Ion migration law in flotation pulp and its influence on the separation of smithsonite and quartz

This study investigated the migration law of ion release and adsorption in the flotation pulp of oxide zinc ore, and found that numerous different ions existed in the pulp. The total concentrations and major sources of various ions (Pb²⁺, Zn²⁺, Fe³⁺, Ca²⁺, Mg²⁺, SO₄^2-, etc.), released from the minerals after grinding, were determined. The zeta potential tests indicated that a mixed-ion solution strongly influences the surface charge of the minerals. The flotation tests show that the migration law of ions is detrimental to the separation and concentration of minerals.     

Preparation and characterization of acid-activated bentonite powders

The Kütahya calcium bentonite (CaB) from Turkey shows significant changes in crystal structure, chemical composition and porosity with H₂SO₄ activation realized by heating its acidic aqueous suspension at 97 °C for 6 h. The acid content was changed from zero to 70% by mass, based on the dry bentonite-acid mixture. It was estimated from chemical analysis (CA) and X-ray diffraction (XRD) data that the CaB contains 65% calcium montmorillonite (CaM) and 30% opal-CT (OCT) by mass, and also illite (I) and other impurities in lower extents. The decrease in crystallinity of the CaM by the activation was discussed as regards to the decrease in the relative intensity (I / I₀) and increase in the full width at half-maximum peak height (FWHM) of the 001 XRD peak for CaM with the H₂SO₄%. The CA data reveals that the relative content of the undissolved cations in the CaB increase in the order of Ca²⁺, Na⁺, Mg²⁺, Fe^2+,3+, Al³⁺, K⁺, Si⁴⁺, and Ti⁴⁺ with H₂SO₄%. The specific micropore volume (V_mi) and specific mesopore volume (V_me) of the samples were estimated from N₂-adsorption and desorption data, by standard methods. The V_me shows a ‘zig-zag’ increase from 0.104 cm³g^− 1 to a maximum of 0.232 cm³g^− 1 at 40% and then decrease to 0.149 cm³g^− 1 at 70% H₂SO₄, respectively. The V_mi increases about from zero to 0.055 cm³g^− 1 at 10% H₂SO₄ and then stayed approximately constant.     

Enhancement of Palmarumycins C12 and C13 Production in Liquid Culture of Endophytic Fungus Berkleasmium sp. Dzf12 after Treatments with Metal Ions

The influences of eight metal ions (i.e., Na⁺, Ca²⁺, Ag⁺, Co²⁺, Cu²⁺, Al³⁺, Zn²⁺, and Mn⁴⁺) on mycelia growth and palmarumycins C₁₂ and C₁₃ production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12 were investigated. Three metal ions, Ca²⁺, Cu²⁺ and Al³⁺ were exhibited as the most effective to enhance mycelia growth and palmarumycin production. When calcium ion (Ca²⁺) was applied to the medium at 10.0 mmol/L on day 3, copper ion (Cu²⁺) to the medium at 1.0 mmol/L on day 3, aluminum ion (Al³⁺) to the medium at 2.0 mmol/L on day 6, the maximal yields of palmarumycins C₁₂ plus C₁₃ were obtained as 137.57 mg/L, 146.28 mg/L and 156.77 mg/L, which were 3.94-fold, 4.19-fold and 4.49-fold in comparison with that (34.91 mg/L) of the control, respectively. Al³⁺ favored palmarumycin C₁₂ production when its concentration was higher than 4 mmol/L. Ca²⁺ had an improving effect on mycelia growth of Berkleasmium sp. Dzf12. The combination effects of Ca²⁺, Cu²⁺ and Al³⁺ on palmarumycin C₁₃ production were further studied by employing a statistical method based on the central composite design (CCD) and response surface methodology (RSM). By solving the quadratic regression equation between palmarumycin C₁₃ and three metal ions, the optimal concentrations of Ca²⁺, Cu²⁺ and Al³⁺ in medium for palmarumycin C₁₃ production were determined as 7.58, 1.36 and 2.05 mmol/L, respectively. Under the optimum conditions, the predicted maximum palmarumycin C₁₃ yield reached 208.49 mg/L. By optimizing the combination of Ca²⁺, Cu²⁺ and Al³⁺ in medium, palmarumycin C₁₃ yield was increased to 203.85 mg/L, which was 6.00-fold in comparison with that (33.98 mg/L) in the original basal medium. The results indicate that appropriate metal ions (i.e., Ca²⁺, Cu²⁺ and Al³⁺) could enhance palmarumycin production. Application of the metal ions should be an effective strategy for palmarumycin production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12.     

