Method for determining platinum content in platinum-tungsten alloy slag

Abstract

The invention relates to a method for determining the platinum content in platinum-tungsten alloy slag. The invention aims to solve the problems of incomplete digestion, platinum loss, matrix interference and the like when the high-tungsten low-platinum alloy slag is treated by the existing wet digestion technology. The method is based on a fire assaying enrichment principle, and comprises the following steps: mixing and melting a sample, lead powder and pure gold with known mass, carrying out soot blowing to obtain platinum alloy particles, dissolving the platinum alloy particles through aqua regia, determining the total amount of impurities in combination with ICP (Inductively Coupled Plasma) spectrum, and finally calculating the platinum content according to Pt (%) = (W2-W1-W3) / W0 * 100%. According to the method, efficient separation of platinum and tungsten is effectively achieved, the determination accuracy and reproducibility are remarkably improved, and the method is suitable for rapid, safe and high-precision analysis of various platinum-tungsten alloy slag.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and in particular to a method for determining the platinum content in platinum-tungsten alloy slag. Background Technology

[0002] Platinum-tungsten alloy slag, a typical byproduct of precious metal recovery and high-purity material preparation, is complex in composition and dense in structure, holding significant value in resource recycling and precious metal refining. Platinum, a strategically scarce metal, is crucial for accurate content determination, impacting not only economic accounting precision but also the parameter setting and efficiency optimization of subsequent purification processes. Therefore, establishing an efficient, accurate, and reliable method for platinum content analysis has become a key aspect of quality control and process optimization for this type of material. For a long time, wet chemical digestion combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) has been widely used for the simultaneous determination of platinum and tungsten in this type of alloy slag. This method typically relies on strong acid pretreatment of the sample, followed by instrumental quantification of the elements. Specifically, given that tungsten exhibits strong chemical inertness to single inorganic acids (including hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and even aqua regia) at room temperature, conventional wet digestion often requires a mixture of hydrofluoric acid and concentrated nitric acid, with specific temperature conditions to promote tungsten dissolution. Based on this, the resulting solution is appropriately diluted, and inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to simultaneously determine the platinum and tungsten content. This technical approach has effectively supported the basic needs of related industries for component control in early analytical practices, demonstrating good applicability, especially when processing materials with relatively homogeneous composition and fine particle size.

[0003] However, with the increasing diversification of raw material sources for precious metal recycling and the continuous upgrading of smelting processes, the physicochemical properties of platinum-tungsten alloy slag have also undergone significant changes. Its structure is more compact and its crystalline phase more stable, leading to unprecedented challenges for traditional wet digestion. The reason for this is that even under optimized mixed acid systems and heating conditions, some high-melting-point, highly crystalline tungsten phases are still difficult to completely dissolve, forming so-called "residue" or "undigested material." This residue not only coats some platinum particles, causing the loss of target elements, but may also introduce matrix interference or clog the atomization system in subsequent ICP analysis, seriously affecting the accuracy and repeatability of the measurement results. Furthermore, excessively extending the digestion time or increasing the acid concentration in pursuit of complete digestion may lead to platinum volatilization loss or container contamination, thus exacerbating systematic errors. Therefore, the wet digestion pathway inherently contains an irreconcilable contradiction: on the one hand, it relies on a highly corrosive medium to disrupt the stable tungsten lattice; on the other hand, it must avoid irreversible physicochemical loss of trace platinum. This contradiction is particularly prominent when dealing with alloy slag that is high in tungsten and low in platinum and has a dense structure, which makes the existing technology show obvious limitations in terms of accuracy, robustness and universality.

[0004] Therefore, it is necessary to design a new measurement method to solve the above problems. Summary of the Invention

[0005] This invention provides a method for determining the platinum content in platinum-tungsten alloy slag. The method is based on the principle of fire assay enrichment, and achieves efficient separation of platinum and tungsten through high-temperature melting and ash blowing processes. It also combines gravimetric analysis and inductively coupled plasma atomic emission spectrometry to perform high-precision quantification of platinum, thereby overcoming the systematic defects of existing wet digestion technology in treating dense, high-tungsten, low-platinum alloy slags, such as incomplete digestion, platinum loss, and matrix interference.

