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GB/T 10046-2018: PDF in English (GBT 10046-2018) GB/T 10046-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.160.50
J 33
Replacing GB/T 10046-2008
Silver brazing filler metals
银钎料
(ISO 17672:2016, Brazing - Filler metals, MOD)
ISSUED ON: MAY 14, 2018
IMPLEMENTED ON: DECEMBER 01, 2018
Issued by: State Administration for Market Regulation;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 4
1 Scope ... 7
2 Normative references ... 7
3 Model ... 8
3.1 Method of model preparation ... 8
3.2 Model example ... 8
4 Technical requirements ... 8
4.1 Product form ... 8
4.2 Chemical composition ... 9
4.3 Dimensions and tolerances ... 13
4.4 Supply status ... 15
5 Test methods ... 15
5.1 Chemical composition analysis of brazing filler metals ... 15
5.2 Mechanical property test of brazed and soldered joint ... 15
5.3 Wettability test of brazing filler metals ... 15
6 Inspection rules ... 16
6.1 Heat number division ... 16
6.2 Sampling method ... 16
6.3 Acceptance ... 16
6.4 Reinspection ... 16
7 Packaging, marking, quality certification ... 17
7.1 Packaging ... 17
7.2 Marking ... 17
7.3 Quality certification ... 17
Annex A (Informative) Structural changes of this Standard compared with ISO
17672:2016 ... 18
Annex B (Normative) Determination of silver content ... 19
Annex C (Normative) Determination of copper content - Electrolysis-
spectrophotometry ... 24
Annex D (Normative) Determination of zinc and cadmium content - EDTA
titration method ... 29
Annex E (Normative) Determination of nickel content ... 35
Annex F (Normative) Determination of tin content - Potassium iodate titration
method ... 43
Annex G (Normative) Determination of lithium content - Atomic absorption
spectrometry ... 48
Annex H (Normative) Determination of indium content ... 52
Annex I (Normative) Determination of aluminum content - Sodium fluoride
replacement -EDTA titration method ... 59
Annex J (Normative) Determination of manganese content ... 63
Annex K (Normative) Inductively coupled plasma atomic emission spectrometry
... 69
Annex L (Informative) Model comparison of brazing filler metals ... 79
Silver brazing filler metals
1 Scope
This Standard specifies the requirements such as model, technical
requirements, test methods, inspection rules, packaging, marking, quality
certification of silver brazing filler metals.
This Standard applies to silver brazing filler metals used in brazing methods.
2 Normative references
The following documents are indispensable for the application of this document.
For the dated references, only the editions with the dates indicated are
applicable to this document. For the undated references, the latest edition
(including all the amendments) are applicable to this document.
GB/T 6682 Water for analytical laboratory use - Specification and test
methods (GB/T 6682-2008, ISO 3696:1987, MOD)
GB/T 8170 Rules of rounding off for numerical values and expression and
judgement of limiting values
GB/T 11363 Test method of the strength for brazed and soldered joint (GB/T
11363-2008, ISO 5187:1985, NEQ)
GB/T 11364 Test method of wettability for brazing filler metals (GB/T 11364-
2008, ISO 5179:1983, NEQ)
GB/T 12806 Laboratory glassware - One-mark volumetric flasks (GB/T
12806-2011, ISO 1042:1998, NEQ)
GB/T 12808 Laboratory glassware - One mark pipettes
GB/T 12809 Laboratory glassware - Principles of design and construction of
volumetric glassware (GB/T 12809-2015, ISO 384:1978, NEQ)
GB/T 12810 Laboratory glassware - Volumetric glassware - Methods for use
and testing of capacity (GB/T 12810-1991, ISO 4787:1984, IDT)
6 Inspection rules
Finished brazing filler metals are inspected by the manufacturer's quality
inspection department according to the heat number.
6.1 Heat number division
The definition of heat number of brazing filler metals depends on the method of
smelting and refining, as follows:
- In the metal smelting process, slag-metal or gas-metal reactions occur. The
heat number refers to the material obtained from the same furnace smelting.
