Some standard content:
1 Introduction National Standard of the People's Republic of China Methods of testing lac products UDC 634.0.892.6:534.05/.06 GB 8143--87 1.1 Scope This standard applies to the analysis and inspection of granular lac, lac sheet, decolorized lac sheet, dewaxed lac sheet, decolorized and dewaxed lac sheet, military lac sheet, bleached lac and dewaxed bleached lac. 1.2 Others
The determination method of volatile matter (water content) is equivalent to ISO56/11--1979; the determination method of hot ethanol insoluble matter is equivalent to ISO56/11-19791b.
2 Reagents
The determination of color index is equivalent to ISO56/11-1979, the determination of wax
equivalent to ASTMD29--1973
Testing of rosin
Testing of orpiment
Determination of ash
equivalent to ASTM D 29—1973;
Equivalent to ISO56/11-—1979;
Equivalent to ISO56/11—1979,
Determination of water-soluble matter and acid and alkalinity test of water extracts are equivalent to ISO56/11-1979, determination of heat hardening time is equivalent to JISK5909—1962 equivalent to ISO56/11-19793
Determination of acid value
Determination of iodine value
Hanus method of the Federal Republic of Germany ; The determination of chlorine content is equivalent to ISO56/11-19793. The determination of cold ethanol soluble matter is equivalent to JISK5909-19623. The determination of softening point is equivalent to JISK5909-1962; The determination of inorganic acid is equivalent to ISO56/11-1979 and BS3722-1964. The test of free chlorine or peroxide is equivalent to ISO56/11-1979. 2.1 Purity of reagents
Unless otherwise specified, all tests must use A and R analytical grade reagent chemicals. 2.2 Purity of water
Unless otherwise specified, when water is used, it refers to distilled water. 3 Determination of volatile matter (water content)
3.1 Method—(Arbitration method)
3.1.1 Method overview
The determination of volatile matter (water content) is to treat the sample under specified conditions and calculate the percentage of volatile matter (water content) according to the weight loss of the sample.
3.1.2 Apparatus
a, weighing bottle with a diameter of 5 cm and a height of 3 cmz
Approved by the Ministry of Forestry of the People's Republic of China on November 12, 1987 130
Kuan Feiguang
Implemented on May 1, 1988
Vacuum dryer
3.1.8 Reagents
Diameter 15 cm.
Sulfuric acid (GB 625—77): chemically pure.
GB 8143--87
3.1.4 Determination procedure
Weigh more than 2 grams of sample that has passed through a 40-mesh sieve (accurate to 0.0002g), place it in a weighing bottle that has been weighed at 40±2℃ beforehand, put it in a 40±2℃ oven to dry for 4 hours, take it out and place it in a concentrated sulfuric acid dryer, and weigh it after continuous drying under vacuum for 18 hours. Calculation:
Water content (%)
Where: A——Weight of weighing bottle plus sample, g, B—Weight of weighing bottle plus sample after drying, g,
G—Weight of sample, g.
The difference between two parallel determination results shall not be greater than 0.2%. 3.2 Method 2
3.2.1 Overview of the method Same as method 1.
3.2.2 Instruments
a. Weighing bottle
b. Desiccator
diameter 5cm, height 3cm,
diameter 15cm.
3.2.3 Determination Procedure
Weigh 2g of sample (accurate to 0.0002g) that has passed through a 40-mesh sieve, place it in a weighing bottle that has been weighed at 40±1℃ beforehand, put it in a 40±1℃ oven to dry for 6h, take it out and put it in a silica gel desiccator to cool to room temperature and weigh it. Calculation:
Water content (%)
Where: A-—Weight of weighing bottle plus sample, g; B—Weight of weighing bottle plus sample after drying, g3
G—Weight of sample, g.
The difference between two results of parallel determination shall not be greater than 0.2%. 4 Determination of hot ethanol insoluble matter
4.1 Method 1 (Arbitration method)
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4.1.1 Method overview
Use 95% ethanol to heat and extract a known weight of shellac sample. The hot ethanol insoluble matter of shellac is expressed as the percentage of insoluble residue. 4.1.2 Apparatus
Extractor, see Figure 1,
Quick qualitative filter paper, diameter 12.5 cm, pre-extracted with hot ethanol, b.
