Eu Metal Research Articles

Selective Dimerization of Ethene over Lanthanide Catalysts Deposited from Eu or Yb Metal Solutions in Liquid Ammonia

Abstract Europium and ytterbium catalysts obtained by impregnation of active carbon with lanthanide metal (Eu and Yb) solutions in liquid ammonia were found to be active for the dimerization of ethene. Ethene was selectively dimerized at 423–473 K to yield butene isomers with selectivity of 10–62%. The active catalysts were characterized as lanthanide nitride formed by the thermal decomposition of its amide.

Synthesis, characterization, and properties of three europium 2-propoxides: [Eu(4)(OPr(i))(10)(HOPr(i))(3)]*2HOPr(i), Eu(5)O(OPr(i))(13), and EuAl(3)(OPr(i))(12).

The reaction of Eu metal with HOPr(i)/toluene solutions yielded the mixed Eu(2+)/Eu(3+) alkoxide [Eu(4)(OPr(i))(10)(HOPr(i))(3)] x 2HOPr(i) (1), in contrast to the other lanthanide metals, which exclusively yield trivalent lanthanide ions in the alkoxides formed. Metathesis between EuCl(3) and 3KOPr(i) and stoichiometric hydrolysis yielded the square-pyramidal Eu(5)O(OPr(i))(13) (2), and metathesis with EuCl(3) and 3KAl(OPr(i))(4) gave EuAl(3)(OPr(i))(12) (3). The structures of these compounds were determined by single-crystal X-ray diffraction. IR spectroscopic studies showed that the solid-state molecular structure of the three alkoxides remained close to intact in solution. Further characterizations were made with UV-vis spectroscopy, differential scanning calorimetry, and solubility studies. It was also found that 1 can be converted to 2 by oxidation with dioxygen, but 2 was not reduced by Eu metal to 1. The reactions of 2 and 1 with Al(4)(OPr(i))(12) in toluene/HOPr(i) solvent were studied by IR and UV-vis spectroscopy; 2 reacted completely to form 3 in 2 h at 75 degrees C, while 1 reacted to yield 3 and other unidentified Eu(2+) containing product(s) in the same time.

Direct 1H, 13C, and 15N NMR Study of Lanthanum(III), Thulium(III), and Ytterbium(III) Complex Formation with Nitrate and Isothiocyanate

An 1H, 13C, and 15N NMR study has been completed for the complexes of La(III), Tm(III), and Yb(III) with nitrate and isothiocyanate in aqueous solvent mixtures. Signals for four complexes are observed for both the Tm3+–NO3− and Yb3+–NO3− solutions, with the species identified as the mono-, di-, tetra-, and either the penta - or hexanitrato. These results are consistent with those determined for the nitrate complexes of the Ce(III)–Eu(III) metal ions. The chemical shifts for the Tm(III) and Yb(III) nitrate complexes indicate a pseudocontact binding mechanism prevails. The complexes of diamagnetic La(III) with NO3− produce three signals in the 15NO3− spectra, with assignments paralleling those observed with the paramagnetic lanthanides. Three complexes are formed in the La3+–NCS− solutions, with signals assigned to the mono-, di-, and triisothiocyanato species.

Selective Hydrogenation of Benzene to Cyclohexadiene and Cyclohexene by Lanthanide Precipitates Obtained from Eu or Yb Metal Solutions in Liquid Ammonia

Abstract Lanthanide precipitates obtained by decomposition of Eu or Yb metal solutions in liquid ammonia were active at 393 K for the partial liquid-phase hydrogenation of benzene to cyclohexene with high selectivity (≥90%). When the reaction temperature decreased to 323 K, cyclohexadienes were preferentially formed. The reducing behavior was markedly enhanced by the addition of ammonia to the reaction system.