- In the metal smelting process, no obvious chemical reactions occur (such
as induction melting or vacuum melting in a controlled atmosphere). The
heat number refers to a group of materials obtained by continuous smelting
under the same conditions in a smelting furnace, using one lot of metals
and alloy elements with controlled burden. And the chemical composition
of each furnace of smelting material is in line with the purchaser or brazing
filler metal manufacturer's specified range.
6.2 Sampling method
During the inspection of each furnace of brazing filler metals, according to the
required quantity, representative samples shall be taken from at least three
locations. The sampling method and sampling location shall be recorded.
6.3 Acceptance
The manufacturer of brazing filler metals shall, in writing, provide the main
performance parameters such as chemical composition, dimensions,
appearance of brazing filler metals; declare that "when tested in accordance
with this Standard, the brazing filler metals provided meet the requirements of
this Standard".
6.4 Reinspection
When any one of the inspections fails, this item shall be double reinspected.
For the chemical composition analysis of brazing filler metals, only those
elements that do not meet the requirements are reinspected. The results of the
doubled reinspection shall meet the requirements of this item.
If the reinspection result is still unqualified, brazing filler metals in this furnace
cannot be delivered as finished products, which meet this Standard.
Annex B
(Normative)
Determination of silver content
B.1 Silver chloride gravimetric method
B.1.1 Scope
This method is suitable for the determination of silver content in silver brazing
filler metals. Determination range (mass fraction): 25.0%~99.95%.
B.1.2 Method summary
USE nitric acid to decompose the test portion. If there is precipitation, after
filtration, add hydrochloric acid to form silver chloride precipitation; USE a glass
crucible to separate it; and, weigh its mass after drying (the filtrate may be used
to determine the copper content).
B.1.3 Reagents
B.1.3.1 Nitric acid (1+1).
B.1.3.2 Nitric acid (1+100).
B.1.3.3 Hydrochloric acid (1+9).
B.1.4 Analytical procedures
B.1.4.1 Test portion
WEIGH 1.0 g of sample, accurate to 1 mg.
B.1.4.2 Determination
B.1.4.2.1 PLACE the weighed test portion (B.1.4.1) in a 300 mL tall beaker;
ADD 10 mL of nitric acid (B.1.3.1) and cover with a watch glass; slowly heat to
decompose; BOIL to allow nitrogen oxides to escape. USE water to rinse the
inner wall of the beaker; ADD warm water to 50 mL. At this time, if there is
precipitation, it shall let it stand for 1 h in a place where the temperature is
slightly higher; then use slow-speed filter paper to filter it. USE hot nitric acid
(B.1.3.2) to wash the precipitation.
B.1.4.2.2 ADD water to 150 mL; while stirring, add hydrochloric acid (B.1.3.3)
solution after calibration, in moles per liter (mol/L);
V0 - The value of the volume of ammonium thiocyanate standard titration
solution consumed for calibration, in milliliters (mL);
107.868 - The value of the molar mass of silver, in grams per mole (g/mol).
Calibrate three parts in parallel. The range of the volume of the ammonium
thiocyanate standard titration solution consumed shall not exceed 0.10 mL.
TAKE the average. Otherwise, re-calibrate.
B.2.4 Analytical procedures
B.2.4.1 Test portion
WEIGH 0.50 g of sample, accurate to 1 mg.
B.2.4.2 Determination
B.2.4.2.1 PLACE the weighed test portion (B.2.4.1) in a 300 mL conical beaker;
ADD 15 mL of nitric acid (B.2.3.1) and cover with a watch glass; slowly heat to
decompose; BOIL to allow nitrogen oxides to escape. After cooling, use water
to rinse the inner wall of the beaker; then add water to dilute to 150 mL.
B.2.4.2.2 ADD 3 mL of ferric ammonium sulfate solution (B.2.3.2) as an
indicator; while shaking, use ammonium thiocyanate standard titration solution
(B.2.3.3) to titrate, until the solution just appears reddish-brown, which is the
end point.