[0006] To achieve the above-mentioned objective, this invention provides a method for determining the platinum content in platinum-tungsten alloy slag, characterized by the following steps: First, accurately weigh the mass W0 of the platinum-tungsten alloy slag sample to be tested, wherein the sample mass range is 0-1g and the weighing accuracy is 0.1mg; simultaneously, take an equal amount of sample for subsequent compensation analysis to correct any possible systematic bias. Second, add a collecting agent to a flaming cup, wherein the collecting agent consists of lead powder and a known mass W1 of pure gold, wherein the mass of lead powder is ten times the mass of the sample, and the pure gold is used as an internal standard element for subsequent quantitative calculation of platinum. After the two are thoroughly mixed with the sample, a covering agent is applied to prevent metal oxidation and volatilization during the melting process. Subsequently, place the flaming cup in a muffle furnace and melt it at a constant temperature of 1100℃ for 1 hour, so that the base metal components in the sample are oxidized and enter the slag phase, while platinum and gold are effectively captured by lead to form lead buckles; after melting, quickly pour the melt into a preheated mold, cool it, break the slag, remove the lead buckles, and clean off any surface deposits. Next, the obtained lead buckle was placed in a crucible and subjected to ash blowing treatment at 1100℃ for 1 hour to completely oxidize and volatilize the lead, leaving only the precious metal granules composed of platinum and gold. After ash blowing, the mixture was cooled to room temperature, and the total mass W2 of the granules was accurately weighed. Subsequently, the granules were completely dissolved in aqua regia, and after being brought to a constant volume, the total mass W3 of all trace element impurities other than platinum and gold was determined using inductively coupled plasma optical emission spectrometry. Finally, based on the principle of mass conservation, the mass percentage of platinum in the original sample was calculated using the formula Pt(%)=(W2-W1-W3) / W0×100%.

[0007] Furthermore, the covering agent is a mixture of anhydrous sodium carbonate and borax in a 3:1 mass ratio, with a covering thickness of not less than 5 mm, ensuring that lead and precious metals are protected from oxidizing atmosphere corrosion during the melting process. The cremation cup is made of high-purity magnesia or zirconium oxide refractory material, which has the characteristic of not undergoing significant chemical reactions or physical peeling during long-term use below 1200℃. The mold is made of graphite or cast iron, with a thin layer of talc powder coated inside to facilitate melt demolding and reduce metal adhesion loss. The crucible has a porosity of less than 5%, stable lead absorption performance, and can be reused no more than ten times to avoid cross-contamination.

[0008] In a preferred embodiment of the present invention, the melting process is carried out under a reducing atmosphere. Specifically, a small amount of flour or starch is pre-laid at the bottom of the furnace as a reducing agent to control the oxygen partial pressure inside the furnace and inhibit the excessive oxidation of tungsten into the noble metal phase. The ash blowing process adopts a stepped heating program. In the initial stage, the temperature is raised to 800°C at a rate of 10°C / min and held for 15 minutes to remove residual organic matter. Then, the temperature is raised to 1100°C to complete the main ash blowing stage, ensuring that the lead is completely volatilized while the platinum aggregate remains intact and without splashing loss.

[0009] Furthermore, the aqua regia dissolution step was carried out in a closed polytetrafluoroethylene digestion vessel. A mixture of concentrated hydrochloric acid and concentrated nitric acid at a volume ratio of 3:1 was added, and the mixture was heated to 80°C and maintained for 30 minutes until the granules were completely dissolved, resulting in a clear, transparent solution without any precipitate residue. The volumetric flask used for final volume determination was a Class A volumetric flask, and the volumetric medium was a 2% (v / v) aqueous solution of hydrochloric acid to maintain platinum ion stability and match the ICP analysis injection conditions. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was performed in axial observation mode with an integration time of at least 10 s. Background correction points were selected at 0.02 nm on both sides of the analytical spectral line to ensure that the determination uncertainty of the total trace element impurities W3 was less than 0.5%.

