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Rosco Bodine
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Quote: Originally posted by Hennig Brand  | Don't worry when I try for a clathrate I will go with your method.
When using your method keeping the temperature as close to boiling as possible, and of course giving the reaction the time it needs, seems to be the
key. |
It isn't necessary to be "as close as possible" to bp, for example 99.9C depending on your barometer
what it might be. It isn't that critical. I think I said 95-98C is fine. | Quote: |
I was thinking of using a flask and putting a reflux condenser on it (section of glass tubing maybe for an air condenser) which would allow staying
at the boiling point without losing as much water to evaporation and making it easier to keep the temperature maximized. What do you think?
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It is an unnecessary complication. If you need to add some makeup water to offset evaporation, just add some.
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A vessel that would allow increasing the pressure would allow raising the boiling point (pressure cooker). This is not needed I guess. Just thought
I'd mention it. |
Right it is not needed. KISS principle.
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Hennig Brand
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Ok, I was just trying to have a little fun with this, but I can see that isn't appreciated. How is the following for an application of the KISS
principle?
I have used this arrangement many times in the last while for doing recrystallizations. It is simple and works very well. It is just a dessert bowl
placed in the mouth of a beaker. Even without adding ice and/or cooling water to the bowl reflux is fairly close to complete in most cases (meaning
loss of solvent is barely detectable). A thermometer can be inserted through the spout of the beaker; also additions can be made through the spout of
the beaker.
[Edited on 8-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Hennig Brand
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I think I should just let this one go, but anyway. I did another experiment. I kept the temperature at 95 C or greater the whole time. An indirect
heating method was used as can be seen in the pictures. Copper from a piece of heavy gauge 3 inch copper pipe was cut lengthwise then hammered flat on
an anvil. The copper sheet was placed on the homemade magnetic stirrer with half of its length hanging over. It was this overhanging section which was
heated with flame. A small alcohol wick type homemade burner was used to maintain the temperature at 95 C or greater. Homemade ethanol was used for
heating fuel. A propane torch was used to get the beaker up to near boiling temperature in a shorter time than would be possible with the alcohol
burner alone. Copper not only has terrific electrical conductivity but also terrific thermal conductivity. Copper also has no noticeable effect on the
stirrer’s ability to function properly.
Not to get off track but apparently nichrome wire can be placed right in an oil bath and that placed on top of a homemade stirrer. Obviously the
vessel for the bath will need to be a material compatible with the stirrer.
I took Rosco's advice from a previous post in this thread and made a stock solution of sodium hydroxide and then titrated it against lead acid battery
electrolyte. I did two titrations and found that my sodium hydroxide solution needed to be added in excess by about 25%.
I did a half scale reaction; 2.3 g picric acid, 3.75 g lead nitrate. The sodium hydroxide solution previously prepared and tested was used in 25%
excess. Both the picric acid and lead nitrate were homemade and carefully purified. Lead nitrate solution was heated to 95 C and then addition was
started. Addition was made a drop at a time over the course of about an hour. Temperature was maintained at over 95 C the entire time. After all the
sodium picrate-sodium hydroxide solution was added the reaction mixture was left on heat for over 30 minutes with vigorous stirring. It was noted that
during the 30 minute period the temperature rose to 98-99 C. It seems the product is still nowhere near as dark as it should be. It is however
energetic and sensitive to percussion. It is not as energetic as the darker material which was given the heat treatment in the oven however.
Theoretical Yield = 4.54 g
Actual Yield = 3.92 g
Of course there was loses during filtering and I didn't let the reaction mixture cool much before filtering. Solubility is very low even at elevated
temperatures so the loses from dissolved product should be minimal (I think).
  
[Edited on 12-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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Please explain what you mean in molar notation or exact grams of NaOH your statement that the NaOH was used in 25% excess. For basic lead picrate the
amount of theory required for the NaOH is 2X the molar amount of picric acid or twice the neutralization equivalent for the picric acid if it is pure.
That provides an equimolar solution of sodium picrate and sodium hydroxide, which is added to a slight excess of an equimolar near boiling hot
solution of lead nitrate. These proportions must be very close because otherwise different complex compounds are possible to form as a significant
impurity and if the proportions are far enough off in deviation from theory an entirely different complex or multiple salt can result as the single
product.