B.2.5 Expression of analysis results
The silver content is expressed in (Ag). The value is expressed in %, calculated
according to formula (B.3):
Where:
c - The actual concentration value of ammonium thiocyanate standard titration
solution after calibration, in moles per liter (mol/L);
V - The value of the volume of ammonium thiocyanate standard titration solution
consumed in the titration, in milliliters (mL);
m0 - The value of the mass of test portion, in grams (g);
107.868 - The value of the molar mass of silver, in grams per mole (g/mol).
Annex C
(Normative)
Determination of copper content - Electrolysis-spectrophotometry
C.1 Scope
This annex applies to the determination of copper content in silver brazing filler
metals. Determination range (mass fraction): 14.00%~60.00%.
C.2 Method summary
USE nitric acid to decompose the test portion; ADD hydrochloric acid for
precipitation to separate silver; USE sulfuric acid to smoke away hydrochloric
acid; after cooling, add water and nitric acid for low-current electrolysis. After
the electrolysis is terminated, the platinum cathode is washed using water and
absolute ethanol, dried, cooled, and then weighed. USE spectrophotometry to
measure the copper content remaining in the solution after electrolysis and
correct it to obtain the copper content.
C.3 Reagents
C.3.1 Absolute ethanol.
C.3.2 Nitric acid (1+1).
C.3.3 Nitric acid (1+100).
C.3.4 Hydrochloric acid (1+9).
C.3.5 Sulfuric acid (1+1).
C.3.6 Aqueous ammonia (1+1).
C.3.7 Ammonium citrate solution (500 g/L).
C.3.8 Dicyclohexanone oxalyl dihydrazone (BCO) solution (1 g/L): WEIGH 0.5
g of BCO in a 300 mL beaker; ADD 50 mL of ethanol, 200 mL of warm water to
dissolve; TRANSFER to a 500 mL volumetric flask; USE water to dilute to the
mark and mix well.
C.3.9 Copper standard stock solution: WEIGH 0.1000 g of pure copper into a
150 mL beaker; ADD 10 mL of nitric acid (C.3.2) and cover with a watch glass;
MAKE it completely decomposed at low temperature; BOIL to remove nitrogen
replace it with another tall beaker containing 180 mL of water; continue
electrolysis for 15 min.
C.5.2.6 Immediately take out the platinum electrode and immerse it in another
250 mL beaker filled with water; MOVE it up and down 3 times. TURN off the
power and remove the electrode; PUT it in a beaker containing absolute ethanol
(C.3.1); TAKE it out and place it in a 105 °C electrothermal constant-
temperature drying oven for drying for 3 min~5 min; then take it out and place
it in a desiccator to cool to room temperature.
C.5.2.7 WEIGH the platinum electrode after electrolytic deposition of copper,
accurate to 0.0001 g.
C.5.2.8 According to the following method, determine the amount of residual
copper in the solution after electrolysis.
C.5.2.8.1 Blank test: TAKE 10 mL of sulfuric acid (C.3.5), 5 mL of nitric acid
(C.3.2) in a 500 mL volumetric flask; do a blank test with the test portion.
C.5.2.8.2 COMBINE the electrolyte after electrolysis and a glass of water
obtained from electrolysis for 15 min into a 500 mL volumetric flask; USE water
to dilute to the mark and mix well.
C.5.2.8.3 PIPETTE 10.00 mL~20.00 mL of solution into a 50 mL volumetric flask;
ADD 2 mL of ammonium citrate solution (C.3.7); USE water to dilute to about
25 mL; ADD 2~3 drops of neutral red ethanol solution (C.3.11). USE aqueous
ammonia solution (C.3.6) to neutralize, until the red color fades and add 1.0 mL
in excess. ADD 8.0 mL of BCO solution (C.3.8); USE water to dilute to the mark
and mix well; and let stand for 20 min.
C.5.2.8.4 USE a 2 cm cuvette; USE the blank test as a reference. At a
wavelength of 600 nm, measure the absorbance; FIND out the corresponding
amount of copper from the working curve.