[0010] All weighing operations in this method are performed on an electronic balance with an accuracy of 0.01%, which is periodically calibrated according to national metrological standards. The ambient temperature is controlled at 20-25℃ and the relative humidity is below 60% to eliminate the influence of buoyancy and static electricity on micro-weighing. All reagents are of analytical grade or higher purity, and the experimental water is ultrapure water with a resistivity of not less than 18.2 MΩ·cm. The compensation analysis uses parallel samples from the same batch. If the relative deviation between two independent measurements exceeds 0.5%, the entire set of data is discarded and resampled for analysis.

[0011] The method described in this invention thoroughly destroys the dense lattice structure of platinum-tungsten alloy slag through a high-temperature melting mechanism using fire assays. This allows tungsten to stably enter the slag phase in the form of oxides or aluminosilicates, while platinum is selectively captured by lead. This fundamentally avoids the platinum encapsulation loss problem caused by the insolubility of tungsten in wet digestion. The ash blowing process further removes the lead matrix, obtaining pure platinum granules, whose mass W2 directly reflects the total amount of precious metals. Introducing pure gold with a known mass W1 as an internal standard can effectively correct for physical losses throughout the melting and ash blowing process. The precise determination of the total impurities W3 by ICP eliminates the interference of non-platinum and non-gold components on the gravimetric method. The synergistic effect of these three factors results in highly accurate, reproducible, and interference-resistant final platinum content calculation results.

[0012] The method is applicable to various platinum-tungsten alloy slags, including but not limited to electrolytic anode mud, high-temperature sintering waste, catalyst regeneration residues, and metallurgical intermediates, regardless of their tungsten content, particle size, or crystallinity. The entire process eliminates the need for highly toxic and corrosive reagents such as hydrofluoric acid, significantly improving operational safety compared to traditional wet methods. Furthermore, the single analysis cycle is controlled within 4 hours, meeting the rapid quality control requirements of industrial settings. In addition, this method can simultaneously obtain gold recovery rate data, providing additional information support for multi-metal synergistic recovery processes.

[0013] In summary, this invention achieves high-precision determination of platinum content in platinum-tungsten alloy slag by constructing a three-level quantitative system with fire assay as the core and gravimetric method and ICP analysis as auxiliary methods. It solves the systematic error problem caused by incomplete digestion and matrix interference in the prior art, and has clear technological progress and broad industrial application prospects. Attached Figure Description

[0014] Figure 1 This is a schematic flowchart of the method for determining the platinum content in platinum-tungsten alloy slag according to the present invention. Detailed Implementation

[0015] This invention provides a method for determining the platinum content in platinum-tungsten alloy slag. The technical solution is based on the principle of fire assay enrichment, achieving efficient separation of platinum and tungsten through high-temperature melting and ash blowing processes. It further combines gravimetric analysis and inductively coupled plasma atomic emission spectrometry (ICP-AES) for high-precision quantification of platinum. The following will systematically describe the technical implementation of this invention in detail, including specific operating steps, material specifications, instrument parameters, and data processing logic.

[0016] First, accurately weigh the platinum-tungsten alloy slag sample W0, with a sample mass range of zero to one gram and a weighing accuracy of 0.1 mg. The weighing operation was performed on an electronic balance with an accuracy of 0.01 g / 10,000, which was periodically calibrated according to national metrological standards. The experimental environment temperature was controlled at 20-25℃, and the relative humidity was below 60% to eliminate the influence of buoyancy and static electricity on the micro-weighing. Simultaneously, an equal amount of sample was taken for subsequent compensation analysis to correct for any potential systematic biases. The compensation analysis used parallel samples from the same batch. If the relative deviation between two independent measurements exceeded 0.5%, the entire data set was discarded, and a new sample was taken for analysis.