Cotton thread or thin copper wire, the cotton thread is pre-extracted with hot ethanol; c.
Beaker, 150 mL,
Weighing bottle, tall type, diameter 3.5 cm, height 7 cm. 131
4.1.3 Reagents
450 standard mill
95% ethanol (GB679-80).
4.1.4 Measurement procedures
GB 8143—87
Length 32-36
Two holes 3
Two hooks symmetrical
Figure 1 Extractor
1—Condenser, 2—Siphon, 3—Flask Two holes symmetrical
Weigh 2g of sample that passed 40 self-sieve (accurate to 0.0002g), wrap it tightly with filter paper that has been weighed at 100±2℃ (the thread, filter paper and weighing bottle are weighed at the same time) and tie it up with thread, put this paper bag in a 150mL beaker, add ethanol to immerse the paper bag, put it in a water bath and heat it to boiling for not less than 30 minutes to dissolve the sample completely, immediately move this paper bag to the siphon cup of the extractor, and heat it with 100mL ethanol for extraction for 4h. When the ethanol fills the cup, the paper bag should be kept below the liquid surface and extracted quickly (the extractor is immersed in a boiling water bath). After extraction, take out the paper bag, put it in a weighing bottle, place it in an oven at 100±2℃ to dry for 2h, take it out and place it in a desiccator to cool to room temperature and weigh it. Repeat the drying for 1h, cool to room temperature and weigh it. Until the difference between the two weights does not exceed 0.0010g. Calculation:
GB 8143—87
Hot ethanol insoluble matter (%) =
wire, filter paper, residue plus weighing bottle weight, g, where: A-
wire, filter paper plus weighing bottle weight, g,
-sample weight, g.
The difference between two parallel determination results shall not be greater than 0.1%. 4.2 Method 2
4.2.1 Method Overview
Same as the method
4.2.2 Apparatus
Gooch crucible, volume 25-30mL,
Beaker, 100mL,
Filter bottle, 500mL
Medium-speed qualitative filter paper.
4.2.3 Reagents
95% ethanol (GB 679-80).
4.2.4 Determination Procedure
× 100
Weigh 1g of sample that has passed through a 40-mesh sieve (accurate to 0.0002g), place it in a beaker, add 40mL of ethanol, heat it in a water bath to dissolve, and after it is completely dissolved, pour it into a Gooch crucible that has been weighed constant at 100±2℃ and has filter paper placed on it, and filter it by suction, and wash the residue with hot ethanol until the filtrate is colorless. Take it out and rinse the outside. Put it in an oven at 100±2℃ and dry it for 1h. Take it out and put it in a desiccator to cool it to room temperature and weigh it. Repeat the drying for 30min, cool it to room temperature and weigh it. Until the difference between the two weights does not exceed 0.0008g. Calculation:
Hot ethanol insoluble matter (%)
-Gooch crucible weight, g,
Where: A-
B Gooch crucible weight, g,
G——sample weight, g.
The difference between two parallel determination results shall not be greater than 0.1%. 5 Determination of color index
5.1 Overview of the method
Compare the color of the filtered shellac ethanol solution with the color of the iodine standard solution, dilute the darker solution until the colors of the two solutions are equal to determine the corresponding color index. 5.2 Apparatus
Colorimetric tube, 25 or 50mL,
Ground-mouth conical flask, 50mL,
Glass funnel, 6cm diameter
Pipette, 1, 5 and 25mL,
Volume flask, brown 100mL,
Quick qualitative filter paper:
Iodine value bottle 250mL
Graduating cylinder 10 and 100mL.
