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GB 25559-2010: The national food safety standards of food additives calcium dihydrogen phosphate
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Basic data | Standard ID | GB 25559-2010 (GB25559-2010) | | Description (Translated English) | The national food safety standards of food additives calcium dihydrogen phosphate | | Sector / Industry | National Standard | | Classification of Chinese Standard | X42 | | Classification of International Standard | 67.220.20 | | Word Count Estimation | 14,171 | | Date of Issue | 2010-12-21 | | Date of Implementation | 2011-02-21 | | Regulation (derived from) | Ministry of Health Bulletin No. 19 of 2010 | | Issuing agency(ies) | Ministry of Health of the People's Republic of China | | Summary | This Chinese standard applies to dicalcium phosphate, tricalcium phosphate, lime or calcium carbonate with one prepared by the reaction of thermal phosphoric acid food additive calcium phosphate. | GB 25559-2010: The national food safety standards of food additives calcium dihydrogen phosphate
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The national food safety standards of food additives calcium dihydrogen phosphate
National Food Safety Standard
Food additive calcium dihydrogen phosphate
Issued on. 2010-12-21
2011-02-21 implementation
National Standards of People's Republic of China
People's Republic of China Ministry of Health issued
Foreword
Appendix A of this standard is a normative appendix.
National Food Safety Standard
Food additive calcium dihydrogen phosphate
1 Scope
This standard applies to calcium hydrogen phosphate, tricalcium phosphate, calcium carbonate or milk of lime and one thermal phosphoric acid prepared by the reaction of phosphoric acid food additives
Monocalcium.
2 Normative references
The standard file referenced in the application of this standard is essential. For dated references, only the edition date of the note
Apply to this standard. For undated references, the latest edition (including any amendments) applies to this standard.
3 formula and relative molecular mass
Formula 3.1
Dihydrogen phosphate anhydrous calcium. Ca (H2PO4) 2
Dihydrogen phosphate monohydrate Ca. Ca (H2PO4) 2 · H2O
3.2 relative molecular mass
Anhydrous calcium phosphate monobasic. 234.05 (according to 2007 international relative atomic mass)
Calcium dihydrogen phosphate monohydrate. 252.07 (according to 2007 international relative atomic mass)
4. Technical Requirements
4.1 Sensory requirements. comply with Table 1.
Table 1 Sensory requirements
Project requires test methods
Colorless or white color proper amount of sample is placed in 50mL beaker, observe the color in natural light
And texture. State organization triclinic crystal or powder
4.2 Physical indicators. to comply with Table 2.
Table 2. Physical and chemical indicators
Item Index Test Method
Dihydrogen phosphate, calcium (Ca to count), w /%
Anhydrous 16.8 ~ 18.3
Appendix A A.4
Monohydrate 15.9 ~ 17.7
Heavy metals (Pb)/(mg/kg) ≤ 10 Appendix A A.5
Lead (Pb)/(mg/kg) ≤ 2 Appendix A A.6
Arsenic (As)/(mg/kg) ≤ 3 Appendix A A.7
Table 2. Physical and chemical indicators (cont.)
Fluorides (as F)/(mg/kg) ≤ 25 Appendix A A.8
LOI a, w /% 14.0 ~ 15.5 Appendix A, A.9
Loss on drying b, w /% ≤ 1 Appendix A A.10
Clarity through test A.11 in Appendix A
Carbonate by test A.12 in Appendix A
Free acid and auxiliary salt by test A.13 in Appendix A
Anhydrous measurement project.
Monohydrate measurement project.
Appendix A
(Normative)
Testing method
A.1 Warning
Reagents used in this test method are toxic or corrosive, be careful when operating! As should be immediately washed with water splashed on the skin
Wash, severe cases should be treated immediately. Use virulent, should be strictly managed in accordance with relevant regulations; should be used to avoid inhalation or contact with the skin, will
Should be carried out in a fume hood, exposed parts of a person can not touch the wound.
A.2 General Provisions
This standard reagents and water, did not indicate when the other requirements, refer to three analytical reagent and GB/T 6682-2008 specified in
water. Used in the test standard titration solution, impurity standard solution, preparations and products, did not indicate when the other requirements, according to HG/T 3696.1,
HG/T 3696.2, the provisions of HG/T 3696.3 of preparation.
