Investigation of Preparation, Solubility and Stability Properties of Nickel Hydrazine Nitrate (Nihn)

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1 DOI: 10.1002/prep.201700255 2 3 4 Investigation of Preparation, Solubility and Stability 5 Properties of Nickel Hydrazine Nitrate (NiHN) 6 7 Michael Cartwright[a] 8 9 10 11 Abstract: Following an initial, brief, review of the environ- ductivity of the solutions obtained was used as an indicator 12 mental problems associated with the use of lead based pri- of the processes involved in the solubility. Using the critical 13 mers, and also some of their potential replacements, this pH conditions for precipitation from aqueous solutions of 14 study investigated the preparation of the promising, lead hydrazine and nickel nitrate the formation constant for the 15 free, energetic material nickel hydrazine nitrate by different tris hydrazine complex was determined. Also using the sol- 16 methods. All three methods trialed produced the same, an- ubility of the tris-hydrazine complex in concentrated hydra- 17 alytically indistinguishable, compound but with minor zine hydrate an equilibrium constant for the formation of 18 changes in visual appearance. The solution properties gov- the soluble hexa-hydrazine complex from insoluble tris hy- 19 erning the precipitation process were investigated in a con- drazine complex was determined. These values were com- 20 trolled pH titration experiment. Product solubility in a num- pared with similar values for nickel hydrazine complexes 21 ber of common solvents was investigated. Aqueous with other anions. The origins of these differences were dis- 22 ammonia and hydrazine hydrate proved the best “non-de- cussed. Further work on controlling and measuring the par- 23 structive solvents” for the solid. UV spectroscopy and con- ticle size of the NiHN produced should be considered. 24 Keywords: 25 26 27 28 1 Introduction ceptance. Some promising alternatives include nitro- 29 tetrazole complexes [8], Bis-(5-nitro-2H tetrazolato-N2) Tet- 30 Lead based primary explosives, lead styphnate and lead raamino Cobalt (III) Perchlorate (BNCP) and Mercuric-5- 31 azide, are widely used in energetic systems because they Nitrato Tetrazole (MNT) [9]. The mercury and cobalt com- 32 are comparatively cheap, reliable and effective. The azide is pounds are also toxic and very sensitive so are not partic- 33 principally used in missile warheads and demolition charg- ularly suitable. The nitrotetrazoles are difficult to synthesize. 34 es, since it invariably burns to detonation except under very There are a number of publications [10] which reviewed the 35 unusual conditions [1]. Lead based initiators are sensitive to more recent efforts. 36 a number of accidental stimuli making synthesis, process- Some promising materials are the long established com- 37 ing, storage and transport extremely hazardous. Azides are plexes formed by metal cations with the nitrogen donor li- 38 more toxic than cyanide [2]. Lead is toxic and has a cumu- gand, hydrazine [11]. A whole series of products for this li- 39 lative effect on both humans and the environment alike. gand with ions of the first series transition metals with a 40 Measurements have shown unacceptable levels of lead par- number of oxidizing anions have been prepared [12]. The

41 ticulates in the enclosed conditions in armoured vehicles fir- nickel salts Nickel Hydrazine Nitrate (NiHN), Ni(N2H4)3(N03)2, 42 ing heavy caliber machine guns [3]. More recently the long- and corresponding perchlorate complex have shown prom- 43 term effects of continuous exposure on health and environ- ise. The perchlorate was extremely powerful explosive with 44 mental issues associated with the contamination of firing estimated VoD of >8000 ms1 but unfortunately it is highly 45 ranges have come to light. The United States of America En- sensitive even exploding during the preparation process 46 vironmental Protection Agency [4] has numerous reports [13] hence the absence of accurate performance data [14]. 47 concerning lead contamination on firing ranges and over Research in China [15], India [16,17] and at Cranfield Uni- 48 700 ranges have had to be cleaned by the US military alone versity [18] have examined the nitrates explosive properties. 49 [5]. Most of the lead contamination has resulted from the There is some disagreement between centres on the sensi- 50 lead projectiles; however lead dust from small arms ini- tivity of NiHN. (See Table 1). Problem areas are impact sensi- 51 tiators and detonations also has a significant impact [6,7]. tivity,(is the compound a primary, F of I 18, or secondary ex- 52 The ideal solution would be a compound that has sim- plosive, F of I 80) electrostatic spark sensitivity and 53 ilar performance, is safer to handle, easier to synthesise and 54 could replace the lead explosives. In this way only slight 55 modifications would be required to the manufacturing [a] M. Cartwright 56 process, thereby accelerating its implementation and ac- Faringdon, Oxfordshire, UK, SN7 7JY