The sample you show looks a little darker than your earlier result but is still not the rust color expected. It doesn't look way far off but still
not quite there so it would be my guess it is a mixed result. I'll probably be doing this synthesis again but when that will be possible I do not
know.
Yields should be higher so that alone indicates something is off, and if it was hydrate impurity it would be expected that the yield would be in
excess of the theoretical, not less.
[Edited on 13-8-2013 by Rosco Bodine]
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Hennig Brand
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Yes, the synthesis requires two molar equivalents of NaOH. The same amount of NaOH needed to neutralize 1 mole of sulfuric acid is what is needed to
run a synthesis with 1 mole of picric acid. I made up a 4% solution of NaOH by weighing the sodium hydroxide prills, placing them in a graduated
cylinder, and then adding water to the appropriate volume. It took about 25% more NaOH solution than it should have (by weight of NaOH prills) to
neutralize the sulfuric acid, therefore it was concluded that 25% more NaOH solution should be used for the basic lead picrate syntheses.....Oh, now
that I am looking back at my scratch notes I can see that I didn’t actually prepare a 4% solution I prepared something more dilute. I assumed I had
made a 4% solution because that is what is stated in the patent. So the excess thing is inaccurate but the amount of NaOH solution used in the
synthesis was based off of what was needed to neutralize the sulfuric acid battery electrolyte so it should still be correct.
The truth is I have tested several different NaOH proportions over the last while, from 10% excess all the way up to 40% excess. I guess it is
possible that the temperature requirement was not dialed in at the same time though.
Very rare to get a 100% yield in any synthesis. I am not a professional chemist, but I would say almost never. The molecular weight of water is ~ 18.
The molecular weight of basic lead picrate is ~452.3. If basic lead picrate forms a monohydrate it would be less than 4% heavier than the dehydrated
form. Four percent is small but it is significant I guess.
[Edited on 13-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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Quantitative yields are nothing special when the reaction mechanism cooperates. Process is important here and the physical manipulation especially
important is the agitation that is almost a wet milling of a suspension of solids kept vortexed in suspension in near boiling aqueous medium. It is a
low solubility reactant that must be kept from stubborn duning which is difficult because the crystals are dense and settle quickly unless the vortex
and agitation is sufficiently vigorous, so that there is contact with the hot liquid for every crystal in suspension kept aloft in the vortex like a
herd of cows picked up into the sky by an F4 tornado. When you can do that, then the product should gradually change in color right before your eyes
to a rust colored glittering crystalline material like the fine quartz sand that is on a beach in the surf line. It should look almost like normal
lead styphnate but not quite as dark red brown. Quicksilver posted this picture which is a good illustration of the color.
http://www.sciencemadness.org/talk/files.php?pid=183983&...
Something is still off about your process and the yield tells that much but don't despair. Something was also off about the German chemist who
invented the material because he actually incorrectly stated the formula in the original patent, filed in England and also in the U.S. and never
amended with any error correction so far as I know. Of course maybe you already did the math yourself on the stoichiometry to discover and/or confirm
this. What should I know about errors in the literature including those by German Ph.D chemist inventors of some renown  It may have been a tongue in cheek bit of humor by the old professor to see who is
sleeping in class. Regardless of all that impairment of cognition from which it has been suggested by some I suffer, Dr. Friedrich is never the less
still incorrect about the formula for basic lead picrate which he invented and then identified by formula incorrectly in his original patent. So let's
put that somewhat perceptive but errant Ph.D. of chemistry or philosophy or whatever field of cluelessness about stoichiometry in school right now to
set the record straight. We wouldn't wish to be led down the primrose path about molecular formula arithmetic where things just don't add up as
advertised. So on with checking facts to tell the rest of the story. Kenney later got it right in his patents but we should double check that to be
thorough. Let me have a little fun with this. The mystery remains which experiments I have suggested may answer. I just love the task of calibrating
the scales of a Ph.D. so that a hundred milliliters of distilled H2O actually weighs a hundred grams. After that we can really get down to business.
Next we check the thermometers and see if melting ice is at 0C and boiling H2O at 1 atmosphere is at 100C. Then we are golden, all calibrated and
ready for serious business. BTW I think Rathsburg also got it right in other patents. Rathsburg was a contemporary and coworker of Friedrich. In
fact Hans and Walter (Ph.D's both) jointly hold a patent concerning ....wait for it....basic lead complex salts of.....drum roll .......azotetrazole.