A.3 Identification Test
A.3.1 Reagents and materials
A.3.1.1 nitric acid solution. 18.
A.3.1.2 ammonia solution. 11.
A.3.1.3 silver nitrate solution. 20 g/L.
A.3.1.4 ammonium oxalate solution. 33 g/L.
A.3.2 Analysis step
A.3.2.1 Identification of calcium ions
It weighs about 0.1 g sample add 20 mL of water after shaking filtered and the filtrate was added 5 mL of ammonium oxalate solution, a white precipitate.
A.3.2.2 Identification of phosphate
Weigh about 1g sample was dissolved in 20 mL of water, adding a silver nitrate solution to form a yellow precipitate, this precipitate was dissolved in nitric acid solution or aqueous ammonia solution
liquid.
A.4 Determination of calcium dihydrogen phosphate
A.4.1 redox titration (Arbitration Act)
A.4.1.1 Method summary
Sample was dissolved with hydrochloric acid, ammonium oxalate is added after pH was adjusted with aqueous ammonia solution, boiled in a boiling water bath to produce calcium oxalate precipitation,
Titration with potassium permanganate standard solution of calcium oxalate precipitation titration, the results.
A.4.1.2 Reagents and materials
A.4.1.2.1 hydrochloric acid solution. 1 + 3.
A.4.1.2.2 ammonium oxalate solution. 33 g/L.
A.4.1.2.3 washing solution. 10 mL of ammonium oxalate solution was diluted with water to 1000 mL.
A.4.1.2.4 ammonia solution. 1 + 1.
A.4.1.2.5 sulfuric acid solution. 1 + 6.
A.4.1.2.6 standard potassium permanganate titration solution. c (1/5KMnO4) ≈0.1 mol/L.
A.4.1.2.7 methyl orange indicator solution. 1 g/L.
A.4.1.2.8 methyl red indicator solution. 1 g/L.
A.4.1.3 instruments and equipment
A.4.1.3.1 constant temperature water bath.
A.4.1.3.2 sand glass crucible. aperture 5 μm ~ 15 μm.
A.4.1.4 analysis step
Weigh about 0.5 g samples, accurate to 0.000 2 g, placed in 250 mL beaker, add 10 mL of hydrochloric acid solution so as to dissolve the sample, add
3 drops of methyl orange indicator solution, boiled for 5 min. If necessary, addition of hydrochloric acid solution or boiling water in the course of the pH of the test solution and the volume
constant. Add 2 drops of methyl red indicator solution, 30 mL ammonium oxalate solution, followed by aqueous ammonia solution was added dropwise with stirring until the pink solution of
Just disappeared. The beaker was placed in boiling water bath tank 30 min, cooled to room temperature. Precipitant settlement, by decantation the upper layer in a clean
Drying sintered glass crucible by suction filtration, washed with 30 mL of cold liquid (20 ℃ or less) in the beaker was washed precipitate, washing liquid was transferred to a sintered glass crucible
Crucible filtration, washing was repeated until all of the precipitate was transferred to a sintered glass crucible, and finally with 10 mL each of water and washed twice. The glass crucible into the burning sand
Cup, add 100 mL of water and 50 mL sulfuric acid solution was added 35 mL burette with potassium permanganate standard titration solution, stirring to eliminate color
Loss, heated to about 70 ℃, titration with potassium permanganate standard solution titration until the solution was pink, and does not disappear shall end within 30 s.
At the same time a blank test.
In addition to the blank test without the sample, the addition of reagents and other operations of the kind and amount (other than the standard titration solution) with the same Test.
A.4.1.5 Calculation Results
Dihydrogen phosphate, calcium content of calcium (Ca) mass fraction w1 and its value is expressed in%, according to formula (A.1) calculated as follows. []
1000) 0
1 × - = m
cMVV
((A.1)
Where.
Numerical potassium permanganate titration V-- standard titration solution consumed by the solution volume in milliliters (mL);
Numerical standard potassium permanganate titration V0-- blank test solution consumed volume in milliliters (mL);
Accurate c-- potassium permanganate standard titration solution concentration value in units of moles per liter (mol/L);
m-- sample mass value in grams (g);
Calcium M-- value (1/2Ca) molar mass in grams per mole (g/mol) (M = 20.039).
Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.2%.