[0017] Next, a collecting agent is added to the ignition beaker. This agent consists of lead powder and a known mass W1 of pure gold, where the mass of lead powder is ten times the mass of the sample. The pure gold serves as an internal standard for subsequent quantitative calculations of platinum. The lead powder and pure gold are thoroughly ground and mixed evenly in an agate mortar beforehand. Then, they are transferred to the ignition beaker along with the weighed platinum-tungsten alloy slag sample, and gently stirred again to ensure uniform mixing. After mixing, a covering agent is applied to the surface of the material, with a thickness of not less than five millimeters, to prevent metal oxidation and volatilization during melting. The covering agent is a mixture of anhydrous sodium carbonate and borax in a mass ratio of 3:1. Both are analytical grade reagents and were dried at 150°C for 2 hours before use to remove adsorbed moisture.

[0018] The cremation cup is made of high-purity magnesia or zirconium oxide refractory material, which has the characteristic of not undergoing significant chemical reactions or physical spalling during long-term use below 1200℃. The cremation cup has an inner diameter of 40mm, a height of 80mm, a flat bottom, and uniform sidewall thickness to ensure consistent heat conduction. Subsequently, the cremation cup containing the sample, accumulator, and covering agent is placed in a muffle furnace and melted at a constant temperature of 1100℃ for 1 hour. The melting process is carried out in a reducing atmosphere, specifically by pre-laying a small amount of flour or starch at the bottom of the cremation cup as a reducing agent, controlling the oxygen partial pressure in the furnace to inhibit excessive oxidation of tungsten into the noble metal phase. After melting, the melt is quickly poured into a mold preheated to 300℃. The mold is made of graphite or cast iron and coated with a thin layer of talc powder inside to facilitate demolding of the melt and reduce metal adhesion loss. After cooling, the slag is broken, the lead clasp is removed, and surface adhering substances are cleaned. The lead clasp is a silver-gray metallic sphere with a diameter of approximately 8-12mm.

[0019] Next, the obtained lead clasps were placed in a crucible and subjected to ash blowing treatment at 1100°C for 1 hour. The crucible had a porosity of less than 5%, stable lead absorption performance, and could be reused no more than ten times to avoid cross-contamination. The ash blowing process adopted a stepped heating program. In the initial stage, the temperature was increased to 800°C at a rate of 10°C / min and held for 15 minutes to remove residual organic matter. Then, the temperature was increased to 1100°C to complete the main ash blowing stage, ensuring that the lead was completely volatilized while the platinum granules remained intact without splashing loss. After ash blowing, the granules were cooled to room temperature, and the total mass W2 of the granules was accurately weighed. The weighing operation was also performed on the aforementioned electronic balance, and the result was recorded to four decimal places.

[0020] Subsequently, the granules were completely dissolved in an aqua regia system. The dissolution step was carried out in a sealed polytetrafluoroethylene digestion vessel. A mixture of concentrated hydrochloric acid and concentrated nitric acid at a volume ratio of 3:1, with a volume of 10 mm, was added. The mixture was heated to 80°C and maintained for 30 minutes until the granules were completely dissolved, and the solution was clear, transparent, and free of precipitate. After dissolution, the solution was transferred to a Grade A volumetric flask and brought to a final volume of 25 mm with a 2% (v / v) hydrochloric acid aqueous solution. The volume-adjusting medium was prepared with ultrapure water with a resistivity of not less than 18.2 MΩ·cm to maintain platinum ion stability and match the injection conditions for ICP analysis.

[0021] The diluted solution was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine the total mass (W3) of all trace element impurities except platinum and gold. The instrument was used in axial observation mode with an integration time of at least 10 s. Background correction points were selected at 0.02 nm on either side of the analytical spectral line to ensure that the determination uncertainty of the total trace element impurity W3 was less than 0.5%. Standard curves for all analytes were established using a multi-point calibration method, with concentration gradients covering the expected impurity content range and correlation coefficients not less than 0.999. Impurity elements included, but were not limited to, common base metals and some metalloids such as iron, copper, nickel, cobalt, chromium, molybdenum, tin, antimony, bismuth, and lead. Their total mass (W3) was obtained by summing the concentrations of each element multiplied by their corresponding atomic weights.