1 Table 1. Comparison of properties for lead azide and NiHN. 2.3 Method 2 2 Property Lead Azide NiHN NiHN 3 0.4 g of hydrazine mononitrate solid, previously prepared [31] [15] [30] 4 by potentiometric titration of hydrazine hydrate with nitric 5 Velocity of Detonation (ms1) 4630 7000 7000 acid, was dissolved in 10 cm3 of a 10% nickel nitrate sol- 6 Impact (F of I (RDX =80)) 20 24 80 ution. The very limited quantity of cloudy material pro- 7 Figure of Friction N 0.1– 2–3 10 duced was separated off and then dilute ammonia, 0.5 M, Electro-Static Discharge J 0.007 0.02 0.001 8 was slowly added dropwise (>20 minutes), with constant Temperature of Ignition 8C 327–360 167 219 9 stirring. When the solution reached pH 7, addition of am- 10 monia was stopped. Stirring was continued for a further 11 30 minutes before cooling in ice. The solid was filtered off 12 temperature of ignition. Differences in the crystal morphol- and dried as described above. Yield 1.1 g (93%). Again 13 ogy, such as particle size and crystal defects, of the solid when the scale was increased for batch production the 14 produced could explain the discrepancy in sensitivity be- yield increased to 98%. 15 tween authors even though both groups reportedly used 16 the same preparation method. The first stage of this study 17 examines the preparation conditions and stability proper- 2.4 Method 3 18 ties of the title compound. 19 Nickel nitrate solution (50 cm3 at 8%) was slowly added 20 over 20 minutes to hot, 333 K, well stirred, 98% hydrazine 21 2 Experimental hydrate. The initially clear solution started to turn a pale 22 blue with the initial additions and the blue colouration 23 All materials used both for the preparation and the analysis deepened until ~15% of the nickel solution was added 24 were supplied by Fisons of Loughborough, U.K. Nickel ni- when the purple precipitate started to appear. When the

25 trate hexahydrate, Ni(N03)2 ·6H20, and hydrazine hydrate, nickel solution addition was complete the mixture was di- 26 N2H4 ·H20, 98% were reagent grades and used for the solid gested for 10 minutes then cooled, the solid filtered off and 27 preparations. All chemicals used in the analysis procedures treated as described above. After drying at 608C o/n the 28 were of analytical grade, AR, or Chromatographic grade for yield was less than expected from the Nickel added. The fil- 29 the solvent used in the modified Andrews titration. trate still had a dark blue colour. 30 31 32 2.1 Preparation of NiHN 2.5 Analysis of Products 33 34 Three preparation methods were used in an attempt to The dried products were analysed for nickel and hydrazine 35 control the solid crystallinity of the powder product. All by the following methods. 36 methods were used on the 1 g scale initially as a safety pre- The nickel contents of 0.1 M hydrochloric acid solutions, 37 caution until the sensitivity had been evaluated before 10 g produced by acid digestion of weighed samples with hy- 38 and larger preparations were attempted for a more detailed drochloric acid, were determined by Atomic absorption 39 study. The first method was a modified literature method, spectroscopy using a Varian AA 10 spectrometer, calibrated 40 and the other methods were developed in-house as part of with Nickel standard solutions, supplied by Fischer scientific 41 the study. Ltd. of Lougborough, Leicestershire U.K. 42 Hydrazine content was determined by titration with 43 standard potassium iodate in the modified Andrews titra- 44 2.2 Method 1 tion [19] using accurately weighed samples (0.1 g). The hy- 45 drazine content was calculated using the relationship 46 The literature preparation [12] was modified by adding hy- 47 drazine hydrate as a 20% solution rather than the 98% sol- I03 N2H4 48 ution in the original method. This reduced the effective hy- 49 drazine concentration in the initial contact with the hot, 50 333 K, nickel nitrate solution (8%). The solution changed 51 colour from pale green to pale purple within 0.5 cm3 of re- 2.6 Spectroscopic Analysis 52 agent added, with a purple solid being produced. The solid 53 was separated by vacuum filtration, washed three times Infrared spectra of the 10 mm diameter pellets, 4% in dry 54 with ice cold water, three times with dry methanol and “analar” potassium bromide, were recorded on a Bruker 55 oven dried at 333 K. Yield was 1.05 g(90%). Following sensi- FTIR using Opus software for comparison with the literature 56 tivity trials the yield from the scale up was 99%. data. The complementary Raman spectrum, which would