硫铝酸盐与硅酸盐矿物合成高性能水泥

主要阐述以硅酸盐矿物阿利特(C3S)或贝利特(C2S)与硫铝酸盐矿物硫铝酸钙(C4A3S↑-)或硫铝酸钡钙[C(B)1A3S↑-]为主导矿物的复合型水泥的组成设计、低温合成技术及其性能与应用,同时还阐述了具有突出快硬旱强特点的硫铝酸钡钙矿物的性能以及由该矿物复合成的新型水泥的研究进展,对以阿利特-硫铝酸钡钙为主导矿物的新型高胶凝性水泥的发展前景进行了展望。     

Structural-microstructural characterization and optical properties of Eu3+,Tb3+-codoped LaPO4·nH2O and LaPO4 nanorods hydrothermally synthesized with microwaves

Rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄·nH₂O single-crystal nanorods with the compositions La_0.99999-xEu_xTb_0.00001PO₄·nH₂O (x?=?0–0.03), La_0.99999-yTb_yEu_0.00001PO₄·n′H₂O (y?=?0–0.010), and La_0.99999-zTb_zEu_0.000007PO₄·n′′H₂O (z?=?0–0.012) were hydrothermally synthesized with microwaves. It is shown that the Eu³⁺,Tb³⁺ codoping does not affect the thermal stability of these nanorods, which is due to the formation of substitutional solid solutions with both Eu³⁺ and Tb³⁺ replacing La³⁺ in the crystal lattice. Moreover, it is also shown that monazite-type Eu³⁺,Tb³⁺-codoped LaPO₄ single-crystal nanorods can be obtained by calcining their rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄·(n,n′ or n′′)H₂O counterparts at moderate temperature in air, and that they are thermally stable. It is also observed that, for the same Eu³⁺,Tb³⁺-codoping content, the monazite-type Eu³⁺,Tb³⁺-codoped LaPO₄ nanorods exhibit higher photoluminescent efficiency than the rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄· (n,n′ or n′′)H₂O nanorods. Moreover, it is found that the highest photoluminescence emission corresponds to the monazite-type La_0.96999Eu_0.02Tb_0.00001PO₄ nanorods for the La_0.99999-xEu_xTb_0.00001PO₄ system. However, for those compositions energy transfer from Tb³⁺ to Eu³⁺ does not occur. In addition, for an efficient energy transfer to occur, a content of at least 1?mol% Tb³⁺ is needed in all the studied materials.     

Studies on the Stability of Calcium Sulphoaluminate

High calcium sulpho-aluminate (3CaO. Al₂O₃. 3CaSO₄. 31H₂O—C.S.A.) is a deterioration product of Portland cement found in concrete. It is formed by the attack of sulphate solutions on two of the Portland cement components: hydrated calcium Aluminate and lime. These phenomena fostered a study of the synthesis and stability of calcium sulpho-aluminate. Results of the experiments on stability of calcium sulphoaluminate in different media are discussed. Measures for preventing the formation of C.S.A. in Portland cement are described.     

Monodisperse nanospheres of yttrium oxysulfide: Synthesis,characterization, and luminescent properties

A red long-lasting phosphorescent material, monodisperse Y₂O₂S: Eu³⁺, Mg²⁺, Ti⁴⁺ nanospheres have been prepared successfully. Y(OH)(CO₃): Eu³⁺ nanospheres were firstly synthesized via an urea-based homogeneous precipitation technique to serve as the precursor. Nanospheres long-lasting phosphors Y₂O₂S: Eu³⁺, Mg²⁺, Ti⁴⁺ were obtained by calcinating the precursor in CS₂ atmosphere. XRD investigation shows a pure phase of Y₂O₂S, indicating no other impurity phase appeared. SEM observation reveals that the structures are nanosphere. The Y₂O₂S: Eu³⁺, Mg²⁺, Ti⁴⁺ nanospheres with particle size about 100–150 nm show uniform size and well-dispersed distribution. After irradiation by ultraviolet radiation with 325 nm for 5 min, the phosphor emitted red color long-lasting phosphorescence corresponding to typical emission of Eu³⁺ ion. The main emission peaks are ascribed to Eu³⁺ ions transition from ⁵D_J (J = 0, 1, 2) to ⁷F_J (J = 0, 1, 2, 3, 4). Both the PL spectra and luminance decay revealed that this phosphor had efficient luminescent and long-lasting properties. It was considered that the red-emitting long-lasting phosphorescence was due to the persistent energy transfer from the traps to the Ti⁴⁺ and Mg²⁺ ions.     

