Melting Tin Research Articles

Insight into the optical evaluation of sunlike LED devices with full-visible spectrum emission based on ultra-low melting tin fluorophosphate glass for human centric lighting

Full spectrum sunlike light-emitting diode (LED) devices in the wavelength range of 380–670 nm have received much attention for their applications in human centric lighting. Herein, the inorganic color converter of the sunlike phosphor-in-glass (PiG) has been developed by embedding the green-emitting (Lu3-xYxAl5O12: Ce3+) and red-emitting (Sr0.6Ca0.4AlSiN3: Eu2+) phosphor powders in ultra-low melting tin fluorophosphate glass. Notably, the sunlike PiG exhibits the full spectrum in the wavelength range of 380–670 nm under the excitation of a near-ultraviolet (NUV) chip. Tunable color temperature (2785 K–5806 K) and high color rendering index (Ra = 95) were obtained by varying the mix ratio of the red-emitting component in the glass matrix. Further, the full visible spectrum emission was regulated by adjusting the Lu/Y ratio of the green phosphor Lu3-xYxAl5O12: Ce3+ and the color quality was further optimized (Ra = 97). The color quality of white light-emitting diode (WLED) was systematically investigated using Illuminating Engineering Society (IES) of North America evaluation systems and the LED devices exhibit fidelity index (Rf) and gamut index (Rg) close to sunlight (Rf = 95, Rg = 101). Compared with the traditional phosphor-in-silicone (PiS), the sunlike PiG based WLED exhibits a low working temperature of ∼37 °C for high power LED. Therefore, the WLED devices based on sunlike-PiG can be regarded as promising candidates for ultra-high color rendering index light sources because of the adjustable color temperature, high color quality, low-efficiency loss, excellent thermal properties and water stability.

Microstructure, mechanical properties and wear behaviors of TiN/Ti composite coating on laser surface textured Ti6Al4V alloy fabricated by MHz picosecond laser surface alloying

Ceramic-reinforced metal matrix composites (MMCs) coating fabricated by laser surface melting effectively improves the surface mechanical and wear properties of titanium alloys. However, power of several hundred watts is generally used in traditional laser processing, which introduces excessive heat input and leads to thermal deformation and thermal effects, resulting in cracks and reducing mechanical properties and service life of coatings. In order to improve the microhardness and anti-wear properties of Ti6Al4V alloy and extend the service life, a picosecond laser (ps-laser) with a power of 23 W and repetition rate of 19 MHz was utilized to fabricate the uniform and crack-free MMCs coating (TiN/Ti) by melting TiN powders on the textured Ti6Al4V surface. Three different textures with different texture densities and depths were used to evaluate their effects on coatings. Results showed that the reinforced TiN phase was in the form of fine dendrites with an average secondary dendrite arm spacing of 0.84 µm. The microhardness and the anti-wear properties were both inversely proportional to the texture densities because of controlling the volume fraction of TiN in the coating. The microhardness of the sample with greatest microhardness increase was significantly improved from 355 HV0.5 (base material) to 1000 HV0.5 due to the addition of the TiN phase. The sample with a texture density of 5% showed the best anti-wear properties (about 22 times that of the substrate) due to the effective suppression of three-body abrasive wear.

Contacting Inkjet-Printed Silver Structures and SMD by ICA and Solder

Digitally printed conductive structures often need to be electrically connected to batteries, microcontrollers, or other devices. A consensus of industry and research is that such hybrid printed electronics will play a major part in the future of printed electronics. To promote the technology of hybrid printed electronics, surface mount technologies for electronic components using isotropic conductive adhesives (ICAs) and low melting tin bismuth solders on inkjet-printed silver structures on injection molded liquid crystal polymer (LCP) substrates were investigated in this publication. The special needs for inkjet-printed electronics were considered as well as the reliability of assembled surface mounted devices (SMDs) and their failure mechanisms. Connected 0603 and 1206 SMD components achieved a characteristic fatigue life of more than 3500 cycles during thermal cycling at +125 °C/−40 °C and withstood over 1000 h under a damp-heat atmosphere of +85 °C/85% RH. The coefficient of thermal expansion (CTE) of the substrate and the selection of solder have major impacts on the reliability of the assemblies.