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1 have indicated the nature of the symmetry within the struc- 2 ture, was unobtainable because the products from all prep- 3 arations were ignited by the lowest power setting available 4 on the Ocean Optics laser Raman spectrometer. 5 The low solubility of the solid in any of the non UV ab- 6 sorbing solvents prevented the recording of a conventional 7 UV/Vis solution spectrum. The reflectance spectrum ob- 8 tained from loose powder samples spread out on white 9 card were recorded on a Perkin Elmer spectrometer. Prepa- 10 ration method 3 indicated the compound was soluble in 11 concentrated Hydrazine Hydrate and the UV/Vis spectra 12 were recorded on a series of solutions containing increasing 13 quantities of NiHN. 14 None of the common, dry, NMR solvents dissolved suffi- 15 cient quantity of the compound for a solution NMR to be Figure 1. UV/Visible reflectance spectrum from NiHN powder. 16 obtained. 17 18 monia solution was added dropwise and the solution pH 19 3 Results and Discussion monitored, Figure 2. At pH 2.5, the ammonia drops of pro- 20 duced a trace of purple solid on the surface, but this re-dis- 21 3.1 Analysis solved with continued stirring. At pH ~3 the precipitate was 22 permanent and the pH remained at ~3 until precipitation 23 Analysis, Table 2, showed all three preparations produced was complete when the pH started to increase. The stoi- 24 the same compound. chiometric equation for formation of the complex is 25 2þ 26 NiðH2OÞ6 þ 2NO3 þ 3N2H4 ¼ NiðN2H4Þ3ðNO3Þ2 þ 6H2O Table 2. Analytical Results. 27 28 Preparation method 1 2 3 Theory In the titration experiment and the normal preparation 29 the first signs of a precipitate appear long before the ratio Nickel Content % 22.33 22.22 22.18 22.29 30 of free hydrazine to Nickel reaches the 3:1 given in the stoi- Hydrazine content % 33.89 33.91 34.15 33.98 31 chiometric equation. The precipitation is driven by the very 32 low solubility of the hydrazine complex. Reaction with three 33 hydrazine molecules must be energetically favoured over 34 Electron microscopy indicated differences in product any of the intermediate species. Amine compounds are bet- 35 particle sizes. Method 1 produced a larger particle size than ter donors than water molecules [21]. The two nitrogen 36 the powders from method 2 and 3. atoms in the hydrazine molecule are too close together, 37 0.147 nm, to occupy two adjacent positions in the Nickel 38 coordination octahedron, minimum distance 0.197 nm, 39 3.2 Spectroscopy therefore these complexes must involve bidentate hydra- 40 41 The IR spectrum agreed with the literature confirming the 42 identity of the product. 43 The UV reflectance spectrum of the powder, Figure 1, 44 shows absorbance, ~560 nm, due to nickel ions in an octa- 45 hedral nitrogen field [20]. 46 47 48 3.3 Precipitation Process 49 50 Mixing hydrazine nitrate and nickel nitrate solutions pro- 51 duced a slight cloudiness but no precipitate. The concen- 52 tration of free hydrazine in the solution is less than that re- 53 quired for precipitation. However if ammonia, a stronger

54 base than hydrazine, pKb NH3 4.75, pKb1 N2H4 6.07, is in- + 55 troduced neutralization of the hydrazinium ion, N2H5 , will Figure 2. Plot of precipitation solution pH as function of added am- 56 generate free Hydrazine. In a titration experiment dilute am- monium hydroxide solution.