Catalysis of lanthanides deposited on oxide from Eu or Yb metal solutions in liquid ammonia

The catalytic properties of lanthanides (Ln) deposited on oxides (MnO, TiO 2 and MgO) from Eu or Yb metal solutions in liquid ammonia were studied. The catalysis of Ln/oxide varied markedly with differences in the oxides used and changes in levels of lanthanide content. The thermal treatment of Ln/oxide in vacuo also led to appreciable changes in catalytic activity. The lanthanides were used more efficiently for the hydrogenation and dehydrogenation when deposited on MnO. Ln/MnO showed the highest activity for the hydrogenation of ethene. Upon introduction of more than ca. 8 mass% Eu or Yb onto MnO, the activity for the hydrogenation appeared even at a reaction temperature of 199 K. The adsorption characteristics of hydrogen evaluated by temperature-programmed desorption (TPD) were improved at the same time. The lanthanide species present on MnO were characterized by FT-IR, combined with TPD studies. The increase in catalytic activity of Ln/MnO with evacuation temperature was responsible for changes of lanthanide amide to imide. In particular, when Ln/MnO was evacuated around 673 K, some synergetic actions between the lanthanides and MnO maximally develop, leading to enhanced activities.

Synthesis and Properties of Europium Complex of Polybenzimidazole Containing N-Eu Bond

NaH promoted deprotonation of the NH groups in poly(benzimidazole)s, [-Im-C6H4-]n (1a) (Im: 5,5′-dibenzimidazole-2,2′-diyl) and [{-Im-(CH2)11O(CH2)11-}0.98{-Im-(CH2)10}0.02-]n (1b) followed by addition of 4 equiv. of EuCl3 gave new soluble Eu complexes of poly(benz-imidazole)s (2a and 2b) having N-Eu bonds in 66 and 42% yields, respectively. The Eu polymer complexes 2a and 2b have two molecules of Cl and DMSO as ligands, which was revealed from IR and 1H NMR spectra and elemental analysis. Energy transfer from the benzimidazole group in polymer main chain to the Eu(III) metal was occurred upon irradiation with UV light in the solid state. This resulted in light emission from both the polymer chain and the Eu(III) center, although the Eu(III) itself could not be excitated by irradiation with the UV light.

Evidence for replicate5pcore levels in photoelectron spectra of Eu metal due to nonconstant kinetic-energy resonant Auger decay

Satellites on the low-binding-energy side of core-level photoelectron emission due to extra $4f$ screening are a well-known feature in the x-ray photoelectron spectra of valence fluctuation materials and rare-earth metals. A notable exception is Eu metal, where up to now no low-binding-energy satellite has been observed. In this paper we show that in Eu metal the $4d\ensuremath{-}4f$ resonance can decay via a resonant Auger decay, which is not a constant kinetic-energy feature due to a rapid change of the strength of $4f$ screening with excitation energy, establishing a low-binding-energy replica of the $5p$ core-level photoelectron emission.

Dehydrogenation of Cyclohexane to Benzene on Lanthanide Catalysts Formed by Thermal Decomposition of Eu or Yb Metal Solutions in Liquid Ammonia

Dehydrogenation of Cyclohexane to Benzene on Lanthanide Catalysts Formed by Thermal Decomposition of Eu or Yb Metal Solutions in Liquid Ammonia

Lanthanide (Eu or Yb)-promoted Ni, Cu and Ag-catalyzed transfer hydrogenation with NH 3 as a hydrogen donor

Novel lanthanide (Ln)-promoted Ni, Cu and Ag catalysts prepared by the reaction of Ni/SiO 2, Cu/SiO 2 and Ag/ZrO 2 with the dissolved Eu or Yb metals in liquid ammonia have been studied for the catalytic transfer hydrogenation of ethene, buta-1,3-diene and propyne. The transfer hydrogenation with the aid of ammonia as a hydrogen donor was greatly enhanced by the Ln-promoted catalysts. The catalytic activity for the transfer hydrogenation increased with increasing lanthanide content in the bimetallic catalysts, which evidently reflected synergetic effects between the lanthanide and transition metals. The transfer hydrogenation of ethene with ammonia over Eu–Ni/SiO 2 proceeded to form ethane and nitrogen, maintaining the following stoichiometric relationships: 3C 2H 4+2NH 3→3C 2H 6+N 2 The catalytic hydrogen transfer from ammonia to buta-1,3-diene or propyne similarly followed the stoichiometric relationships. The Ln-promoted catalysts showed substrate selectivity for the transfer hydrogenation using ammonia as the hydrogen source; Ln–Ni/SiO 2 was reactive for ethene and buta-1,3-diene, but not for propyne. Ln–Cu/SiO 2 was active for propyne and buta-1,3-diene. Ln–Ag/SiO 2 was relatively active for buta-1,3-diene. The major factors governing the catalytic transfer hydrogenation seem to be involved in the participation of the acceptor and donor molecules in the hydrogen transfer step rather than the ease of dehydrogenation of ammonia and the processes of hydrogen addition to the acceptor. The catalytic hydrogen transfer from ammonia to acceptor molecules occurs concertedly.

