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Author: Subject: picramic acid from picric
prometheus1970
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[*] posted on 24-1-2011 at 09:11


I'd really prefer to avoid any disonsety like the plague when pursuing this hobby. I fear that, should it come up, the fact that I lied aboutsomething is more likely to make me look like a criminal (somebody with evil intent rather than just somebody who intends to break the law, because it should not apply to those without ill intent). If my honesty precludes me from obtaining certain things, then I'll look to another primary to synthesize.

Speaking of which, I just read Mr. Anonymous' thread on azo clathrates and he described that as an OTC synth l don't know of where to get azides for that synthesis, so how is it OTC?




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[*] posted on 24-1-2011 at 09:43


Yeah, I know the feeling . . .
But if the honest approach drives you to experiment with unsafe materials then it'll be misplaced honesty!

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[*] posted on 24-1-2011 at 09:54


I have been reading about all the many things that people have been trying and proposing to get picramic acid.
I was once in a similar position, I had tried several experiments with ascorbic acid for example. I did not try the sodium hydroxide/sulfur reaction since it had so many poor reviews at the E&W. Eventually I decided that I was going to do it right and use Na2S and that was that. The options that I felt I had were as follows:

(1) Reduce sodium sulfate with carbon at 900-1000 C (could be done in steel plumbing pipe. If it is galvanized be sure to dissolve the Zinc with HCl first).

(2) Reduce CaSO4 with carbon at 900-1100C then react the CaS with Na2CO3 in a solvent.

(3) Bubble H2S through NaOH in some solvent ( methanol comes to mind, you want to eliminate water as much as possible since it is virtually impossible to properly dry the Na2S)

I ended up buying the Na2S before I tried the above options, and I must say that the classical sodium picramate synthesis is wonderful and produces a beautiful, pure, free flowing product from which high quality DDNP can be made.

I eventually did try to produce Na2S via method 2 above. The carbon reduction went well but just takes time, an advantage is that any unconverted gypsum is insoluble and can be easily filtered out with the excess/unreacted carbon. However, in the metatheses reaction with aqueous sodium carbonate the sulphide solution is fairly rapidly oxidized by the air turning yellow. I attempted to get by this by just working quickly and while I was able to get some hydrate of sodium sulphide, I did not titrate it. I tried to run the reaction in methanol and could not get is to go, despite running it under magnetic stirring for a month.

I think that directly reducing sodium sulfate would be easy to do, it has the advantage of directly producing an anhydrous product that is easily soluble in methanol allowing separation from reactants. (Anhydrous Na2S is quite soluble in methanol, Na2SO4 and hydrated Na2S are not)

Option 3 would only have been done as a last resort as the risks inherent with handling largish volumes of a fairly pure H2S gas stream are not to be taken lightly.

[Edited on 24-1-2011 by markgollum]
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Rosco Bodine
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[*] posted on 24-1-2011 at 10:23


H2S is easy to produce either by acidifying a sulfide/polysulfide or possibly by heating paraffin and sulfur together...and this could be used as in your scheme #3
or similar scheme. However, the sulfide route is one of many different methods which could work.

With regards to azides, sodium azide is itself producible via OTC materials.
The particulars for that have been described more than once in discussions
here and elsewhere. If I can search and locate those discussions for posting
a link here, then so can other people search and find. It has been an idea
of mine for a long time that some folks need to do a lot more reading before
they post to avoid covering things already covered before. Spoonfeeding gets old
and it just leads to more and more indulgence while the level of discussion
is not advanced. Reverse engineering has already been done, seek and ye shall find.
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[*] posted on 24-1-2011 at 15:24


Many thanks for the ideas about producing sodium sulphide Markgollum! I will surely give the carbon reduction of gypsum a try one day. It is good to know that producing (presumably) high purity picramic acid is possible using Na2S. The polysulphide reduction (NaOH and S) never gave good results, either with homemade nitrite, (Lead+NaNO3 --> CO2) or reagent grade nitrite. The step to produce Na2S myself however was too much for me, given the substantial danger of working with H2S and the uncertanty whether the picramic acid was the problem or the diazotization itself. :)



[Edited on 24-1-2011 by nitro-genes]
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[*] posted on 24-1-2011 at 21:10


I would actually prefer to directly reduce sodium sulfate for the following reasons.

1) After extraction of fused product with methanol then boiling down the Na2S would be obtained in a fairly anhydrous form.

2) The reaction occurs in the liquid phase and would presumably be faster.

3) A lot more product could be produced.