A.4.2 zinc sulfate back titration
A.4.2.1 Method summary
In the test solution, adding an excess of disodium EDTA standard titration solution, and calcium ion complexation, indicating the mixture to KB
Agent, zinc standard titration solution titrate excess of disodium edetate standard titration solution.
A.4.2.2 Reagents and materials
A.4.2.2.1 hydrochloric acid solution. 1 + 1.
A.4.2.2.2 ammonia - ammonium chloride buffer solution (A). pH≈10.
A.4.2.2.3 disodium EDTA standard titration solution. c (EDTA) ≈0.05 mol/L.
A.4.2.2.4 acid chrome blue K- naphthol green B mixed indicator solution (KB indicator solution).
A.4.2.2.5 zinc sulfate standard titration solution. c (ZnSO4 · 7H2O) ≈0.05 mol/L;
Preparation. Weigh 15 g zinc sulfate, dissolved in water, diluted with water to 1000 mL, shake.
Calibration. Pipette 25.00 mL zinc sulfate standard titration solution prepared, placed in a conical flask, add 10 mL of ammonia - ammonium chloride buffer solution (A)
And 75 mL of water, add about 0.02 g chrome black T indicator, with 0.05 mol/L disodium EDTA standard titration solution titrated to the solution
Purple to pure blue, and held 30 s does not fade, is the end. At the same time a blank test.
In addition to the blank test without the sample, the addition of reagents and other operations of the kind and amount (other than the standard titration solution) with the same Test.
The concentration of zinc sulfate standard titration solution according to the formula (A.2) Calculated.
c =
cVV 101) (- (A.2)
Where.
Numerical V1-- consumed titration Disodium EDTA standard titration solution volume in milliliters (mL);
Numerical V0-- blank test consumed disodium edetate standard titration solution volume in milliliters (mL);
Accurate c1-- disodium edetate standard titration solution concentration value in units of moles per liter (mol/L);
Numerical volume V-- Pipette zinc sulfate standard titration solution, in milliliters (mL).
A.4.2.3 analysis step
Weigh about 0.5 g samples, accurate to 0.000 2 g, placed in 100 mL beaker with a small amount of water wet, add 5 mL of hydrochloric acid solution so that the whole sample
Ministry of dissolution, all transferred to 250 mL volumetric flask, dilute with water to the mark. If necessary dry filter, discard before going 20mL filtrate.
Pipette 25.00 mL above test solution, placed in 500 mL conical flask, and then the other pipetted into 25.00 mL of ethylenediaminetetraacetic acid disodium
Sodium Standard Solution, add 50 mL of water, 10 mL of ammonia - ammonium chloride buffer solution (A) shake for 5 min. Add about 2 to 3 drops drops KB
Indicator solution, titration with zinc sulfate standard solution titration until the solution changed from blue to blue-violet, purple and held within 30 s does not fade, is the end.
At the same time a blank test.
In addition to the blank test without the sample, the addition of reagents and other operations of the kind and amount (other than the standard titration solution) with the same Test.
A.4.2.4 Calculation Results
Dihydrogen phosphate, calcium content of calcium (Ca) mass fraction w1 and its value is expressed in%, according to formula (A.3) calculated as follows. [] 01
) 1000
VV cM
- = ××
% (A.3)
Where.
Numerical zinc sulfate standard titration V0-- blank test solution consumed volume in milliliters (mL);
Numerical zinc sulfate standard titration solution consumed V1-- titration solution volume in milliliters (mL);
Accurate c-- zinc sulfate standard titration solution concentration value in units of moles per liter (mol/L);
m-- sample mass value in grams (g);
Numerical M-- calcium (Ca) molar mass of the units of grams per mole (g/mol) (M = 40.078).
Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.2%.
A.5 Determination of Heavy Metals
A.5.1 Reagents and materials
A.5.1.1 hydrochloric acid solution. 1 + 4.
A.5.1.2 sodium sulfide solution. This solution should be shading, stamped sealed in a brown bottle. Effective within three months after preparation.
A.5.1.3 Lead standard solution. 1 mL solution containing lead (Pb) 0.01mg;
Pipette 1.00 mL of lead standard solution according to HG/T 3696.2 requirements formulated and placed in 100 mL volumetric flask, dilute with water to the mark,
Shake well. The solution is using now.
A.5.1.4 other agents with GB/T 5009.74-2003 Chapter 3.
