Method for marking ferric trichloride solution of porcelain crucible

Abstract

The invention provides a ferric trichloride solution marking method for a porcelain crucible, and relates to the technical field of marking of crucibles. The marking method comprises the following steps: marking at the bottom of a porcelain crucible by adopting a ferric trichloride solution, and then firing to finish marking. According to the preparation method, a gradient cooling firing mode is adopted for firing, firstly, high-temperature firing is conducted on an electric furnace at the temperature of 800-1200 DEG C, ferric chloride is rapidly decomposed into ferric oxide, and the ferric oxide is converted into a stable crystal form at the sufficient high temperature; and then burning in a muffle furnace at a constant temperature of 500-600 DEG C for a period of time to further improve the coloring chromaticity of the mark, avoid darkening or blackening of the mark color and further promote the complete conversion reaction of iron oxide so as to achieve the purposes of strong mark firmness, good tinting strength, acid resistance, alkali resistance and organic solvent resistance.

Description

Technical Field

[0001] The invention relates to the technical field of crucible marking, in particular to a method for marking a ferric chloride solution of a porcelain crucible. Background Art

[0002] Ash content is an important indicator for evaluating the quality of various substances such as food and medicine. Realizing online monitoring of ash content is very necessary for the processing and utilization of medicines. Ash content is the residue after the calcination of the substance. In the process of ash content testing, it is necessary to weigh a certain amount of dry test product, place it in a porcelain crucible, put it in a heating furnace, and heat it at a certain temperature until the mass is constant. Ash content testing requires the use of porcelain crucibles, which must be marked for sample tracking. However, the ash content test temperature is generally 500-600°C, and the marks made by ordinary pens and oil pens will disappear at high temperatures. The marking method of porcelain crucibles is generally numbered with 2B pencils, or the manufacturer provides a numbered porcelain crucible. The 2B pencil mark is easily lost due to friction, resulting in experimental failure. The manufacturer's own number is a fixed mark and is not very flexible.

[0003] At present, there are also methods of marking with non-fading ceramic pigments in the prior art. For example, CN115124859A discloses a method for preparing a high-temperature resistant non-fading ceramic pigment, which includes the following steps: (1) fully mixing and dissolving 0.5-1.5 parts of metal cobalt and 0.5-1.5 parts of dilute nitric acid; (2) adding 0.5-1 parts of potassium carbonate and 0.5-1 parts of boric acid, and stirring thoroughly; (3) adding an appropriate amount of glycerol according to the situation to make the prepared pigment present a flowing liquid; (4) drawing the prepared pigment on a high-temperature resistant object such as a crucible to be marked, and then burning it at high temperature for several minutes, taking it out and cooling it. In this method, heavy metal cobalt and dilute nitric acid are used, which are more harmful, and the marking of this method is not firm, and the marking color is easy to change after acid and alkali washing.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a method for marking a porcelain crucible with a ferric chloride solution. The marking method uses a ferric chloride solution for marking, the method is repeatable, and the marking is firm and durable.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0007] The present invention provides a method for marking a ferric chloride solution of a porcelain crucible, the marking method comprising the following steps:

[0008] The bottom of the porcelain crucible is marked with ferric chloride solution, and then burned to complete the marking;

[0009] The calcination is carried out by a gradient temperature reduction calcination method: first calcination is carried out at 800-1200°C, and then a second calcination is carried out at 500-600°C.

[0010] Furthermore, the mass percentage of ferric chloride in the ferric chloride solution is 0.1 to 20%, preferably 1 to 10%.

[0011] Furthermore, the solvent in the ferric chloride solution is selected from water and / or ink, preferably water.

[0012] Furthermore, the step of marking the bottom of the porcelain crucible with the ferric chloride solution is specifically as follows: using a writing tool to dip into the ferric chloride solution and marking symbols on the bottom of the porcelain crucible.

[0013] Furthermore, the dosage of the ferric chloride solution is 20 to 100 μL per marker.

[0014] Furthermore, the ferric chloride solution also includes a colored pigment.

[0015] Furthermore, the added amount of the colored pigment is 0.1 to 10 v / v%.

[0016] Furthermore, the primary burning is carried out in an electric furnace.

[0017] Furthermore, the burning time is 3 to 7 minutes.

[0018] Furthermore, the secondary calcination is carried out in a muffle furnace.