One possible problem is that the carbon dust could float up to the top of the melt.
If this happens then it should be no problem to add so much carbon that the melt is more of a paste than than a liquid. The extra carbon should also reduce the strength of the fused product making is easier to chip/hammer it out of the pipe.
One possible idea would be to melt and carbonize a mixture of sugar and Na2SO4 in a pan then use the black lumps in the pipe.
Of course you would want to prevent oxygen from the air from entering the pipe. One setup which I have applied in making calcium cyanamide (I haven't characterized the cyanamide, but I basically followed the method Rosco has described: converting cyanuric acid to a sodium salt then precipitating the calcium salt) in a pipe is in threading a short 6" section of steel air brake line to the top end cap. I stand the pipe up in my electric furnace allowing the steel air brake line to protrude from a hole in the lid, this allows me to keep track of the reaction progress by lighting "flaring" the evolving gasses (if excess cyanuric acid is used, it sublimes and can plug the tube so I keep a torch handy to heat the tube as well as a stiff steel wire I can use to check for blockages).
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[*] posted on 16-12-2013 at 13:21


Thread seems old, anyway I want to ask if reduction of PA with oxalic acid will work yield picramate in boiling basic solution? This thought came to me as I expect oxalic acid to decarboxylate on heating(basic solutions promote that, isn't it?) to give HCOOH which may be able to do the work. Sorry, no real references can I provide, since searching on reductions with oxalic(or salts) gave nothing very interesting, except maybe unrelated this: http://pcat.cat.hokudai.ac.jp/document/pdf/NTB2009.pdf
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[*] posted on 17-12-2013 at 14:32


I was under the impression that the reduction required a basic solution to prevent over reduction to triaminophenol, hence the neutralization to picrates and scorbates that were discussed earlier. If so, then an oxalate salt would be required.
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[*] posted on 18-12-2013 at 06:15


Reading several papers it turns out that aromatic nitro reductions can yield different products depending on conditions and reducing agents. This paper (final pages missing) http://www.sciencemadness.org/talk/files.php?pid=215569&...
"The Alkaline Reduction of Aromatic Nitro Compounds with Glucose" Though the paper starts with
"The fact that aromatic nitro compounds may be reduced by glucose in alkaline solution was apparently first discovered in 1865 by Braun who found that on heating an alkaline glucose solution with picric acid a red color developed, which he believed was due to the formation of picramic acid."
it doesn't give any information if that was further confirmed, and their own findings indicate that glucose reduces nitro aromatics to azo- and azoxy- compounds (coupling).
Same conclusions from book "FUNDAMENTAL PROCESSES OF
DYE CHEMISTRY", see chapter "reducion in general" it states "Reduction by glucose and alkali is used only in a very special field: the
reduction of nitro compounds to azoxy and azo compounds."

On the bright side, "THE REDUCTION OF SOME NITROBENZENES WITH ASCORBIC ACID"
http://dergiler.ankara.edu.tr/dergiler/31/1438/16170.pdf
it states that dinitrophenol is partially reduced to amino- nitrophenol with ascorbic acid, alkali and FeSO4 catalyst, I think that's going to work also with PA.

What are your thought, especially on glucose - may it be that reaction with PA still yields picramic acid, regardless how differently glucose gives azoxy- compound in other cases (though were with mono nitro), because sombody spoke here about blood(urine) sugar tests based on reaction with PA if I remember correctly.
How do you people confirm that what you got is what you intended to get?





[Edited on 18-12-2013 by papaya]
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[*] posted on 27-1-2014 at 14:10


I have been reading about DDNP for about 6 years now, off and on, and it has always seemed sort of illusive. Reading posts here and from the old Rogue science forum it was clear that the big problem was obtaining a suitable reducing agent. The most common and effective selective reducing agents seem to be sodium sulfide, sodium hydrosulfide and ammonium sulfide. After reading one of the excerpts from an early twentieth century chemistry book posted on this forum, I decided to try generating hydrogen sulfide gas and bubble it through a sodium hydroxide solution in order to obtain sodium sulfide or hydrosulfide. The method involves heating a mixture of low volatility hydrocarbon with sulfur. In this case Vaseline was used, but I have seen examples where paraffin was specified. A pdf of the excerpt is also attached at the end of this post.

I have taken a lot of pictures, which should do most of the explaining. A Vaseline and sulfur mixture was put in a mason jar, which had a perfect hole cut in its top to accept a rubber stopper. A piece of mild steel brake line was used to lead and cool the hot gas from the generator to the clear vinyl tubing and bubbler at the other end. An aquarium air stone or bubbler was used as the diffuser.