A.5.2 Instruments and Equipment
With GB/T 5009.74-2003 Chapter 4.
A.5.3 Analysis step
After weighing 2.00 g ± 0.01 g sample was placed in a 50 mL beaker, add 5 mL hydrochloric acid solution and 10 mL of water, dissolved by heating, cooling
Aqueous ammonia was added dropwise until a white precipitate appeared, then add a small amount of hydrochloric acid to precipitate disappears, if necessary, dried by filtration (washed with water 5 times). All were transferred to
50 mL colorimetric tube, add 5 mL of acetate buffer solution, mix, add 5 drops of sodium sulfide solution, and diluted with water to volume, and mix at
Dark place 5 min. The color was not be deeper than the standard colorimetric solution.
Color than the standard preparation solution. Pipette 2.00 mL of lead standard solution was placed in 50 mL colorimetric tube, add 25 mL of water, from the "plus 5 mL
Acetate buffer solution "began to operate simultaneously with the test solution the same treatment.
A.6 Determination of Lead
A.6.1 dithizone colorimetry (Arbitration Act)
A.6.1.1 Method summary
With GB/T 5009.75─2003 Chapter 2.
A.6.1.2 Reagents and materials
With GB/T 5009.75─2003 Chapter 3.
A.6.1.3 instruments and equipment
With GB/T 5009.75─2003 Chapter 4.
A.6.1.4 analysis step
Weigh 5.00 g ± 0.01 g sample was placed in 100 mL beaker, add 10 mL of water was dissolved, placed in a separatory funnel. Pipette pipette
1.00 mL of lead standard solution, placed in a separatory funnel, as a standard for the solution. The following according to GB/T 5009.75─2003 in Chapter 6
Provisions were measured.
A.6.2 Atomic absorption spectrophotometry
A.6.2.1 Reagents and materials
A.6.2.1.1 hydrochloric acid.
A.6.2.1.2 chloroform.
A.6.2.1.3 nitrate.
A.6.2.1.4 sodium hydroxide solution. 250 g/L.
A.6.2.1.5 Pyrrolidine dithiocarbamate (The APDC) solution. 2%;
Weigh 2 g Pyrrolidine dithiocarbamate (The APDC) was dissolved in 100 mL of water. If insoluble material filtered before use.
A.6.2.1.6 Lead standard solution. 1 mL solution containing lead (Pb) 0.010 mg;
Pipette 1.00 mL of lead standard solution according to HG/T 3696.2 requirements formulated and placed in 100 mL volumetric flask, dilute with water to the mark,
Shake well. The solution is using now.
A.6.2.1.7 precision pH test paper. pH0.5 ~ 5.0.
A.6.2.1.8 two Water. comply with GB/T 6682-2008 of.
A.6.2.2 instruments and equipment
A.6.2.2.1 separating funnel. 250 mL.
A.6.2.2.2 constant temperature water bath.
A.6.2.2.3 atomic absorption spectrophotometer.
A.6.2.3 analysis step
A.6.2.3.1 Determination of lead standard preparation and assay solutions
Pipette 2.00 mL of lead standard solution, placed in a 150 mL beaker, add 30 mL of water, 10 mL of hydrochloric acid, (surface covered dish) heating boiling
Teng 5 min, cooled, the solution was adjusted with a sodium hydroxide solution of pH 1.0 to 1.5 (pH paper with a precision test). The solution was transferred to a separatory funnel over
Bucket, diluted to about 200 mL. Added 2 mL of pyrrolidine dithio carbamate (APDC) solution, shake. With chloroform
Extracted twice, each added 20 mL, the extract (i.e., organic phase) was collected in a 50 mL beaker, (in a hood) with a bath heating
And evaporated to dryness. 3 mL of nitric acid was added to dissolve the residue, heated nearly dry. Was added 0.5 mL of nitric acid and 10 mL of water and heated to solution volume of 3
mL ~ 5 mL, transferred to 10 mL volumetric flask, dilute to the mark with water. Selection of air - acetylene flame at 283.3 nm wavelength, water transfer
Zero, measuring the absorbance of the solution.
Preparation and determination of sample measurement solutions A.6.2.3.2
Weigh 10.0 g ± 0.1 g sample is placed in a 150 mL beaker, add 30 mL of water, 10 mL of hydrochloric acid (surface covered dish) plus
Heat to dissolve the sample, and boiled 5 min. Then press A.6.2.3.1 from the "cooling with sodium hydroxide solution to adjust the pH," begins operating,
Measuring the corresponding absorbance values.