[0022] Finally, based on the principle of conservation of mass, the mass percentage of platinum in the original sample was calculated using the formula Pt(%)=(W2-W1-W3) / W0×100%. This formula is valid only if the granules obtained after ash blowing contain only platinum, gold, and trace amounts of impurities that were not completely removed; the mass of gold, W1, is the known amount added, and the total mass of impurities, W3, is accurately determined by ICP. Therefore, the mass of platinum in the granules is W2 minus the sum of W1 and W3.

[0023] In one specific embodiment, a platinum-tungsten alloy slag sample from an electrolytic anode mud was taken. The sample appeared as a black powder with a particle size distribution (D50) of 45 μm. The sample mass W0 was accurately weighed as 0.5023 g, and a parallel sample of 0.5018 g was taken for compensation analysis. The trapping agent contained 0.5023 g of lead powder and 0.0100 g of pure gold W1. The covering agent was a mixture of 7.5 g of anhydrous sodium carbonate and 2.5 g of borax, with a covering thickness of approximately 6 mm. The melting process was carried out in a muffle furnace at a constant temperature of 1100 °C for 1 hour, with 0.2 g of flour placed at the bottom of the flaming cup. The melt was poured into a preheated graphite mold, and after cooling, the mass of the lead coin was 5.03 g. A stepped heating program was used for ash blowing, ultimately yielding a platinum granule mass W2 of 0.0187 g. After the granule was completely dissolved in aqua regia, the volume was adjusted to 25 mL, and ICP analysis determined the total impurity mass W3 to be 0.0009 g. Substituting into the formula, the platinum content is calculated as follows: Pt(%)=(0.0187-0.0100-0.0009) / 0.5023×100%=1.553%; The parallel sample test result was 1.548%, with a relative deviation of 0.32%, which is within the allowable error range of the method.

[0024] As a comparative example, the same batch of samples was treated using a traditional wet digestion method: 0.5 g of sample was weighed, and 10 mL of hydrofluoric acid, 5 mL of concentrated nitric acid, and 15 mL of concentrated hydrochloric acid were added. The mixture was heated under reflux for 2 hours in a polytetrafluoroethylene beaker. After cooling, the mixture was evaporated to near dryness, then reconstituted with aqua regia, and the concentration was determined directly by ICP after volume adjustment. The results of three parallel determinations were 1.21%, 1.18%, and 1.23%, respectively, with an average of 1.207%, significantly lower than the results obtained by the method of this invention. X-ray diffraction analysis confirmed that incompletely decomposed platinum tungstate phases were still present in the wet digestion residue, indicating that platinum was not completely released due to the encapsulation effect, resulting in a systematically low concentration.

[0025] The table below summarizes the measurement results and key process parameters of the embodiments and comparative examples of the present invention:

[0026] Furthermore, the method of this invention is applicable to various platinum-tungsten alloy slags, including high-temperature sintering waste, catalyst regeneration residues, and metallurgical intermediate products. For dense, blocky samples with a tungsten content of over 70%, only pre-crushing to a particle size of less than 100 μm is required; no adjustments to the remaining steps are necessary. For regenerated catalyst residues with high organic content, they can be calcined in a muffle furnace at 400°C for 1 hour before melting to remove carbonaceous material and prevent deflagration during the ash blowing stage.

[0027] All reagents used in the method are of analytical grade or higher purity, and the experimental water is ultrapure water with a resistivity of not less than 18.2 MΩ·cm. Aqua regia is prepared and mixed immediately before use to avoid a decrease in its oxidizing capacity due to prolonged storage. The PTFE digestion vessel is soaked in 5% nitric acid for 24 hours and rinsed five times with ultrapure water before and after use to ensure no trace metal contamination. The ICP spectrometer undergoes wavelength calibration and sensitivity checks daily before startup, and is verified using nationally certified standard solutions during operation.