Unraveling the link between mantle upwelling and formation of Sn-bearing granitic rocks in the world-class Dachang tin district, South China

AbstractIncreasing evidence shows that the mantle contributes (directly or indirectly) to Sn-bearing granites worldwide. However, the specific role of mantle in the formation of tin granites and related mineralization remains poorly understood. In the world-class Dachang district, South China, tin mineralization is related to the Longxianggai equigranular/porphyritic biotite granites and tin orebodies are cut by granite porphyry dykes hosting mafic microgranular enclaves (MMEs). A combination of zircon U-Pb dating and Hf-O isotopes, mineral chemistry, and whole-rock elemental and Sr-Nd isotopic compositions—for granitic rocks and MMEs, is employed to constrain the petrogenesis and to unravel the link between tin fertility and mantle upwelling. Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon U-Pb dating indicates that the biotite granites were emplaced at ca. 93 Ma, and the granite porphyry dykes and MMEs were formed at ca. 86 Ma. The biotite granites are silica- and alkali-enriched with A/CNK ratios of 1.04–1.36, and exhibit elevated concentrations of Li, F, P, Rb, Cs, Ta, Sn, W, and U, showing affinities with highly fractionated S-type granites. Whole-rock geochemical and Nd isotopic (εNd(t) = −10.0 to −7.8) data, and in situ zircon Hf-O (εHf(t) = −9.9 to −3.9, δ18O = 6.2–8.9‰) isotopes indicate that the biotite granites were formed by partial melting of metasedimentary rocks at relatively high temperatures (≥782 °C), possibly with minor input of mantle material. Likewise, the post-ore granite porphyry dykes have similar chemical and mineralogical characteristics as fractionated S-type granites. Zircon Hf-O isotopes (εHf(t) = −9.0 to −4.9, δ18O = 6.5–8.2‰) and whole-rock geochemical data suggest they were derived from a similar source as the biotite granites, whereas elevated εNd(t) values of −5.0 to −3.3 for granite porphyry dykes relative to biotite granites reveal an increasing mantle input. Distinct εNd(t) (−0.4 and −0.3) and zircon Hf-O (εHf(t) = 1.5–5.0, δ18O = 6.5–7.2‰) isotopes of the MMEs, suggest that the mafic melt could be sourced from the asthenospheric mantle, contaminated by subcontinental lithospheric mantle/continental crust during magma ascent, and hybridized by felsic melt at emplacement-level. The magmatic sequence in the Dachang district is indicative of an extensional tectonic setting where mantle-derived magmas are predicted to migrate to shallower crustal levels as the crust progressively becomes thinner and hotter. High-temperature partial melting of mature metasedimentary crust triggered by heat input from the upwelled mantle, may contribute to biotite breakdown, which is important for concentrating tin in melts. Fractional crystallization of initially Sn-rich felsic melts under reduced conditions makes further tin enrichment and produces Sn-bearing granites (the Longxianggai pluton). Prolonged mantle upwelling results in distinct magma mixing and the formation of granite porphyry dykes and MMEs. These dykes are highly fractionated with elevated Sn and W contents, which show great potential to form hydrothermal Sn-W mineralization.

The analysis methods of electron-microscopic images for automation of building histograms of nanoparticle size distribution

In that work a describing of automated system is made an introduction, which allow to identify particles, that are look after on electron-microscopic images, and to determine their size, area and length of borders independently. Particle identification is based on a threshold criterion, which has low computational complexity, but has proven to be quite effective when applied to SEM and TEM images. Visual control of correct particle identification is facilitated by colorizing images. The proposed software system has a high performance, and the processing of a typical SEM imagine usually take less than 10 seconds. The proposed approach was tested on different vacuum condensates and shown high efficiency for different SEM and TEM images. It is effective for simple pictures, which are characteristic for samples, formed by melting of sufficiently thick polycrystalline films. This approach can also be used for quantitative processing of images obtained from films condensed by the vapor-liquid mechanism. Usually such images are difficult for automatic processing. Data on the size dependence of the most probable particle radius formed during melting tin films, full width at half maximum of histograms of their size distribution and excess energy, stimulating the process of de-wetting of films were received by using the proposed software. It is shown that particle size distribution for samples obtained by melting initially continuous polycrystalline films is single-mode and has normal character. The ratio of the full width at half the height of the distribution histogram to the most probable particle radius does not depend on the film thickness. Applying offered method for alloys films let to establish the effect of composition on films’ de-wetting and to show, that sequential vacuum condensation and subsequent melting are a easy method of forming arrays both single-component particles and alloys particles.