A.6.2.4 results found
Determination of the sample solution is not greater than the absorbance of lead standard measuring the absorbance of the solution.
A.7 Determination of Arsenic
A.7.1 Reagents and materials
A.7.1.1 hydrochloric acid solution. 1 + 1.
A.7.1.2 arsenic standard solution. 1 mL solution containing arsenic (As) 0.0010 mg;
Pipette 1.00 mL of arsenic standard solution according to HG/T 3696.2 requirements formulated and placed in 1000 mL volumetric flask, dilute with water to the mark,
Shake well. The solution is using now.
A.7.1.3 other agents with GB/T 5009.76-2003 Chapter 9.
A.7.2 Instruments and Equipment
With GB/T 5009.76-2003 Chapter 10.
A.7.3 Analysis step
Weigh 0.50 g ± 0.01 g sample was placed in a given arsenic bottle, add a small amount of water wet, add 5 mL of hydrochloric acid solution to dissolve the sample.
Limits formulated solution. Pipette 1.50mL [1mL solution of arsenic (As) 0.0010mg] arsenic standard solution with the same sample at the same time
deal with. The following press GB/T 5009.76-2003 Chapter 11 was measured.
A.8 Determination of fluoride
A.8.1 Reagents and materials
A.8.1.1 hydrochloric acid solution. 14.
A.8.1.2 total ionic strength buffer. sodium acetate solution was mixed with an equal amount of sodium citrate solution, and the solution using now.
A.8.1.3 sodium acetate solution. c (CH3COONa · 3H2O) = 3 mol/L;
Weigh 204 g of sodium acetate dissolved in about 300 mL of water, cooled, 1 mol/L acetic acid adjusted pH≈7.0, all transferred to 500 mL
Volumetric flask and diluted with water to the mark.
A.8.1.4 sodium citrate solution. c (Na3C6H5O7 · 2H2O) = 0.75 mol/L;
Weigh 110 g of sodium citrate, dissolved in about 300 mL of water, heightening acid 14 mL, all transferred to 500 mL volumetric flask, dilute with water
Release to the mark.
A.8.1.5 fluoride standard solution. 1 mL solution of fluorine (F) 0.010 mg;
Pipette 1.00 mL of fluoride standard solution according to HG/T 3696.2 requirements formulated and placed in 100 mL volumetric flask, dilute to the mark with water
Degree, shake. The solution now with the existing, stored in a polyethylene bottle.
A.8.2 Instruments and Equipment
A.8.2.1 fluorine electrode.
A.8.2.2 calomel electrode.
A.8.2.3 potentiometer.
A.8.2.4 magnetic stirrer.
A.8.3 Analysis step
A.8.3.1 Drawing standard working solution
Pipette fluoride standard solution 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, 5.00 mL were placed in five 50 mL volumetric flask
, Each of the hydrochloric acid solution was added 4 mL, add 25 mL of total ionic strength buffer, diluted with water to the mark.
A.8.3.2 Preparation of test solution
Weigh about 1.5 g samples, accurate to 0.01 g, was added 4 mL of hydrochloric acid solution, 25 mL of total ionic strength buffer, dissolved in 100
mL volumetric flask, dilute to the mark, shake.
A.8.3.3 Determination
The fluoride ion selective electrode and calomel electrode and the potentiometer negative and a positive terminal coupled to the electrode insert filled with water 50 mL polyethylene plastic beaker,
Preheat the instrument, on a magnetic stirrer with constant stirring, to read the value of the equilibrium potential, the replacement of electrodes immersed in water 2 to 3 times, to illustrate electrode
After a predetermined potential value of the book, to the standard working solution and the potential of the sample solution was measured.
Equilibrium potential fluoro standard working solution were measured from low to high concentrations. Electrode potentials as ordinate, the fluorine ion concentration (mg/mL)
As abscissa, the curve on semi-logarithmic graph paper.
The same method the equilibrium potential of the sample solution, the concentration of fluoride ions in the sample (mg/mL), isolated from the working curve.
A.8.4 Calculation Results
Fluoride content of fluorine (F) mass fraction w2 and its value in mg/kg according to formula (A.4) Calculated.