Ah ha! The plot thickens
Please reference the Friedrich patent does not correctly identify the formula for basic lead picrate which as a simplest expression should be
C6H2(NO2)3OPbOH mol. wt. 452.3 or in the alternative the double salt expression Pb[C6H2(NO2)3O]2 - Pb(OH)2 mol. wt. 904.6 or the further simplified
double salt expression Pb(C6H2N6O7)2 - Pb(OH)2 mol. wt. 904.6 This last double salt expression is used by Kenney which indicates he understands
correctly what is the formula for the basic lead picrate.
Your own figures indicate you already also get it about the error of Friedrich so you are probably smarter than most who read the Friedrich patent and
have done your homework following up with Kenney and others. Reduction of your homework to practice is another matter. A couple of years ago you
posted diagrams showing structure for the normal picrate (anhydrous, normally a monohydrate) and the basic picrate (normally anhydrous) which are
correct.
http://www.sciencemadness.org/talk/viewthread.php?tid=501&am...
So you are past the incorrect identification of the formula by the inventor Friedrich which may have been simply an overlooked typo in 2 patents. The
significant thing is that if an error involving the formula can be published by the inventor in 2 patents with no correction page in the nearly
hundred years subsequent to that publication, you, we are already ahead of the curve just recognizing that error and working around it. It also
illustrates Murphy's Law can apply whether we are looking at patents or attempting to reproduce the described reaction with whatever modifications or
tweaks will make it work better or will make it work at all. Not always but sometimes the patent is not precisely correct but is only a general
starting point as a not quite specific but generalized description of the art. So a patent may be dead on about the details or it may be a bit cryptic
on the details where it is necessary for "those skilled in the art" to read between the lines.
Now back to the Hans and Walter fun with intriguing experiments show. Read GB195344 and GB185555 for background page 2 example 3. [ Please Note:
There is also likely a formula error IMO in the Rathsburg - Friedrich patent GB195344 for compound 1, as there should be a 2 outside the (PbOH) so it
reads correctly (PbOH)2 ] See those 2 hydrogens on azotetrazole and reference compound 1 and 2 of the GB195344 patent. If compound 2 corresponds with
basic lead picrate (and it does), then with what would compound 1 correspond ? The normal lead picrate. Or perhaps a normal lead styphnate. In
either case the double salt of the normal with the basic salt might be anhydrous. It might not. But it could be. And there could be synergy exhibited
by the double salt if it exists. It is also possible that other metal normal salts might substitute and might have an anhydrous double salt result
which exhibits synergy. Some of those metal salts might be oxidizers, or they might be tetrazoles, and there is a good possibility that such
"designer compounds" could follow the scheme generally as described by Kenney.
I should elaborate upon the significance of the Rathsburg - Friedrich patent GB195344 where compound 2 is analogous to basic lead picrate but is more
specifically analogous to basic lead styphnate because the azotetrazole like styphnic acid is a dibasic acid, whereas picric acid is a monobasic acid
although the behavior of the basic lead salts is what is the greater influence for defining the scheme of these complex salt formations. For example a
whole series of double salts are identified for lead nitrate basic salts where the anions are specific defined ratios of nitrate and hydroxyl. A
similar scheme evidently follows for the case where the anion may be a divalent value. The ratios may then differ but the general scheme holds true
that these complex salts can form.
The most specific styphnate analogue for compound 1 of GB195344 would be a double salt of normal lead styphnate with basic lead styphnate. It is
intriguing what may be the effect if such a compound were made and then while stirred in near boiling hot water picric acid just sufficient to
neutralize 1 of the 2 hydroxide values, (or in the alternative sufficent to neutralize both both) was added. Suppose 1 hydroxide was neutralized with
1 monobasic acid, and the other hydroxide was neutralized with a different monobasic acid as another variation. [ See note above regarding formula
error for compound 1 ] Would the picric acid completely disrupt the styphnate double salt or simply combine and form an entirely new compound which is
a double salt of normal lead styphnate with a lead hemi-styphnate / hemi-picrate? Analogously what would be the effect of using other monobasic
titrant acids such as hydrazoic, or nitric, or perchloric? Similarly would basic lead picrate form a double salt with normal lead picrate and would
that possible double salt be anhydrous? If existent would the energetic properties exceed that of either the normal picrate or the basic picrate
alone? What would result from similar application of the same titrant acids? Would a neutral complex double hemi-salt(s) result as a "substituted"
basic double salt, or would the compound be disrupted by the attempted titrations seeking to incorporate another energetic or oxidizer anion? And of
course even if the basic lead value must remain intact absent any titration to serve as the "backbone" for the sequencing of additional neutral lead
salts, either energetic or oxidizing, such a scheme would follow the outline identified by Kenney which is already proven as a scheme for multiple
salts and clathrates particularly where the basic salt serves as the cage or scaffold for the additional components included as normal lead salts.
