Some standard content:
This standard is a replacement for JB/T7993-1999 Chemical Analysis Method. This standard is a revision of JB/T7993-95 (source GB9255-88> Boron Carbide. This standard is consistent with the technical content of JB/T7993--95. It has only been re-edited according to relevant regulations. This standard replaces JB/T7993-95 from the date of implementation. This standard is proposed and managed by the National Abrasives Standardization Technical Committee. The chapter unit of this standard is Zhengzhou Abrasives Research Institute. The main drafters of this standard are Ge Suping and Chen Wenyu. 200
Machinery Industry Standard of the People's Republic of China
Boron Carbide
Chemical Analysis Method
JB/T79931999
Replaces JB/T 799395
This standard specifies the determination method of total, ferric oxide, silicon dioxide, vanadium trioxide, total carbon and free carbon in carburizer materials and product blocks.
This standard is applicable to the determination of the chemical composition of the previous generation of industrial carbonization products. General provisions
2.1. When performing secondary analysis, the number of parallel copies of the same sample shall not be less than three. If the difference (absolute deviation) of the analysis results is within the allowable range, the mathematical mean value shall be taken as the final analysis result.
2.2 Except for the special specifications indicated, the reagents used in the analysis shall not be less than analytical grade, and the ones used as the benchmark shall be The standard test method is used. 2.3 All liquid reagents counted in the method are water-soluble reagents except those specified. 2.4 All liquid reagents with specified concentrations in the method are standard reagents, such as hydrochloric acid (density 1.19), nitrogen solution (density D.90). Unspecified reagents, such as carbonate, are original reagents. 2.5 The concentration ratios of liquid reagents listed in the method: (1+1), (15+85), etc., refer to the ratio of the volume of the liquid to the volume of water. For example, (15+85) distilled water refers to 15 unit volume of hydrochloric acid with a density of 1.19 mixed with 85 unit volume of water. 2.6 The percentage of the solution listed in the method The concentration refers to the number of grams of solute contained in 100 mL of solution, for example, 40% potassium hydroxide solution means 40 g of potassium hydroxide dissolved in water and diluted to 100 mL. 2.7 Preparation of reagents and analytical materials, except for those specified, are all distilled water or deionized water. 2.8 The balance used in the method, unless otherwise specified, should have a capacity of 0.1 mg. The analytical balance, calibration and volumetric instruments should be calibrated before use. 2.9 All operations in the method, except for those specified, are carried out in glassware or glassware. 3 Preparation of samples. 3.1 Block abrasives. First Use a sow to beat the steel plate into small pieces with a diameter of about 30mm, use the quartering method to reduce 50~60g, and then use a steel grinder to crush until all of them pass through a 250xm sieve. Use a magnet with a suction force of 9.8~14.7N to remove the iron in the crushed. Then put it into a sample bag, dry it in an oven at 105~110C for 1b, take it out, and cool it in a dryer for use. 3.2 Light abrasives
Single materials finer than 250μm do not need to be crushed, use the quartering method to reduce 50~60g, put it into a sample bag, and dry it in an oven at 105~110C for 1h. Take it out, and cool it in a dryer for use. 4 Determination of total iodine
4.1 Key points of the method
The sample is melted with anhydrous sodium carbonate and sodium hydroxide, extracted with cold acid solution to convert boron into alkoxide, and calcium carbonate is added to neutralize the melt. At this time, iron, aluminum, etc. form hydroxide precipitates and are separated. Approved by the State Bureau of Machinery Industry on May 20, 1999, and implemented on January 1, 2000
JB/T7993—1999
The iodine in the liquid forms a strong acidic complex in the presence of mannitol. With phenol as the indicator and sodium hydrochloride standard solution as the indicator, the content of iodine can be calculated. The reaction is: H,BO,+CH,OH(CHOH),CH,OH+H[BO,(CH,);(CHOH),(CH,OH),J+2H,OH[BO,(CH,);(CHOH),(CH,OH),J+NaOH→+Na[BO, (CH,);(CHOH),(CH,OH),J+H,O4.2 Reagents
Sodium carbonate anhydrous.
