Method for measuring gold content in K gold ornament based on fire assaying method

Abstract

The invention relates to a fire assaying measurement method, in particular to a method for measuring gold content in a K gold ornament based on a fire assaying method, which comprises the following steps: step 1, weighing materials, and preparing a sample and a standard sample; 2, a fluxing agent and a catalyst are prepared, and the catalyst is used for increasing the reaction rate and reducing gold and silver residues in slag; 3, a fluxing agent, a catalyst and a cupel are pretreated, the inner surface of the cupel is thinly coated with the catalyst, the cupel is preheated, 10-15 wt% of borax is calcined at the same time, and the borax is dehydrated for use; step 4, filling a cupel; 5, soot blowing is conducted, specifically, the cupel filled with the lead buckles is placed in a soot blowing furnace, after the lead buckles are melted, a furnace door is slightly opened, the temperature is kept at 950 DEG C for 10-15 minutes, and after the furnace door is closed, the temperature is kept for 3-5 minutes; 6, separating gold; and step 7, calculating the content of K gold, and by thinly coating a catalyst in the cupel, in the soot blowing process, the silicone oil is boiled and decomposed and continuously penetrates through the melt from the surface of the cupel, so that the elemental gold and silver particles are far away from the slag.

Description

Technical Field

[0001] The invention relates to a fire assay measurement method, in particular to a method for measuring the gold content in K-gold jewelry based on the fire assay method. Background Art

[0002] Fire assay uses solid flux and collectors to mix with the material to be tested, and then heats and melts it in a crucible at high temperature. The base metal oxides in the material react with silicon dioxide, sodium carbonate, etc. to form slag, while the precious metals form an alloy with the reduced collector, thereby completing the separation of the precious metals.

[0003] The assay formula plays an important role in the formation of melt and slag during the smelting process. It affects the fluidity of the slag, the boundary between the slag and the melt, and the smelting time. Among them, borax has excellent fluidity after melting and forms a complex salt with metal oxides after melting, effectively separating metal oxides and elements.

[0004] It should be noted that during the calcination process, the crystal water in borax evaporates, causing the borax to expand and easily causing the material in the crucible to overflow. The number of samples of K gold jewelry is small, and the loss during smelting needs to be strictly controlled. Although the use of anhydrous borax avoids the overflow of the material, the material does not move at all, which also prevents the solvent and sample particles from fully contacting.

[0005] In addition, during the static reaction of the melt in the furnace, the material lacks stirring, the precious metal capture efficiency is low, and the precious metal particles may be dispersed in the slag, affecting the precious metal recovery rate. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for measuring the gold content in K-gold jewelry based on fire assay method, so as to solve the above technical problems.

[0007] A method for measuring the gold content in karat gold jewelry based on fire assay method comprises the following steps:

[0008] Step 1: weigh the materials and prepare samples and standards;

[0009] Step 2: Prepare flux and catalyst. The flux includes 30 wt% borax, 25 wt% sodium carbonate, 20 wt% quartz powder, 15 wt% oxidant, and 10 wt% reducing agent. The catalyst is used to accelerate the reaction rate and reduce the gold and silver residue in the slag.

[0010] Step 3: Pre-treating the flux, catalyst and ash dish, applying a thin layer of catalyst on the inner surface of the ash dish, preheating the ash dish, and calcining 10-15 wt% borax to dehydrate it for later use;

[0011] Step 4: Fill the ash tray;

[0012] Step 5: Ash blowing: Place the filled ash dish in the ash blowing furnace. After the lead button melts, slightly open the furnace door and keep the temperature at 950℃ for 10-15 minutes. Close the furnace door and keep the temperature for another 3-5 minutes. Turn off the power.

[0013] Step six, divide the gold;

[0014] Step seven, calculate the karat gold content.

[0015] Furthermore, the catalyst is high molecular weight silicone oil.

[0016] Furthermore, the catalyst is thinly coated on the surface of the ash dish.

[0017] Furthermore, the boiling point of the catalyst is greater than 650°C and less than 950°C.