There is a definite interaction and overlap for the work of Friedrich and Rathsburg and Kenney, but the literature is incomplete for not investigating
the aforementioned possibilities, IMO. It is possible that such investigations were made but produced negative results and were unreported, and it is
possible that the experimenters simply did not go there with their investigations. Experiments are done to solve for the unknowns and there are some I
have identified here.
This suggests an assortment of possible compositions of complex salts, multiple salts, and clathrates. Synergy would be the thing to be hoped to be
found with some of those combinations.
The really intriguing aspect about this is that azides, tetrazoles, nitrates, styphnates, picrates, chlorates, perchlorates, ect. can all in some
specific combinations possibly form definite crystalline molecular compositions put together like lego blocks at the molecular level of intimate
incorporation in a multiple salt having interesting energetic properties.
I'll take a wild guess here that the Chinese are probably busily experimenting to check my allegedly inane chemistry related speculations.
Attachment: GB185555 Tetrazole Initiator Compounds.pdf (286kB)
This file has been downloaded 445 times
Attachment: GB195344 Tetrazole Priming Compounds.pdf (206kB)
This file has been downloaded 541 times
Attachment: GB192830 Basic Lead Picrate.pdf (250kB)
This file has been downloaded 539 times
It's deja vu all over again. Must be a method to my ScienceMadness, coming full circle on the hydrazine, azides, tetrazoles, clathrates...connecting
the dots from ten years ago. What makes a 10 earth year orbit, something beyond Mars in the vicinity of Jupiter? Maybe a monolith? It's full of stars!
https://www.youtube.com/watch?v=HnjiGx-6pII
Doctor Who?
https://www.youtube.com/watch?v=eNrs2iDsccw
Don't Cross The River
https://www.youtube.com/watch?v=merf6oe6oWY
[Edited on 14-8-2013 by Rosco Bodine]
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Hennig Brand
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You have made a real study of this! Thanks for sharing. You give me too much credit though. After you confirmed that the diagrams I posted were
correct back on page 2 of this thread I simply added up the atomic weights of the constituent elements. I also saw a post by Quicksilver a while back
and he had used the same molecular weight for basic lead picrate, so that was confirmation again. Thanks for the compliment though. Anything I lack in
intelligence I make up for doubly in stubbornness.
I checked to make sure my scales and thermometer were working correctly first. The thermometer was off by 2 C or so at boiling water temperature,
which is expected of a cheap thermometer. I very carefully weighed out 6 g of NaOH prills into a graduated cylinder and added water up to 150 mL. I
titrated this very carefully against my battery electrolyte, which judging by the specific gravity given for 60 F on the side of the container should
be about 35.2 wt% sulfuric acid. I weighed out a gram of this acid very carefully with scales accurate to hundredths of a gram. The gram of acid was
diluted with distilled water and titrated against the NaOH solution previously prepared. I found I needed to add almost exactly 22% more than would
have been needed if the NaOH prills were completely pure and dry. I am now quite sure that the amount of NaOH I am using is very accurate.
I ran another experiment and got a much better yield (4.21 g), but the color is still quite light. My lead nitrate was made from lead flashing and
hydroponics grade nitric acid so that should be fine. The purity of my picric acid is probably to blame. I had the temperature and the quantities of
reactants carefully dialed in this time. I made the additions over the course of an hour and the temperature was always hovering around 98 C.
Temperature was maintained at 98-99 C for 30 minutes after the last addition. It most likely is a materials issue. Too much DNP or something else
maybe.
Thanks for all your help.