5.3.1 95% ethanol (GB 679-80);
5.3.2 Iodine (GB 675-77);
5.3.3 Potassium iodide (GB1272-77);
5.3.4 Hydrochloric acid (GB 622-77).
5.3.5 Preparation steps of 0.1N iodine solution
GB 8143-87
5.3.5.1 Weigh 35g potassium iodide and 13g iodine tablets, dissolve in 100mL water, stir well, wait until the iodine is completely dissolved, add 3 drops of concentrated hydrochloric acid and 900mL water, shake well, and store the solution in a brown bottle for later use. Store in a cool and dark place. 5.3.5.2 Accurately take 25mL of the above iodine solution, add 100mL of distilled water and 5mL of 0.1N hydrochloric acid respectively, and titrate with 0.1N sodium thiosulfate standard solution. When it is close to the end point (the solution is pale yellow), add 2mL of 0.5% starch indicator, and continue to titrate until the blue color just disappears. At the same time, take another 100mL of distilled water and 5mL of 0.1N hydrochloric acid, and titrate as above, and correct the volume of sodium thiosulfate consumed. Adjust the concentration to 0.1000N according to the calibration results. Calculate:
h: N-
equivalent concentration of iodine solution;
volume of iodine solution, mL,
- volume of sodium thiosulfate standard solution consumed by blank, mL; V- volume of sodium thiosulfate standard solution consumed by sample, mL, N, equivalent concentration of sodium thiosulfate standard solution. 5.3.6 Preparation of 0.005N iodine standard solution
Use a pipette to accurately draw 5mL of 0.1N iodine standard solution, place it in a 100mL brown volumetric flask, dilute it to the mark with distilled water, and shake it well. The color index of this solution is equivalent to 5. 5.3.7 Preparation of 0.001N iodine standard solution
Use a pipette to draw 1mL of 0.1N iodine standard solution, place it in a 100mL brown volumetric flask, dilute it to the mark with distilled water, and shake it well. The color index of this solution is equivalent to 1.
5.4 Determination Procedure
5.4.1 Determination of Color Index of Dark (5* and above) Shellac Products Weigh 2g of sample crystals that have passed through a 40-week sieve (accurate to 0.001g), place in a conical flask, accurately add 20mL of ethanol, plug the flask tightly and shake. After the shellac is completely dissolved, filter quickly, discard the first few drops, and use a pipette to draw 5mL into a colorimetric tube. Take about the same volume of newly prepared 0.005N iodine standard solution into another colorimetric tube. The diameter and transmittance of the two colorimetric tubes should be consistent. Place the two colorimetric tubes on a fluorescent lamp colorimetric stand for colorimetric comparison, use a burette to add ethanol to the shellac solution, and shake the colorimetric tubes until the color of the shellac solution is the same as that of the iodine standard solution.
Calculation:
Color index (number) = number of milliliters of ethanol added + 5 The difference between the two results of the determination shall not be greater than number 1. 5.4.2 Determination of color index of light-colored (less than 5*) shellac products (6)
Use a pipette to draw 5 mL of decolorized or bleached shellac solution (prepared in the same way as for shellac sheets) into a colorimetric tube, and take the same volume of newly prepared 0.001N iodine standard solution into another colorimetric tube. The diameter and transmittance of the two colorimetric tubes should be consistent. Place the two colorimetric tubes on a fluorescent lamp colorimetric stand for colorimetric comparison. If the color of the sample is lighter than that of the standard solution, use a burette to add distilled water to the iodine standard solution until the colors of the two tubes are the same; if the color of the sample is darker than that of the standard solution, add ethanol to the shellac solution until the colors are the same. Calculation:
Where: V
GB 8143-87
Color index (number)
The volume of ethanol added to the shellac solution, mL
The volume of distilled water added to the iodine standard solution, mL. The difference between two parallel determination results shall not exceed 0.2. 6
Determination of wax
6.1 Method Overview
Dissolve a certain amount of shellac in a hot solution of sodium carbonate. After cooling, separate the wax by filtration and then extract it with a solvent. This is a general method for determining wax.
6.2 Instruments
Beaker, 250mL,
Table l, diameter 5-7cm;
Soxhlet extractor, 150mL,
Glass funnel, true diameter 9cm.
Anhydrous sodium carbonate (GB639-77)),
Carbon tetrachloride (GB688-79).
