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Quince
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The patent was useful for the solubility data (ASA/acetone w/w 0.62 @ 55*C, 0.22 @ 10*C).
The method itself is not suited to home use due to the replacement solvents given (carbon tetrachloride or benzene).
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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Rosco Bodine
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@quince
Denatured alcohol is a common article of commerce , a solvent / fuel that the Canadian revenue page lists a dozen different formulations in virtual
agreement with US formulas , so I can't imagine why there is any problem finding it in Canada .
Aspirin sold in bottles labeled " Aspirin " should be pure aspirin as required by law consistent with the label , containing only inert
binders for holding the tablets together , and it should be the cheapest medicene on the shelf anywhere even in grocery stores . Aside from that you
could just get veterinary aspirin powder by the pound which is probably pure acetylsalicylic acid . If neither of these options are available , then
you might try using oil of wintergreen ( methyl salicylate ) instead . I haven't tried it myself , but it has been reported by others to
sulfonate and then nitrate in a similar way to aspirin , and requires no purification .
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Quince
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Accident report
Well, I had my first runaway nitration. I had the NaNO3 in one beaker, and the ASA in another. Since I didn't have enough NaNO3, I made up the
difference with KNO3, except I mistakenly added the KNO3 to the beaker with the ASA instead of the one with the NaNO3. You can guess what happened
when I started adding H2SO4 to the former. Instant huge brown cloud. I reacted quickly, but nonetheless I did breathe in some, especially in the
time after the cloud dissipated, but there must have been a good deal left due to the poor ventilation, as I'm feeling the pain now in the lungs.
I did breathe in ammonia several times, so I don't know if it's an excess of nitric acid or ammonia in my lungs that's causing the
pain. The beaker was filled with hot brown stuff, which is hard to wash, so I tried bleach, which turned it PA yellow. I don't know if I should
go to emergency, as they'll probably call the cops and I'll be in shit. Should I breathe in more ammonia, or is too much danger of
overdoing it?
[Edited on 29-7-2005 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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neutrino
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I doubt they'll ask too many questions. If they do, tell them that something at school/work went wrong.
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Bert
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To quote ATSDR:
| Quote: |
There is no antidote for nitrogen oxide poisoning. Treatment for exposure usually involves giving the patient oxygen and medications to make breathing
easier.
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ATSDR/Nitrous oxides poisoning
To quote Roscoe on page 3 of this thread:
"The fumes produced by the nitration are deadly poisonous and extreme caution
should be observed to provide some sort
of * steady * ventilation to carry the fumes away . If such ventilation cannot be provided , then the reaction should not be done until that necessity
is met .
Otherwise , the " surprise " for the oversight or carelessness will be
much more serious than some stained fingers . The insidious nature of the fumes is that you won't even realize the exposure in real time as it
occurs , but 12 to 24 hours later , when the unforgiving learning experience is an unexpected visit from the grim reaper chuckling to himself about
how yeah here's another one who just didn't get it . "
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Rosco Bodine
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@Quince
I hope it isn't serious , and you learn something from the carelessness at no greater cost than some worry .
If with passing time you are feeling worse instead of better , seek medical attention .
They will probably have you inhale some sort of mist medication like albuterol or similar medication such as used for people
having asthma or having gotten smoke inhalation near a fire .
Really I don't mean to make you feel worse for saying so , but you should do more reading and thinking about what you are doing , and have more
situational awareness when you are handling chemicals and doing experiments .....or
else you should find a different interest than experimental chemistry .
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Rosco Bodine
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Betaine
In another thread the usefulness of
Betaine ( vitamin B14 , IIRC ) as a stabilizer referenced in GB191405737 is mentioned . Betaine binds chemically with up to one half its own weight
with nitrous and nitric radicals which makes it a useful stabilizer . Since betaine is also
a low toxicity naturally occurring substance in the body , actually a vitamin ,
it would seem to be a good candidate as an antidote for exposure to inhaled nitric
oxides . In exactly what form it may be useful as an aerosol mist inhalant , perhaps as some buffered lactate or citrate or combination in proportion
with
the freeform betaine , is unknown . But the possible usefulness of betaine as an antidote is there , if the betaine formulation could be taken as an
inhalant
without causing some adverse reaction itself . Medicene is not my area of expertise , but if betaine has not been investigated as an inhalant
antidote for nitric oxide specifically , but some betaine medication for inhalation use already exists for some other purpose , this may be something
for a doctor to consider as
an off label use in certain circumstances .