Structure and conformation of (dibenzyldiaza-18-crown-6)-Nd(III) and Eu(III) thiocyanates: infrared spectroscopic and X-ray crystallographic studies

Dibenzyldiaza-18-crown-6 was utilised as a host to accommodate Nd(III) and Eu(III) metal ions together with thiocyanate as counter ion. The crystalline complexes formed were studied for their absorption in the infrared region and their crystalline structure by X-ray diffraction. The coordination of the metal ions to the counter ion and also to the donor atoms of the crown ether was clearly seen from the shift of the absorption band of the pure compound by up to nearly 15 cm −1. From these absorption it was found that each lanthanide ion was coordinated to six donor atoms (2 N and 4 O) from crown ether and three donor atoms, N from NCS −. This nine coordination number complex was found to have the stoichiometry of 1:1:3 (crown ether:lanthanide; NCS −). This ratio was further confirmed by X-ray crystallographic method. The lanthanide thiocyanate salts existed as an isolated (separate) entity in the center of the macrocyclic cavity. The three N atoms surrounded the Ln cation in a nearly planar trigonal arrangement with Ln ion being slightly out of plane. The trigonal plane was perpendicular to and bisects the plane of the macrocycle.

Infrared spectra of dinitrogen adsorbed on bimetallic lanthanide (Eu or Yb)-Ni/SiO2 catalysts

Bimetallic lanthanide (Ln: Eu or Yb)–Ni/SiO2 catalysts prepared by the use of dissolution of lanthanide metals in liquid ammonia have been studied by infrared spectroscopy for dinitrogen adsorption. The infrared spectra were measured at 133–300 K using Ln–Ni/SiO2 obtained when the Eu or Yb metal dissolved in liquid ammonia reacted with 20 mass% Ni/SiO2 in different ratios. Infrared spectra for Eu–Ni/SiO2 showed absorption bands at 2336, 2265, 2254 and 2227 cm−1 at 133 K, which disappeared upon evacuation. The adsorbed state was found to be all molecular from the isotope shift using 28N2 and z30N28. The bands at 2254 and 2227 cm−1 of them were assigned to new adsorbed dinitrogen species resulting from synergetic interactions between the europium and nickel metal. The concentration of adsorbed dinitrogen on Eu–Ni/2 varied markedly with the Eu/Ni ratios, and particularly, it increased in the region of high Eu content. Upon introduction of ytterbium onto nickel, new bands at 2254 and 2226 cm−- similarly appeared. However, the dependence of dinitrogen adsorption as a function of Yb content in Yb–Ni/SiO2> was somewhat different from that for Eu–Ni/SiO2. The effects of lanthanide on the surface of Ln–Ni/SiO2 were discussed in connection with the variation in catalytic properties.

How mafic is the lower continental crust?

Crustal structures for nine broad tectonic units in China, except the Tarim craton, are derived from seismic data for 18 geophysical refraction profiles, which include twelve geoscience transects and have a total length of 16 216 km. All the tectonic units except the Qinling orogen show a four-layered crustal structure, consisting of upper, middle, upper lower, and lowermost crust. If corrections are made to room temperature and 600 MPa, the upper lower crust has P-wave velocities of 6.7–6.8 km s −1 and the lowermost crust 7.0–7.2 km s −1. Velocities of the bulk lower crust and total crust are 6.8–7.0 and 6.4–6.5 km s −1, respectively. They are slower by 0.2–0.4 km s −1, than the global averages. By correlation with experimental results on velocities of typical lower crustal rocks, the upper lower crust is suggested to be intermediate, while the lowermost crust is mafic in composition. Due to dominance of the former, the bulk lower crust is still intermediate for most tectonic units. However, inter-unit compositional variations are also evident, as indicated by large variations in the thickness ratio (0.3–3.0) of the upper lower to lowermost crust. The lower crust in East China as a whole is suggested to have ∼57% SiO 2. The results contrast with generally accepted models of mafic lower crust. Our estimates of the total crust composition in central East China show a more evolved character compared to models of Rudnick and Fountain, and Taylor and McLennan and are characterized by a prominent negative Eu anomaly (Eu/Eu * = 0.80), higher SiO 2 (61.8%), and lower Sr/Nd (∼10) as well as lower Sr/Nd, Cr/Nd, Ni/Nd, Co/Nd, V/Nd and Ti/Nd ratios. This, together with slower crustal velocities and remarkably thin crustal thicknesses (34 km) for the Paleozoic–Mesozoic Qinling–Dabie orogenic belt, leads to the suggestion that lower crustal delamination played an important role in modification of the East China crust. Mass balance modeling further suggests that eclogite from the Dabie–Sulu ultrahigh pressure metamorphic belt is the most likely candidate as the delaminated material, and that a cumulative 37–82 km thick eclogitic lower crust is required to have been delaminated in order to explain the relative Eu, Sr and transition metal deficits in the crust of central East China. Delamination of eclogites can also explain the significantly higher than eclogite Poisson's ratio in the present Dabie lower crust and upper mantle and lack of eclogite in Cenozoic xenolith populations of the lower crust and upper mantle in East China.