Potassium nitrate,
4.2-3 Calcium carbonate,
4.2.4 Hydrochloric acid.
4.2.5 Glycol.
Methyl red indicator: 0.1%. Weigh 0.1g monomethyl red and dissolve it in 100mL water. 4.2. 6
4.2.7 Acid indicator: 1%. Weigh 1g acid and dissolve it in 60mL 95% ethanol, then dilute it with water to 100mL. Neutralize it with 0.15N sodium hydroxide standard solution until it just turns red. 4.2.8 Standard solution of sodium hydroxide: 0.15M
Dissolve 6.0 g of sodium hydroxide in freshly boiled and cooled water, add a small amount of oxidizing agent, and dilute to 1000 mL. Allow to settle, and absorb the clear solution and store it in a flask for later use.
Calibration: Accurately weigh three portions of potassium hydrogen phthalate (standard reagent > 0.6g) that has been dried at 105-110°C for 1h, and place them in three 250mL conical flasks respectively. Add 100mL of freshly boiled water, dissolve it in a flask, add 2-3 phenolic acid indicators, and titrate with sodium hydroxide standard solution until it turns red. Calculate the equivalent of sodium hydroxide standard solution according to formula (1): G
Where: N--equivalent concentration of sodium hydroxide standard solution; G--weighed amount of potassium hydrogen phthalate g:
V--volume of sodium hydroxide standard solution consumed during titration, mL ; 0.2040 milliliters of potassium dicarbonate. 4.3 Preparation of test solution
Accurately weigh 0.2000g of the sample into a platinum flask, add 3g of anhydrous sodium carbonate and 0.1g of nitric acid, and after evaporation, add 1g of anhydrous sodium carbonate. The lid of the flask is half open to allow the decomposed gas to escape quickly. The flask is sent to a high-temperature furnace and treated at 650°C for 2h, 700°C for 1h, and 750°C for 1h. After heating to 900°C, it melts for 30min, and is taken out. The flask is turned to make the molten metal adhere to the flask. After cooling, the flask is cleaned with water and added to 250mL of calcined water containing 100mL (15+85) hydrochloric acid. In the beaker, shake the beaker continuously to accelerate the dissolution of the block. After the sample is completely extracted, wash the drain and cover with water, transfer to a 250mL container, cool, dilute with water to 300mL, shake, and set aside. 4.4 Operation method
Take 50mL of the sample prepared in 4.3 in a 250mL beaker, dilute with water to 70~80mL. Add 1 drop of methyl red indicator, add carbendazim in batches and continue to stir until no carbon dioxide gas is emitted, heat and boil for 5~10min, filter with a medium-speed filter, collect the solution in 500mL of distilled water, wash the beaker with hot water 3~4 times, wash the precipitate 10~12 times, and concentrate to about 16mL. 0mL, add (1+1) acid to make the solution red, continue boiling for 5-10min, cool with running water, titrate with 0.15N sodium hydroxide standard solution until the test wave turns from red to gray (not counting this number), add 10-15g of ester acid indicator, add 2-3g of mannitol and drip with 0.15N sodium hydroxide standard solution until the color turns red, then add a small amount of mannitol. If the red color disappears, drip with 0.15N sodium hydroxide standard solution until it turns slightly red. Repeat this process until the red color does not fade after adding mannitol, which is the end point, and make a blank test under the same conditions. Calculate the percentage of the total content according to formula (2):
w(B,) _ 0.010 81NY
×100%
..-...(2)
Wherein, N
0.010 81-
JB/T 7993-1999
equivalent concentration of sodium hydroxide standard
the volume of sodium hydroxide standard reported by the filter (with the room self-value subtracted), ml: sample mass·g;
Ponker equivalent.
allowable error
see Table 1.
Containing range
50. 0070, 00
Determination of trivalent iron
Method points
Allowable error
Same laboratory
Different laboratory
In ammonia solution (pH 8~11.5), trivalent iron reacts with sulfosalicylic acid to form yellow ferric salicylate complex, and its content is determined by colorimetry.
5.2 Reagents
5.2.1 Sulfosalicylic acid solution (15%), weigh 15g of sulfosalicylic acid, dissolve it in water and dilute to 100mL, 5.2.2 Ammonium hydroxide (density 0.90).