It may be that this is already known and tried , or used but not commonly known ,
or something already ruled out for some reason . Or it may be one of those things that has never been tried , in which case it may be an idea worth
testing .
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Quince
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I feel fine now. From what I read, medication is supportive only, at most steroids are given. I think quickly going for the ammonia may have helped
me out here. The problem with the ammonia is that it itself has a fairly unpleasant feeling. I guess the worst that happened this time is all the
wasted time I spent purifying the ASA...
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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Rosco Bodine
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An ounce of prevention ......
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Ajantis
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Ok, I attempted my first picric acid Synth, with powerlabs procedure.
I started from 20g salycilic acid and my yield is 25g, 70% of the theoretical, some PA had been lost during the filtering. I had no problems with the
procedure exept when adding nitric acid to phenol 4 sulphonic acid... i perfomed this step outdoor, my acid were chilled to -15C so the reaction took
about 20 min to begin but when it started a HUGE cloud of NO2 developed, i've never seen so much NO2 in a time, the cloud was about 6m long, and
at 10m distance i could clearly smell its odour  So, Be careful with this step!
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Joeychemist
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RLMAO!!
| Quote: | Originally posted by Ajantis
I had no problems with the procedure exept when adding nitric acid to phenol 4 sulphonic acid... i perfomed this step outdoor, my acid were chilled to
-15C so the reaction took about 20 min to begin but when it started a HUGE cloud of NO2 developed, i've never seen so much NO2 in a time, the
cloud was about 6m long, and at 10m distance i could clearly smell its odour
So, Be careful with this step! |
That sounds to me like you had a partial runaway reaction There should not be
a giant cloud of Nitrogen Oxides, but only a very small amount produced during the entire reaction. Did the temperature rise considerably?
If it was a partial runaway you are very lucky that you did not get hurt, but next time you may not be so lucky...
[Edited on 4-8-2005 by Joeychemist]
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Rosco Bodine
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picric acid ? from methyl salicylate
Many years ago around the first time I made picric acid from aspirin , I also tried
using methyl salicylate . It is also called oil of wintergreen for the product steam distilled from the natural leaf , 99.7% pure for the expensive
medicinal grades .
Anyway my first experiment was not successful , but some years later about three and a half years ago a post was made at E&W by vonK reporting
success ,
and I have done a couple more experiments to study the reaction further ,
and also to evaluate some ideas that may be more general with regards to picric acid synthesis from any precursor . Alternative precursors to phenol
are of most interest since phenol is expensive and not essential . Refinements to the nitration are also of interest . After only two preliminary
experiments which are not yet fully completed I am still far from being able to provide description of a good working method or optimized synthesis
from start to finish . However I can share some interesting observations and ideas for others who may also want to work on this line of research . I
would encourage the novices to be patient and let the more experienced pursue the experiments , especially any of the sizeable scale batches . These
experimental nitrations have not yet been evaluated fully or established to be predictable or safe .
Two experiments have been performed which have produced substantial amounts of picric acid from methyl salicylate . The product is not yet isolated
and dried so I cannot give the yield .
Experiment 1 :
50.5 grams ( 43 ml ) of methyl salicylate was added to 250 ml of 92% H2SO4 .
A mild exotherm 10C rise on mixing was observed . The mixture was heated to 135C and held at 135-145C for 3 hours .
A white thin vapor appearing like wisps of steam would slowly come off during the sulfonation , but the vapor had a stifling odor like formaldehyde or
dimethyl sulfate and was avoided , taken away by powered ventilation .