Ligand dehydrogenation in ruthenium trinitrogen complexes: synthesis,structure and chirality of the cations [Ru(LH4)(L)]2+ [LH4=2,6-bis(pyrrolidin-2-yl)pyridine]

Reaction of 2,6-bis(pyrrolidin-2-yl)pyridine (LH₄) with RuCl₃·3H₂O in refluxing methanol/water mixtures gives rise to the formation of the octahedral complexes [Ru(LH₄)(L)]²⁺, in which one of the two trihapto ligands has been dehydrogenated as 2,6-bis(3,4-dihydro-2H-pyrrol-5-yl)pyridine (L), even if LH₄ was present in excess. With the three stereoisomers of LH₄, the complexes [Ru(R,S-LH₄)(L)]²⁺ (meso), [Ru(R,R-LH₄)(L)]²⁺ and [Ru(S,S-LH₄)(L)]²⁺ have been isolated as the perchlorate salts and characterised by X-ray structure analysis and by CD spectra.     

Dissolution of alumina ceramics in HCl aqueous solution

Dissolution of a cold isostatically pressed high purity alumina ceramics in aqueous HCl solutions was studied as a function of immersion time and acid concentration. From the amounts of Al³⁺, Mg²⁺, Ca²⁺, Na⁺, Si⁴⁺ and Fe³⁺ ions released in the corrosive solution, a degree of dissolution χ_i for each component was calculated according to the equation χ_i = A/B, where A and B are respectively the amount of the element released in the corrosive solution and the amount of the element in the untreated material. The determination of the amounts of ions released in the corrosive solutions was carried out by means of atomic absorption spectrometry (AAS). The corrosion of alumina ceramics in the HCl aqueous solution is determined by the solubility of alumina and the solubility of grain-boundary impurities. Very low dissolution values of Al³⁺, Mg²⁺, Ca²⁺, Na⁺, Si⁴⁺ and Fe³⁺ ions after the corrosion test of alumina ceramics showed a very good corrosion resistance in the HCl aqueous solution.     

Studies on the Stability of Calcium Chloraluminate

Calcium chloraluminate (3CaO · Al₂O₃ · CaCl₂ · 10H₂O) is a deterioration product of Portland cement found in concrete. It is formed by the attack of chloride solutions on two of the Portland cement components: hydrated calcium aluminate and lime. A study of the synthesis and stability of calcium chloraluminate in different media are described. Calcium chloraluminate enhances the growth of high calcium sulphoaluminate crystals (3CaO · Al₂O₃ · 3CaSO₄ · 31H₂O).     

IFCC recommendation on sampling,transport and storage for the determination of the concentration of ionized calcium in whole blood,plasma and serum

The substance concentration of ionized calcium (c _Ca²⁺) in blood, plasma or serum preanalytically may be affected by pH changes of the sample, calcium binding by heparin, and dilution by the anticoagulant solution.pH changes in whole blood can be minimized by anaerobic sampling to avoid loss of Co₂, by measuring as soon as possible, or by storing the sample in iced water to avoid lactic acid formation. c_Ca ²⁺ and pH should be determined simultaneously.Plasma or serum: If centrifuged in a closed tube, and measured immediately, the pH of the sample will be close to the original value. If a delay has occurred between centrifugation and the measurement, causing substantial loss of Co₂, equilibration of the sample with a gas mixture corresponding to pCO2= 5.3 kPa prior to the measurement is recommended. Conversion of the measured values to c_Ca ²⁺ (7.4) is only valid if the pH is in the range 7.2-7.6.Ca²⁺ binding by heparin can be minimized by using either of the following:(1) A final concentration of sodium or lithium heparinate of 15 IU/ml blood or less(2) Calcium titrated heparin with a final concentration of less than 50 IU/ml blood.Dilution effect can be avoided by use of dry heparin in capillaries or syringes. When heparin solutions are used, errors due to dilution or calcium binding can be reduced by using syringes with a heparin solution containing free calcium ions corresponding to the mean concentration of ionized calcium in normal plasma.Conditions for blood collection, storage, and transport to avoid preanalytical errors are described in this paper.     