5.2.3 Blank liquid;
Put 4g of anhydrous sodium carbonate in a platinum tube, melt in a high-temperature furnace at 950C for 20min, take it out and cool it. Wash the outer wall of the tube, heat and condense it with 100mL of (15+85) hydrochloric acid, put it into a 250mL volumetric flask, cool it and dilute it with water to the specified scale, and then mix it and use it to create a standard curve.
5.2.4 Ferrous oxide standard solution
Accurately weigh 0.1000 g of ferric oxide (standard reagent) that has been dried at 110°C for 2 h in a 250 ml beaker, add 40 ml of (1+1) hydrochloric acid, cover with a watch glass, heat on low heat to dissolve, and after complete dissolution, cool and transfer to a 1000 ml volumetric flask, dilute to the mark with water, shake to make sure that the required liter contains 0.10 mg of ferric oxide. Take 50 ml of this solution and place it in a 250 ml volumetric flask, dilute to the mark with water, shake and set aside. This drop contains 0.02 mg of ferric oxide in each liter. Draw the standard curve. Pipette 25 mL of blank solution and put it into nine 50 mL volumetric bottles respectively. Use a microburette to add 0, 00.0, 50, 1.00, 2.00, 4.00, 5.00, 6.00, 8.00, 10.00 mL of ferric oxide standard solution (i.e., the percentage of ferric oxide is 0.00, 0.05, 0.10, 0.20, 0.40, 0.50, 0.60.0.80, 1.00) in sequence. Add 5 mL of 15% basic aqueous solution while adding hydroxide until it turns a stable yellow color. Add 4 to 5 drops of excess, drain all, dilute with water to concentration and mix well. Use 1cm colorimetric phase, measure the extinction value at 420nm on the colorimeter with water as reference solution, then subtract the extinction value of the reagent blank and draw the standard curve. 5.4
Operation method
Put 25mL of the test solution prepared in 4.3 in a 50mL volumetric flask, and measure its extinction value according to the operation of 5.3. At the same time, do a blank test under the same conditions, subtract the blank extinction value, and calculate the content of dihydrogen trioxide on the standard curve. The allowable error
is specified in Table 2.
Total volume
>0. 25 ~0. 50
>-0. 50~3. 00
>1. 00~ 2. 00
Determination of silicon dichloride
Key points of the method
JB/T 7993—1999
Same laboratory
Allowable error
Different laboratories
± 0, 09
In 0.08~0.32N acid medium, silicic acid and the corresponding acid form a yellow silicic acid complex, which is then reduced to a silicon group with a reducing agent and determined by colorimetry. The reaction is
H,SiO,+12H,MoO,→+H,[Si (Mo,0,),J+-10H,0Mo,O,
H.Si(Mo,O),J+E reducing agent)+H-+H,
6.2 Reagents
anhydrous sodium carbonate,
hydrochloric acid: ((15+85)
(Mo,O,),
+[chrysanthemum oxide]+H,O
6.2.3 Group acid iron liquid: 5%. Drop width 5g ammonium hydroxide Dissolve in water and dilute to 100mL with water. Place it for 24 hours before use. If precipitation occurs, stop using it.