After allowing to cool to 45C , 40 grams of NaNO3 was added in small portions to the well stirred mixture , about a third teaspoon at a time . Rate of
addition was used to maintain about 70 C , each addition allowed to dissolve and slight foaming to subside before the next portion being added . The
intended mononitration seemed to peak on its own exotherm at about 74C and then began cooling . Likewise addition of a second 40 gram portion of
NaNO3 was begun . This
went more rapidly due to lower exotherm after each addition . Foaming was observed but appeared to be decarboxylation foaming predominately , with no
substantial red fumes below 74C ,
but at 75C and induction of sorts with sudden foaming of the threatening sort appearing . In hindsight , this is where I should have probably added
supplemental heating to force induction and slowed the additions to keep the reaction controllable but driving it at a higher temperature . But what
I did instead was to allow the exotherm to peak at 75C for the dinitration . 90-95C would have probably been better , and some holding time for maybe
20 minutes
before proceeding to the trinitration stage . A final addition of 30 grams NaNO3 was made at the 75C , with little
change being noticed during the time the portions were being added . 75C was too low and so after a few minutes some
supplemental heating was applied , and all it took was the little nudge of 5C for the nerve wracking little third stage runaway . I managed to
mitigate the foaming with increased stirring and a few
small squirts of water from a wash bottle onto the surface of the foam . But the frothing continued and the mercury was at 115 C and climbing rapidly
when I aborted the uncontrolled reaction by dumping the flask into a large bowl of water . There was a red cloud of nitrous
fumes roiling from the angry looking mixture which wasn't quenched a moment too soon , and some of the fragments of reaction mixture were molten
picric acid way above the safe temperature . Some of the material I think actually sublimed from the heat and condensed onto my ringstand a couple of
inches away . But most of the flask contents got into the water quickly and the batch was salvaged at the point of reaction which was well towards
completion when the runaway occurred . Picric Acid was definitely made
from methyl salicylate , but the reaction conditions need some more experimentation and refinement . The purity of the product by color appears to be
excellent , very pale yellow . The crystallization for some reason seems to go much slower than for the product made from aspirin . The initial yield
after dilution of the reaction mixture looks poor , but the crystals continue to precipitate slowly over many hours in the cooled mixture and even
more when it is cooled very cold to freezing temperature to harvest the crystals by filtration for recrystallization from boiling water . Whatever is
the impurity from the use of methyl salicylate , seems to make the crystallization not as crisp as the product from aspirin , solutions seem to linger
in superstauration and then deposit more slowly a finer and softer product . It may require a second recrystallization to get the same quality , or
refinement of the nitration may clean up the crystallization which follows . Admittedly I did not stop the crystallization as I usually do with the
solution still slightly warm at filtering which produces a more shiny and crunchy product , but cooled the solution to drop more of the product out
because I was in a hurry to simply salvage the batch , and see what sort of weight I salvaged . I knew I could recrystallize later when I can add the
product to a crystallization of a larger batch(es) and save labor fooling around with separate crystallizations for each small yield from several test
batches . I like to work up at least 3 liters of solution for a crystallization of picric acid because it seems to require that minimum amount to get
good crystals . Smaller quantities don't seem to have the thermal mass for slow enough cooling to form good crystals .
Others have observed the same peculiarity .
Experiment 2 :
This experiment took a different track for the nitration , where I decided to try some ideas I have kept wanting to test concerning the presence of
water in greater amounts in the nitration mixture .
After sulfonation I diluted the mixture with some added water before the nitration . And instead of portionwise additions of a solid nitrate , I used
a dropwise addition of a strong solution of a nitrate . Departing from convention I also used ammonium nitrate because of its high solubility , and
because its conversion to nitric acid in sulfuric acid is actually facilitated by the presence of water . This scheme worked and produced a good yield
in the end , but like the first experiment the process definitely needs refinement . The mononitration stage was extremely slow and sensitive to
temperature at about 50 C seeming optimum , and requiring literally all day to complete . This would likely have to be automated , unless some
workaround could be devised to expedite the mononitration . The dinitration and trinitration go smoothly and fairly rapidly at 95C and 115C
respectively , but the mononitration is tediously slow . Much of the decarboxylation seems to occur in the mononitration stage which is good , and I
believe it is the water content which accounts for this . In nitration mixtures having low water content , for aspirin the decarboxylation seems to
occur in the trinitration stage when the viscosity of the mixture makes the foaming problematic if the reaction rate surges even a moderate amount .