Determination procedure
Weigh 10g of the sample that has passed through a 40-round sieve (accurate to 0.001g), put it in a beaker, add 150mL of hot water containing 2.5g of sodium carbonate, heat it in a boiling water bath, and stir. After the sample is dissolved, heat it for another 2-3 hours without stirring. Take the beaker out of the water bath and cool it to room temperature. A layer of wax will appear on the surface of the solution. Filter it with qualitative filter paper extracted with carbon tetrachloride, wash it with water until the filtrate is colorless, take out the filter paper and put it in an oven at 60±2℃ to dry out the moisture, then wrap it with a piece of filter paper (extracted with carbon tetrachloride), tie it tightly, and put it in a Soxhlet extractor that has been weighed at 100±2℃ beforehand. Use carbon tetrachloride to extract the wax, extract it for 4 hours, recover the carbon tetrachloride in the extraction bottle, put it in an oven t, dry it at 100±2℃ for 30 minutes, cool it to room temperature in a desiccator t and weigh it. Repeat the drying for 30 minutes, cool it to room temperature and weigh it. The difference between the two weights before and after is no more than 0.002g. Calculation:
Wax content (%) =
Formula: A-
Weight of wax added to an extraction bottle, g,
Weight of extraction bottle B, g,
× 100
Weight of a sample, g.
The difference between two parallel determination results shall not be greater than 0.2%. For dewaxed glue, the difference between two parallel determination results shall not be greater than 0.03%.
7 Test for rosin (Liebermann-Storch reaction) 7.1 Method overview
The acetic anhydride solution of rosin containing shellac will immediately produce a purple color that is easy to disappear when it encounters sulfuric acid. This reaction can be used to test the rosin in paint, resin and tall oil fatty acids.
7.2 Instrument
Porcelain drip plate.
7.3 Reagents
Acetic anhydride (GB677+78),
Sulfuric acid (GB625—77)
GB 8143--87
Sulfuric acid reagent: Slowly add 35.7mL of concentrated sulfuric acid into 34.7mL of water, cool to room temperature, and store in a bottle with a glass stopper. 7.4 Determination procedure
Put about 0.01g of powdered sample into the concave part of a white porcelain drop plate, add about 1mL of acetic anhydride and let it dissolve for a while, then add a drop of sulfuric acid reagent. If it contains rosin, a purple color that disappears easily will appear immediately. At the same time, compare it with a control sample containing rosin to determine whether the color of the sample is produced by the rosin in the sample. 8 Test for orpiment
8.1 Method Overview
If the lac sheet contains orpiment, it will have an opaque yellow appearance; if the lac sheet does not contain dirt, even a trace of orpiment can be precipitated from ethanol.
8.2 Apparatus
Conical flask, ground mouth, 50mL.
8.3 Reagents
95% ethanol (GB 679-80).
8.4 Determination Procedure
Weigh 4g of the sample that has passed through a 40-mesh sieve, place it in a conical flask, add 20mL of ethanol that is preferably cooled to 0℃, dissolve it, let it stand, and orpiment will be deposited at the bottom of the flask. The presence of yellow particles indicates the presence of orpiment. 9 Determination of ash
9.1 Method Overview
Using ashing method to completely destroy organic matter is an applicable method for determining the ash content of lac. As long as the temperature is strictly controlled, satisfactory results can be obtained.
9.2 Apparatus
Porcelain crucible, 30mL. wwW.bzxz.Net
9.3 Determination procedure
Weigh 3g of sample that has passed through a 40-mesh sieve (accurate to 0.0002g), put it into a porcelain crucible that has been calcined to constant weight at 500-550℃ in advance, first carbonize it completely at low temperature, then move it into a Muffle furnace, calcine it at 500-550℃ for 1h, until it is completely ash-coated, take it out and cool it slightly, put it in a desiccator to cool it to room temperature and weigh it. Repeat the calcination for 30min, cool it to room temperature and weigh it. Until the difference between the two weights does not exceed 0.0005g. Calculation:
Ash content (%)
Where: A-
Add the weight of the residue, g
B—empty crucible weight, g;
G——sample weight, g.
