas.  When gas is released the liquid rises and reacts with the solid. When the tap is closed the back pressure returns the liquid to the lower reservoir and the reaction ceases.

3.   A 2 L reaction vessel can contain most of the evolved gas when connected to a push pull gas trap/scrubber.  A low temperature dry ice condenser fabricated from 1/4" SS tubing could also be implemented.  A 3 L pressurized vessel (aka bomb) would also be capable of containing the fumes from this reaction and allow for easier agitation of solution.  A small portion of THF may be added as dilute providing an excellent solvent for increasing reaction rates and yields by improving gas permeability.

4.   The hydroxy group is reduced to an Iodate under high acidity (45-50%) where by the reaction is hydrated and acidity slightly diluted.

5.   The second half of the reduction will succeed with a lower acid concentration (35-40%) under light reflux (70 C). In a theoretical molar perfect reaction resulting mixture should be easily quenched with distilled water to yield a low volatile solution.  A second volume of gassing would accelerate the reaction but result in a more volatile end solution.  If reaction is preformed in situ FeCl2 acts as drying agent and yields 1,2,4,6 hydrates, furthermore, initial H2O is introduced via muriatic acid solution.


lsd

  • Guest
Re - 115% concentration?
« Reply #79 on: November 12, 2004, 04:07:00 AM »
How do you get a concentration of 115%?
100% is a whole portion isn't it or is it like your yanky over proof alcohol?