From: Anonymous
To: (my e-mail address)
Subject: azo-clathrate synthesis
Please allow me to share a good link for some printable basic tables and charts which are useful. http://chemdat.merck.de/cdrl/services/labtools/en/tools_body...
The tables for aqueous solutions of common acids and bases are very good for handy reference.
Near the end of my third message posted here, I made brief mention regarding a patent about a class of energetic materials, which are complexes called
clathrates. Experiments with that class of compounds have produced very positive results. I wish to share the results of my experiments and other
information to emphasize and explain the importance and usefulness of the outstanding basic lead picrate complexes of US3431156. The compounds
described by the patent are truly exceptional energetic materials, quite unlike the ordinary picrate salts which are poor initiators by comparison.
The azo-clathrates are small critical mass unequivocal primaries which demonstrate very high brisance. For example, a small test pellet of the
material (formed by making a stiff putty of a small amount of the dry material wet with a minimum amount of saturated aqueous dextrine solution and
allowing small droplets of the paste to dry upon a plastic film) shows the power of the composition. A small droplet of the dried, dextrine bindered
material weighing 35 milligrams, will produce a clear aperture, clean edged hole when placed upon a thin aluminum witness plate and detonated by
touching with a glowing splint. The metal is not merely punctured nor is there any deep dent nor any significant "banana peeling" effect for
the metal on the underside of the witness plate. The metal adjacent even such a small charge is simply granulated and blown away, atomized to dust in
its disintegration. The effect is much the same as if a hollow drive punch like is used for sheet metal work had been placed upon the witness plate
and struck by a hammer. This sort of cutting effect upon metal is demonstrated only by high velocity explosives. It is especially unusual and
interesting when the effect is observed for such very small charges. Miniature shaped charges are a reality.
There simply are no comparable materials to my knowledge anyway, which can be readily made from OTC raw materials. And there are only a very few of
the most exotic and much more difficult to make materials discovered which are comparable or marginally superior as substitutes for these more easily
and cheaply made materials. If you have been looking for the "good stuff", delving through the literature and experimenting away, do
yourself a favor and dont try to reinvent the wheel, while failing to directly evaluate these much more simple, economical materials and witness their
excellent performance firsthand.
I have made these compounds several times from precursors every one of which was also made from OTC materials. The synthesis of the sodium azide is
the most difficult part, but worth the trouble if no convenient source for sodium azide is available. Going on record as a purchaser of sodium azide
could be unwise, so I have chosen to avoid that potential worry. Since the sodium azide is the most difficult precursor the effort was made to
develop the most efficient use for the sodium azide, in producing the highest quantity possible of a satisfactory initiator.
After referring to my lab notes, I saw that it was actually a slight variation of example compound 5 of the patent US3431156 which I synthesized, and
my variation had produced a quantitative yield, which is a marked improvement over the 82 per cent yield reported by the patent. The patent had
reported (line 10 page 6) that up to 13 moles of lead azide were possible to be absorbed by each 4 moles of the host complex, but that an upper limit
of 11 moles would be used for production to reduce the potential precipitation of lead azide which may not be trapped in the matrix of the host
complex. By a modified reaction sequence and higher temperatures, I achieved good results increasing to 12 moles the entrapped azide for each 4 moles
the host compound of example 5, and achieved a quantitative yield of end product, agreeing with the increased molecular weight for the added 1 mole of
lead azide. The molecular weight for the clathrate compound of example 5 is 9311.85, while the variation I made has a molecular weight of 9603.08.
When it comes to molecular weights, all of the clathrates are astonishing, as is their ease of synthesis, storage stability, chemical stability, and
initiatory power. The azo-clathrates have "the right stuff". The compounds retain the desirable initiating quality of lead azide, while
eliminating its faults.
My theory is that the way in which the host complex is made and the conditions under which the azide is subsequently added to the host complex has a
bearing upon increasing the upper limit of how many moles of entrapped lead azide it may contain, and the saturation limit can vary also according to
the particular host compound, 16 moles of included lead azide may be possible from indications in some of my experiments with host compounds mentioned
but not specifically detailed in the patent US3431156 as experimental examples. This is what I meant by saying that "A similar process can be
used to provide enrichment to the properties of the compound in example 4 of US3293091."
To my thinking the patent US3431156 is a "goldmine" of data as a technical disclosure itself, as well as suggesting further general
experiments or refinements related to the example compounds it discloses. It really surprises me there are no subsequent patents having been
published since 1969 regarding further work on the same general type of compounds. Perhaps Remington Arms and DuPont have done further experiments but
kept the research confidential for business reasons. There was an earlier mention of the formation of complexes of this sort in a 1922 patent
GB180605, by the German chemist Dr. Walter Friedrich, (see line 98 page two), however there were no detailed examples. It seems likely that some of
the early references to "mixed salts" may have in fact been clathrates, but many years would pass before the details would be described
extensively for the first time as an advanced art in US3431156.