Photoluminescence properties of Ce3+/Mn2+ doped calcium zirconium silicate phosphors with energy transfer for white LEDs

A series of Ce³⁺ doped and Ce³⁺/Mn²⁺ co-doped calcium zirconium silicate CaZrSi₂O₇ (CZS) phosphors have been synthesized via conventional high temperature solid state reactions. The luminescence properties, energy transfer between Ce³⁺ and Mn²⁺ have been investigated systematically. Under 320 nm excitation, the phosphor CZS: 0.05Ce³⁺ exhibit strong blue emission ranging from 330 nm to 500 nm, attributed to the spin-allowed 5d-4f transitions of Ce³⁺ ions. There are two different emission centers of Ce³⁺ ions, Ce³⁺(I) and Ce³⁺(II). The emission spectra of Ce³⁺, Mn²⁺ co-doped phosphors shows a broad emission around 550 nm corresponding to the ⁴T₁(⁴G)-⁶A₁(⁶S) spin-forbidden transition of Mn²⁺. The energy transfer between Ce³⁺ and Mn²⁺ is detected and the transfer efficiency of Ce³⁺(II) to Mn²⁺ is faster than that of Ce³⁺(I) to Mn²⁺. The resonant type is identified via dipole-dipole mechanism. Additionally, a blue-shift emission of Ce³⁺ and a red-shift emission of Mn²⁺ have been observed following the increase of Mn²⁺ content in relation to the energy transfer. Thermal quenching has been investigated and the emission spectra show a blue-shift with the temperature increases, which have been discussed in details. CZS: 0.05Ce³⁺, yMn²⁺ phosphors can be tuned from blue to white and even to yellow by adjusting the Mn²⁺ content. All the results indicate that CZS: Ce³⁺, Mn²⁺ phosphor have a potential application for near-UV LEDs.     

Preparation of synthetic rutile and metal-doped LiFePO4 from ilmenite

The synthetic rutile and metal-doped LiFePO₄ are prepared from the high-titanium residue and iron-rich lixivium, which are obtained from the ilmenite by a mechanical activation and leaching process. ICP results show that the rutile contains 92.01% TiO₂, 1.59% Fe₂O₃, 0.034% MnO₂ and 0.60% (MgO + CaO), which meet the requirement of the titanium dioxide chlorination process. The results also reveal that small amounts of Al³⁺, Ca²⁺ and Ti⁴⁺ precipitate in the FePO₄·xH₂O precursor. XRD and Rietveld-refine results show that the metal-doped LiFePO₄ is single olivine-type phase and well crystallized, and Ti⁴⁺ occupy M1 site, Ca²⁺ occupy M2 site and Al³⁺ occupy both sites, which indicates the formation of cation-deficient solid solution. The sample exhibits a capacity of 123 mAh g⁻¹ at 5C rate, and retains 94.3% of the capacity after 100 cycles.     

Separation performance of a nanofiltration membrane influenced by species and concentration of ions

Nanofiltration (NF), which has been largely developed over the past decade, is a promising technology for the treatment of organic and inorganic pollutants in surface and ground waters. The ESNA 1 membrane from the Nitto Denko Corporation of Japan is made of aromatic polyamide, which provides salt rejection from 50% to 90%. In this paper permeation experiments of aqueous solutions of five chlorides (NH₄Cl, NaCl, KCl, MgCl₂ and CaCl₂), three nitrates (NaNO₃, Mg(NO₃)₂ and Ca(NO₃)₂), and three sulfates (NH₄)₂SO₄, Na₂SO₄ and MgSO₄) were carried out. The effects of species and concentration of salts on the separation performance of the ESNA 1 membrane were investigated. The experimental results showed that the rejection to most salts by the ESNA 1 membrane decreased with the growth of the concentration. Then, the reflection coefficient and solute permeability of ESNA 1 membrane were calculated by the Spiegler-Kedem equation from experimental data. The reflection coefficients of the ESNA 1 membrane to salts are all above 0.95. The salt permeabilities, except for magnesium and calcium salts, increased with the growth of concentration. The sequence of rejection to anions by the ESNA 1 membrane is R(SO²⁻₄) > R(Cl⁻) > R(NO⁻₃) at the same concentration which ranges from 10 mol/m³ to 100 mol/m³. The sequence of rejection to anions by the ESNA 1 membrane can be written as follows: R(Na⁺) > R(K⁺) > R(Mg²⁺) > R(Ca²⁺) at 10 mol/m³ concentration and R(Mg²⁺) > R(Ca²⁺) > R(Na⁺) > R(K⁺) at 100 mol/m³ concentration.     