C.5.2.8.5 Drawing of working curve
PIPETTE 6 parts of 20.00 mL of blank solution (C.5.2.8.1); PLACE them in a
set of 50 mL volumetric flasks. ADD 0 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL,
5.00 mL of copper standard solution respectively. Then proceed according to
C.5.2.8.3 and C.5.2.8.4. USE copper content as the abscissa and absorbance
as the ordinate; DRAW the working curve.
C.6 Expression of analysis results
The copper content is expressed in ω(Cu). The value is expressed in %,
calculated according to formula (C.1):
Annex D
(Normative)
Determination of zinc and cadmium content - EDTA titration method
D.1 Scope
This annex applies to the determination of zinc content in silver brazing filler
metals. Determination range (mass fraction): 4.00%~45.00%.
This annex applies to the determination of cadmium content in silver brazing
filler metals. Determination range (mass fraction): 10.00%~30.00%.
D.2 Method summary
USE nitric acid to decompose the test portion. The tin is removed by
metastannic acid precipitation and filtration. USE silver chloride precipitation
method to separate silver, electrolysis method to separate copper. Adjust the
solution after separation of silver and copper to ammoniac. Indium and nickel
are separated by filtration in the form of hydroxide precipitation and
dimethylglyoxime nickel precipitation, respectively. Adjust the pH value within
the range of 5.5~6.5; USE thiourea to mask the remaining copper and silver;
USE EDTA standard titration solution to titrate the total amount of zinc and
cadmium. ADD excess potassium iodide to the test solution to release the EDTA
in Cd-EDTA; then use zinc standard solution to back-titrate the released EDTA,
to indirectly measure the cadmium content. Zinc is calculated by subtraction
method.
D.3 Reagents
D.3.1 Potassium iodide, analytically pure.
D.3.2 Ammonium persulfate, analytically pure.
D.3.3 Nitric acid (1+1).
D.3.4 Nitric acid (3+100).
D.3.5 Hydrochloric acid (1+1).
D.3.6 Hydrochloric acid (1+99).
D.3.7 Sulfuric acid (1+1).
TAKE 3 parts for calibration. The range of the volume of the consumed EDTA
standard titration solution does not exceed 0.10 mL. TAKE the average.
Otherwise, re-calibrate.
D.3.15 Xylenol orange solution (2.5 g/L).
D.4 Apparatus
D.4.1 Electrolysis device equipped with automatic stirring device, precision
ammeter and voltmeter.
D.4.2 Platinum cathode: USE a platinum wire with a diameter of 0.2 mm to
weave into a mesh with a mesh size of about 36 μm per square centimeter, to
make a mesh cylinder (see Figure C.1 in Annex C).
D.4.3 Platinum anode: Spiral (see Figure C.2 in Annex C).
D.5 Analytical procedures
D.5.1 Test portion
WEIGH 0.40 g of sample, accurate to 1 mg.
D.5.2 Determination
D.5.2.1 PLACE the test portion (D.5.1) in a 250 mL beaker.
D.5.2.2 ADD 5 mL of nitric acid (D.3.3); COVER with a watch glass; slowly heat
to decompose the test portion; REMOVE nitrogen oxides, remove and cool.
D.5.2.3 USE water to rinse the watch glass and beaker wall; HEAT and
evaporate at a low temperature to make the solution volume about 5 mL. Take
off and wash the watch glass and beaker wall. Adjust the volume to about 50
mL; HEAT it at a low temperature for 10 min~20 min; REMOVE it to cool.
D.5.2.4 USE medium-speed double-layer quantitative filter paper to filter by
decanting method. USE hot nitric acid (D.3.4) to wash the precipitate in the
beaker 3 times; then move the precipitate into the funnel; continue to use nitric
acid (D.3.4) to wash the precipitate in the beaker and the funnel 8~10 times.
DISCARD the precipitate and adjust the volume of the filtrate to about 120 mL.
D.5.2.5 While stirring, add 2 mL of hydrochloric acid (D.3.5); COVER with a
watch glass; HEAT at low temperature to make the solution clear and remove
it.