 
[Edited on 14-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Bot0nist
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I have nothing to add other than I have really enjoyed and learned from this thread, and am very happy to see serious discussion and experimentation
in the energetics. Basic lead pirate, and a greater understanding of it, have been gained, by me, from this sticky.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Rosco Bodine
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Earlier I think I stated the specific gravity wrong for standard battery electrolyte which should be 1.260 = 35.00% H2SO4
441 grams H2SO4 / liter
4.496 moles / liter
222.4 ml = 1 mole H2SO4
That yield is 92.5% so it is high enough to be a probable. You want over 90% and 96-98 is much better. Could you turn on a reading lamp or use a flash
so the color contrast is clearer for your photos. It looks like the density is low for some reason by the clumping. This stuff should be like fine
sand very gritty and shouldn't stick together caking in slabs, but should be free running pourable like hourglass sand.
In bright light you should see the suspension flashing reflectively from the tiny crystal faces like glitter, and the wet material on the filter will
sparkle in sunlight, dulling on drying.
The product should absolutely not be at all hygroscopic and should be virtually clump free, just pour it from the filter paper when dry, nothing
caking or lumping to scrape or break apart.
When I have the batch size going that I described back on page 2 I think it was, the vortex raises the liquid close to the top of the beaker so there
is literally a cone of air almost down to causing cavitation of the stirbar that may be running 2500 rpm or more. If that photo is showing the stirrer
running then you haven't got nearly the agitation that is needed for this process to run. That could be the issue because I have a note in my old lab
notebook that the stirring vigor and temperature are both critical, and that the color shift from the yellow to the rust orange is a visible
transition. It looks like you may be picking your fruit there before it has ripened. Try heating and stirring the shit out it until it is convinced
to cooperate turning from yeller to orange.
[Edited on 14-8-2013 by Rosco Bodine]
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Hennig Brand
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After I gravity filter the product I always press/blot the product in folded over filter paper between two pieces of paper towel. This gets most of
the water out of the product, but also presses it into a cake. I then fill a bowl with boiling water from a kettle, put an upward facing plate over
the top of the bowl, and place the sample with filter paper on top to dry. The sample is completely dry by this method in less than an hour. The
product breaks into fine particles when dry just by folding over the filter paper and putting slight pressure on the clumps or by gentle pressure from
a plastic spoon. The density does seem a little low though. A little bit fluffy really.
The stirring for most of the synthesis was on the verge of a vortex, but not quite there. I know this because at different times during the synthesis
I turned the speed up ever so slightly and a vortex formed. I will try and keep a vortex next time though.
Here is a picture of the product taken with the flash on.
[Edited on 14-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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Historical context is important to understand to follow the development of the art from Friederich and Rathsburg which is further illuminated by
Kenney who gives the same line of research a better understanding, but the scope of all the examples is recognized not to be a full disclosure of all
similar possible compounds. In the original post beginning the thread I mentioned the Friederich patent GB180605 which seems to be an early patent
literature description
of the notice being taken of multiple basic salt formation for the lead compounds. I think there are probably earlier mentions possibly by Von Herz
or others so who is actually credited for the earliest discovery I am not certain.
A much later patent GB986631 revisits the basic lead azotetrazole which is compound 2 of the earlier Friederich - Rathsburg patent GB195344 showing
how modifications of temperature and precursors can greatly increase the density and quality of the product which proves that the process is important
and suggests that is general for these type of complex salts, showing results will differ for small changes in conditions not just a small difference,
but a nearly threefold bulk density increase for the product depending upon the reaction conditions, which is a drastic difference when the usefulness
of an energetic material is precisely the application where the higher density is very important as a parameter of performance. It is not just
important that the target energetic material be chemically correct but that its crystalline form be what is needed in order for the performance
desired to be realized. This will hold true generally for all energetic materials. So getting the chemistry correct is often the easy part. It is
not so straightforward to get the density and crystalline form optimized and that is where the nuances of process come into play which usually involve
both the chemistry and the physical conditions under which that chemistry is done.
It is not unusual for there to be found a precise and narrow range of "target window" conditions which produce the desired result and resolutely defy
any deviaton or alteration outside that window which will predictably cause a different result. That is just the nature of the beast.