In the thinner
mononitration stage , with water present and the precursor being methyl salicylate the effervescing foam dissipates easily .
Then the higher nitration proceeds smoothly with any remaining decarboxylation occuring just before the end of the nitration . The nitration mixture
is a transparent yellow liquid as it approaches the endpoint at 115 C and is effervescing freely as if an alka seltzer was boiling away but producing
no red fumes , only a thin wisp of azeotropic nitric acid vapor from the acid in excess .
The effervescing stops and then the mixture becomes cloudy but no solid picric acid precipitates until the mixture is dumped onto an equal volume of
ice cubes and allowed to stand for several hours when a heavy precipitation occurs .
The precipitation is not immediate as occurs when aspirin is the precursor . Because of the delayed precipitation the yield at first appeared poor ,
but a few hours and some time in the freezer brought the precipitation to completion .
Experiment 2 details :
Methyl Salicylate ( 82 ml ) was added to 395 ml of 92% H2SO4 and the mixture was heated to and held at 145C for 4 hours . The heating was
discontinued and after an hour the mixture had cooled to 85C and was covered and set aside overnight .
The next day the sulfonated mixture was diluted with 70 ml distilled H2O dripped slowly onto a thermometer leaning in the flask . The water flowed
down the thermometer into the stirred mixture without causing any undue heating or acid splattering . The valve on the funnel was preadjusted to a
slow drip rate while held over an empty beaker , and then the funnel emptied before positioning over the flask . Then the dilution water was added in
small portions to the funnel to keep it replenished , so it acted as a preset flow regulator and the addition rate was controlled from the first drop
.
While the sulfonated mixture was diluting ,
a nitrating agent was prepared separately . 194 grams of NH4NO3 was dissolved in 130 ml hot distilled H2O . Total volume was about 255 ml for the
solution . It was filtered through a cotton plug to remove a small amount of suspended matter . A first portion of 100 ml was used for the
mononitration of the diluted sulfonated precursor . The addition literally required all day at a very slow drip rate of about 8 drops per minute and
reaction temp ~50C for the most of the time . The reaction was very sensitive to any attempts to drive it faster and would respond to any increases
with foaming and red fumes . An infusion pump and a close temperature controller might be necessary for any practical use of this method , if the
conditions cannot be modified to improve efficiency . I suspect that the high ratio of water to nitric in such a mixture is highly oxidizing instead
of preferentially a nitrating mixture in its effect . The desirable aspect is that most of the decarboxylation
is achieved simultaneously . There is likely some modification of this mixture which can run faster and still be stable and this will require some
process engineering , otherwise known as trial and error, to discover what is optimum 
At the end of a long day , when all the first 100 ml of NH4NO3 solution had been added to the stirred mixture . The stirring was stopped and the dark
red mixture set aside to fizz and stew overnight .
The mixture was returned to the hotplate stirrer and the temperature was gradually raised to 90C for the addition of the 80 ml
of solution estimated for the dinitration .
The rate of addition was allowed to bring the temperature up to 95C which was maintained by rate of addition . As the reaction proceeded there was no
red fumes but continued mild effervescence .
Supplemental heating was increased to maintain 95C at the end of the addition .
And then the final portion of 70 ml NH4NO3 solution was added to complete the trinitration , with supplemental heat ramped slightly and maintaining
110 degrees with endpoint at 115C held for about thirty minutes past the end of the addition . Stirring was stopped and the clear yellow liquid
gradually became cloudy as the nitration completed . Heating was stopped and about 15 minutes later the mixture 800 ml in volume was dumped onto an
equal volume of ice cubes to dilute and cool and precipitate . The crude crystals are still in the filter , pressed to a hard lump and drained , a
coffee filter full to the top edge weight unknown .
Anyway , from these two experiments is some information which may be useful in further experiments towards refining the method for methyl salicylate ,
and perhaps applicable to aspirin as well .