6.2.4 Citrate solution; 5%,
6.2.51, 2.4-acid reducing agent solution: Dissolve 0.15g of 1.2.4-acid (1-hydrogen-2-phthalic acid-4.sulfonic acid), 0.7g of anhydrous sodium sulfite, and 9g of sodium bisulfite in water, dilute to 100mL with water, and store. Store in a plastic bottle for future use. The shelf life is 14 days. 6.2.6 Silicon dioxide standard solution
Accurately weigh 0.1000g of silicon dioxide (standard reagent) burned at 980~1000℃ for 1h in a platinum clamp, add 2g of anhydrous sodium carbonate (standard reagent). Carefully sieve and place in a high-temperature furnace at 860~900℃ for 20min. Take out. Transfer to a cooler. Allow the molten material to adhere to the inner surface of the glass, cool, and clean the outer wall. In a beaker, extract with hot water, cool, and transfer to a 1000mL volumetric plate, dilute to the mark with water, and immediately transfer to a clean and dried plastic container for storage. This solution contains 0.1mg of silicon dioxide per milliliter. Pipette 100mL of this solution into a 250mL volumetric plate pre-filled with 12mL of 2V hydrochloric acid, dilute to the mark with water, and the resulting solution is the silicon dioxide standard solution (1mL contains 0.04 6.2.7 Blank flask
Take 4g of anhydrous sodium carbonate and dissolve it in a platinum-containing solution. Melt it in a high-temperature furnace at 950°C for 20min, take it out, cool it, wash the outer wall of the flask, and add 100mL of (15+85) acid as hot water. Transfer it to a 250mL volumetric flask. After cooling, dilute it with water to the mark, mix well, and set aside. 6.3 Drawing of standard curve
Take eight portions of 10mL of blank solution and put them into eight 100mL volumetric flasks respectively. Use a microtip to add 0.00, 0.20, 0.50, 1,000 of silica standard solution one by one. ,2.00,4.00,6.00,8.00m2 (i.e. the cumulative chemical percentage is 0.00,0.10.0.25,0.50.).00.2.00.3.00.4.00), add 5% ammonium hydroxide solution 5ml.. water 20mL and place with a spoon to make it completely colored (place it at room temperature above 15°C for 15min, and adjust the solution to above 15°C below 15°C and then place it for color measurement). Add 5X alcohol 20mL of right acid solution.1,3.4-acid reducing agent 3ml., hook, place for 20min, dilute with rice to the desired degree, and evenly distribute. Use 10 mL of the test solution prepared in 4.3 to put it in a 100 mL volumetric flask, add 5 mL of 5% tris(II) acid solution, and determine its extinction value according to the following procedure of 6.3. At the same time, do a blank test. After subtracting the blank extinction value, calculate the silicon dioxide content from the standard curve. 6.5 Permissible error
According to the provisions of Table 3,
Content range
Same laboratory
>0.50~2.00
>2.00~4.00
± 0, 08
Filling and adjusting
Different natural laboratories
Construction phase color development is complete under 0.08~0.32N deionization, too small or too large acidity will result in incomplete color development. The stability of the silicon phase is slightly affected by the environment. At 35C, it can only be stable for 30min. Therefore, after adding the recovery, 1.2,4-acid source avoidance should be added immediately after the color development is complete. The color measurement conditions should be strictly controlled. A blank test should be performed with a mesh sample each time to correct the result. a
Determination of three-step reaction
7.1 Key points of the method
Boron carbide does not react with stagnant water. The surface-determined ketone fruit is easily soluble in hot water. After dissolution, it is determined by acid reduction volumetric method in the form of mannitol boric acid. 7.2 Reagents
7.2.1 Hydrochloric acid: (1+1).
Methyl indicator: 0.1% aqueous solution,
7.2.3 Alcohol indicator: 1%,
Weigh 1g phenol and dissolve it in 60mL 95% ethanol, then dilute it to 100mL with water and neutralize it with 0.1N sodium hydroxide standard solution until it turns red,
7.2.4 Mannitol.
Potassium hydrogen phthalate: standard reagent,
7.2.6 Sodium hydroxide standard solution: 0.1N
Weigh 4.00g sodium hydroxide and dissolve it in freshly boiled and cooled water, add a little cyanide, dilute it to 1000mL, let it stand, absorb the excess water and store it in a plastic bag for later use.