Safety was of utmost importance, as very small amounts of this gas can kill you. It was a very cold (-20C) and breezy day. The generator was outside and I was inside, behind a glass door that is reasonable airtight, controlling the power to the hotplate remotely with a variac (variable auto transformer).

I increased the power to the hotplate gradually over the course of 30 minutes or so until a fairly steady, but slow, stream of bubbles was coming from the diffuser. I didn't increase the power to the hotplate at this point because I believed slower production was safer. After an hour and a half I was forced to stop as the sulfide/hydroxide solution started to freeze and the diffuser also froze which filled the backyard with H2S stink for 10-15 minutes. It was such a cold day, however, that no one was outside anywhere near where I was operating which was fortunate. Judging by the volume increase at least 3/4 of the sodium hydroxide was converted to sulfide. According to Wiki the yellow colour of the solution is from polysulfide contamination.

The last picture shows the reactants which were to be used for the following partial reduction producing sodium picramate. The sodium (hydro)sulfide solution is on the left and picric acid made (days ago) from aspirin is on the right.

Simple and Cheap Sealed Vessel.jpg - 402kB H2S Bubbler or Diffuser.jpg - 231kB Hydrogen Sulfide Generator.jpg - 414kB Hydrogen Sulfide Bubbling.jpg - 419kB Near End.jpg - 407kB Variac or Variable Auto Transformer.jpg - 413kB Hydrogen Sulfide or Hydrosulfide Solution.jpg - 431kB Reactants for TNP Reduction.jpg - 204kB


Attachment: Hydrogen Sulfide Gas Preparation_prothiere1903_abstract.pdf (100kB)
This file has been downloaded 483 times


[Edited on 27-1-2014 by Hennig Brand]




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[*] posted on 27-1-2014 at 15:14


Next, a reduction of the ortho nitro group of picric acid, the one in the 2 position, was performed. Five grams of picric acid (from ASA) was dissolved in a methanol-water solution and neutralized with sodium hydroxide. The solution was made from about 75% methanol and 25% water by volume.

I found a page with the reaction equations, going from TNP to DDNP, which was part of a Chinese primary explosives presentation. I have included a jpg of that reaction equations page, as well as a link to the whole presentation.

http://www.cecd.umd.edu/documents/presentations/Hong-Kong/Yi...

The article I was reading when I performed the reduction is attached, and was also found on this forum. I believe Rosco posted it. I didn't follow it accurately unfortunately, because of not knowing the process well and being distracted. The reaction time was much longer than recommended by the article and it took me a long time to get the temperature up to where it should have been. I also was unsure of the concentration of my previously prepared sulfide solution and I am sure I didn't use enough. A ferrous sulphate solution was used to test for reaction completion, but in retrospect it was obvious that the endpoint hadn't been reached. I obtained about a 60% yield, and the article reported yields in some cases in the high 90's. I still have at least 3/4 of my sulfide solution, so I will try again.

The colour change going through the reduction reaction is really very beautiful. The product in the last picture is (or should be) sodium picramate.

Conversion of the sodium picramate to picramic acid was easily accomplished by dissolving it in water and acidulating with sulfuric acid. Pictures of the picramic acid produced, as well as the DDNP produced from it, will be shown in the DDNP thread.

DDNP from Picric Acid Reaction Equations.jpg - 53kB Ferrous Sulphate Solution.jpg - 314kB Reduction 1.jpg - 256kB Reduction 2.jpg - 254kB Reduction 3.jpg - 235kB Reduction 4.jpg - 236kB Reduction 5.jpg - 236kB Sodium Picramate (1).jpg - 282kB Sodium Picramate (2).jpg - 226kB

Attachment: Picramic Acid using Sodium (Hydro)Sulfide J[1]. Chem. Soc., 1945, 663 - 665,.pdf (344kB)
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[Edited on 27-1-2014 by Hennig Brand]




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[*] posted on 27-1-2014 at 16:23


"According to Wiki the yellow colour of the solution is from polysulfide contamination."

I've been told that sulfur contamination is detrimental, and you've gotten around that by going for H2S. Do you know what effect the polysulfides would have on the final DDNP?
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[*] posted on 27-1-2014 at 17:17


I think the polysulfide contamination is only present in very small quantities. The yellow colour gradually developed after an hour and a half of bubbling hydrogen sulfide into the sodium hydroxide solution. I believe a lot of lab grade solutions have a slight yellow tinge to them for the same reason. If it was absolutely pure it would be clear, from what I have read.