The difference between two parallel determination results shall not exceed 0.05%. 10 Determination of water-soluble matter and acid and alkalinity test of water extract 10.1 Method overview
Powdered shellac is treated with water under specified conditions to extract the water-soluble matter, filter it, and evaporate the filtrate to calculate the weight of the water-soluble matter. The filtrate should be neutral to methyl red and bromothymol blue respectively. 10.2 Instruments
Erlenmeyer flask, with stopper,
Beaker, 150mL,
Glass funnel, 6cm in diameter;
Volume flask, 100mL.
GB 8143-87
Methyl red (HG3958-76): indicator, 0.1g dissolved in 100mL.60% ethanol, bromothymol blue (HG3-1222-79): indicator, 0.05g dissolved in 100mL20% ethanol. 10.4 Determination procedures
Weigh 10g of sample that passes through a 60-mesh sieve (accurate to 0.001g), put it into a conical flask, add 80mL of water, shake it intermittently, leave it at room temperature for 4h, and filter it. Wash the filter residue with 20mL of water several times, collect the filtrate and washing liquid in a 100mL volumetric flask, add water to the scale, and shake it well. Take 50mL of filtrate and put it into a beaker that has been kept at a constant weight at 100±2℃, evaporate it on an electric stove or hot plate, put the beaker in an oven at 100±2℃, dry it for 1h, take it out, put it in a desiccator to cool it to room temperature and weigh it. Repeat the drying for 30min, cool it to room temperature and weigh it. Until the difference between the two weights does not exceed 0.001g. Calculate:
Water-soluble matter (%)
Where: A
-beaker plus residue weight, gz
B-—beaker weight, g,
G—sample weight, g,
V—filtrate volume, 50mL.
The difference between two parallel determination results shall not be greater than 0.05%. AB
× 100 × 100
If used for calculating the water-soluble content of bleached glue with a water content greater than 2, the following formula is used: AB
Water-soluble content (%) = × G(1-m)
Wherein: m is the water content of the sample, expressed as a decimal. 10.5 Test of acidity and alkalinity of water extract
× 100 × 100
From the remaining filtrate, take 2 20mL and put them into two test tubes respectively. Add a few drops of methyl red to one test tube and no red color should appear. Add a few drops of bromothymol blue to another test tube and no blue color should appear. If tested with an acidometer, the pH is 5.4-7.0. 11 Determination of heat hardening time (heat life) 11.1 Overview of the method
Lac dehydrates and polymerizes when heated. The heat hardening time is the time required for the polymerization of lac under specified conditions. 11.2 Instruments
The heat hardening time measuring instrument is shown in Figure 2,
Electric furnace, 1kW with adjustable transformer,
Thermometer, 150～200℃, each scale is 0.1℃; stopwatch, each scale is 0.2s.
Measurement procedure
Weigh 0.05g (accurate to 0.001g) of the sample that has passed through the 40 sieve, and evenly put it into the copper block of the heat hardening measuring instrument at a temperature of 170±0.5℃. When the sample is completely melted, press the stopwatch immediately. The measuring needle is about 30° at the same angle as the horizontal plane, and the needle tip is used to stir at a speed of 60 revolutions per minute. When approaching the end point, the needle tip is often used to stir the sample. When the measuring needle can lift the sample off, it is the end point. At the same time, quickly stop the stopwatch. The time recorded by the stopwatch is the heat hardening time. Each sample is measured 2 to 3 times, and the shorter time of the two times with a difference of less than 5s shall be taken as the standard. If the difference exceeds 5
Thermometer
12 Determination of acid value
Method overview
GB 8143—87
, re-measure until it meets the requirements.
Measurement plate
Measurement plate
Temperature regulator
Part A is embedded in Part B static fit
Part A material: brass
Part B material: ordinary carbon steel
All83y
Figure 2 Heat hardening time measuring device and device diagram
Use potassium hydroxide ethanol standard solution to titrate the ethanol solution of shellac film, and use basic blue 6B as an indicator. 12.2 Apparatus
Conical flask, ground mouth, 250mL;
b. Burette, basic type, 25mL.