Numerical simulation of impact and solidification of melting dust on spherical bead surface and experimental validation

The impact and solidification processes of single melting tin dust at the micron scale on a spherical bead were numerically studied with hot flue gas flow. The geometrical evolution of dust impacting on hot bead and spreading without solidification involved initial spreading, retraction and oscillation, and stabilizing. The increased impact angle was found to reduce maximum spread area, weaken retraction and oscillation, and raise steady spread area. Dust impacting on cold bead completely solidified after liquid spreading and solidification without retraction and oscillation. Increased impact angle raised solidification sliding distance, whereas it reduced solidification spread area. Then, the effects of bead temperature, dust inlet velocity and size on the sliding and spreading of dust were studied, and the results indicated that increasing bead temperature, dust inlet velocity and size could raise solidification sliding distance and solidification spread area. With the dusts continually impacting on the bed, a dust layer forms at the front of bead, being different from that of solid dust, which becomes thick firstly, and then spreads from bead front to sides.

In Situ Observation of the Precipitation, Aggregation, and Dissolution Behaviors of TiN Inclusion on the Surface of Liquid GCr15 Bearing Steel

In this study, the precipitation, aggregation, and dissolution behaviors of TiN inclusions on the surface of liquid GCr15 bearing steel have been investigated by combining the observations of confocal laser scanning microscope (CLSM) and field emission scanning electron microscope (FE-SEM) with those obtained from energy dispersive spectrometer (EDS) and theoretical analysis. The kinetic results show that the initial concentration of Ti and N are 0.0078 and 0.0049, respectively, the precipitation temperature is between 1640 K and 1680 K (1367 °C and 1407 °C), and the local cooling rate is between 0.5 and 10 K/s; TiN inclusion can precipitate only when the solid fraction is higher than 0.847 and its precipitation radius is between 1 and 6 μm. The precipitation radius of a TiN inclusion in the GCr15 bearing steel sheet can be reduced by decreasing the N content and increasing the cooling strength. The aggregation and densification of multi-particle aggregated TiN inclusions are verified by CLSM observation and theoretical analysis. The inclusions are aggregated by the cavity bridge force (CBF), and the aggregated TiN is formed by solid-phase sintering. The results of force analysis show that CBF plays a dominant role in the aggregation process of the inclusions. The atomic ratio of Ti and V obtained by EDS is 18:1, which may melt TiN and form the liquid inclusion at 1688 K (1415 °C) observed by CLSM. The theoretical analysis is conducted for the dissolution of the TiN inclusions observed by CLSM, which shows that the dissolution of the TiN inclusions is related to the size of the inclusions; the larger the size, the greater the dissolution rate. The long-strip TiN inclusion may be formed by the Ostwald ripening of two TiN inclusions. The TiN inclusions smaller than 3 μm in the GCr15 bearing steel may be formed by the dissolved Ti and N generated by the dissolution of TiN.

Melting metal on a playing card

Many of us are familiar with the demonstration of boiling water in a paper cup held over a candle or a Bunsen burner; the ignition temperature of paper is above the temperature of 100 °C at which water boils under standard conditions. A more dramatic demonstration is melting tin held in a playing card. This illustration is from Tissandier's book on scientific recreations.

ChemInform Abstract: Synthesis and Properties of Nanocrystalline π‐SnS — A New Cubic Phase of Tin Sulfide.

AbstractCubic π‐SnS nanoparticles are precipitated by melting tin ethylxanthate as precursor and octadecylamine (120 °C, 30 min) after which (Tms)2NH is added under further heating to 220 °C (2 h) before being transferred to a 1:1 mixture of CHCl3 and MeOH.

Fuel Efficiency of Ancient Copper Alloys: Theoretical Melting Thermodynamics of Copper, Tin and Arsenical Copper and Timber Conservation in the Bronze Age Levant*

The melting of pure or alloyed copper, tin and arsenical copper ingots or recycled objects was a drain on the timber and dung fuel resources of many cultures. This paper suggests formulae grounded in thermodynamic principles in an attempt to estimate the energy requirements necessary to melt copper alloys common to both Old and New World cultures, with the goal of identifying consumption and conservation patterns. It has been suggested that tin bronze metallurgy was first adopted in the Levant during the Early Bronze Age (EB) IV, at the onset of the Late Holocene climate episode (c.2300–2000 bc), becoming the most desired alloy by the Middle Bronze Age (MB) II (2000–1530 bc) due to the ease of melting tin. To test this hypothesis, the formulae are applied here to all published Levantine EB IV – MB II copper alloys. Fuel conservation rates are proposed based on the thermodynamic formulae. Tin bronze is demonstrably more fuel efficient than pure copper. Due to the inherent difficulties in predicting the behaviour of arsenical copper compounds, it is suggested that melting experiments with representative alloys are conducted to further test and refine these energy relationships.