[0018] Furthermore, in step three, the preheating temperature is greater than 400°C and less than 650°C.

[0019] Furthermore, in step 4, 10 wt% of uncalcined borax is sprinkled into the ash dish, and then the material is placed in the ash dish.

[0020] Furthermore, in step 4, uncalcined borax and calcined borax are mixed and added into an ash dish, and quartz powder, sodium carbonate, an oxidizing agent and a reducing agent are added to cover the surface of the material.

[0021] The beneficial effects achieved by the present invention using the above structure are as follows:

[0022] 1. By applying a thin layer of catalyst silicone oil in the ash dish, during the ash blowing process, the silicone oil boils and decomposes, continuously passing through the melt from the surface of the ash dish, keeping the gold and silver particles away from the slag.

[0023] 2. Similarly, when the silicone oil boils, bubbles are constantly generated, causing the melt to be continuously stirred, which speeds up the reaction rate.

[0024] 3. When the aluminum foil melts, the borax releases the crystal water inside it and expands, which accelerates the mixing speed of the aluminum foil and its internal materials. DETAILED DESCRIPTION

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] The present invention proposes a method for measuring the gold content in karat gold jewelry based on fire assay method, comprising the following steps:

[0027] Step 1: Weigh the materials and prepare samples and standards:

[0028] Weigh 6 portions of 0.400g gold standard sample, weigh about 4.20g of lead foil, fold it into a funnel shape, and then take 1.02g of pure silver and 0.007g of pure copper and put them into the lead foil respectively.

[0029] The K gold material is weighed according to the mass of the standard sample. The gold content is equivalent to the gold content in the weighed standard gold. Multiple samples are prepared, and the same pure silver and pure copper as the standard sample are added and placed in lead foil;

[0030] Step 2: Prepare flux and catalyst:

[0031] Weigh 30 wt% of borax, 25 wt% of sodium carbonate, 20 wt% of quartz powder, 15 wt% of an oxidizing agent, 10 wt% of a reducing agent, and a small amount of silicone oil;

[0032] The reducing agent is flour or charcoal powder;

[0033] wherein the oxidant is a nitrate or a carbonate;

[0034] Wherein, the silicone oil is a high molecular weight silicone oil;

[0035] The boiling point of high molecular weight silicone oil is greater than 650℃ and less than 950℃;

[0036] High molecular weight silicone oil does not participate in the chemical reaction during the sootblowing process and only acts as a catalyst.

[0037] Step 3: Pre-treat flux, catalyst and ash tray:

[0038] A thin layer of high molecular weight silicone oil is applied to the ash dish, the ash dish is preheated at 650°C for 20 minutes, and 10-15 wt% of borax in the flux is placed in an ash blowing furnace and calcined to dehydrate it;

[0039] The preheating temperature should be lower than the boiling point of silicone oil to avoid volatilization of silicone oil during the preheating stage.

[0040] Step 4: Fill the ashtray:

[0041] Sprinkle 10 wt% of uncalcined borax into an ash dish, then place the material in the ash dish, mix the remaining uncalcined borax and calcined borax and add them into the ash dish, and add quartz powder, sodium carbonate, oxidant and reducing agent to cover the surface of the material.

[0042] Step five, ash blowing.

[0043] Place the filled ash dish in the ash blowing furnace. After the lead button melts, slightly open the furnace door and keep the temperature at 950℃ for 10-15 minutes. Close the furnace door and keep the temperature for another 3-5 minutes. Turn off the power.