The ability to add the nitrate as a solution is definitely of interest , as is the use of NH4NO3 for the nitrate . It may be of benefit to use the
solid nitrate for the mononitration in the absence of so much added water in the stage where it causes oxidation to be aggravated , and then bring the
added water into the system at the dinitration stage where it seems beneficial . The reactions work , but refinements and streamlining the process
are definitely needed for this to be a straightforward method as with aspirin .
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IPN
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I recently made a batch of picric acid from ASA (50g) by the method D from lambdasyn.tk
So, nitration went well and a good yeild of product was obtained and I started to recrystallize it by dissolving in 1l of boiling DH2O.
After dissolving, I placed the 2l beaker aside and wrapped it in some cloth. Some hours later it was still warm and to my suprise the picric acid had
formed _big_ platelike crystals. Would it be safe to crush the crystals or should I reheat and let it cool a bit faster?
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neutrino
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Definitely reheat and cool faster, e.g. dump onto ice. Big crystals are much more sensitive and dangerous than smaller ones.
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IPN
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Ok, that's what I'm doing now.
Here's a pic of the crystals.
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Rosco Bodine
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don't fear the crystals of picric acid
@IPN
Crystals are what you want , and slow cooling of hot concentrated solutions is the way to get them . When the solution is even still slightly warm ,
the best crystals have already formed . More crystals will precipitate with time , and at cooler temperatures if weight is what you want instead of a
desirable physical form .
So if shiny well formed crystals which filter easily and dry more quickly are your desired form for the product , then you have to give up some weight
and filter while still slightly warm . Then you concentrate the residual solution and take a second crop while still warm , or just cool it and drop
out the remaining yield as the finer more powdery form .
I am experimenting with simplifying and taming the synthesis so that large batches of even several hundred grams can be made in a crock pot by a
reaction which may take awhile but can be run unattended for most of the process . From what I am observing a presence of some water content in the
nitration mixture is desirable , and also the greatest exotherm for the nitration occurs in the mononitration . It may be possible to start the
mononitration at about 55-65C and then use a cooling bath in order to hold down the temperature at about 50C and allow for a more rapid completion of
the mononitration stage . The remaining nitration goes much more smoothly once the mononitrated phenolsulfonic stage is completed , and the final
nitration is more safely conducted , absent any tendency for runaway . The precursor becomes more resistant to oxidation or decomposition in the
mixture after it reaches mononitration , so that is the first hurdle to get past , and decarboxylation early in the process is a bonus , which gets
most of any foaming problems out of the way early in the nitration .
Some futher experiments are definitely in my plans , for both aspirin and methyl salicylate starting material , and using a solution of ammonium
nitrate instead of solid nitrates . These potential improvements should make it possible to make sizably larger batches in a safe and controlled
predictable way , which involves a lot less labor than the solid nitrate and more anhydrous nitration mixture methods . I really think I am onto
something here with these experiments .
It is something which has probably been done before since it seems so simple ,
and the reaction conditions and behavior of the reactions is in agreement with the descriptions of industrial methods found in several old patents
from nearly a hundred years ago . This is sort of "lost art" which I am looking into , and there is already experimental evidence that such
technique can simplify synthesis of picric acid in ways which are entirely scalable upwards without difficulty or danger .
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neutrino
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Sorry, I must have been thinking of some other explosive I came across in Mega's lab. I could have sworn that PA and dumping onto ice went
together somehow.
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Rosco Bodine
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The time that ice is used is when the spent nitration mixture is diluted . An equal volume to twice the volume of ice seems about right . I like
about twice the volume of ice cubes because that dilution is one which allows for a paper filter to survive the filtration so long as the filtration
is completed within a couple of hours . A less diluted reaction mixture will complicate filtration by weakening the filter paper to the point it is
disintegrating some time later when the crystals are rinsed from it into water for the boil and recrystallization . The reason ice is used is to
absorb the exotherm from the heat of dilution for the highly acidic spent nitration mixture which is itself still warm and carrying a lot of heat in
its mass already which must also be dissipated ,
along with the heat of crystallization which is given off as the picric acid drops out of solution . If just the right amount of ice is used , it
should all be just finished melting about twenty minutes after dilution of the spent nitration mixture and the mixture should be cold .