D.5.2.6 USE quantitative filter paper to filter by decanting. USE hot hydrochloric
acid (D.3.6) to wash the precipitate in the beaker 3 times; then transfer the
precipitate into the funnel; continue to use hot hydrochloric acid (D.3.6) to wash
the precipitate in the beaker and the funnel 8~10 times. DISCARD the
precipitate.
D.5.2.7 ADD 2 mL of sulfuric acid (D.3.7) to the filtrate; evaporate to smoke,
cool; ADD water and 5 mL of nitric acid (D.3.3) to dissolve the salts; adjust the
volume of the solution to about 150 mL. INSERT the platinum electrode pre-
installed on the electrolysis device into the solution; USE two semicircular watch
glasses to cover the beaker; under stirring, electrolyze with 2 A~2.5 A current,
until the blue color disappears; rinse the watch glasses and the beaker wall;
continue electrolysis for 2 h~3 h. Without disconnecting the current, move the
electrode up and leave the liquid surface. USE water to rinse the electrode; then
disconnect the power supply. HEAT and evaporate to adjust the volume of the
electrolyte to about 120 mL.
D.5.2.8 ADD aqueous ammonia (D.3.8) to the electrolyte, until a strong
ammonia smell appears in the test solution; and then add 5 mL in excess. ADD
1 g of ammonium persulfate (D.3.2) and boil for 1 min. COOL to room
temperature; TRANSFER the solution into a 200 mL volumetric flask.
D.5.2.9 While shaking, add dimethylglyoxime ethanol solution (D.3.11) (add 7
mL of dimethylglyoxime ethanol solution (D.3.11) per 10 mg of nickel); COOL
to room temperature; USE water to dilute to the mark and mix well; and dry filter.
D.5.2.10 Accurately pipette 50.00 mL of filtrate into a 300 mL conical flask; ADD
nitric acid (D.3.3) until the solution is acidic (can be tested with pH test paper);
and then add 5 mL in excess. ADD 2 mL of thiourea solution (D.3.9), 40 mL of
hexamethylenetetramine solution (D.3.10); then add 5 drops of xylenol orange
indicator (D.3.15); USE EDTA standard titration solution (D.3.14) to titrate, until
the solution turns from purple-red to yellow. RECORD the volume V1 of the
EDTA standard titration solution. This is the volume of the EDTA standard
titration solution consumed by zinc and cadmium.
D.5.2.11 ADD about 30 g of potassium iodide (D.3.1) to the test solution and
shake well; HEAT and boil for 3 min until the test solution is clear, remove and
cool. USE zinc standard solution (D.3.12) to titrate, until the solution becomes
stable rose red. RECORD the volume V2 of the zinc standard solution (D.3.12)
consumed. This is the volume of zinc standard solution consumed by EDTA
released from Cd-EDTA.
Note 1: If there is no tin in the test portion, D.5.2.3~D.5.2.4 can be omitted.
Note 2: If there is no nickel in the test portion, then D.5.2.8~D.5.2.9 and "ADD nitric acid
(D.3.3) until the solution is acidic; and then add 5 mL in excess" in D.5.2.10 can be
omitted.
Note 3: If there is no manganese in the test portion, then "ADD 1 g of ammonium persulfate
(D.3.2) and boil for 1 min" in D.5.2.8 can be omitted.
Note 4: If the test portion contains only zinc, V1 is the volume of the EDTA standard solution
consumed by zinc alone; the next step does not need to be performed.
D.6 Expression of analysis results
The zinc content is expressed in ω(Zn). The value is expressed in %, calculated
according to formula (D.2):
Where:
c - The actual concentration value of the EDTA standard titration solution after
calibration, in moles per liter (mol/L);
ρ - The value of the concentration of zinc standard solution, in milligrams per
milliliter (mg/mL);
V1 - The value of the volume of EDTA standard titration solution consumed when
titrating the total amount of zinc and cadmium, in milliliters (mL);
V2 - The value of the volume of the zinc standard solution consumed by titrating
the EDTA released in Cd-EDTA, in milliliters (mL);
m0 - The value of the mass of test portion, in grams (g);
65.38 - The value of the molar mass of zinc, in grams per mole (g/mol).