Attachment: GB180605 Friederich early patent.pdf (290kB)
This file has been downloaded 429 times
Attachment: GB986631 Basic Lead Azotetrazole.pdf (180kB)
This file has been downloaded 415 times
https://www.youtube.com/watch?v=SGrobzDz30A
https://www.youtube.com/watch?v=dfWPlu1ZZnA
[Edited on 14-8-2013 by Rosco Bodine]
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Rosco Bodine
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There are some more dots that I want to connect to show a nexus, a correlation with the work of Friederich, Rathsbirg, Kenney and others and this will
again require reference to an example of a complex salt of lead involving a tetrazole. This example shows more specifically what I described as an
idea above that involves further reaction of a basic salt of an energetic acid with a different energetic acid to possibly form a multiple complex
salt that is neutral, or a double neutral salt. This is the logical progression and further development of the idea I proposed is suggested by the
existence of compound 1 of the patent GB195344 which should as a corrected formula be C2N10Pb - C2N10(PbOH)2 compared with a similar salt desribed
early in the tetrazole thread, which is a neutral salt following the structural scheme generally I have proposed is the inference. That neutral
double salt identified later is essentially a basic lead salt of Diazoaminotetrazole which has been converted to a neutral complex salt with styphnic
acid. The free hydroxyls of the 2 leads comprising the basic salt of Diazoaminotetrazole are neutralized by the styphnic acid to form the neutral
complex salt. See attached page T-121 from PATR Vol.9 Q-T which shows the structure for the neutral complex salt gotten by neutralization of the
basic salt, which does not disrupt the basic compound but adds to it as a condensation reaction via the elimination of H2O.
http://www.sciencemadness.org/talk/viewthread.php?tid=8144&a...
There is reason to expect this could be general, and similarly then there may be possible or even likely a similar compound which is the Azotetrazole
analogue of Diazoaminotetrazole compound illustrated on page T-121.
IMO the literature by inference suggests the possible existence of a series of compounds which may be obtained by similar condensation reactions where
a basic salt may be then converted into a neutral complex salt via a titration condensation reaction using a different acid from what has formed the
original basic salt. It would seem probable that some of the different acids would work better for such a scheme than would others, or that some
interactions of reacting salts might accomplish the same result if the solubility favored the formation of the desired compound.
I think the scheme is more or less general but not in an unqualified way. There likely are some cases where the condensation would probably occur as
predicted or desired and other combinations where it may not work. How to predict that probaility is another matter entirely which would put this
scheme in the realm of the experimental, to see if what is expected to occur does occur on a case by case basis where it is tested by experiment using
varying reaction conditions.
Anyway, I hope this further explains what I was describing above as a point of interest about the complex salt scenario where either case may apply.
The 2 things of note are [1] the formation of a complex salt between the basic salt and the normal salt, and [2] the potential for a condensation
reaction to be possible for the free hydroxyls of the basic salt which does not necessarily disrupt the existing salt acid substrate, which may be
incorporated into a newly formed neutral complex salt upon neutralization of the hydroxyls by an acid different from the acid used to form the
original basic salt. It is possible that the precursor salt will not exchange one acid for the other as would be true and usual for a double
decomposition, but instead a sharing of different anions may occur with the metallic or cation acting as the bridge linking together the two acids as
a mixed neutral salt.
Factors that would effect the outcome are pH and solubilities so the concentrations and solvent and temperature would also be factors having bearing
on what product results.
Attachment: Page T-121 from PATR Vol. 9 Q-T.pdf (93kB)
This file has been downloaded 513 times
[Edited on 18-8-2013 by Rosco Bodine]
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Hennig Brand
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I have been away for a few days on an apartment hunt, but before I left I did do another experiment. A huge vortex was maintained throughout the
experiment. Temperature of the reaction mixture was held at 98 C throughout the experiment. Addition of the sodium picrate-sodium hydroxide solution
was made drop by drop over the course of 45-60 minutes. Stirring and heating were maintained for a full hour after the last addition. Alas, the
product is only slightly darker than the last time and explosive properties are very similar as well. The only times I have gotten the darker colored
product, that detonates in small quantity when lit unconfined, was when I added a certain excess of sodium hydroxide.
I wonder if I have been oxidizing my ASA or an intermediate along the way when making picric acid. The results when using TNP from phenol were about
the same though which doesn't support that theory.
 
[Edited on 19-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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There is a definite color shift in the right direction. Is distilled water being used and the beaker size are only 2 potential issues remaining that
I can think may be a factor. The density still looks low which could account for the lighter color development. I notice the smudge on the paper
where the fines are clinging and the product seems dustier instead of being a crisp granular.