Mesoporous carbon nanofibers with large cage-like pores activated by tin dioxide and their use in supercapacitor and catalyst support

The mesoporous carbon nanofibers (MCFs) with large cage-like pores have been fabricated by thermally treating electrospun fibers of polyvinyl alcohol containing tin compound. During the process, tin oxide is reduced to melting tin and the carbon is activated to form the porous carbon. The results of X-ray diffraction and transmission electron microscopy at different temperatures show that particles of SnO2 (∼1.9nm) exist in the fibers at 300°C while mixtures of Sn and SnO with rod-like shapes appear in the matrix when the fibers are heated at 400°C, and that Sn migrates to the surface of fibers and pores are formed in the fibers at higher temperature. Specific surface area of MCFs can reach 800m2g−1 and the average diameter of interior pores is about 10.3nm while the entrance pores are small. The specific capacitance of MCFs is 105Fg−1 and the fabricated symmetrical capacitors exhibit high-rate capacitive properties and excellent stability, Pt nanoparticles which can be densely loaded on MCFs exhibit relatively high activity and stability toward electro-oxidation of methanol, which indicate that MCFs may be used as electrodes for high-rate energy storage and support for catalyst. This approach may be extended to prepare other porous carbon materials.

Numerical simulation of fragmentation of melt drop triggered by external pressure pulse in vapor explosions

The fragmentation of molten drops is the key process in the fuel–coolant interaction (FCIs) which may occur during the course of a severe accident in a light water reactor (LWR). However, the mechanisms of this complicated process cannot be clarified sufficiently by experimental studies due to the rapid reaction. In this paper, a multi-phase thermal hydraulic code with the volume of fluid method (VOF) is developed and the fragmentation process of melt drops triggered by external pressure pulse is numerically analyzed to investigate the mechanism of fragmentation in vapor explosions. The simulation results show that the fragmentation process can be divided into several stages, including vapor film collapse, melt drop-coolant direct contact, formation of high pressure spots, rapid growth of a filament around the molten metal drop, rapid fuel coolant interaction area expansion, breaking up of the filament, and mixing of fragments with water. The calculation results are similar to Ciccarelli and Frost’s (Nucl. Eng. Des., 146, 109–132) experiment data. The simulation results suggest that growth and breaking up of a filament are the essential mechanism of melt tin drop fragmentation. Penetration and evaporation of the water jets, which are assumed as fragmentation mechanism in Kim’s model (Nucl. Sci. Eng., 98, 16–28, 1988), are not observed. In the calculation case, when molten metal density is hypothetically smaller, the water penetration is observed. Besides, the effects of external pressure pulse and molten metal temperature on the growth of filament and the explosion bubble are discussed.

Picosecond time scale dynamics of short pulse laser-driven shocks in tin

The dynamics of high strain rate shock waves driven by a subnanosecond laser pulse in thin tin slabs have been investigated. These shocks, with pressure up to 1 Mbar, have been diagnosed with an 800 nm wavelength ultrafast laser pulse in a pump-probe configuration, which measured reflectivity and two-dimensional interferometry of the expanding rear surface. Time-resolved rear surface expansion data suggest that we reached pressures necessary to shock melt tin upon compression. Reflectivity measurements, however, show an anomalously high drop in the tin reflectivity for free standing foils, which can be attributed to microparticle formation at the back surface when the laser-driven shock releases.