[0019] Furthermore, the secondary burning time is 55 to 65 minutes.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention provides a ferric chloride solution marking method for a porcelain crucible, which solves the problem that the marking of the porcelain crucible disappears and is unclear at high temperature, and establishes a ferric chloride solution marking method with clear method steps, easy operation and easy promotion, so as to achieve the purpose that the marking of the porcelain crucible is clear, reusable, acid and alkali resistant, washing resistant, simple to operate and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 Observation diagram of the porcelain crucible marked by the method provided in Example 1. DETAILED DESCRIPTION

[0024] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0025] It should be noted that specific details are described in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] As an optional embodiment of the present invention, the present invention provides a method for marking a ferric chloride solution of a porcelain crucible, the marking method comprising the following steps:

[0028] The bottom of the porcelain crucible is marked with a ferric chloride solution and then burned to complete the marking.

[0029] In the present invention, a marking method for a ferric chloride solution is provided, which is suitable for a porcelain crucible. After the ferric chloride is burned at a high temperature, the color of the marking symbol changes to reddish brown to dark brown. The method solves the problem that the marking of the porcelain crucible disappears and is unclear at a high temperature, and a marking method for a ferric chloride solution with clear method steps, easy operation and easy promotion is established, so as to achieve the purpose of clear marking of the porcelain crucible, reusability, acid and alkali resistance, washing resistance, simple operation and easy promotion.

[0030] As an optional embodiment of the present invention, the burning adopts a gradient temperature reduction burning method:

[0031] First, a primary calcination is performed at 800-1200°C, and then a secondary calcination is performed at 500-600°C.

[0032] In the present invention, the calcination adopts a gradient temperature reduction calcination method, firstly, high-temperature calcination is carried out at 800-1200°C on an electric furnace to rapidly decompose ferric chloride into ferric oxide, and the ferric oxide is converted into a stable crystal form at a sufficiently high temperature; then, the calcination is carried out at a constant temperature of 500-600°C in a muffle furnace for a period of time to further improve the chromaticity of the marking color, avoid the darkening or blackening of the marking color, and further promote the complete conversion reaction of the ferric oxide, so as to achieve the purpose of strong marking fastness, good tinting strength, acid resistance, alkali resistance, and organic solvent resistance.

[0033] As an optional embodiment of the present invention, the temperature of the primary calcination is 800-1200°C, for example, it can be 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1040°C, 1050°C, 1100°C, 1150°C, 1200°C, etc.

[0034] As an optional embodiment of the present invention, the temperature of the secondary calcination is 500-600°C, for example, it can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, etc.

[0035] As an optional embodiment of the present invention, the mass percentage of ferric chloride in the ferric chloride solution is 0.1-20%, for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20% and the like.

[0036] As a preferred embodiment of the present invention, the mass percentage of ferric chloride in the ferric chloride solution is 1-10%.

[0037] In the present invention, the concentration range of the ferric chloride solution is required to ensure that the method is repeatable and further improve the firmness and durability of the marking.

[0038] As an optional embodiment of the present invention, the solvent in the ferric chloride solution is selected from water and / or ink, preferably water.

[0039] As a preferred embodiment of the present invention, the solvent in the ferric chloride solution is water, or a combination of ink and water.

[0040] As a preferred embodiment of the present invention, the water is further preferably purified water.

[0041] In the present invention, the color of the marking symbol can be changed by adding a colored pigment to the ferric chloride solution, such as adding blue ink to change the color of the writing to purple-black.

[0042] As an optional embodiment of the present invention, the step of marking the bottom of the porcelain crucible with a ferric chloride solution is specifically as follows:

[0043] Dip a writing instrument into the ferric chloride solution and mark the symbol on the bottom of the porcelain crucible.

[0044] As an optional implementation of the present invention, the porcelain crucible needs to be cleaned and dried before marking the bottom of the porcelain crucible with the ferric chloride solution.

[0045] As an optional embodiment of the present invention, the drying includes natural air-drying and / or oven-drying.

[0046] As an optional embodiment of the present invention, the writing tool includes but is not limited to a pen and / or a thin wooden stick.

[0047] As an optional embodiment of the present invention, the dosage of the ferric chloride solution is 20 to 100 μL / marker, for example, it can be 20 μL / marker, 30 μL / marker, 40 μL / marker, 50 μL / marker, 60 μL / marker, 70 μL / marker, 80 μL / marker, 90 μL / marker, 100 μL / marker, etc.

[0048] In the present invention, by requiring the range of the amount of the ferric chloride solution, it is ensured that the symbols are written on the bottom of the porcelain crucible. If the amount of the ferric chloride solution is too much, the handwriting is easily deformed. If the amount of the ferric chloride solution is too little, the coloring is too light and the mark is unclear.