Calibration: Accurately weigh three portions of potassium hydrogen phthalate (reference reagent) dried at 105~110℃ for 1h, about 0.4g, and put them into three 250mL bottles respectively. Add 100mL of freshly boiled and cooled distilled water, and dissolve it in a bottle. Add 2~3 drops of acid indicator, and titrate with sodium cyanide standard solution until it turns slightly red. Formula (3) Calculate the equivalent concentration of sodium hydrofluoride standard solution: G
N= 0.204 0V
Where: N——equivalent weight of sodium hydroxide standard solution. G-—the amount of potassium hydrogen phthalate weighed. V.—the volume of sodium hydroxide standard sieve solution consumed in titration. TaL: 0.2040---milligram equivalent weight of potassium hydrogen phthalate. 7.3
Extraction method
(3)
JB/T 7993-1999
Weigh 1g of sample into a 250mL beaker, add 100mL of distilled water, heat to a boil and keep for 30~40min, add 1~2 drops of methyl red indicator, add 3~5 drops of (1+1) salt, add calcium carbonate in batches until the liquid turns yellow, heat and boil for 3~5min, filter with medium-speed micro-paper, quickly saturate the beaker with hot water 3~4 times, wash the precipitate and filter 7~8 times. Collect the filtrate in a 500mL chain bottle, add 2 drops of (1+1) hydrochloric acid, heat and boil for 5~10min n. Cool to room temperature with running water, drip 0.1N sodium hydroxide standard solution until the test color changes from red to yellow (ignore the reading), add 10 drops of indicator, add 1-2g of mannitol, drip 0.1N sodium hydroxide standard solution until it turns slightly red, then add a small amount of mannitol. If the red color disappears, drip 0.1N sodium hydroxide standard solution until it turns slightly red, repeat this process until the slightly red color does not fade after adding mannitol. Perform a blank test under the same conditions. Calculate the percentage of boron trioxide by weight according to formula (4): w(B, O,)
Wherein: N-
0. 034 81
equivalent concentration of sodium hydride standard solution; 0. 034 81 NV
×100%
volume of sodium hydroxide standard solution consumed (blank subtracted), mL; try to select mass g!
Ponke equivalent of trioxide limit.
Allowable error
According to the provisions of Table 4.
Total amount range
>6. 50~1. 00
Free adjustment
Allowable error
Same tester
...........( 4)
Different laboratories
Key points of the method
Free boron is oxidized to trioxide with hydrogen peroxide and nitric acid, acidified to form borate, and in the presence of mannitol to form chelated acid, which is titrated with sodium hydroxide standard drop to calculate the boron content. 8.2 Reagents
8.2.1 Hydrogen peroxide: (1+2).
8.2.2 Nitric acid.
8.2.3 Glycerol,
8.2.4 Calcium carbonate,
8.2.5 Methyl red indicator 0.1X aqueous solution, 82.6 Potassium hydrogen phthalate (reference reagent). 8.2.7 Acid indicator (see 7.2.3).
Complex sodium hydroxide standard solution (see 7.2.6)
8.3 Operation method|| tt||Weigh or sample 0.5g and place it in a non-obstructive glass flask with a reflux device, add 20mL of hydrogen peroxide (1+2) and 10 drops of sodium hydroxide, connect a condenser, connect cooling water, carefully heat to a low temperature, then reflux for 30-40min, wait until the free element is completely decomposed, take it off, wash the condenser with cold water 2-3 times, add methyl red as an indicator 1-2 times, add calcium hydroxide in batches and stir continuously until no carbon dichloride bubbles are generated, boil for 3-5min, cool slightly, filter with medium-sized filter paper and wash the flask with hot water 3-4 times, wash the precipitate 7-8 times, collect it in a 500ml conical flask, add (1+1) hydrochloric acid 1-2 times, heat to a high temperature for 5-10min, cool to room temperature with water, and titrate with 0.1N sodium hydroxide standard solution until it is equal to 60% red.
JB/T 7993—1999
When the color is just yellow (ignore the reading), add 10 drops of phenol indicator and 1-2g of mannitol. Use 0.1N oxychloride to drip until it turns slightly red. Then add a small amount of glycol. If the red color disappears, use 0.1N sodium hydroxide standard solution to drip until it turns slightly red. Repeat this process until the slightly red color disappears after adding mannitol. This is the end point. Perform a blank test under the same conditions. Calculate the percentage of boron according to formula (5): te(Bg) - 2.010.81 NV
Wherein, N
equivalent concentration of sodium hydroxide standard solution
X 1006 w(B,O,) × 0. 310 5
V·the volume of sodium hydroxide standard solution consumed (minus the blank value), mL; G—the mass of the sample·g+
0.01081—milligram equivalent of boron:
0.3105—the coefficient for converting boron into trisodium ions. 8.4
Allowable error
According to the provisions of Table 5,
Content rangebzxZ.net
>1. 50~1. 00
Determination of total carbon
Key points of the method
one laboratory
Allowable error
...( 5)
Different acid test rooms
The sample is burned with flux in a high-temperature furnace through oxygen. The carbon is oxidized to produce carbon dioxide, which is absorbed by potassium hydroxide. The difference in volume after absorption is the carbon dioxide. The carbon dioxide content is calculated based on the temperature and atmospheric pressure. 9.2
Instructions for reagents, instruments and accessories
Gas volumetric carbonization device, as shown in Figure 1, oxygen, oxygen purity 99%.