If the test portion contains cadmium, the cadmium content is expressed in
ω(Cd). The value is expressed in %, calculated according to formula (D.3):
Where:
V2 - The value of the volume of the zinc standard solution consumed by titrating
the EDTA released in Cd-EDTA, in milliliters (mL);
ρ - The value of the concentration of zinc standard solution, in milligrams per
milliliter (mg/mL);
m0 - The value of the mass of test portion, in grams (g);
E.1.5.3 Determination
E.1.5.3.1 PLACE the test portion (E.1.5.1) in a 100 mL polytetrafluoroethylene
beaker; ADD 10 mL of mixed acid (E.1.3.6); and warm it to decompose all the
sample. ADD 10 mL of boric acid solution (E.1.3.7); TRANSFER to a 100 mL
volumetric flask; USE water to dilute to the mark and shake well. (samples that
do not contain tin can be directly dissolved in 10 mL of nitric acid (E.1.3.4);
boiled to drive off nitrogen oxides; cooled; transferred to a 100 mL volumetric
flask; diluted with water to the mark and shaken well.) For the test solution that
does not need to be divided, proceed directly according to E.1.5.3.3.
E.1.5.3.2 PIPETTE 10.00 mL of test solution in a 100 mL volumetric flask; USE
water to dilute to the mark and shake well.
E.1.5.3.3 USE an air-acetylene flame; at the wavelength of 232.0 nm of the
atomic absorption spectrometer, use water for zero setting; MEASURE the
absorbance of the test solution simultaneously with the nickel standard solution
series. The absorbance of the blank solution along with the test portion is
subtracted from the measured absorbance. The corresponding nickel content
is found from the working curve.
E.1.6 Drawing of working curve
E.1.6.1 WEIGH a group or one of silver, copper, and tin equivalent to the test
portion in Table E.1; PUT it into a 100 mL polytetrafluoroethylene beaker; ADD
10 mL of mixed acid (E.1.3.6); and warm until the sample is completely
decomposed; ADD 10 mL of boric acid solution (E.1.3.7); TRANSFER to a 100
mL volumetric flask [For samples that do not need to be divided, it is possible
to directly add 0.00, 2.00, 4.00, 6.00, 8.00, 10.00 mL of nickel standard solution
(E.1.3.9) respectively; USE water to dilute to the mark; and proceed according
to E.1.6.3.]; USE water to dilute to the mark.
E.1.6.2 PIPETTE 6 portions of 10 mL of test solution (E.1.6.1) into a series of
100 mL volumetric flasks; ADD 0.00 mL, 2.00 mL, 4.00 mL, 6.00 mL, 8.00 mL,
10.00 mL of nickel standard solution (E.1.3.9), respectively; USE water to dilute
to the mark.
E.1.6.3 Under the same conditions as the determination of test portion solution,
use water for zero setting; MEASURE the absorbance of the standard solution
series; subtract the absorbance of the "zero" nickel solution in the standard
solution series. USE the nickel content as the abscissa and absorbance as the
ordinate; DRAW the working curve.
E.1.7 Expression of analysis results
The nickel content is expressed in ω(Ni). The value is expressed in %,
EDTA standard titration solution; in the ammonia solution, use chrome black T
as an indicator; USE the zinc standard solution to back-titrate.
E.2.3 Reagents
E.2.3.1 Aqueous ammonia (ρ=0.90 g/mL).
E.2.3.2 Nitric acid (1+1).
E.2.3.3 Nitric acid (1+100).
E.2.3.4 Hydrochloric acid (2+1).
E.2.3.5 Hydrochloric acid (1+1).
E.2.3.6 Hydrochloric acid (1+9).
E.2.3.7 Hydrochloric acid (1+50).
E.2.3.8 Sulfuric acid (1+1).
E.2.3.9 Ammonium chloride solution (250 g/L).
E.2.3.10 Tartaric acid solution (250 g/L).
E.2.3.11 Dimethylglyoxime ethanol solution (10 g/L).