Effect of A+ (A = Li,Na and K) co-doping on enhancing the luminescence of Ca5(PO4)2SiO4:Eu3+ red-emitting phosphors as charge compensator

A series of Ca_5-x(PO₄)₂SiO₄:xEu³⁺ red-emitting phosphors were synthesized through solid-state reaction, and alkali metal ions A⁺ (A = Li, Na and K) were co-doped in Ca₅(PO₄)₂SiO₄:Eu³⁺ to improve its luminescence property. The impacts of synthesis temperature, luminescence center Eu³⁺ concentration and charge compensator A⁺ on the structure and luminescence property of samples were studied in detail. X-ray diffraction results indicated that prepared Ca₅(PO₄)₂SiO₄:Eu³⁺, A⁺ had a standard Ca₅(PO₄)₂SiO₄ structure with space group P6₃/m. Under the excitation of 392 nm, Ca₅(PO₄)₂SiO₄:Eu³⁺ phosphors showed a red emission consisting of several emission peaks at 593 nm, 616 nm and 656 nm, relevant to ⁵D₀→⁷F₁, ⁵D₀→⁷F₂ and ⁵D₀→⁷F₄ electron transitions of Eu³⁺ ions, respectively. Luminescence intensity and lifetime of Ca₅(PO₄)₂SiO₄:Eu³⁺ can be significantly enhanced through co-doping alkali metal ion A⁺, which play an important role as charge compensator. The results suggest that Ca₅(PO₄)₂SiO₄:Eu³⁺, A⁺ red phosphors with excellent luminescence property are expectantly served as red component for white light-emitting diodes excited by near-ultraviolet.     

Biosynthesized magnetite-perovskite (XFe2O4-BiFeO3) interfaces for toxic trace metal removal from aqueous solution

X-modified magnetite (XFe₂O₄; X?=?Cr, Mn, Fe, Co or Ni) was synthesized from goethite reduction, and inserted into the Fe-vacancy of perovskite (BiFeO₃), via microbial Fe³⁺→Fe²⁺ reduction by Shewanella (e.g. Shewanella oneidensis MR-1 and Shewanella putrefaciens CN32). We demonstrated that the average adsorption intensities of nine toxic trace metals (Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Hg²⁺), in Freundlich mode were 8.29–10.79 multiples higher than that in Langmuir mode, being more competitive than previously reported values. The fluorescence quenching is attributed to the orbital hybridization of molecular oxygen activation and trace metal (M) ions, which weakens the X²⁺-O-Fe³⁺-O-(Fe³⁺) coupling orbital. In addition Shewanella putrefaciens CN32 creates more oxygen vacancies to modify Ni↓-Fe↓-O↑ d*-p hybridized orbitals for enhancing the local spin-orbit coupling with Cd-4d¹⁰. This design idea can be extended to other direct biosynthetic magnetite-perovskite as highly efficient toxic trace metal removal agents.     

Structure stability,bond characteristics and microwave dielectric properties of co-substituted NdNbO4 ceramics

Structure-property relationship of co-substituted (Mg²⁺_1/4Mo⁶⁺_3/4)⁵⁺, (Al³⁺_1/3Mo⁶⁺_2/3)⁵⁺, (Si⁴⁺_1/2Mo⁶⁺_1/2)⁵⁺, (Zr⁴⁺_1/2Mo⁶⁺_1/2)⁵⁺ for Nb⁵⁺ in NdNbO₄ ceramics was investigated systematically. The remarkable differences in dielectric properties of each composition originated from their bond characteristics and structure stability. The elongated/compressed bonds have an effect on the cell volume and polarization. And the average bond covalency of Nb-O bond was responsible for the development of permittivity. Q×f values and the total lattice energy went up to maximum when (Si_0.5Mo_0.5) occupied Nb-site. Variations of lattice energy together with Nb-O bond energy suggest that a more stable structure was obtained through co-substitution. The optimal microwave dielectric properties is: ε_r =?18.97, Q×f?=?49466?GHz, τ_f =?7.34?ppm/°C for NdNb_0.97(Si_0.5Mo_0.5)_0.03O₄, sintered at 1250?°C.     