[0049] As an optional embodiment of the present invention, the ferric chloride solution also includes a colored pigment.

[0050] As an optional embodiment of the present invention, the colored pigment includes but is not limited to blue ink.

[0051] As an optional embodiment of the present invention, the added amount of the colored pigment is 0.1-10 v / v%, for example, it can be 0.1 v / v%, 0.5 v / v%, 1.0 v / v%, 1.5 v / v%, 2 v / v%, 3 v / v%, 4 v / v%, 5 v / v%, 6 v / v%, 7 v / v%, 8 v / v%, 9 v / v%, 10 v / v% and the like.

[0052] As an optional embodiment of the present invention, the primary burning is carried out in an electric furnace.

[0053] As an optional embodiment of the present invention, the time of the single burning is 3 to 7 minutes, for example, it can be 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, 5.5 minutes, 6 minutes, 6.5 minutes, 7 minutes, etc.

[0054] As an optional embodiment of the present invention, the secondary calcination is carried out in a muffle furnace.

[0055] As an optional embodiment of the present invention, the time of the secondary burning is 55 to 65 minutes, for example, it can be 55 minutes, 56 minutes, 58 minutes, 60 minutes, 62 minutes, 64 minutes, 65 minutes, etc.

[0056] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0057] Example 1

[0058] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible, the marking method comprising the following steps:

[0059] S1. Pre-treatment:

[0060] Clean the porcelain crucible with water and dry it at 100°C.

[0061] S2, prepare ferric chloride solution:

[0062] Use an electronic balance to weigh 4.18 g of ferric chloride hexahydrate and place it in a 250 mL beaker. Use a measuring cylinder to measure 25 mL of purified water and add it to the beaker. Stir with a glass rod to dissolve and shake well to obtain a 10.0 wt% ferric chloride solution.

[0063] S3. Write the marking symbol on the bottom of the porcelain crucible:

[0064] Dip a thin wooden stick into an appropriate amount of the ferric chloride solution and write symbols 1, 2, 3, 4, and 5 on the bottom of five porcelain crucibles. The amount of the ferric chloride solution used is 50 μL per mark.

[0065] S4. Porcelain crucible marking symbol High temperature burning reinforcement:

[0066] First, place the marked porcelain crucible on a 2000W experimental electric furnace and adjust the power to medium. Burn it at 1000℃±10℃ for 5 minutes, then move it to a muffle furnace and burn it at 550℃ for 1 hour. Then move it to the mouth of the muffle furnace and cool it to below 200℃. Take it out and place it in a desiccator to cool to room temperature. The marking is completed and the color of the marking symbol turns brown (such as Figure 1 shown).

[0067] Example 2

[0068] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible, the marking method comprising the following steps:

[0069] S1. Pre-treatment:

[0070] Clean the porcelain crucible with water and dry it at 100°C.

[0071] S2, prepare ferric chloride solution:

[0072] Use a pipette to draw 10 mL of 10.0 wt% ferric chloride solution into a beaker, add 10 mL of purified water, stir with a glass rod to dissolve, and shake well to obtain a 5.0 wt% ferric chloride solution.

[0073] S3. Write the marking symbol on the bottom of the porcelain crucible:

[0074] Dip a thin wooden stick into an appropriate amount of the ferric chloride solution and write symbols 6, 7, 8, 9, and 10 on the bottom of five porcelain crucibles. The amount of the ferric chloride solution used is 50 μL per mark.

[0075] S4. Porcelain crucible marking symbol High temperature burning reinforcement:

[0076] First, place the marked porcelain crucible on a 2000W experimental electric furnace and adjust the power to medium. Burn it at 1000℃±10℃ for 5 minutes, then move it to a muffle furnace and burn it at 550℃ for 1 hour. Then move it to the mouth of the muffle furnace and cool it to below 200℃. Take it out and place it in a desiccator to cool to room temperature. The marking is completed and the color of the symbol turns brown.

[0077] Example 3

[0078] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible, the marking method comprising the following steps:

[0079] S1. Pre-treatment:

[0080] Clean the porcelain crucible with water and dry it at 100°C.

[0081] S2, prepare ferric chloride solution:

[0082] Use a pipette to draw 2 mL of 10.0 wt% ferric chloride solution into a beaker, add purified water to 20 mL, stir with a glass rod to dissolve, and shake well to obtain a 1.0 wt% ferric chloride solution.