Catalytic properties of lanthanide amide, imide and nitride formed by thermal degradation of liquid ammonia solutions of Eu and Yb metal

The catalytic properties of lanthanide amide, imide and nitride prepared by the use of liquid ammonia solutions of lanthanide metals (Ln=Eu and Yb) were studied for catalytic hydrogenation. The reaction of Eu or Yb metal solutions in liquid ammonia with silica yielded SiO2-grafted lanthanide amide in the divalent state. The divalent amide showed catalytic activity for the selective hydrogenation of dienes and benzene. It was found that partial hydrogenation of benzene occurred with a very high selectivity for cyclohexene. Amides of calcium, strontium and barium were examined similarly in connection with catalytic studies on divalent amides. Imide and nitride, into which the lanthanide (Ln/AC) deposited by impregnation of active carbon (AC) with liquid ammonia solutions of lanthanide metals were converted thermally, were studied catalytically. It was concluded that imide or imide-like species generated during the thermal degradation of lanthanide amide to nitride were very active in the hydrogenation of ethene. Lanthanide nitride was virtually inactive, but the nitride highly dispersed on active carbon was activated when subjected to evacuation treatment above about 1000K.

Chemical composition of the continental crust as revealed by studies in East China

We report abundances of sixty-three major, trace, and rare earth elements in the upper crust in five tectonic units (the interior and southern margin of the North China craton, the North and South Qinling orogenic belts, and the Yangtze craton) of central East China and the study area as a whole. The estimates are based on sampling of 11,451 individual rock samples over an area of 950,000 km 2, from which 905 large composite samples were prepared and analyzed by thirteen methods. Some of the trace elements (i.e., Ag, As, Ge, Mo, Pd, Pt, Sb, Se, Sn, W) have never been subjected to systematic analysis in previous regional crustal composition studies. The middle, lower, and total crust compositions of the tectonic units are also estimated from studies of exposed crustal cross-sections and granulite xenoliths and by correlation of seismic data from eleven regional seismic refraction profiles with lithologies. The proposed granodioritic total crust composition has the following ratios of element pairs exhibiting similar compatibility, that are identical or close to the primitive mantle values: Zr/Hf = 37, Nb/Ta = 17.5, Ba/Th = 87, K/Pb = 0.12 × 10 4, Rb/Cs = 25, Ba/Rb = 8.94, Sn/Sm = 0.31, Se/Cd = 1.64, La/As = 10.3, Ce/Sb = 271, Pb/Bi = 57, Rb/Tl = 177, Er/Ag = 52, Cu/Au = 3.2×10 4, Sm/Mo = 7.5, Nd/W = 40, Cl/Li = 10.8, F/Nd = 21.9, and La/B = 1.8. The μ ( 238U/ 204Pb) value is calculated at ∼5. The upper crust composition is less evolved and higher in TiO 2, total FeO, Co, Cr, Ni, Sc and V, and lower in Na 2O, K 2O and Nb, Ta, Rb, Th, U, and Zr, than previous estimates based on shield samplings. Because usually the uppermost layer of the crust, where mafic volcanics tend to concentrate, has been removed from Precambrian shields, and since our study involves Phanerozoic orogenic belts, the results are suggested to be better representative of the upper crust in a general sense. Trace elements associated with mineralization (e.g., B, Cl, Se, As, Bi, Pd, W, Th, Cs, Ta, Tl, Hg, Au, and Pb) show considerable inter-unit variations by a factor of 2–5 in the upper crust. In addition, the North Qinling paleoactive margin is characterized by anomalous enrichment in Th, U, and Pb in particular and has a marked lower μ value (3.3) compared to the two cratons and the South Qinling paleopassive margin (μ = 4.5–6.2). Each tectonic unit has a relatively homogenous middle crust composition which is broadly similar to the composition of the total crust. The lower crust in East China can be divided into two layers both seismically and chemically. The upper lower crust is characterized by Vp = 6.7 km s −1 and an intermediate composition and the lowermost crust by Vp = 7.1 km s −1 and a mafic composition. The bulk lower crust is still intermediate in composition with 58% SiO 2 due to the dominance of the upper lower crust. P-wave velocities of both the lower and total crusts in East China are slower by 0.2–0.4 km s −1 compared to various global estimates. Correspondingly, the total crust shows an more evolved composition and is characterized by a significant negative Eu anomaly (Eu/Eu∗ = 0.80), low Sr/Nd (10.4), and high La/Nb (3.0) ratios. The obtained SiO 2 is 64% on a volatile-free basis. The near arc magma La/Nb ratio implies that intraplate crustal growth contributes <10% of the continental crust. The relative deficits in Eu, Sr, and transition metals (Cr, Ni, Co, V, and Ti) in the derived crustal compositions of East China, along with slower crustal velocity and thin crustal thickness for the Paleozoic to Mesozoic Qinling-Dabie-Sulu orogenic belt, strongly suggest that lower crust delamination of eclogites, as represented by those from the Dabie-Sulu belt, had played an important role in modification of the East China crust during the Phanerozoic era.