High performance of Ni-substituted calcium aluminosilicate for partial oxidation of methane into syngas

Newly synthesized calcium aluminosilicate, in which oxide anions were occluded, was tested as a catalyst for partial oxidation of CH₄ into CO and H₂. Substitution of a part of Ca²⁺ with Ni²⁺ resulted in a marked increase in CH₄ conversion (93% at 800 °C) and in CO and H₂ selectivities (94% and 95%, respectively), while Cr³⁺, Co³⁺, Fe³⁺ and Cu²⁺ slightly increased CH₄ conversion with a considerable decrease in CO and H₂ selectivities. Such a high performance may be attributed to the ability of Ni-substituted sample for CH₄ steam reforming appearing during CH₄ partial oxidation.     

Ultra-sensitive low-temperature thermometer regulated by the crystal field strength

Developing novel optical thermometry with ultrahigh relative sensitivity and temperature resolution has become a cutting-edge topic. For this purpose, under obeying Boltzmann distribution, a series of Li₂Zn_0.9992-xA_xGe_3-yB_yO₈:0.08% Cr³⁺ (B= Sc³⁺, In³⁺, A = Si⁴⁺) phosphors were studied, which the luminescence intensity ratio between the transition of ⁴T_2g→⁴A_2g emission and the R line based on thermally coupled energy levels constitutes a temperature sensing work with a relative sensitivity of 9.46% K^?1, 9.73% K^?1, and 10.38% K^?1, respectively. It is worth mentioning that the luminescence intensity of the R line (peak 1) increases significantly with the increase of temperature, while the transition of ⁴T_2g→⁴A_2g (peak 2) with high intensity at low temperature gradually quenching, and this opposite trend is an important advantage for the design of excellent thermometers. Compared the best relative sensitivity of Li₂Zn_0.9992-xA_xGe_3-yB_yO₈:0.08%Cr³⁺ (B= Sc³⁺, In³⁺, A = Si⁴⁺) with the crystal field Dq/B, it can be concluded that relative sensitivity increasing gradually with decreasing the intensity of crystal field. Finally, by testing the stability of the sample at 50 K, a thermal resolution of 0.082 K, 0.080 K and 0.077 K was obtained, respectively, which is one of the best thermal resolutions so far, while the repeatability of the sample stability at 50 K and 300 K cycles was higher than 99%. Our work is expected to provide guiding insights for optimizing the sensitivity of Cr³⁺-based luminescence intensity ratio thermometers.     

Chemical forms of ash-forming elements in woody biomass fuels

Advanced fuel characterization helps to predict ash fouling and slagging. Chemical fractionation analysis, i.e. sequential leaching in H₂O, NH₄Ac(aq), and HCl(aq), was applied to the biomass of spruce, pine, birch, and aspen. All of the Cl in the samples and most of the K, Na, and P were water-soluble; most of the Mg and Mn, and some of the Ca were leached in NH₄Ac; most of the Ca was leached in HCl; and most of the Si and S remained insoluble in the biomass. Ion Chromatography found the water-soluble Cl, P, and S present as Cl⁻, , and , respectively, and equimolar concentrations of as leached Ca in the acid fraction. The biomass solids were determined for anionic groups by methylene blue sorption. The contents were lowest in the wood samples (22-118 mmol/kg_D.S.) and highest in the bark samples (130-453 mmol/kg_D.S.). The closing of the ion charge balance led to a quantitative model for the ash-forming matter: water-soluble salts (KCl, K₂HPO₄, and K₂SO₄), acid-soluble minerals (CaC₂O₄), non-soluble minerals (SiO₂), and organically associated ash-forming elements (ionically bonded Ca²⁺, Mg²⁺, Mn²⁺, and K⁺, and covalently bonded P and S).