- ×
× =
cw (A.4)
Where.
Fluoride concentrations c-- value from the working curve of Richard, in milligrams per milliliter (mg/mL);
m - value the quality of the sample, in grams (g).
Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 10 mg/kg.
A.9 Determination of loss on ignition
A.9.1 Instruments and Equipment
A.9.1.1 porcelain crucible. 30 mL.
A.9.1.2 furnace temperature. The temperature can be controlled at 800 ℃ ± 50 ℃.
A.9.2 Analysis step
Was used at 800 ℃ ± 50 ℃ condition 30 min burning porcelain crucible, weighed approximately 1.5 g sample (anhydrous), accurate to 0.0002 g,
In a high temperature furnace at 800 ℃ ± 50 ℃ condition burning 30 min, then cool to room temperature, and weighed.
A.9.3 Calculation Results
LOI mass fraction w3 and its value is expressed in%, according to formula (A.5) Calculated.
0213 × - = m
mmw (A.5)
Where.
Numerical m1-- before burning the sample and crucible mass in grams (g);
After m2-- residue on ignition value and quality of the crucible in units of grams (g);
m-- sample mass value in grams (g).
Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.1%.
A.10 Determination of loss on drying
A.10.1 instruments and equipment
A.10.1.1 weighing bottle. Φ50 mm × 30 mm.
A.10.1.2 electric oven. the temperature can be controlled at 60 ℃ ± 2 ℃.
A.10.2 Analysis steps
Was used at 60 ℃ ± 2 ℃ 3 h dried weighing bottle, weigh about 1.5 g sample (monohydrate), accurate to 0.000 2 g, placed
In the electric oven at 60 ℃ ± 2 ℃ dried 3 h, then cool to room temperature, and weighed.
A.10.3 Calculation Results
Loss on drying mass fraction w4 and its value is expressed in%, according to formula (A.6) Calculated.
0214 × - = m
mmw (A.6)
Where.
Numerical quality prior m1-- dried sample and weighing bottle in grams (g);
Value quality m2-- after drying and weighing the sample bottles in grams (g);
m-- sample mass value in grams (g).
Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.1%.
A.11 Determination of Clarity
A.11.1 reagents and materials
A.11.1.1 hydrochloric acid.
A.11.1.2 nitrate solution. 1 + 2.
A.11.1.3 silver nitrate solution. 20 g/L.
A.11.1.4 chloride standard solution. 1 mL solution of chlorine (Cl) 0.010 mg;
Pipette 1.00 mL of chloride standard solution according to HG/T 3696.2 requirements formulated and placed in 100 mL volumetric flask, dilute to the mark with water
Degree, shake. The solution is using now.
A.11.2 instruments and equipment
Constant temperature water bath.
A.11.3 Analysis steps
Weigh 2.00 g ± 0.01 g sample was placed in a 50 mL beaker, add 18 mL of water and 2 mL of hydrochloric acid, heated in boiling water bath for 5 min
Dissolved. All transfer After cooling to 50 mL colorimetric tube, diluted with water to the mark. The turbidity of the solution was not greater than the standard turbidity solution
liquid.
Turbid than the standard preparation solution. Pipette 1.2 mL chloride standard solution, placed in 50 mL colorimetric tube, add 20 mL water, 1 mL Glass
Dilute acid solution, 1 mL of silver nitrate solution with water to the mark. Placed 15 min in the dark.
Determination A.12 carbonate
A.12.1 reagents and materials
hydrochloric acid.
A.12.2 Analysis steps
Weighed 2.0 g samples, accurate to 0.1 g, placed in a 50 mL conical flask, add 6 mL of boiling water, cooled solution of 2 mL of hydrochloric acid, again
Test solution should not have bubbles.
A.13 Determination of free acid and auxiliary salt
A.13.1 reagents and materials
A.13.1.1 sodium hydroxide solution. 1 mol/L.
A.13.1.2 methyl orange indicator solution. 1 g/L.
A.13.2 Analysis steps
Weigh 1.0 g samples, accurate to 0.1 g, placed in a mortar, add 3 mL of water lapping all transferred to a 250 mL beaker, add 100 mL
Water, shake, add 1 drop of methyl orange indicator solution, add 1 mL of sodium hydroxide solution, the test solution should be yellow.
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