Flowmeter: oxygen meter (buoy-type industrial flowmeter) Drying tower: the upper layer is filled with asbestos, the lower layer is filled with anhydrous calcium chloride, the middle layer is filled with glass wool, and the top and the bottom are covered with a layer of glass wool. Tubular electric protection: with platinum/zirconium thermoelectric and temperature controller. Level: Contains (1+1000) sulfuric acid solution (add 1ml sulfuric acid to 1000mL steamed water, add a few drops of 0.1% methyl alcohol to make it red",
Absorber: Contains 40% potassium hydroxide solution Competitive tube: Check for gas before use, 9.2.9
Life: Before use, it must be burned in a high-temperature furnace at 800~900C for 3~4h, and stored in a dryer after cooling. 9.2. 10
Long hook, made of 3~4mm low-carbon chrome-inlaid wire or. 9.2. 11
Atmospheric barometer; measure atmospheric pressure
Calcium carbonate: standard reagent.
Aluminum tetroxide.
JB/T7993—19995g was placed in a non-obstructive glass flask with a reflux device, and 20mL of hydrogen peroxide (1+2) and 10 drops of sodium hydroxide were added. A condenser was connected and cooling water was connected. Carefully heated to a luminous state, and then refluxed for 30-40min. When the free element was completely decomposed, it was removed and the condenser was washed with cold water for 2-3 times. Methyl red was added as an indicator for 1-2 times to eliminate the ions. Calcium hydroxide was added in portions and stirred continuously until no carbon dichloride bubbles were generated. Boil for 3-5min, cool slightly, filter with medium-sized filter paper, wash the flask with hot water for 3-4 times, wash the precipitate 7-8 times, collect it in a 500ml conical flask, add (1+1) hydrochloric acid 1-2 times to clear it, heat it at a heating point for 5-10min, cool it to room temperature with water, and titrate it with 0.1N sodium hydroxide standard solution until it is equal to 60% red. 7993—1999
When the color is just yellow (ignore the reading), add 10 drops of phenol indicator and 1-2g of mannitol. Use 0.1N oxychloride to drip until it turns slightly red. Then add a small amount of glycol. If the red color disappears, use 0.1N sodium hydroxide standard solution to drip until it turns slightly red. Repeat this process until the slightly red color disappears after adding mannitol. This is the end point. Perform a blank test under the same conditions. Calculate the percentage of boron according to formula (5): te(Bg) - 2.010.81 NV
Wherein, N
equivalent concentration of sodium hydroxide standard solution
X 1006 w(B,O,) × 0. 310 5
V·the volume of sodium hydroxide standard solution consumed (minus the blank value), mL; G—the mass of the sample·g+
0.01081—milligram equivalent of boron:
0.3105—the coefficient for converting boron into trisodium iodide. 8.4
Allowable error
According to the provisions of Table 5,
Content range
>1. 50~1. 00
Determination of total carbon
Key points of the method
one laboratory
Allowable error
...( 5)
Different acid test rooms
The sample is burned with flux in a high-temperature furnace through oxygen. The carbon is oxidized to produce carbon dioxide, which is absorbed by potassium hydroxide. The difference in volume after absorption is the carbon dioxide. The carbon dioxide content is calculated based on the temperature and atmospheric pressure. 9.2
Instructions for reagents, instruments and accessories
Gas volumetric carbonization device, as shown in Figure 1, oxygen, oxygen purity 99%.