[0028] In terms of optimizing the ash blowing process, the lead absorption rate of the crucible directly affects the morphology of the aggregate. Experiments show that when the crucible porosity is higher than 8%, the rapid lead volatilization can easily lead to a rough surface or even breakage of the aggregate; while when the porosity is lower than 3%, the ash blowing time needs to be extended to more than 1.5 hours. Therefore, using a high-density bone china crucible with a porosity controlled between 4% and 5% can balance efficiency and integrity. In addition, the endpoint of ash blowing can be determined by observing the change in the gloss of the aggregate surface: initially, the aggregate surface is dark gray, gradually turning to a bright metallic luster as the lead volatilizes, and finally exhibiting a mirror-like reflective state; at this point, heating can be stopped.

[0029] During the melting stage, the proportion of the covering agent has a decisive influence on the slag fluidity. Anhydrous sodium carbonate acts as a flux to lower the slag melting point, while borax provides a glassy network structure to enhance the sealing performance. A 3:1 mass ratio, verified through multiple experiments, allows the slag to form a low-viscosity liquid phase at 1100℃, effectively encapsulating the lead buckle and isolating it from air. If the borax proportion is too high, the slag becomes too viscous, hindering the settling of the lead buckle; if there is an excessive amount of sodium carbonate, the slag becomes too alkaline, potentially corroding the inner wall of the incineration cup.

[0030] The particle size of lead powder in the collector also needs to be controlled, preferably in the range of 45-75 μm. Lead powder that is too fine is prone to oxidation during mixing, reducing collection efficiency; lead powder that is too coarse will result in insufficient reaction in the initial melting stage, leading to fluctuations in precious metal recovery rate. The pure gold internal standard is added in the form of foil or microparticles, which are first ultrasonically cleaned in acetone for five minutes to remove surface oil, dried, and then weighed before use.

[0031] The theoretical basis of this invention lies in the selective enrichment mechanism of precious metals during fire assaying. Under high-temperature reducing melting conditions, platinum, in its metallic state, is dissolved by liquid lead to form a lead-platinum solid solution, while tungsten is oxidized to WO3 or forms tungsten silicates with silicon and aluminum components, entering the slag phase. Since lead and tungsten oxides are immiscible, and the melting point of tungsten oxides is much higher than the melting temperature, tungsten is almost completely excluded from the lead ingot. During the ash blowing stage, lead is oxidized by air to PbO and absorbed by the crucible, while platinum and gold are retained due to their high melting points and chemical inertness. This process achieves complete separation of platinum from the high-concentration tungsten matrix, fundamentally avoiding co-precipitation or adsorption losses caused by the poor solubility of tungsten in wet processes.

[0032] At the data processing level, accurate determination of W3 is crucial to ensuring the reliability of the final results. In ICP analysis, special attention must be paid to correcting for spectral interferences. For example, iron spectral lines may overlap with certain platinum isotopes, which must be subtracted using the interference coefficient method or high-resolution mode. The detection limits for all impurity elements must be below 0.1 mg / L to ensure that the cumulative error of W3 is controllable. Experiments show that when the total impurities in the sample are less than 5% of the total mass, the introduction of W3 can reduce the systematic error of the gravimetric method from approximately 2% to less than 0.5%.

[0033] In summary, this invention utilizes high-temperature melting of fire assay to disrupt the dense structure of platinum-tungsten alloy slag, and then employs selective lead capture and ash blowing purification to obtain high-purity platinum particles. Combined with a known internal gold standard and ICP total impurity correction, a three-stage quantitative system is constructed. This system not only solves the accuracy problem of platinum determination in high-tungsten, low-platinum samples, but also possesses engineering advantages such as safe operation, short cycle time, and wide applicability. It can be widely applied in fields such as precious metal recovery, metallurgical quality inspection, and resource recycling.