Spectator states in resonant photoemission of Eu and Gd metal

We report on a resonant photoemission study of Gd and Eu metal at the x-ray absorption threshold. The 4f photoemission signal exhibits a strong enhancement at resonance which is due to a true resonant photoemission process. For a photon energy corresponding to a satellite structure in the absorption spectra, a final state assigned to a spin-flip phenomenon in the excitation process is observed. Resonant photoemission spectra of the 4d states of Gd and Eu metal at the thresholds are also presented. No enhancement of the 4d emission is found. However, the appearance of a large emission at higher binding energy is observed. It is proposed that this feature originates from a more probable Auger transition, which reduces the probability of a resonant photoemission of the 4d states.

Coordination chemistry of lanthanides with transition metal anions

In coordinating solvents such as CH3CN, pyridine, and DMF, solvent separated ion pairs result when the transition metal centers and the bidentate ligands of the transition metal anions are not sufficiently nucleophilic to coordinate to lanthanide ions. With highly nucleophilic transition metal carbonylates, direct transition metal-lanthanide bonds as well as lanthanide-isocarbonyl linkages are possible. Direct bonds between ytterbium and iron are present in [(CH3CN)3YbFe(CO)4]2·CH3CN∞ a one-dimensional ladder, and (CH3CN)3YbFe(CO)4∞, a two dimensional sheet. The ladder polymers (DMF)4EuNi(CN)[in4]∞ and (DMF)4EuPt(CN)4∞, are formed2− in DMF. In these complexes the Eu(II) and transition metals are bridged by the cyanide ions, and no direct lanthanide-transition metal bonds are present. Two types of one-dimensional polymers of general formula (DMF)10Ln2[M(CN)4]3∞ that contain a cyanide bridge between the lanthanide(III) and the transition metal(II) have been prepared. Type A: Ln = Yb, Er, Sm; M = Ni. Type B: Ln = Yb, M = Pt; Ln = Eu, M = Ni. Both types of complex contain the same repeating unit. But the type A complex contains diamond shaped Ln2M2 cores linked together in an infinite array by M(CN)42− anions generating a single strand chain, while the type B complex contains two parallel zigzag chains that are inverted with respect to each other and are linked by M(CN)42− ions. By blocking one of the available trivalent lanthanide coordination sites with a chloride ion, the commonly observed zigzag chain structure of the tetracyanometallates(II) is adopted by (DMF)5Sm[Ni(CN)4]Cl∞ and (DMA)4YbNi(CN)4Cl∞

151Eu Mössbauer study of transition-metal/Eu multilayers.