12.3 Reagents
95% ethanol (GB679-80),
Potassium hydroxide (GB1919-80): 0.1N ethanol standard solution, basic blue 6B indicator: weigh 1g basic blue 6B (weigh to 0.01g), add 10mL distilled water, wait until most of it is dissolved, c.
Add 40mL ethanol and reflux on a water bath for 1h, filter after cooling, if necessary, the boiled precipitate should be neutralized with 0.05N potassium hydroxide ethanol solution or 0.05N hydrochloric acid until the blue color is restored after cooling.
12.4 Determination procedures
GB 8143-87
Until adding 1-2 drops of the above alkaline solution can make the indicator solution change from blue to light red, and weigh 0.25-0.3g (weighed to 0.0001g) of the sample that passes through the 40-sieve in a cold 250mL conical flask, add 50mL of ethanol to dissolve it, add 3-5 drops of alkaline blue 6B indicator, and titrate with 0.1N potassium hydroxide ethanol standard solution until purple-red appears as the end point. At the same time, make a blank test.
Calculation:
Acid value (mgKOH/g)
(V - V.) N× 56.11
Where: V—volume of potassium hydroxide standard solution consumed by the sample, mL, V. —Blank consumption volume of potassium hydroxide standard solution, mL; N—equivalent concentration of potassium hydroxide standard solution, G———sample weight, g3
56.11-The number of milligrams of potassium hydroxide contained in 1mL potassium hydroxide standard solution. The difference between two parallel determination results shall not be greater than 2.13 Determination of iodine value
13.1 Method overview
Organic compounds containing double bonds or triple bonds in their molecules are called unsaturated compounds, which can produce "addition reactions". In organic quantitative analysis, it is based on this special property of unsaturated compounds that the addition method is used to determine their content, which is generally expressed as "iodine value". 13.2 Instruments
Iodine value bottle, 500mL,
Pipette, 20mL,
Pipette, with scale, 5mL
Graduating cylinder, 10, 50 and 100mL.
Glacial acetic acid (GB 676-78);
Iodine (GB 675-77)*
Bromine (GB 1281—77);
Sodium thiosulfate (GB 637-77): 0.1N standard solution Potassium iodide (GB1272-—77): 10% solution 0.2N iodine bromide Glacial acetic acid solution: Weigh 13g iodine (accurate to 0.01g), dissolve in 900mL glacial acetic acid (slightly heat to promote iodine dissolution), after cooling, accurately add 2.60mL bromine solution, transfer to a 1000mL volumetric flask, and dilute to the mark with glacial acetic acid. Store in a brown glass bottle for later use. Store in a cool and dark place. 13.4 Determination Procedures
Weigh 0.25-0.3g (accurate to 0.0002g) of the sample that has passed through a 40-mesh sieve, place it in a 500mL iodine value bottle, add 10mL glacial acetic acid, wait for the sample to dissolve, accurately add 20mL of 0.2N iodine bromide glacial acetic acid solution, plug the bottle tightly, shake well, seal the bottle mouth with a small amount of potassium iodide solution (do not allow it to flow into the bottle), and let it stand in a dark place for 30 minutes. Then, gradually pour 15mL of 10% potassium iodide solution into the bottle mouth, gently turn the bottle stopper to allow the potassium iodide solution to slowly flow into the bottle, shake well, open the bottle stopper, add 50mL of distilled water, titrate with 0.1N sodium thiosulfate standard solution to light yellow, add 2mL of 1% starch indicator, shake vigorously, and drop until the blue color just disappears. Perform a self-test under the same conditions.
Calculation:
武t:V
GB 8143-87
Iodine value (gl/100g) =
(V.-V) Nx 126J9
G×1000
Blank volume of sodium thiosulfate standard solution consumed, mL; Sample volume of sodium thiosulfate standard solution consumed, mL; Equivalent concentration of sodium thiosulfate standard solution; Sample weight, g,
Gram equivalent of iodine.
The difference between two results of parallel determination shall not be greater than 1. 14 Determination of fluorine content
14.1 Method overview
·(13)
The quality and stability of bleaching glue are closely related to the presence of chlorine. The bleaching glue is treated with metallic sodium to convert all chlorine into soluble chlorides, which are determined by volumetric method.