Described below are the synthesis details for my experiment with a slightly enhanced variation of the general type of compound described in US3431156,
example 5. It is interesting when when a synthesis produces quantitative yields, for several reasons. It is a rare result, and many times the
stability of a product from a quantitative yield synthesis is excellent. The resulting product has formed from a synergy of reactions which went to
completion without side reactions and byproducts, and efficiently formed the target compound as the single "most probable" result, excluding
other possible products. The intended product of a high yield synthesis will often prove to be very stable and high purity compound. The inherent
quality control involved is desirable for materials to be used as explosives. A synthesis of 4 (basic lead picrate, lead nitrate, lead azide) 12
(lead azide) molecular weight 9603.08
NOTE: In my opinion the proportional formula designation for clathrates is somewhat arbitrary, but the ratios are correct. For example the
theoretical minimum molecular weight might be only one fourth of 9603.08, or the actual molecular weight could be any one of several multiples of
that number. Its a damn mystery, so I shall leave the true structural determination to others who have the instruments required and the interest to
pursue such questions. Crystallographers are sure to enjoy pondering the actual structure of this energetic "Buckyball" sort of molecular
matrix.
Experimental :
An alkaline solution of sodium picrate is made as follows:
4.6 grams (four and six tenths gram) pure dry pale yellow picric acid is dissolved with stirring in 180 ml hot distilled water, and to the stirred
solution is added a solution of 1.7 grams (one and seven tenths grams) NaOH in 40 ml distilled water. The sodium picrate solution is transferred to an
addition funnel and kept warm in a hot water bath.
Into a tall form (Berzelius) 500 ml beaker is placed a magnetic stirbar and 100 ml of distilled water. On a stirrer hotplate is made a hot solution
of lead nitrate by adding 25 grams (twenty-five grams) lead nitrate to this stirred 100 ml of hot water. While stirring, this lead nitrate solution
is heated to and maintained just below the boiling point. 95 degrees centigrade is fine.
The warm sodium picrate solution is added dropwise slowly at a rate of about one drop every two or three seconds, into the vortex of the vigorously
stirred hot lead nitrate solution, continuing stirring and heating for ten minutes after the addition is completed. The precipitated material will
initially be bright yellow, and change slowly in color to a darker orange, as a more mature crystalline precipitate is developed towards the end of
this step in the synthesis, which results in a suspension of crystalline basic lead picrate, possibly basic lead picrate / lead nitrate double salt,
in residual lead nitrate solution.
The valve on the addition funnel is closed, and in the addition funnel is placed a solution of 5.3 grams (five and three tenths grams) of sodium azide
dissolved in 50 ml of distilled water. This sodium azide solution is added very slowly by drops, at a rate of about one drop every four or five
seconds, to the vigorously stirred suspension of crystals. These basic lead picrate crystals suspended in the stirred mixture with remaining lead
nitrate will be changed in color and size as they react with the sodium azide being introduced. This change is due to the formation of the host
complex and its subsequent saturation with entrapped lead azide formed within the "cage-crystal matrix" of the host complex. Heating and
stirring is continued past the end of this sodium azide addition, for an additonal ten minutes and the heating is then discontinued, yet vigorous
stirring of the slowly cooling suspension of microcrystals is continued, maintaining the crystals in suspension for an additional 1 hour as the beaker
and its stirred contents slowly air cools. These slow additions and extended periods of stirring are necessary for good completion of the reactions
and good crystal formation. The clathrate complex has a very low solubility and so its crystal development is a bit sluggish, and requires the very
gradual, steadily maintained and controlled reaction conditions be followed as described for best results.
The stirring is stopped and the reaction mixture is allowed to cool to room temperature. The supernatant liquid is decanted from the crystals, and
the crystals are rinsed with 50 ml of distilled water, and washed from the beaker onto a coffee filter with a stream of distilled water from a wash
bottle. The filter is placed upon a stack of paper towels to blotter away most of the residual moisture. The granulation mesh of the microcrystals is
extremely fine, and there is a point at which the drying crystals are not quite completely dry, when the material may be freed of lumps by light
pressure applied by a plastic spoon. The yield of dried crystals is 24 grams, which is 100 per cent of theory.
Try obtaining a 24 gram yield of a first class primary any other way from only 5.3 grams of sodium azide, and the economy of this compound is soon
realized. |
or it isn't right 
.....you know how that one goes, if it isn't right then you get no joy on the result.