REDOX AND SPECIATION OF TIN IN HYDROUS SILICATE GLASSES: A COMPARISON WITH Nb, Ta, Mo AND W

The speciation of tin in nine hydrous haplogranitic silicate glasses (0.1–1 wt.% SnO2) was investigated by XAFS spectroscopy at the tin K -edge. Three compositions of granitic melt were investigated [peralkaline (ASI 0.6), metaluminous (ASI 1.0), and peraluminous (ASI 1.2)] and, for each of these, tin-bearing glasses were synthesized at three different redox conditions (~FMQ, ~FMQ + 1.1, and ~FMQ + 2.4). The hydrous glasses were quenched from H2O-saturated melts at 850°C and 2 kbar. Redox states estimated from XANES are in good agreement with those estimated from SnO2 dissolution experiments. There are, however, some unresolved discrepancies. Tetravalent Sn is dominant in all peralkaline melts investigated, even at FMQ. In contrast, Sn(II) is dominant in the peraluminous compositions investigated, even at FMQ + 2.4. The tin K -edge XAFS spectra for the oxidized glasses resemble that of eakerite [Ca2SnAl2Si6O18(OH)2·2H2O]. Tetravalent Sn thus behaves in a similar manner to Zr(IV), a network modifier, but is markedly different from Ti(IV), a network former. In the most reduced glasses, highly ionic Sn(II)-bearing moieties are formed. Thus, Sn(II) is comparable to Ca2+, i.e. , it is an efficient network modifier, in sharp contrast to Sn(IV). Consequently, Sn(IV) is soluble in silicate melts that contain non-bridging oxygen (NBO) atoms, such as peralkaline compositions. In contrast, in peraluminous magmas, in which NBO are lacking, Sn(II) preferentially forms highly ionic moieties that can be easily “complexed” and transported by, for instance, chlorine. If the redox conditions become oxidizing, Sn(IV) forms, but cannot accommodate itself within the framework of tetrahedra of the melt structure, which results in nucleation of cassiterite. In a comparison of speciation information for Nb(V), Ta(V), W(VI) and Mo(VI) in similar compositions of glass, Sn(IV) acts more like Nb(V), Ta(V) or Zr(IV), whereas Mo(VI) and W(VI) form highly covalent complexes ( sensu stricto ) that are disconnected from the framework of tetrahedra. Tin geochemistry in melts appears to be dominated by an exchange between two highly different structural positions for Sn(IV) and Sn(II), which is highly sensitive to peralkalinity under conditions of moderate fugacity of oxygen. In contrast, the mineralogy of tin is dominated by Sn(IV). The difference in the valence of tin in melts vs minerals makes it a very unusual cation as compared to other highly charged cations to which tin is commonly associated, such as Mo, W, Ta and Nb.

LEAD GLAZES IN ANTIQUITY—METHODS OF PRODUCTION AND REASONS FOR USE*

Transparent high lead and tin‐opacified lead‐alkali glazes have been extensively used throughout Europe and the Near East from their first appearance in the Roman era and the tenth‐ to eleventh‐century Islamic world, respectively, up until the present day. Using, to a large extent, information which is widely scattered through a diverse range of literature, the methods employed in the production of these two glaze types are first outlined and their merits are then compared with those of alkali glazes in terms of ease of preparation of the glaze mixture, ease of application of the glaze, ease of firing, cost of production, glaze‐body fit and visual appearance. The principal advantages of transparent high lead glazes as compared to alkali glazes are shown to be ease of preparation and application of the glaze suspension, low susceptibility to glaze ‘crazing’ and ‘crawling’ and high, optical brilliance. Factors that influence the choice of tin‐opacified lead‐alkali glazes include ease of production of tin oxide by melting tin and lead metals together; a reduced risk of reduction of lead oxide to lead metal and consequent blackening of the glaze; and, again, low susceptibility to ‘crazing’ and ‘crawling’. Limits of current knowledge regarding these two glaze types and requirements for future research are outlined.

Petrochemistry of Late Miocene Peraluminous Silicic Volcanic Rocks from the Morococala Field, Bolivia