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[*] posted on 27-1-2014 at 18:51


I can vouch for the yellow color of lab grade stuff. I have tech grade Na2S.3H2O and it forms slightly yellow solutions.
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[*] posted on 27-1-2014 at 20:00


Actually after reading a bit more, it seems that sodium hydrosulfide is easily converted to polysulfides by oxygen. There could be more polysulfides in that solution than I thought. There is a very good chance that I converted a lot of the sodium hydroxide all the way to sodium hydrosulfide.

From Wiki page on sodium sulfide:

"Sodium sulfide is the chemical compound with the formula Na2S, or more commonly its hydrate Na2S·9H2O. Both are colorless water-soluble salts that give strongly alkaline solutions. When exposed to moist air, Na2S and its hydrates emit hydrogen sulfide, which smells like rotten eggs. Some commercial samples are specified as Na2S·xH2O, where a weight percentage of Na2S is specified. Commonly available grades have around 60% Na2S by weight, which means that x is around 3. Such technical grades of sodium sulfide have a yellow appearance owing to the presence of polysulfides. These grades of sodium sulfide are marketed as 'sodium sulfide flakes'. Although the solid is yellow, solutions of it are colorless."

From Wiki page on sodium hydrosulfide:

"Solutions of HS− are sensitive to oxygen, converting mainly to polysulfides, indicated by the appearance of yellow."





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[*] posted on 29-1-2014 at 15:33


Just so it's clear, the green solution in the second picture above is slightly acidic aqueous ferrous sulphate. It was used as an indicator in order to test for the presence of sulfide. A little of the reduction reaction mixture was extracted with a pipette from time to time and placed in a small beaker, to which a little ferrous sulphate solution was added. A black precipitate of iron sulfide would show that the reduction was complete and that there was unreacted sulfide in the reaction mixture. Obviously waiting a certain length of time after a sulfide addition before doing the test is required.

Fe2(SO4)3 (aq) + 3 Na2S (aq) ---> 3 Na2SO4 (aq) + Fe2S3 (s)

The ferrous sulphate solution was prepared by dissolving fine steel wool in dilute sulfuric acid.


[Edited on 30-1-2014 by Hennig Brand]




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[*] posted on 29-1-2014 at 18:39


I was thinking just now, 'gee what about the excess NaOH in the reducing solution that you failed to neutralize, what will happen when it enters the reduction reaction'. Its a good thing actually because the picric acid will over-reduce if done in an acidic solution. The sodium picrate is formed to allow an alkaline solution for the reaction, using excess NaOH. I love it when a plan comes together.
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[*] posted on 30-1-2014 at 02:37


I am pretty sure all, or most, of the NaOH was converted to at least sodium sulfide and probably mostly to sodium hydrosulfide actually. I didn't actually test it, just judging by the quantities needed to reduce a give quantity of picric acid and the color of its solution, etc. Yeah, that was my thought too, that a little extra NaOH in the reaction mixture wouldn't be a problem most likely.


[Edited on 30-1-2014 by Hennig Brand]




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[*] posted on 1-2-2014 at 10:19


Quote: Originally posted by Hennig Brand  
I am pretty sure all, or most, of the NaOH was converted to at least sodium sulfide and probably mostly to sodium hydrosulfide actually. I didn't actually test it, just judging by the quantities needed to reduce a give quantity of picric acid and the color of its solution, etc. Yeah, that was my thought too, that a little extra NaOH in the reaction mixture wouldn't be a problem most likely.


[Edited on 30-1-2014 by Hennig Brand]


S-2, much like oxide does not properly exist in solution. In solution, it exists as equimolar HS- and OH-.




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[*] posted on 4-2-2014 at 08:27
Sodium Picramate - Experimental


Some more sodium picramate was made and this time greater care was used to record some of the reaction conditions and quantities used. This process is not optimized and neither are the quantities used.

Five grams of picric acid (from ASA), of greater than 98% purity as indicated by melting point, was dissolved in 100 mL of methanol and heated to 50-55C. Sodium hydroxide (0.9g) was dissolved in 20 mL of water and with stirring was slowly poured into the alcoholic picric acid solution neutralizing the picric acid and forming sodium picrate. While maintaining the temperature of the reaction mixture between 50-55C, sodium (hydro)sulfide solution was pipetted in, with magnetic stirring, a mL at a time over the course of 20-30 minutes. The sodium (hydro) sulfide solution was made by bubbling hydrogen sulfide gas through an aqueous solution of sodium hydroxide. Four grams of sodium hydroxide was used for the solution. The amount of Vaseline and sulfur placed in the H2S generator was at least 50% more than would be needed if all H2S was absorbed and converted to dissolved sulfide salt. The volume of sodium (hydro)sulfide solution obtained was ~45mL. About 15 mL was used to reduce the 5g of sodium picrate to sodium picramate. Ferrous sulfide solution was used to test for reduction reaction completion. After the last sulfide addition, heating was maintained for an additional 10-15 minutes and then the heating was stopped and the reaction mixture allowed to cool. Once the reaction mixture had cooled to about 40C, about 75 mL of ice cold water was added and the beaker was set into an ice-water bath and cooled very quickly to 10C or below. The sodium picramate was then filtered out and washed with small quantities of ice cold water.