The solubility of the picric acid is low in the cold diluted nitration mixture and most of it will precipitate within three hours if the mixture is
kept cold and allowed to stand .
Picric acid readily forms supersaturated solutions in nitration mixtures and also in plain water , and takes its time crystallizing from solution ,
there being several hours delay to achieve the crystallization endpoint for a given temperature which defines the solubility .
So patience is required to see what amount of crystals will finish forming at any given temperature , and the warmer the finishing temperature for the
crystallization , the more noticeable is the sluggishness for the crystallization . There is no way to rush the process at near ambient finishing
temperatures . I let my crystallizations stand at room temperature for a day or two before regarding them as complete , but at least six hours would
be a good rule of thumb .
A lot of still dissolved product will be lost if the process is rushed and filtered too early . When boiling down a concentrated solution of picric
acid , the solution will become cloudy at the point where the boiling down needs to be ended , after adding a little makeup water to reclarify it and
drop it below saturation . If any filtration of suspended material is needed to be done in advance of the first crystallization , an addition of
maybe 5% of the cloudpoint volume of fresh water back to the boiling mixture will
be sufficient to keep the solution from crystallizing during the cooling it encounters while being filtered through a cotton plug in a funnel .
Sometimes this may be needed if impurities are evident in the solution in the first boiling , and it is desired to clarify the solution for a cleaner
first crystallization . Better crystals are obtained from a very transparent solution which has been polished by minimal filtration to remove any
overt particulate impurities .
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Ajantis
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| Quote: | Originally posted by Joeychemist
| Quote: | Originally posted by Ajantis
I had no problems with the procedure exept when adding nitric acid to phenol 4 sulphonic acid... i perfomed this step outdoor, my acid were chilled to
-15C so the reaction took about 20 min to begin but when it started a HUGE cloud of NO2 developed, i've never seen so much NO2 in a time, the
cloud was about 6m long, and at 10m distance i could clearly smell its odour
So, Be careful with this step! |
That sounds to me like you had a partial runaway reaction There should not be
a giant cloud of Nitrogen Oxides, but only a very small amount produced during the entire reaction. Did the temperature rise considerably?
If it was a partial runaway you are very lucky that you did not get hurt, but next time you may not be so lucky...
[Edited on 4-8-2005 by Joeychemist] |
I don't know if temperature raised considerably because i stayed safely far away  however Sam said that large amounts of nitrogen dioxide would develop during this step...
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Rosco Bodine
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Extreme cold is likely counterproductive for the mononitration , unless you are using nearly anhydrous acids and are using the cold to hold down the
reaction rate . Because of the extreme cold slowing the reaction , what would be likely is an accumulation of unreacted acid and then an uncontrolled
sudden rise in reaction rate when after the temperature
clowly climbed to an induction point . The idea for controlling a reaction is to have your reaction proceeding smoothly at a temperature where the
reaction rate can be controlled by the addition rate . Once those conditions are identified , then you can scale up or down without having any
uncontrolled surges to cause difficulty or danger .
The induction temperature may be above or below the steady reaction temperature by some amount , and it may change somewhat as the reaction proceeds .
But usually there is a sort of happy medium temperature where most of the reaction will proceed smoothly for each stage .
The best mononitration temperature is going to depend somewhat on the water content and acid ratio in the nitration mixture . And the mononitration
stage is more sensitive to rate and temperature than are the dinitration and trinitration .
For your particular nitration mixture you will have to experiment and take notes to identify the conditions which give good results . From these
notes you can then develop a sort of graph from which you can learn the optimum conditions and then have a reproducible method .
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Quince
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Hi, the cheapest ASA here contains propylene glycol. When looking up solubility, it dissolves in acetone and alcohol. What if I wash the aspirin
with a bit of water first (which I already do to remove the hydroxypropyl methylcellulose)? ASA solubility in water is about 1/100 w/w. For
propylene glycol, the datasheets just say "miscible" for water solubility, so I'm not sure if that's more or less soluble than the
ASA.