Bolivia, define a layered stratigraphy of basal andalusite-, biotite(‐ muscovite)-bearing rhyolite tuVs (AR), overlain by cordierite-, biotite-bearing rhyolite tuVs (CR), and capped by biotite-bearing quartz latite tuVs, lavas, and late domal flows (QL). Mineral and whole-rock compositions become more evolved from top to bottom, INTRODUCTION with diVerentiation reflected by decreasing Ca, Ba, Mg, Fe, and Peraluminous granitic rocks are important beyond their rare earth elements (REE) versus increasing F, Na/K, and al- relative volumes in the crust because they host many of uminosity from QL to AR. Mineral, whole-rock, and glass inclusion the world’s ore deposits of Li, Be, Sn, W, Nb, and Ta. compositions are consistent with derivation of all three rock types These and other minor- to trace-level elements and from a single stratified magma reservoir, but age and spatial relations fluxing components (e.g. B, Cs, F, Cl, H2O, etc.) behave between the three units make this unlikely. Genesis of the QL incompatibly and are likely to be mobile in plutonic involved biotite-dehydration melting of an aluminous source at T settings. Fresh peraluminous volcanic rocks, and their > 750∞C and P [ 4‐6 kbar. If not co-magmatic with QL, the mineral-hosted melt (glass or devitrified) inclusions, may other units were generated primarily by muscovite-dehydration melting thus provide better estimates of the original magmatic at T = 730‐750∞C and P [ 3·5‐4·5 kbar for CR, and T concentrations of these important components. Although Z 750∞C for AR with pre-eruptive residence at low pressure peraluminous granitoids are common in collisional tec(1·5‐3·0 kbar). Low hematite contents (XHem Z 0·06) of ilmenite tonic settings, few examples of their volcanic equivalents grains in AR, CR, and early grains (as inclusions in plagioclase have been described. and sanidine cores) in QL indicate reduced conditions imposed by a The Bolivian tin belt (Fig. 1, inset) represents one of graphite-bearing source. Compositional variability among texturally the great strongly peraluminous igneous provinces of the later oxides (ilmenite with XHem= 0·06‐0·50, primary magnetite), world, and is one of few such regions bearing voluminous however, apparently records progressive increases in pre-eruptive f(O2) silicic peraluminous volcanic rocks. Most studies of the in QL. Plagioclase‐melt equilibria and electron microprobe analysis Bolivian igneous rocks have addressed their relations to diVerence for quartz-hosted glass inclusions suggest pre-eruptive melt tin mineralization, which typically is associated with H2O contents [5‐7 wt % for the AR, ~4‐6 wt % for the CR, pervasive alteration and/or veining of shallow porphyritic and ~3‐5 wt % for the QL.

The behavior of tin in granitoid magmas

The spatial and temporal relationship between tin mineralization and granitoid rocks is well documented. A great deal of work, including mineralogic, geochemical, fluid inclusion, and stable and radiogenic isotope studies, has been undertaken on numerous cassiterite-bearing deposits in order to resolve the problem of their genesis. Despite this exhaustive research, the association between tin mineralization and felsic magmatism remains poorly understood. Experimental investigations into the behavior of tin in melts have been undertaken to evaluate the physical and chemical constraints on the mobilization of tin from magmas.The concentrations of tin in equilibrium with SnO 2 -saturated, synthetic, peraluminous granitoid melts have been examined as a function of temperature (700 degrees -800 degrees C), pressure (2.0-3.0 kbars), oxygen fugacity (from 0.7 log units more reduced to 1.5 log units more oxidized than the quartz-fayalite-magnetite buffer) and granitoid composition (haplogranite, K feldspar-quartz, and albite-quartz). Melts were found to contain between 400 and 2,500 ppm tin. The solvent capacity of the granitoid melts is increased by decreasing oxygen fugacity and by increasing the alkali/alkali + aluminum ratio (ALK/AL), i.e., K 2 O + Na 2 O/K 2 O + Na 2 O + Al 2 O 3 (Naski and Hess, 1985) and the Na/K ratio of a melt. Changes in temperature or pressure do not exert a significant influence over the concentration of tin in melts. Nuclear gamma resonance analysis of haplogranite glasses indicates that both Sn (super +2) (sub (melt)) and Sn (super +4) (sub (melt)) are stable over the range of oxygen fugacities typically attending the crystallization of granitoids. The coordination and likely speciation of Sn (super +2) and Sn (super +4) in melts is discussed. The basicity of a melt (activity of free oxygens, a (sub O (super -2) ) ), which is often strongly correlated with the ALK/AL of a melt (cf. Hess, 1980; Mysen, 1986), is likely to be very important in influencing the acidity of a coexisting fluid phase. Peraluminous melts (low ALK/AL) will generally display low melt basicities and therefore will buffer the acidity of a magmatic aqueous phase at far higher values than a peralkaline melt.These results indicate that granitoid melts derived from common crustal sources will be markedly SnO 2 undersaturated. Consequently, alternative processes must be sought to explain the elevated tin concentrations in many plutons. The complex distribution of tin in any batholith will be largely controlled by the redox conditions accompanying the crystallization of assemblages capable of accommodating tin and the physical processes which can influence their distribution.