E.2.3.12 Zinc standard solution [c(Zn)=0.02 mol/L]: WEIGH 1.3076 of pure zinc
(purity above 99.99%) into a 250 mL beaker; ADD 35 mL of hydrochloric acid
(E.2.3.5); HEAT to decompose and remove nitrogen oxides, cool; TRANSFER
to 1000 mL volumetric flask; USE water to dilute to the mark and shake well.
E.2.3.13 EDTA standard titration solution [c(C10H14N2O8Na2 • 2H2O)=0.02
mol/L].
E.2.3.13.1 Preparation: WEIGH 7.45 g of ethylene diamine tetraacetic acid
disodium in a 300 mL beaker; ADD water to dissolve; TRANSFER to a 1000 mL
volumetric flask; USE water to dilute to the mark and mix well.
E.2.3.13.2 Calibration: PIPETTE 25.00 mL of EDTA standard titration solution;
ADD 10 mL of ammonium chloride solution (E.2.3.9) and 2~3 drops of chrome
black T indicator (E.2.3.14); USE water to dilute to 100 mL; ADD aqueous
ammonia (E.2.3.1) dropwise, until the solution turns blue; USE zinc standard
solution (E.2.3.12) to titrate, until the solution turns purple-red as the end point.
According to formula (E.2) and formula (E.3), calculate the actual concentration
of EDTA standard titration solution:
nitric acid (E.2.3.2) and cover with a watch glass; slowly heat until the test
portion is dissolved, boil, and remove nitrogen oxides. USE water to rinse the
watch glass and the inner wall of the beaker (if there is precipitation at this time,
it shall add warm water to a volume of 50 mL; and let it stand for 1 h~2 h in a
place with higher temperature; then use slow-speed filter paper to filter; wash
the beaker and the precipitate; discard the precipitate.). Adjust the volume of
the solution to 150 mL; while stirring, add hydrochloric acid (E.2.3.6) dropwise
to generate silver chloride precipitation; ADD hydrochloric acid (E.2.3.6)
dropwise, until no precipitation is formed; then add 1 mL of hydrochloric acid
(E.2.3.6) in excess, to make it saturated. After fully stirring, heat and boil for 5
min; COOL and stand for 2 h, filter; USE nitric acid (E.2.3.3) to wash several
times; and then use water to wash thoroughly. The filtrate and washing liquid
are combined in a 500 mL conical cup.
E.2.5.2.2 Then, add 10 mL of sulfuric acid (E.2.3.8) to the filtrate; HEAT and
evaporate to make the sulfuric acid smoke. After standing and cooling, add 50
mL of water and 5 mL of nitric acid (E.2.3.2); HEAT to dissolve the soluble salts;
and boil for 1 min~2 min to allow nitrogen oxides to escape. REMOVE it and
slightly cool; TRANSFER to a 300 mL tall beaker; USE water to wash the wall
of the cup; and dilute the solution volume about 150 mL.
E.2.5.2.3 INSERT the platinum electrode pre-installed on the electrolysis device
into the solution; USE two semicircular watch glasses to cover the beaker;
under stirring, electrolyze with 2 A~2.5 A current, until the blue color disappears;
rinse the watch glasses and the beaker wall; continue electrolysis for 2 h~3 h.
Without disconnecting the current, move the electrode up and leave the liquid
surface. USE water to rinse the electrode; then disconnect the power supply.
E.2.5.2.4 TRANSFER the electrolyte into a 500 mL beaker; ADD 20 mL of
tartaric acid solution (E.2.3.10) and 20 mL of ammonium chloride solution
(E.2.3.9). USE methyl red solution (E.2.3.15) as an indicator; USE aqueous
ammonia (E.2.3.1) to neutralize, until the solution turns from red to yellow, with
an excess of 3 mL; adjust the volume of the solution to 300 mL.
E.2.5.2.5 HEAT the solution to 90 °C; while stirring, add dimethylglyoxime
ethanol solution (E.2.3.11) (add 7 mL of dimethylglyoxime ethanol solution
(E.2.3.11) per 10 mg of nickel). After stirring well......
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Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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