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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Rosco Bodine
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The amount of propylene glycol is likely
very small , and used as an anti-dusting agent . Simply leaving a small amount of alcohol when the bulk is evaporated from the growing mound of pure
aspirin crystals will likely trap the small amount of propylene glycol in that residual alcohol .
At cool temperature it won't be carrying much aspirin , but the residual alcohol can be diluted with water to precipitate the bit of aspirin
still remaining and leave the propylene glycol in the diluted alcohol . It would likely be better to go this route than to crash the entire batch into
water .
From what I have seen from my experiments with methyl salicylate , I will never again go through the trouble of purifying aspirin for use as a
precursor again , so long as the wintergreen oil is available without too great of an expense or difficulty . The yield was 75% from my first
clumsily done experiment described above , which would have been more if there had not been the runaway I encountered for carelessness and
unfamiliarity with visual markers for the progress of the nitration . And the yield appears even better for the second experiment which I will be
filtering soon .
I really like the advantage of being able to use a liquid 60% solution of Ammonium Nitrate for the nitration , which eliminates the labor of purifying
and recrystallizing sodium nitrate fertilizer in advance and then later having to make portionwise additions of the solid nitrate , conducting a
" spoon fed " nitration and getting a thick and ill behaved mixture towards the end . It is really a quantum leap in simplification to be
able to work with a liquid 60% solution of the nitrate , and an even cheaper nitrate as a bonus , and be able to regulate the addition by drops from
an addition funnel instead of adding a solid by fractions of a spoonful at a time over what can become a long period of tedious labor .
The purity of the product is also excellent with none of the red colored byproducts often seen from aspirin nitrations . I have a lot of purified
aspirin on hand which I plan to use up also in testing the new nitration technique using 60% NH4NO3 solution . I see no technical reason why this
same method would not be general for phenol as well , and also for other nitrophenols , styphnic acid , ect. and it
is on early evaluation a technical improvement in the nitration methods which do not use nitric acid , perhaps even superior also to those methods
which do .
Picric Acid is such a fundamentally versatile energetic material that it would seem worthwhile to add to the knowledge available about its synthesis
and purification particularly in terms of lab methods which are efficient and safe .
Sorry for being longwinded , but the sight of my two liter Erlenmeyer with a beautiful layer of sparkling glitterflake picric acid at the 450 ml mark
in 1650 ml of clear pale yellow liquid volume , from a never before described nitration method using 60% Ammonium Nitrate solution and
92% Sulfuric Acid , has me smiling gleefully like a kid finding a new toy .
Once in awhile I still stumble across something which is an interesting find ,
* very interesting * to the point of raising an eyebrow and making me smile , and this is one of those times where a little advancement in the art or
a lost art just soft landed in one of my flasks as a copious amount of the desired product in highly pure crystalline form
So I am inspired now to try to pin down the details for a method I know works well , and that you probably won't find described in a book or
paper anywhere ,
but is technically superior to anything similar you may find .
Now I must pause , breath on my fingernails and buff them against my chest with pride , realizing how hard it is to be modest when you know
you're great
[Edited on 13-8-2005 by Rosco Bodine]
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Quince
National Hazard
Posts: 773
Registered: 31-1-2005
Location: Vancouver, BC
Member Is Offline
Mood: No Mood
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Well, just at the end of nitration, my thermometer broke and the mercury got mixed with everything. Down the drain goes another batch I worked hard
on...
Rosco, I can't wait until you post the details of your improved procedure.
Well, I guess I have to wait to get a thermometer again...shipping from the US == another couple of weeks 
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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IPN
Hazard to Others
Posts: 156
Registered: 31-5-2003
Location: Finland
Member Is Offline
Mood: oxidized
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You used the thermometer to stir the mixture? And mercury down the drain?