1 boiling hydrazine hydrate (40 cm3, 98%) until no further sol- 2 id dissolved. After cooling to room temperature, residual 3 solid was filtered off, washed dried and weighed and by dif- 4 ference the mass (2.511 g) of the NiHN in the solution was 5 determined. Changes in UV visible spectra of this solution, 6 as the solid increased, Figure 4, shows band, 563 nm, due to 7 nickel in an octahedral nitrogen field [25]. A suggested re- 8 action scheme is that the bidentate hydrazine polymeric 9 cation is converted to a monodentate hydrazine octahedral 10 nickel complex ion viz 11 12 0 2þ ½NiðN2H4Þ3ðNO3Þ2n þ 3n N2H4 ðx sÞ¼n ðNiðN2H4Þ6 Þþ2n NO3 13 14 The requirement for a tenfold excess of hydrazine hy- 15 drate indicates that the hexa-hydrazine complex is unstable 16 Figure 3. Projection perpendicular to axis of polymeric cation with respect to the trishydrazine complex, which only dis- 17 formed by hydrazines bridging nickel ions. solves when the above equilibrium is forced to the r.h.s, by 18 excess of hydrazine hydrate. The insolubility of the trishy- 19 drazine complex is due to the polymeric cation formed by 20 zine ligands bridging two nickel ions forming polymeric cat- bridging hydrazines between Ni centres [26]. In the hexahy- 2+ 21 ions, (Ni(N2H4)3 )n, Figure 3 [22] with a bonding energy drazine complex discrete ions are present and hence it’s sol- 22 contribution from the six membered ring formation [23]. ubility 23 Any suitable anion will then produce an insoluble precip- 24 itate [24] see section 3.4. 25 3.4.1 Conductivity Measurements 26 27 3.4 Solubility The increase in hydrazine hydrate solution conductivity ob- 28 served when NiHN dissolves, see Table 3, is consistent with 29 NiHN was insoluble in any of the following common sol- the formation of a soluble hexahydrazine nickel ion and ni- 30 vents DMSO, DCM, TCM methanol, ethanol, acetonitrile, trate ions. The major contributors to the conductivity are 31 benzene, benzonitrile, pyridine, N-methyl pyrolidinone and the hydronium and hydroxide ions produced by weak ion- 32 dry acetone. Any traces of water catalyze the reaction of hy- ization of the hydrazine hydrate. These are more mobile 33 drazine with two molecules of ketone producing bisiso- than the bulky nickel hexahydrazinate ion hence the small 34 propyl hydrazone thus dissolving the solid and generating increase in conductivity. The trihydrazinate is behaving as a 35 nickel ion solution. Dilute acids >0.01 M readily dissolved 36 the pink material forming hydrazinium salts and a green 37 solution of Ni2+ ions. 38 Addition of the powder to ammonia solution (2M) turns 39 the liquid blue similar to that observed when Nickel nitrate 40 is treated with excess of ammonia. An equilibrium is estab- 41 lished between the tris hydrazine and an aminated species 42 perhaps a triamine tri-hydrazine complex. Conversion of 43 bridging hydrazines to mono coordinate hydrazines would 44 produce soluble species 45 þþ 46 NiðN2H4Þ3ðNO3Þ2 þ 3NH3 ¼ NiðN2H4Þ3ðNH3Þ3 þ 2NO3 47 48 The free energy of formation favours the bidentate hy- 49 drazine over the monodentate hydrazine and ammonia 50 hence the low solubility and the excess of ammonia re- 51 quired. 52 Preparation method 3 failed to produce a precipitate im- Figure 4. UV/Visible absorption spectrum of hydrazine hydrate sol- 3 53 mediately or within a few cm added nickel solution indicat- ution containing increasing quantities of NiHN Lowest trace is hy- 54 ing that the tris hydrazine complex may be soluble in hydrazine hydrate solution. Middle trace first addition of NiHN pow- 55 drazine hydrate. Therefore weighed samples of the pink der. Upper trace 0.1 M NiHN in 98% hydrazine hydrate (1 mm path 56 solid complex were added, under a nitrogen atmosphere, to length).

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1 Table 3. Conductivity of Hydrazine hydrate solutions with added 3.6 Anion Dependency 2 NiHN. 3 The borofluoride and iodide do not produce any pre- Solution Conductivity mS 4 cipitated complex and the solution contains a distribution 5 Distilled water 0.03 of complexes with the number of incorporated hydrazine 6 95% Hydrazine hydrate 15.03 molecules ranging from 1 to 6 depending on the hydrazine 7 “”+ NiHN 15.42 concentration [24]. The sulphate shows similar properties to 5% Hydrazine hydrate 1.53 8 the nitrate. A solid trishydrazine complex is precipitated by “”+ NiHN 1.64 9 the addition of small quantities of hydrazine but, unlike the 10 nitrate, once all the nickel has been precipitated and further 11 hydrazine solution is added the precipitate starts to re-dis- 12 weak electrolyte since it requires such a large excess of hy- solve with the formation of tetra-, penta- and hexa- hydrazi- 13 drazine to produce any significant solubility. nate complexes in solution [24]. The chloride is unusual 14 with the initial precipitate is a bishydrazine complex,