Also if the picture of the beaker is the stirring in progress, that color looks like the observed color shift in the mix from the bright yellow to the
orange, but the depth of the mixture being stirred is way too shallow in the beaker. The waterline should be halfway up that airspace above the
liquid in the picture you are showing. I don't have this in my notes but recalled that during the early addition the initial precipitate is a bright
yellow material that is like a slurry of whiskers like tiny fibers of felt in the liquid, like disintegrated filter paper having a thixotropic effect
which is transient. With continued stirring those tiny whiskers of a suspended felt of needles disintegrate and a new product appears which is much
denser and drops to the bottom as it precipitates from the liquid phase which is darkening in color and in which the lighter colored fibrous material
is more easily suspended. The lighter colored whiskers are easily stirred in suspension, but the more compact and dense material accumulates on the
bottom and is quite difficult to keep mixed and suspended which is the reason for the deep vortexing. The density increases for the darker granular
material which is distinctly crystalline and sparkles in bright light and the density is like sand instead of like the felt material that first
appeared. The darker colored material will settle out in dunes on the bottom adjacent the stirbar even during the deep vortexing because it is that
dense. And towards the end of the reaction if you switch the stirrer off it will all settle completely in a couple of seconds immediately when the
stirrer is switched off, almost like metal filings separating from water. The material is so dense it almost defies stirring.
In a shallow whirlpool in a large beaker relative to the volume of the mixture, you definitely won't get the needed agitation, because the material
will dune on the bottom of the beaker outside the spinning tips of the stirbar. It absolutely must be kept in suspension in a deep and violent vortex
of the hot liquid for the crystal development of the dense material, and that is where the deepening color should be observed.
When I run this reaction the stirbar is run up to a speed where it is destabilizing and gyroscopic precession causes the stirbar to orbit the drive
axis so it sweeps the accumulating dunes from the perimeter of the beaker bottom. It would be like a tornado in a large parking lot making the
rounds so as not to miss any of the cars parked around the outside spaces ....no stone left unturned, over and over again That is the kind of churning up of the dunes of material that is needed to max out
the bulk density and color development that will attend that bulk density increase. Otherwise I think you have gotten what you got and I don't know
what else to tell you.
[Edited on 20-8-2013 by Rosco Bodine]
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Hennig Brand
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I put the sample of basic lead picrate from the last post on a microscope slide and had a look at it. My microscope is not equipped with a camera but
was able to get a couple of half decent shots anyway by holding my digital camera up to the eye piece. It is very crystalline material indeed, but the
crystals haven't grown as large as they should have I guess. Microscope was at 100X magnification for the pictures, but 40X showed the crystals well
also.
BTW, I picked up that microscope a few years ago at a scrap yard for $30. They had just cleaned out a prison and the microscope came out of the prison
medical lab/office along with other equipment. I also got a small rotary vacuum pump and a fairly large centrifuge for 60-70 dollars. Really good
deals!
   
[Edited on 21-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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Yeah it's a density issue that is making the color appear lighter yellow. You can see the deeper color in part of the sample in the last picture, the
crystals on the right side of the field are showing the color depth that will be there for the whole sample when the crystallizing process completes
for an evenly denser sample. There is a food dye called bakers egg shade that is a yellow food coloring, but the concentrated dye looks rust colored
also, it is the same density and color depth effect. Potassium Ferricyanide really shows the same effect dramatically as the crystals are actually
rust red, but if you grind them to a powder they are bright yellow. Exact same chemical composition, but a color shift occurs simply from the way
light reflects based upon the degree of subdivision for the particles, smaller the mesh for the crystals the lighter the color. Amber resin does the
same thing. Dye color printing inks for yellow show the effect too, the concentrate looks red orange, but diluted it is yellow.
[Edited on 21-8-2013 by Rosco Bodine]
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Hennig Brand
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Didn't notice that you got a post in Rosco until after I wrote what is below. Thank you for the explanation. I feel a little better about this now.
BTW, I forgot to answer you about whether or not distilled water was being used. Distilled water has been used for the syntheses.
Ok, so I decided to carefully measure the melting point of the picric acid I have been using for the last few basic lead picrate syntheses using my
improvised apparatus. The picric acid was made from ASA 2 or 3 years ago. I am using a thermocouple probe multi-meter combo for measuring temperature
which is not the most accurate way of measuring temperature. The probe-meter combo was tested at 20 C and gave a reading of 19 C, it was also tested
at 100 C and gave a reading of 98 C. I decided adding 2 C to the melting point obtained with the probe and meter would be fairly close (most likely
off by less than 0.5 C).