The magnetic properties of TM/Eu (TM=V, Cr, Fe, Co, Ni, Cu, and Nb) multilayers have been studied by $^{57}\mathrm{Fe}$ and $^{151}\mathrm{Eu}$ M\ossbauer measurements at 4.2 and 300 K. The $^{57}\mathrm{Fe}$ M\ossbauer spectra at 4.2 and 300 K of the Fe/Eu multilayers were fitted with two components: one with hyperfine parameters typical of bulk \ensuremath{\alpha}-Fe, and the other one with a reduced magnetic hyperfine field, which is attributed to the interface region. The $^{151}\mathrm{Eu}$ M\ossbauer spectra of TM/Eu at 4.2 K were similarly analyzed with two components: component A with hyperfine parameters similar to bulk Eu metal, and component B with a reduced magnetic hyperfine field. Variation of the Eu layer thickness for the systems Fe/Eu and V/Eu showed an enhancement of component B relative to component A with decreasing Eu layer thickness, supporting the analysis with two components given above. The latter component is attributed to the interface region. Possible explanations for the reduction of the magnetic hyperfine field of component B are discussed. \textcopyright{} 1996 The American Physical Society.

Hydrogenation on Supported Lanthanide–Palladium Bimetallic Catalysts: Appearance of Considerable Hydrogen Uptake

Abstract Upon introducing of lanthanide metals (Ln : Eu or Yb) onto a Pd surface by the reaction of Pd/SiO2 with Eu or Yb metal dissolved in liquid ammonia, the ability of considerable hydrogen uptake by the catalyst appeared during the hydrogenation reaction. Hydrogenation over supported lanthanide–palladium bimetallic catalysts was studied at 173—213 K, especially concerning the effects of the reactants, support materials, Pd particle sizes, and dispersion on the hydrogenation behavior with the hydrogen uptake. For the hydrogenation of ethene, propene, butene or butadiene, considerable hydrogen uptake occurred preferentially, followed by hydrogenation using the hydrogen taken up the catalyst. The hydrogenation occurred by a rate-limited hydrogen uptake process. In marked contrast to olefin and butadiene, no hydrogen uptake was observed for the hydrogenation of acetylene, indicating the progress of the reaction by a different mechanism. The support materials (SiO2, Al2O3, ZrO2, MgO, and TiO2), Pd particle sizes and Pd dispersion in Pd/support were important factors in determining the hydrogen uptake by supported Ln–Pd catalysts and the resulting hydrogenation behavior.

Reactivities and Properties of Lanthanide Catalysts Prepared by Thermal Degradation of Liquid Ammonia Solutions of Eu or Yb Metal

Abstract Studies of X-ray diffraction, Fourier-transform infrared spectra and catalytic properties of lanthanide catalysts (Eu/AC and Yb/AC) prepared by impregnation of active carbon (AC) with liquid ammonia solutions of Eu or Yb metal were carried out for the catalytic hydrogenation of ethene. The lanthanides thus deposited on AC were changed through varied steps (metal, amide, imide or nitride) by thermal treatments and simultaneously the hydrogenation activity varied markedly. Eu/AC and Yb/AC which were subjected to the evacuation treatment around 573 and 773 K, respectively, showed a high activity even at 203 K. The catalytic properties of lanthanide amide (Eu(NH2)2, Yb(NH2)2, and Yb(NH2)3) prepared separately, imide and nitride were investigated for comparison. It was concluded that imide or imide-like species formed during the thermal decomposition processes of europium(II) and ytterbium(II and III) amides to nitride at 503—573 and 423—773 K was active catalysts for Eu/AC and Yb/AC, respectively.

Catalytic transfer hydrogenation over bimetallic lanthanide (Eu or Yb)-containing catalysts using NH3 as a hydrogen donor

Catalytic transfer hydrogenation of ethene and buta-1,3-deine with the aid of ammonia as a hydrogen donor is greatly enhanced by lanthanide (Ln)-promoted catalysts (Ln–Ni/SiO2, Ln–Ru/C, Ln–Cu/SiO2 and Ln–Ag/ZrO2), prepared by the reaction with Eu or Yb metal dissolved in liquid ammonia.