[0034] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for determining the platinum content of a platinum-tungsten alloy residue, characterized in that, The method comprises the following steps: S1, accurately weighing the mass W0 of the platinum-tungsten alloy residue sample to be measured, the sample mass being in the range of 0-1 g, and the weighing precision being 0.1 mg; S2, adding a collector composed of lead powder and pure gold with a known mass W1 into the cupel, the mass of the lead powder being ten times the mass of the sample, and covering the collector and the sample with a layer of covering agent; S3, placing the cupel in a muffle furnace, melting the sample at 1100℃ for 1 h, so that the base metal components in the sample are oxidized into the slag phase, and platinum and gold are captured by lead to form a lead button; After the melting is completed, the melt is poured into a preheated mold, and the lead button is taken out after cooling; S4, placing the lead button in a crucible and performing cupellation at 1100℃ for 1 h, so that the lead is completely oxidized and volatilized, and a noble metal particle composed of platinum and gold is obtained; after cooling, the total mass W2 of the particle is accurately weighed; S5, completely dissolving the particle in an aqua regia system, determining the total mass W3 of all trace element impurities other than platinum and gold in the particle after constant volume is achieved by using an inductively coupled plasma spectrometer; S6, calculating the mass percentage of platinum in the original sample according to the formula Pt(%)=(W2-W1-W3) / W0×100%.

2. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 1, characterized in that, The covering agent is composed of anhydrous sodium carbonate and borax with a mass ratio of 3:1, and the covering thickness is not less than 5 mm; the material of the cupel is high-purity magnesia or zirconia refractory material; the mold is graphite or cast iron material, and the inside is coated with a thin layer of talc powder; the porosity of the crucible is less than 5%.

3. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 1, wherein, The melting process is carried out in a reducing atmosphere, specifically by pre-paving flour or starch as a reducing agent at the bottom of the cupel.

4. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 1, wherein The cupellation process adopts a stepwise temperature rising program, the initial stage is raised to 800℃ at a rate of 10℃ / min and kept for 15 min, and then raised to 1100℃ to complete the main cupellation stage.

5. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 1, wherein, In step S5, the specific steps of completely dissolving the particle in the aqua regia system are as follows: adding a mixed solution of concentrated hydrochloric acid and concentrated nitric acid with a volume ratio of 3:1 into a polytetrafluoroethylene sealed digestion tank, heating to 80℃ for 30 min until the particle is completely dissolved.

6. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 5, wherein, The constant volume step uses a class A volumetric flask, and the constant volume medium is 2% by volume hydrochloric acid aqueous solution; the inductively coupled plasma spectrometry adopts an axial observation mode, and the integration time is not less than 10 s, and the background correction points are selected at 0.02 nm on both sides of the analysis spectrum.

7. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 1, wherein, The method further comprises a compensation analysis step: another sample of the same batch of platinum-tungsten alloy residue with the same mass as in step S1 is taken, and the operation processes of steps S2-S6 are independently repeated, if the relative deviation of the mass percentage of platinum obtained by two independent determinations exceeds 0.5%, the whole set of data is discarded and re-sampling analysis is performed.

8. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 1, wherein, All weighing operations in the method are completed on an electronic balance with a precision of one ten-thousandth, and the weighing environment temperature is controlled at 20-25℃, and the relative humidity is less than 60%; the reagents used in the method are of superior or higher purity grade, and the water used for experiments is ultrapure water with a resistivity of not less than 18.2 MΩ·cm.

9. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 1, wherein, The particle size of the lead powder is in the range of 45-75 um; the pure gold internal standard is added in the form of a foil or microparticles, which are cleaned ultrasonically in acetone and dried before use.

10. The method of determining the platinum content of a platinum-tungsten alloy residue according to claim 2, wherein, The number of times the crucible is reused is not more than ten; the anhydrous sodium carbonate and borax in the covering agent are dried at 150 °C for 2 h before use; the mold is preheated to 300 °C before pouring the melt.

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