[0044] When the flux and sample in the cup reach above 328℃, a small amount of non-dehydrated borax expands rapidly to form a porous foam structure, and the lead foil begins to melt. The expanding borax promotes the mixing of the molten lead with the internal materials;

[0045] During this process, the remaining flux on the surface of the material blocks the overflow of the material;

[0046] Above 741℃, borax begins to melt, decompose boric anhydride, and react with metal oxides to form complex salts;

[0047] Above 800℃, part of the liquid lead is oxidized to become lead oxide, part is volatilized, and another part further reacts with borax and other impurities to enhance the impurity trapping effect;

[0048] Between 800℃ and 950℃, lead continues to oxidize and volatilize, taking away a large amount of oxides, and the complex salts in the slag combine with impurities to form slag, while gold and silver remain in solid state, dispersed in the liquid lead to form an alloy melt;

[0049] Between 700℃ and 950℃, the silicone oil continues to volatilize, and the volatilized silicone oil releases small molecule siloxane, which escapes from the surface of the cup and forms tiny bubbles in the melt, increasing the disturbance to the melt and accelerating the reaction speed;

[0050] At the same time, the small molecule siloxane bubbles can make the gold and silver particles near the cup move upwards, away from the slag, reducing the residual gold and silver in the slag.

[0051] Step six, gold separation:

[0052] When the temperature of the cup falls below 750℃, the cup is removed, and the gold is taken out of the cup. The gold is annealed at 850℃ for 5 minutes, then rolled into thin sheets, and then annealed at 750℃ for 5 minutes. After cooling, it is washed with hot water;

[0053] The sheets are placed in a gold separation basket and immersed in 85℃ nitric acid for 30 minutes. After washing with hot water, the operation is repeated once to remove the silver.

[0054] Step seven, calculate the K gold content:

[0055] Weigh the mass of the gold after separation, and calculate the mass percentage of gold according to the following formula:

[0056]

[0057] Where:

[0058] m1 is the measured mass of the gold roll;

[0059] m2 is the mass of the sample;

[0060] m3 is the measured mass of the gold standard roll;

[0061] m4 is the mass of the gold standard;

[0062] D is the mass fraction of the gold standard.

[0063] The above description is merely that of the preferred embodiments of the present patent and is not intended in any way to limit the present patent. Any modification, equivalent replacement and improvement made without departing from the spirit and principle of the present patent shall fall within the scope of protection of the present patent.

Claims

1. A method for measuring the gold content in K-gold jewelry based on fire assay, characterized in that: The following steps are involved: Step 1: weigh the materials and prepare samples and standards; Step 2: Prepare flux and catalyst. The flux includes 30 wt% borax, 25 wt% sodium carbonate, 20 wt% quartz powder, 15 wt% oxidant, and 10 wt% reducing agent. The catalyst is used to accelerate the reaction rate and reduce the gold and silver residue in the slag. Step 3: Pre-treating the flux, catalyst and ash dish, applying a thin layer of catalyst on the inner surface of the ash dish, preheating the ash dish, and calcining 10-15 wt% borax to dehydrate it for later use; Step 4: Fill the ash tray; Step 5: Ash blowing: Place the filled ash dish in the ash blowing furnace. After the lead button melts, slightly open the furnace door and keep the temperature at 950℃ for 10-15 minutes. Close the furnace door and keep the temperature for another 3-5 minutes. Turn off the power. Step six, divide the gold; Step seven, calculate the karat gold content.

2. The method for measuring the gold content in karat gold jewelry based on fire assay according to claim 1, characterized in that: The catalyst is high molecular weight silicone oil.

3. The method for measuring the gold content in karat gold jewelry based on fire assay according to claim 2, characterized in that: Apply a thin layer of catalyst to the surface of the ash dish.

4. The method for measuring the gold content in karat gold jewelry based on fire assay according to claim 3, characterized in that: The boiling point of the catalyst is greater than 650°C and less than 950°C.

5. A method for measuring the gold content in karat gold jewelry based on fire assay according to any one of claims 1 or 4, characterized in that: In step 3, the preheating temperature is greater than 400°C and less than 650°C.

6. The method for measuring the gold content in karat gold jewelry based on fire assay according to claim 1, characterized in that: In step 4, 10 wt% of uncalcined borax is sprinkled into an ash dish, and then the material is placed in the ash dish.

7. A method for measuring the gold content in karat gold jewelry based on fire assay according to any one of claims 1 or 6, characterized in that: In step 4, uncalcined borax and calcined borax are mixed and added into an ash dish, and quartz powder, sodium carbonate, an oxidizing agent and a reducing agent are added to cover the surface of the material.

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