Flowmeter: oxygen meter (buoy-type industrial flowmeter) Drying tower: the upper layer is filled with asbestos, the lower layer is filled with anhydrous calcium chloride, the middle layer is filled with glass wool, and the top and the courtyard are covered with a layer of glass wool. Tubular electric protection: with platinum/zirconium thermoelectric and temperature controller. Level: Contains (1+1000) sulfuric acid solution (add 1ml sulfuric acid to 1000mL steamed water, add a few drops of 0.1% methyl alcohol to make it red",
Absorber: Contains 40% potassium hydroxide solution Competitive tube: Check for gas before use, 9.2.9
Life: Before use, it must be burned in a high-temperature furnace at 800~900C for 3~4h, and stored in a dryer after cooling. 9.2. 10
Long hook, made of 3~4mm low-carbon chrome-inlaid wire or. 9.2. 11
Atmospheric barometer; measure atmospheric pressure
Calcium carbonate: standard reagent.
Aluminum tetroxide.
JB/T7993—19995g was placed in a non-obstructive glass flask with a reflux device, and 20mL of hydrogen peroxide (1+2) and 10 drops of sodium hydroxide were added. A condenser was connected and cooling water was connected. Carefully heated to a luminous state, and then refluxed for 30-40min. When the free element was completely decomposed, it was removed and the condenser was washed with cold water for 2-3 times. Methyl red was added as an indicator for 1-2 times to eliminate the ions. Calcium hydroxide was added in portions and stirred continuously until no carbon dichloride bubbles were generated. Boil for 3-5min, cool slightly, filter with medium-sized filter paper, wash the flask with hot water for 3-4 times, wash the precipitate 7-8 times, collect it in a 500ml conical flask, add (1+1) hydrochloric acid 1-2 times to clear it, heat it at a heating point for 5-10min, cool it to room temperature with water, and titrate it with 0.1N sodium hydroxide standard solution until it is equal to 60% red. 7993—1999
When the color is just yellow (ignore the reading), add 10 drops of phenol indicator and 1-2g of mannitol. Use 0.1N oxychloride to drip until it turns slightly red. Then add a small amount of glycol. If the red color disappears, use 0.1N sodium hydroxide standard solution to drip until it turns slightly red. Repeat this process until the slightly red color disappears after adding mannitol. This is the end point. Perform a blank test under the same conditions. Calculate the percentage of boron according to formula (5): te(Bg) - 2.010.81 NV
Wherein, N
equivalent concentration of sodium hydroxide standard solution
X 1006 w(B,O,) × 0. 310 5
V·the volume of sodium hydroxide standard solution consumed (minus the blank value), mL; G—the mass of the sample·g+
0.01081—milligram equivalent of boron:
0.3105—the coefficient for converting boron into trisodium ions. 8.4
Allowable error
According to the provisions of Table 5,
Content range
>1. 50~1. 00
Determination of total carbon
Key points of the method
one laboratory
Allowable error
...( 5)
Different acid test rooms
The sample is burned with flux in a high-temperature furnace through oxygen. The carbon is oxidized to produce carbon dioxide, which is absorbed by potassium hydroxide. The difference in volume after absorption is the carbon dioxide. The carbon dioxide content is calculated based on the temperature and atmospheric pressure. 9.2
Instructions for reagents, instruments and accessories
Gas volumetric carbonization device, as shown in Figure 1, oxygen, oxygen purity 99%.
Flowmeter: oxygen meter (buoy-type industrial flowmeter) Drying tower: the upper layer is filled with asbestos, the lower layer is filled with anhydrous calcium chloride, the middle layer is filled with glass wool, and the top and the bottom are covered with a layer of glass wool. Tubular electric protection: with platinum/zirconium thermoelectric and temperature controller. Level: Contains (1+1000) sulfuric acid solution (add 1ml sulfuric acid to 1000mL steamed water, add a few drops of 0.1% methyl alcohol to make it red",
Absorber: Contains 40% potassium hydroxide solution Competitive tube: Check for gas before use, 9.2.9
Life: Before use, it must be burned in a high-temperature furnace at 800~900C for 3~4h, and stored in a dryer after cooling. 9.2. 10
Long hook, made of 3~4mm low-carbon chrome-inlaid wire or. 9.2. 11
Atmospheric barometer; measure atmospheric pressure
Calcium carbonate: standard reagent.
Aluminum tetroxide.
JB/T7993—1999
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