15 [Ni(N2H4)2Cl2]n The hydrazines form bridging links between 16 3.5 Equilibrium Formation Constants the nickel ions in a planar polymeric chain and the chloride 17 ions sit on the axial positions [25]. Further hydrazine mole- 18 An equilibrium constant for the formation of the trishy- cules displace chloride from the nickel coordination sphere 19 drazine complex precipitate is producing the tris hydrazine complex with the polymeric 20 cation columns. Further addition of the hydrazine precip- 2þ 2 3 21 K ¼½NiðN2H4Þ3ðNO3Þ2=½NiðH2OÞ6 ½NO3 ½N2H4 itation solution re-dissolves the trishydrazine precipitate 22 forming hexahydrazine complexes as the end product. 3 23 The measured solubility of NiHN is 3 mg in 100 cm of These differences may be attributed to the hydrogen 4 3 24 water, 1.06 3 10 moldm . A value of (4.79 3 bonding of the anion groups to the coordinated hydrazine 6 3 25 10 moldm ) for the free hydrazine concentration in the molecules. The iodide and tetrafluoroborate are not strong 26 solution at pH 3, was calculated from the equilibrium hy- hydrogen bonders and hence will not hold the polymeric 27 drolysis for a salt of a strong acid and weak base [27]. Using nickel hydrazine chains in a potential lattice formation. 3 28 the initial concentrations of [Ni(H2O)6],(0.27 moldm ), Chloride ion is not a particularly strong hydrogen bonding 3 29 [(NO3 )], (0.54 moldm ) a value for the equilibrium con- species and is taken into the nickel coordination sphere en- 30 stant can be calculated. abling bis hydrazine complexes, to be formed as the first 31 stage. The sulphate exhibits hydrogen bonding with the co- 4 2 6 3 32 K ¼ 1:06 10 =0:27 ð0:54Þ ð4:79 10 Þ ordinated hydrazines and hence forms a potential lattice 33 ¼ 1:22 1013 dm15 mol5 configuration of the nickel hydrazine polymeric chains pro- 34 ducing a precipitate however the tetrahedral configuration 35 This value for the nitrate complex is greater than the of the sulphate is not ideal for maximum bonding with the 36 equilibrium constant for the corresponding trishydrazine octahedral polymeric hydrazinate chains. This structure is 37 complexes formed in the presence of any other anion such easily destroyed, when further hydrazine is added, changing 2 38 as SO4 ,Cl ,I or BF4 . See Table 4. Notice also that the sol- hydrazine coordination from a bidentate to monodentate li- 39 ubility product, SP, which is simply the product of the con- gand. 40 centrations, in moldm3, of all the species of the complex The nitrate anion is a strong hydrogen bonder and the 41 present in solution, is also much lower for the nitrate com- trigonal planar structure is ideal for holding three polymeric 42 plex than any other anion complex nickel-hydrazine chains in an almost perfect hexagonal con- 43 figuration structure, Figure 5. This structure will have a high 44 lattice energy and high free energy of formation, resulting 45 Table 4. Comparison of Formation Constants, Kf, for Nickel hydra- in the low solubility of the trishydrazine complex. No other zine compounds and their Solubility Products, S.P. 46 nickel hydrazine nitrate complexes has been isolated prob- 47 Compound Ni(N2H4)3 (X )2 ably because the trishydrazine polymer has a much higher 48 stability than any other alternative. No precipitate solubility XKf S.P. 49 14 22 was observed following further addition of the hydrazine NO3 3 3 10 1.5 3 10 50 2 10 14 precipitation solution to the mixture. Limited solubility was SO4 3.7 3 10 7 3 10 51 (Cl)(83 108)(53 1010) only achieved by adding concentrated hydrazine solution 52 Cl 8 3 103 3.5 3 1011 (>50% hydrazine) to the separated solid precipitate. 7 53 BF4 ~10 soluble It would be interesting to compare data for the chlorate 54 Footnote The bracketed Cl value is for the bishydrazine complex ClO3 and perchlorate ClO4 both of which are potential hy- 55 initially formed drogen bonders for potential lattice formation but un- 56