Anyways, I decided to make the big crystals again as Rosco suggested. I filtered the crystals when temperature was still about 40C (no crystal growth
occurred anymore) and got 26,52g (from 50g of dry crude material) of light yellow, dry, big platelets which were then gently crushed with a plastic
spoon on some tissue paper. Seems to be quite pure (sharp meltingpoint)
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Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
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What I said earlier about the probability of
much knowledge about picric acid having become lost art is confirmed by PATR . It is a very old material which was seriously studied and used in the
time of and by Glauber , and also known to the alchemists even earlier , was used as a dye for a long time , then later as an explosive , before
falling out of use and disappearing for the most part from the literature before it was well documented ,
nearly a hundred years ago . So picric acid is an oldie but a goodie , most of the knowledge about which was once common , but the book on it was
never written and the knowledge lost with the end of the days of those who knew about it . In the present , picric acid is largely a historical
obscurity with regards to finer details concerning its most efficient synthesis and crystallization .
The crystallization behavior of picric acid is peculiar , and I suspect there are different crystalline forms that are temperature dependant , with
both size and form varying with temperature and the concentration . The nature of what trace impurities are present also seems to influence the
crystallization . I keep separate samples from different syntheses and each sample seems a bit different in form from the others gotten from
different processes . The crystals are fragile and even vigorous stirring of the wet crystals will actually mill them to powder . There is a point
where gentle stirring will stir down the crystals to a more dense layer but more stirring beyond that causes the volume of the layer of more and more
broken crystals to increase and keep increasing until a slurry of fine powder results which does not separate . So the stopping point has to be early
so as not to overmanipulate the material and lower its bulk density by
more than minimal action with the stirrer .
The fragile crystals dislike being jostled around , and are readily " fluffed " by even gentle abrasion . The stirrer does the same thing
to solutions having standing crystals as does a coffee grinder do to the beans , first chopping up the chunks , and then multiplying that volume
in chopping the chunks to a light powder .
The best crystals seem to form from a somewhat less than saturated boiling solution allowed to stand undisturbed to grow a crystal " tree "
on very slow cooling to a still barely perceptible warm to the touch temperature , and then filtering the mass broken up only by the minimal
disturbing of the structures needed to transfer them for filtration . Literally spooning the crystals onto the filter is what you have to do to keep
the bulk volume of the final resultant dried product fairly high . I have been trying to find the optimum dilution and holding temperature for the
crystallization . And I suspect that a holding time at maybe 40C may benefit the crystal growth if a batch is simply allowed to stand for an
extended time while held at that slightly warm temperature .
From a dozen crystallizations I have only twice hit the conditions just right and gotten good clean and dense well formed crystals which dry to a
desirable free flowing glittering crystalline form . The other ten times have produced a mixture of those crystals with the fines which clump on
drying . Chemically of course it is all the same , but I really like for the end result to be a consistent physical form . So far I have found no
way to obtain the desirable form crystals except from that portion of the crystallization which occurs in the warm range , and then harvesting that
crop , later
concentrating the solution to a similar point , and repeating the process which is tedious . This is precisely why I like to work with large batches
of picric acid , because of the labor involved in the crystallization . It is almost impossible to get good results unless you are working with
nearly a gallon of the near saturated boiling solution at the beginning , because smaller quantities lack sufficient thermal mass for the slow cooling
rate which is necessary for good crystal formation . I have even considered that
doing these crystallizations in a Dewar flask , or a foam insulated container would
likely be of great benefit , since it would extend the cooling time and thereby allow for the crystals to grow in the more slowly cooling solution .
But even something as simple as wrapping a fiberglass batt around a container of the boiling hot solution , sitting on a sheet of foam , will greatly
extend the cooldown time and result in larger crystals . There is an amazing difference in what drops out of solution slowly over a day or more ,
compared with what preciptitates in a few hours when the cooldown and crystallization is more rapid . This inconvenience about the crystallization
behavior of picric acid has likely accounted for the premature discarding of many experiments by impatient persons who
poured down the drain supersaturated solutions which would have produced crystals in large amounts if simply set aside for a day , or set up solid if
deeply cooled for a few hours . Picric Acid is one fickle bitch to crystallize in the way you might want it to behave , and may have to be coaxed
with varying conditions to produce good clean crystallizations from water solutions . If such efforts for
water solutions are unsatisfactory , and this is likely for smaller batches , then the
more practical approach is to use cold to drop out the greatest yield of precipitated product as fines , and after drying , then recrystallize from
hot alcohol , simply letting the alcohol evaporate to get gritty dense crystals .
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