From 5g of picric acid, 3.8g of sodium picramate was obtained or about a 79% yield. My last experiment produced only a 60% yield. The biggest difference between the two experiments was that the first experiment used less methanol and more water as the reaction solvent/medium. A little greater care was also used when testing for reaction completion, though I am not sure I really got it right yet. There is a lag time, governed by the reaction time, between when the reducing agent is added and when it is consumed.


Sodium Picramate.jpg - 256kB

[Edited on 4-2-2014 by Hennig Brand]




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[*] posted on 4-2-2014 at 10:36


The absence of any sulfur as a trace impurity would be desirable, particulaly for a DDNP destined to be mixed with chlorate since sulfur and chlorate are a bad storage stability, known incompatability. This is one reason why alternative means of reduction were examined.
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[*] posted on 4-2-2014 at 15:44


Are you implying that the sodium(hydrogen)sulfide isn't appropriate for this reduction? It seems to isolate the sulfur from the reaction.
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[*] posted on 4-2-2014 at 19:49


I think he is referring to some of the non sulfide reducing agents that have been experimented with. The mixed polysulfide reducing material (made the cookbook ways from sodium hydroxide and sulfur) is apparently bad for producing a lot of sulfur contamination. I tried the cookbook method a few years back, but it didn't work for me. I don't think that sulfur contamination would be much of a concern with the sodium (hydro) sulfide solution of reasonable purity. My H2S gas generator and absorption setup is a joke though. It does work, but the gas could be cleaned before it got to the bubbler and a lot could be done to improve safety and improve absorption of the gas.

I have made enough chlorate/sulfur/aluminum crackers to know that chlorate and sulfur are not at all storage stable. Small amounts decomposing in storage don't ignite or anything (that I have seen), they just degrade in a matter of weeks to a state where performance is severely diminished.

[Edited on 5-2-2014 by Hennig Brand]




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[*] posted on 5-2-2014 at 07:35
reduction of styphnic acid with tin chloride


on a similar note to the reduction of picric acid, why in the following patent would the use of tin chloride be preferred to the sodium sulphide approach used for picric acid ?



Attachment: USE OF TIN CHLRIDE FOR REDUCTION.pdf (240kB)
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[*] posted on 5-2-2014 at 12:25


There is an inevitable sulfur impurity and diaminonitrophenol impurity in the picramic acid produced by a sulfide reduction. That is why purification schemes have been used for the picramic acid to free it from such impurities. Other reduction schemes for producing picramic acid from ammonium picrate or sodium picrate using other reducing agents are probably superior in terms of avoiding the impurities. Many reducing schemes not involving sulfides can likely be used so long as the reduction is carried out at a temperature and pH that favors the production of picramate, meaning mild temperatures and alkaline reaction systems.

Alternate possible reduction schemes would include sodium ascorbate, ferrous sulfate, manganous sulfate, sodium bisulfite, zinc powder or zinc amalgam, aluminum amalgam, iron filings, magnesium turnings, possibly formaldehyde or hydrazine, or electrolytic reduction.

The hydroxy DDNP analogue of US4246052 attached again here and its salt forming ability looks interesting and promising. The hydroxy DDNP may be subject to forming azide and hydrazine derivatives similarly as does DDNP which could increase its energy even further. Interesting how the hydroxy picramic acid may be obtained from a reduction of styphnic acid in acidic medium, because it may follow the same track and be more easily reducible in alkaline medium, as does occur for the reduction of a picrate to a picramate.

Attachment: GB412460 Lead Dintrophenylazide.pdf (331kB)
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Attachment: GB406228 Lead Dintrophenylazide.pdf (172kB)
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Attachment: US2728760 Kenney , hydrazine derivative lead salt of DDNP.pdf (124kB)
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Attachment: US4246052 SnCl2 reduction of Styphnic Acid and DDNP analogue therefrom.pdf (240kB)
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[Edited on 5-2-2014 by Rosco Bodine]
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