1 tion process. This would explain the solids variable compo- 2 sition. X-ray crystallography of the solid may elucidate the 3 structure produced and clarify this aspect. Other authors 4 [28] have suggested that the hexahydrazinate can be pro- 5 duced by high vacuum, low temperature (270 K) crystal- 6 lization from solutions of anhydrous nickel chloride in abso- 7 lute anhydrous hydrazine systems. This behaviour of the 8 nickel complex is in contrast to the corresponding cobalt 9 complex where the hexahydrazine complex can be isolated 10 from water containing solutions [29]. Further work is re- 11 quired to produce pure trishydrazinate complexes with dif- 12 ferent, measured, particle size distributions and test their 13 sensitivity to various stimuli to eliminate to dichotomy in 14 the literature values by different authors. Also investigation 15 of the solid produced when anhydrous nickel nitrate is add- 16 ed to anhydrous hydrazine under nitrogen might further 17 clarify the nitrates unique properties. 18 19 Figure 5. NiHN crystal lattice looking down the polymer cation axis 20 showing effect of nitrate hydrogen bonding on formation of hex- 4 Conclusions 21 agonal crystal structure. 22 The conditions for the precipitation of the title compound 23 under three different procedures and its solubility in a 24 fortunately they are both so initiation sensitive that there is range of solvents have been determined. Values for the 25 no data available. equilibrium constants governing the title compounds for- 26 mation and solubility in excess hydrazine forming a postu- 27 lated hexahydrazinate complex have been determined. A 28 3.7 Hexahydrazine Complex comparison with other nickel hydrazine complexes with 29 other anions has shown that the nitrate produces the least 30 A value for the formation constant for the hexahydrazine soluble trishydrazinate complex. Strong hydrogen bonding 31 complex can be determined from the solubility of the com- between the nitrate anion and the coordinated hydrazine 32 plex in hydrazine hydrate assuming the solubility of the molecules producing a complete three dimensional poly- 33 trishydrazine complex is unchanged from that of pure water meric crystalline species was suggested as the origin of the 34 1.06 3 104 moldm3 low solubility of the trishydrazinate complex and the failure 35 to form a crystalline hexahydrazinate species. Hexahy- 2þ 2 36 ½NiðN2H4Þ6 ½NO3 drazinate ions were only formed in concentrated hydrazine K ¼ 3 37 ½NiðN2H4Þ3ðNO3Þ2½N2H4 hydrate solution. 38 39 Quantity of NiHN soluble in hydrazine hydrate=2.511 g 3 3 40 in 40 cm =0.221 moldm [N2H4] in 98% hydrazine hy- References 41 drate=19.6 moldm3. Substituting these values into the 42 above equation gives a value for K for the formation of the [1] M. M. Chaudhri, J. E. Field, Deflagration in Single Crystal Lead 43 hexahydrazine complex from trishydrazinate as Azidde, 5th Symposium (International) on Detonation, Pasadena, 44 0.056 dm3 mol1. This result is consistent with the hexahy- CA, USA, August 18–21, 1970, p. 301. [2] EH40/98 Occupational exposure limits, HSE, HMSO Norwich UK 45 drazinate being metastable compared to the trishydrazine 1998. 46 complex and is only formed under excess hydrazine con- [3] Lead Particulates in Armoured fighting vehicles, unpublished 47 ditions. Attempts to produce crystals of the hexahy- ASC report, Royal Military College of Science, Shrivenham, UK 48 drazinate nitrate complex by removal of excess hydrazine, 1988. 49 under vacuum, produced a darker purple material than the [4] a) US Environmental Protection Agency Reports available at 50 prepared trishydrazinate but it analysed as pure trishy- http://www.epa.gov/EPA typical TRW recommendations for 51 drazinate. Similar experiments with the chloride anion did performing Human Health Risk analysis on Small arms Shoot- 52 not produce the hexahydrazinate complex but a product ing ranges. EPA 540R92615 2003; b) Best Management Practi- 53 which analysed as between 4–5 hydrazines per nickel [25]. It ces for Lead at outdoor Shooting Ranges EPA 902B01001 (2005); c) EPA Federal Facilities Forum Issue Paper. Site Charac- 54 is possible this product could be crystals with a hexahy- teristics for ammunition Characteristics 505S11001 2011. 55 drazinate core lattice surrounded by a trishydrazinate 56 formed as the outer layer hydrazine is lost during purifica-

6 www.pep.wiley-vch.de © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Propellants Explos. Pyrotech. 2018, 43, 1–8 ÝÝ These are not the final page numbers! Investigation of Preparation, Solubility and Stability Properties of Nickel Hydrazine Nitrate (NiHN)

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Propellants Explos. Pyrotech. 2018, 43, 1–8 © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.pep.wiley-vch.de 7 These are not the final page numbers! ÞÞ 1 FULL PAPER 2 3 M. Cartwright 4 5 1–8 6 7 Investigation of Preparation, Sol- 8 ubility and Stability Properties of 9 Nickel Hydrazine Nitrate (NiHN) 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56