Heating was accomplished with a low flame on a propane torch. I quickly heated to about 110 C and then turned the flame way down and heated
intermittently, bringing the temperature up to the melting point over the course of about 10 minutes. Accurate control was fairly easy because of the
large thermal mass I was using (aluminum block). The melting point obtained from the probe and meter was 120 C, and by adding 2 C brought the final
result to 122 C. This melting point indicates that the sample of TNP is almost completely pure. According to the equation I obtained using the data
found in a 1940s journal for melting points of DNP-TNP mixtures, ("Problem Detonating Picric Acid" thread), the purity should be 100%. The equation I
obtained actually gives 100.77% for a temperature of 122.5 C so there was an inaccuracy or problem fitting the data. I may go back and investigate in
the next little while. At any rate the picric acid I have is most likely at least 99% pure.
  
edit:
Ok, that 1940's journal stated that good quality commercial picric acid was used, but that it wasn't perfectly pure (nothing is completely pure, but
it was not reagent grade pure either). The Excel software found the best fit through the data points and I believe most of the error came from the
fact that the sample of picric acid used for the testing was not 100% pure. There would have been a small amount of error in the testing methods as
well. The errors from testing are most likely very small however as an R squared value of 0.9986 was obtained when the data points were fit to a
quadratic equation.
[Edited on 21-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Hennig Brand
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According to a Sigma Aldrich MSDS picric acid with a melting point of 121 C indicates >98% purity. According to a fisher scientific MSDS pure
picric acid melts at 121.8 C. There are slightly different values floating around, however I trust these sources the most and as an added bonus the
numbers go well with the data I already have from the 1940s journal.
Using the data from the 1940's journal again, but this time multiplying all picric acid concentrations by 98% (0.98) in the melting point table should
produce a more accurate result. The 1940s journal had pure picric acid melting at 121 C and this same material was used to make the lower
concentrations used for the melting point tests as well. We must assume that the DNP used to form the mixtures was reasonably pure. Excel was used to
plot the data again and a new equation was obtained and is presented below. The R squared value was of course once again 0.9986. A pdf of the new
Excel graph complete with quadratic equation and R squared value is attached.
y = 0.009 x^2 - 0.8256 x + 66.656
Where:
y = concentration of picric acid
x = melting point of sample
The 122 C melting point from the test in the last post now indicates 99.9% purity with the new equation. I really should put a glass slide over the
top of the recession in the melting point apparatus where the sample sits during testing. Even if the measured temperature was high by 1 C (which I
don’t think it was) a 121 C temperature still corresponds to over 98% picric acid.
This equation is still undoubtedly in error to a small degree, but it is much better than it was before. It should provide a good approximation of
picric acid purity if an accurate temperature is obtained first from a melting point determination.
Attachment: Melting Point Graph & Equation for Picric Acid-DNP Mixtures (Revised).pdf (167kB)
This file has been downloaded 504 times
[Edited on 22-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Hennig Brand
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Last post I promise until someone else posts, but I thought this deserved its own post since it is back on the main topic and has relevance.
I think I know what I have been doing wrong. I really don't know a great deal about growing crystals. I found a decent webpage however explaining how
quality crystals are grown. Here is a copy/paste of a section from the page. I made a pdf of the entire webpage as well and have attached it below.
"Nucleation
Crystallization is preceded by nucleation, which happens either spontaneously or is induced by vibration or particles. If nucleation sets in too
quickly, too many too small crystals will grow. The figure below shows an equilibrium diagram of a crystallization from a solution. For a diffraction
experiment you need no more than one good single crystal. The best way of growing a few nice crystals, when opposed to a lot of bad crystals, is to
change the concentration slowly into the area of nucleation, without getting too deep into it. The formation of nuclei (not too many) and the starting
crystallization will reduce the concentration and bring the solution back into the regime of oversaturation. That is where existing crystals grow, but
no new nuclei form. You want to keep your system there. That means all changes of your system need to be slow."
So it seems I have been adding the sodium picrate-sodium hydroxide solution much too fast for the size of the reaction mixture, especially during the
early stages of crystal growth. Lower concentrations (more water) could also help I think.
Attachment: Growing Crystals.pdf (144kB)
This file has been downloaded 407 times
[Edited on 22-8-2013 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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