14.2 Instruments
Erlenmeyer flask, ground mouth, 250 and 500mL,
Pipette, 10mL,
Condenser, spherical,
Metallic sodium: block;
Nitric acid (GB 626-78): 1:4 solution, Silver nitrate (GB670-77): 0.1N solution; Ether (HG3-1002-76);
Potassium thiocyanate (GB 648-78): 0.1N standard solution; Ammonium ferric sulfate (GB1279-77): indicator, saturated solution acidified with nitric acid. Determination procedure
Weigh 0.5g of the sample that has passed through a 40-mesh sieve (accurate to 0.0002g), put it in a 250mL conical flask, add 50mL of anhydrous ethanol, install a condenser, heat and reflux on a water bath, until all the sample is dissolved, and add about 1g of newly cut sodium blocks of about 3mm from the top of the condenser piece by piece. After the reaction is complete and all the sodium is dissolved, remove the condenser, add 50mL of water, transfer the solution to a 500mL conical flask, rinse with 50mL of water 23 times, evaporate the solution on a water bath until the volume is reduced by half to remove the ethanol, cool it, and add dilute nitric acid until the solution is slightly acidic. Use a pipette to add 10mL of silver nitrate solution, 2mL of ether and 1mL of ammonium ferric sulfate solution, and shake vigorously to coagulate the precipitate. Titrate the remaining silver nitrate with potassium thiocyanate standard solution until a persistent light reddish brown color appears. At the same time, do a blank test. Calculation:
Chlorine content (%) =
Formula: Vo-
(V-Vo) N×0.03546
-Volume of potassium thiocyanate standard solution used for blank test, mL; -Volume of potassium thiocyanate standard solution used for sample test, mLN
Equivalent concentration of potassium thiofluoride standard solution, G——sample weight, g
0.03546—Number of grams of fluorine equivalent to each milligram equivalent of potassium thiofluoride. The difference between two parallel determination results shall not exceed 0.1%. 140
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15 Determination of cold ethanol soluble matter
15.1 Method overview
GB 8143--87
The determination of substances soluble in cold ethanol is to determine the soluble resin content in shellac sheets. Dissolve the shellac flakes with cold ethanol, filter to remove impurities, and evaporate the ethanol. Then the content of shellac resin can be weighed and determined. 15.2 Instruments
a. Beaker, 250mL,
b. Conical flask, 100mL
c. Glass funnel, 6cm in diameter,
d. Rapid qualitative filter paper.
15.3 Reagents
95% ethanol (GB 679-80).
15.4 Determination procedure
Weigh 1g of sample that passes through a 40-mesh sieve (accurate to 0.0002g), put it into a conical flask, add 60mL of ethanol, plug the flask and shake it continuously until it is completely dissolved. Use a conical funnel to filter into a beaker that has been kept at a constant weight at 100±2℃. Wash the residue and filter paper repeatedly with ethanol until the filtrate is colorless. Place the beaker on a water bath to evaporate to dryness, then move it to a 100±2℃ oven and dry it for 1h. Take it out and place it in a desiccator to cool it to room temperature and weigh it. Repeat the desiccating for 30min, cool it to room temperature and weigh it. Until the difference between the two weights does not exceed 0.0020g. Calculate:
Cold ethanol soluble matter (%)
Where: A-
Weight of beaker with cold ethanol soluble matter, g,
Weight of beaker, g2
Weight of sample, g.
The difference between two parallel determination results shall not be greater than 1%. AB
If the moisture content of the sample is greater than 2, the moisture content should be substituted in the calculation formula, calculated based on the absolute dry material. Cold ethanol soluble matter (%) =
Formula ih: m-
The moisture content of the sample, expressed as a decimal. 16 Determination of softening point
G(1-m)
（15）
（16)
16.1 Method overview
Lac is a mixture of polyhydroxycarboxylic acids. The softening point measured is only the average softening point of the mixture. It is generally determined by the ring and ball method. 16.2 Instruments
a. Softening point tester, see Figure 3;
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