[0083] S3. Write the marking symbol on the bottom of the porcelain crucible:

[0084] Dip a thin wooden stick into an appropriate amount of the ferric chloride solution and write symbols 11, 12, 13, 14, and 15 on the bottom of five porcelain crucibles. The amount of the ferric chloride solution used is 100 μL per mark.

[0085] S4. Porcelain crucible marking symbol High temperature burning reinforcement:

[0086] First, place the marked porcelain crucible on a 2000W experimental electric furnace and adjust the power to medium. Burn it at 1000℃±10℃ for 5 minutes, then move it to a muffle furnace and burn it at 550℃ for 1 hour. Then move it to the mouth of the muffle furnace and cool it to below 200℃. Take it out and place it in a desiccator to cool to room temperature. The marking is completed and the color of the marking symbol turns reddish brown.

[0087] Example 4

[0088] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible, the marking method comprising the following steps:

[0089] S1. Pre-treatment:

[0090] Clean the porcelain crucible with water and dry it at 100°C.

[0091] S2. Preparation of colored pigment-ferric chloride solution:

[0092] Use an electronic balance to weigh 4.21 g of ferric chloride hexahydrate and place it in a 250 mL beaker. Use a measuring cylinder to measure 25 mL of purified water and add it to the beaker. Stir with a glass rod to dissolve it. Then add 0.5 mL of blue ink and shake well to obtain a 10.0 wt% ferric chloride / blue ink solution.

[0093] S3. Write the marking symbol on the bottom of the porcelain crucible:

[0094] Dip a thin wooden stick into an appropriate amount of the ferric chloride / blue ink solution and write symbols 16, 17, 18, 19, and 20 on the bottom of five porcelain crucibles. The amount of the ferric chloride / blue ink solution used is 100 μL per mark.

[0095] S4. Porcelain crucible marking symbol High temperature burning reinforcement:

[0096] First, place the marked porcelain crucible on a 2000W experimental electric furnace and adjust the power to medium. Burn it at 1000℃±10℃ for 5 minutes, then move it to a muffle furnace and burn it at 550℃ for 1 hour. Then move it to the mouth of the muffle furnace and cool it to below 200℃. Take it out and place it in a desiccator to cool to room temperature. The marking is completed and the color of the marking symbol turns purple-black.

[0097] Example 5

[0098] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible. The difference from Embodiment 1 is that in S4, the temperature of the first burning is 800°C, and the time of the first burning is 7 minutes; the temperature of the second burning is 600°C, and the time of the second burning is 55 minutes. Other settings are exactly the same as those in Embodiment 1.

[0099] Example 6

[0100] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible, which is different from Embodiment 1 in that, in S4, the temperature of the first burning is 1200° C., and the time of the first burning is 3 min; the temperature of the second burning is 500° C., and the time of the second burning is 65 min. Other settings are exactly the same as those in Embodiment 1.

[0101] Example 7

[0102] This embodiment provides a method for marking a porcelain crucible with a ferric chloride solution. The difference from Embodiment 1 is that the amount of the ferric chloride solution is 0.2 mL / marker, and other settings are completely consistent with Embodiment 1.

[0103] Example 8

[0104] This embodiment provides a method for marking a porcelain crucible with a ferric chloride solution. The difference from Embodiment 1 is that the amount of the ferric chloride solution is 10 μL / marker, and other settings are completely consistent with Embodiment 1.

[0105] Example 9

[0106] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible. The difference from Embodiment 1 is that the mass percentage of ferric chloride in the ferric chloride solution is 0.2 wt %. Other settings are completely consistent with Embodiment 1.

[0107] Example 10

[0108] This embodiment provides a method for marking a ferric chloride solution in a porcelain crucible. The difference from Embodiment 1 is that the mass percentage of ferric chloride in the ferric chloride solution is 20wt%, and other settings are completely consistent with Embodiment 1.

[0109] Comparative Example 1

[0110] This comparative example provides a marking method for a porcelain crucible, which is different from Example 1 in that S4 does not perform a primary calcination, but only calcinates at a constant temperature of 550° C. for 1 h in a muffle furnace, and other settings are completely consistent with Example 1.

[0111] Comparative Example 2

[0112] This comparative example provides a marking method for a porcelain crucible, which is different from Example 1 in that S4 does not perform a primary calcination, but only calcinates at a constant temperature of 550° C. for 4 h in a muffle furnace, and other settings are completely consistent with Example 1.

[0113] Comparative Example 3

[0114] This comparative example provides a marking method for a porcelain crucible, which is different from Example 1 in that S4 does not perform secondary burning, but only adjusts the power to the middle range in the experimental electric furnace and burns at 1000° C. for 5 minutes. Other settings are completely consistent with Example 1.

