Submitted by Tenney L. Davis
Checked by H. T. Clarke and Ross Phillips.
1. Procedure
It is strongly recommended that this procedure not be used to prepare
guanidine nitrate. Mixtures of
ammonium nitrate and organic materials not much different from the mixture in the procedure are now used extensively as commercial explosives. The aqueous mixture of (Note
10) is similar to some aqueous mixtures used in sizable quantities for rock blasting; a confined mixture of this sort is especially hazardous. Only a few laboratories devoted to explosives research have the barricades and remote control devices needed to run this preparation of
guanidine nitrate without risk.
In a
1-l. round-bottomed flask is placed an intimate mixture of
210 g. of dicyanodiamide (2.5 moles) and
440 g. of ammonium nitrate (5.5 moles) (Note
1) and (Note
10). The flask is introduced into an
oil bath at 110–120°, and the temperature of the oil is raised during about one-half hour to 160°. The bath is then held at this temperature (Note
2) and (Note
10) for three hours. During the first hour the mass melts to a clear liquid which begins to deposit crystals and finally sets to a solid cake (Note
3). At the end of three hours the flask is removed from the bath; the product is allowed to cool and is extracted on the
steam bath with successive quantities of water (about 2 l. is necessary to bring all soluble material into solution) (Note
4). The solution is filtered to remove white amorphous insoluble material (ammeline and
ammelide) (Note
5).
The filtrate contains
guanidine nitrate along with a small amount of
ammonium nitrate and very small amounts of
dicyanodiamide and
biguanide nitrate (Note
6). The solution is concentrated to about 1 l., and the
guanidine nitrate which crystallizes on cooling is filtered off. A second crop is obtained by concentrating to 250 cc. (Note
7). The combined yield of crude
guanidine nitrate is
520–560 g. (
85–92 per cent of the theoretical amount). The product may be purified by recrystallization from 1 l. of water (Note
8), a second crop being taken after the mother liquor has been concentrated to 250 cc. The yield of recrystallized
guanidine nitrate melting at
213–214° amounts to
500–520 g. (Note
9).
2. Notes
2. When the molten mass reaches 160° its temperature begins to rise above that of the bath, generally reaching 200° during the course of five or six minutes. The mass should not be stirred at any time, especially before the mixture has completely melted; otherwise, the temperature may run somewhat higher.
3. The
guanidine nitrate begins to crystallize soon after the temperature of the mixture begins to fall.
4. The hard cake goes into solution slowly, and sufficient time must be given for each portion of water to become saturated before it is decanted.
5. When the hot filtrate cools, it will deposit flocks of
ammelide along with the crystals of
guanidine nitrate. water may conveniently be added until the crystals dissolve, and the cold solution again filtered for the removal of
ammelide.
6. This filtrate on evaporation to dryness and baking at 100° leaves a residue of
650 g., which is suitable for the preparation of
nitroguanidine (p. 399).
7. At this point the mother liquor (about 200 cc.) may be discarded as it contains mainly
ammonium nitrate.
9. The second mother liquor may advantageously be worked up with a subsequent run.
10. The submitter has prepared
guanidine nitrate in batches of about 1 kg. by heating
dicyanodiamide and
ammonium nitrate in
2-l. flasks in oil baths heated to 160°. If the oil bath is kept at 160° the temperature of the reacting materials rises at times considerably above that point, but apparently the temperature does not mount dangerously high with such sized runs.
It is suggested that the best way to carry out the preparation, particularly on a large scale, is to heat the reagents in an
autoclave, with a convenient amount of water, at 160° for two to three hours. The autoclave is emptied while still warm. The liquid is filtered hot for the removal of white insoluble material, and the
guanidine nitrate crystallizes out as the liquid cools. (T. L. Davis, private communication.)
3. Discussion
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