[0115] Test Example 1

[0116] Test samples: porcelain crucibles marked by the methods provided in Examples 1 to 4, and porcelain crucibles marked by the methods provided in Comparative Examples 1 to 3.

[0117] Test method:

[0118] (1) Soaking in detergent: Soak the samples in 2% detergent at room temperature for 24 hours and observe the markings.

[0119] (2) Detergent washing: Use detergent to wash the above samples. Use a brush dipped in detergent to wash 30 times at room temperature, and then observe the marking symbols.

[0120] (3) Soaking in hydrochloric acid: Soak the samples in 18 wt % hydrochloric acid aqueous solution at room temperature for 24 h, and then observe the marking symbols.

[0121] (4) Nitric acid immersion: The samples were immersed in a 20 wt % nitric acid aqueous solution at room temperature for 24 h, and then the marking symbols were observed;

[0122] (5) Alkali immersion: The samples were immersed in an alkaline ethanol solution containing 10 wt % sodium hydroxide at room temperature for 24 h, and then the marking symbols were observed.

[0123] The test results are shown in Table 1:

[0124] Table 1

[0125]

[0126]

[0127] As shown in Table 2, the present invention provides a method for marking a ferric chloride solution of a porcelain crucible, which solves the problem that the marking of the porcelain crucible disappears and is unclear at high temperature, and establishes a method for marking a ferric chloride solution with clear steps, easy operation, and easy promotion, so as to achieve the purpose of clear marking of the porcelain crucible, reusability, acid and alkali resistance, washing resistance, simple operation and easy promotion.

[0128] From the comparison between Example 1 and Example 4, it can be seen that the color of the marking symbol can be changed by adding a colored pigment to the ferric chloride solution, such as adding blue ink to change the color of the writing to purple-black.

[0129] From the comparison between Example 1 and Comparative Examples 2 to 4, it can be seen that the calcination adopts a gradient cooling calcination method, firstly performing high-temperature calcination at 800 to 1200° C. on an electric furnace to rapidly decompose ferric chloride into ferric oxide, and converting the ferric oxide into a stable crystalline form at a sufficiently high temperature; then calcining at a constant temperature of 500 to 600° C. in a muffle furnace for a period of time to further improve the chromaticity of the marking color, avoid the darkening or blackening of the marking color, and further promote the complete conversion reaction of the ferric oxide, so as to achieve the purpose of strong marking fastness and good tinting strength.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for marking a ferric chloride solution in a porcelain crucible, characterized in that: The marking method comprises the following steps: The bottom of the porcelain crucible is marked with ferric chloride solution, and then burned to complete the marking; The calcination is carried out by a gradient temperature reduction calcination method: first calcination is carried out at 800-1200°C, and then a second calcination is carried out at 500-600°C.

2. The ferric chloride solution marking method for a porcelain crucible according to claim 1, wherein: The mass percentage of ferric chloride in the ferric chloride solution is 0.1-20%, preferably 1-10%.

3. The ferric chloride solution marking method for a porcelain crucible according to claim 1 or 2, characterized in that, The solvent in the ferric chloride solution is selected from water and / or ink, preferably water.

4. The ferric chloride solution marking method for a porcelain crucible according to claim 1, characterized in that: The step of using ferric chloride solution to mark the bottom of the porcelain crucible is specifically: using a writing tool to dip into the ferric chloride solution and mark symbols on the bottom of the porcelain crucible.

5. The ferric chloride solution marking method for a porcelain crucible according to claim 1 or 4, characterized in that: The dosage of the ferric chloride solution is 20-100 μL / marker.

6. The ferric chloride solution marking method for a porcelain crucible according to claim 1, characterized in that: The ferric chloride solution also includes a colored pigment; Preferably, the added amount of the colored pigment is 0.1 to 10 v / v%.

7. The ferric chloride solution marking method for a porcelain crucible according to claim 1, characterized in that: The primary calcination is carried out in an electric furnace.

8. The ferric chloride solution marking method for a porcelain crucible according to claim 1 or 7, characterized in that: The time of the first burning is 3 to 7 minutes.

9. The ferric chloride solution marking method for a porcelain crucible according to claim 1, characterized in that: The secondary calcination is carried out in a muffle furnace.

10. The method for marking a ferric chloride solution of a porcelain crucible according to claim 1 or 9, characterized in that: The secondary burning time is 55 to 65 minutes.

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