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GB 10735-2008: Primary chemical -- Sodium carbonate anhydrous
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Primary chemical -- Sodium carbonate anhydrous
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GB 10735-2008
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| GB 10735-1989 | English | 479 |
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Primary chemical--Sodium carbonate, anhydrous
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Basic data | Standard ID | GB 10735-2008 (GB10735-2008) | | Description (Translated English) | Primary chemical -- Sodium carbonate anhydrous | | Sector / Industry | National Standard | | Classification of Chinese Standard | G61 | | Classification of International Standard | 71.040.30 | | Word Count Estimation | 18,177 | | Date of Issue | 2008-06-18 | | Date of Implementation | 2009-06-01 | | Older Standard (superseded by this standard) | GB 10735-1989 | | Regulation (derived from) | Announcement of Newly Approved National Standards No. 10 of 2008 (total 123) | | Issuing agency(ies) | General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People's Republic of China | | Summary | This Chinese standard specifies the first reference reagent water soda traits, specifications, testing, inspection and marking and packaging rules. This standard applies to the first benchmark test of sodium carbonate reagent water. | GB 10735-2008: Primary chemical -- Sodium carbonate anhydrous---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Primary chemical.Sodium carbonate anhydrous
ICS 71.040.30
G61
National Standards of People's Republic of China
Replacing GB 10735-1989
The first reference reagent anhydrous sodium carbonate
Posted 2008-06-18
2009-06-01 implementation
Administration of Quality Supervision, Inspection and Quarantine of People's Republic of China
Standardization Administration of China released
Foreword
The standard Chapter 4 5.3.3,5.3.4.1 are mandatory, other provisions are recommended.
This standard replaces GB 10735-1989 "first reference reagent (capacity) of anhydrous sodium carbonate," compared with GB 10735-1989, the major change
Of the following.
--- Standard name changed to "first reference reagent anhydrous sodium carbonate";
--- Increasing the normative references (1989 edition Chapter 2, Section 2 of this edition);
--- Modify the description of the determination of the principles of the (1989 version 4.1.1, this version 5.3.1);
--- Modify the constant current coulometric apparatus diagram (1989 version 4.1.3.4, this edition 5.3.2.4);
--- Perfect pre-titration method (the 1989 edition of 4.1.4.2, this edition 5.3.3.3);
--- Modified after introducing nitrogen loading conditions (1989 version 4.1.4.3, this edition 5.3.3.4);
--- Modify the inspection rules (1989 edition Chapter 5, Chapter 6 of this edition);
--- Increasing the content of the calculation method of Uncertainty (Excerpts Appendix B) was measured;
--- Canceled Appendix B, Appendix C (1989 edition Appendix B, Appendix C).
This standard appendix A normative appendix, Appendix B is an informative annex.
The standard proposed by China Petroleum and Chemical Industry Association.
This standard by the Chemicals Branch of the National Chemical Standardization Technical Committee.
This standard is drafted by. China Institute of Metrology, Beijing Institute of Chemical reagents.
The main drafters of this standard. FEI brother, Wu Bing, Han Baoying, strong Jing Lin.
This standard replaces the standards previously issued as follows.
--- GB 10735-1989.
The first reference reagent anhydrous sodium carbonate
Molecular formula. Na2CO3
Molecular Weight. 105.9886 (according to 2005 international relative atomic mass).
1 Scope
This standard specifies the first reference reagent anhydrous sodium carbonate traits, specifications, testing, packaging and inspection rules and signs.
This standard applies to the first reference reagent anhydrous sodium carbonate test.
2 Normative references
The following documents contain provisions which, through reference in this standard and become the standard terms. For dated references, subsequent
Amendments (not including errata content) or revisions do not apply to this standard, however, encourage the parties to the agreement are based on research
Whether the latest versions of these documents. For undated reference documents, the latest versions apply to this standard.
GB/T 602 Determination of impurities in chemical reagents prepared standard solution (GB/T 602-2002, ISO 6353-1. 1982, NEQ) with
GB/T 603 chemical reagent test method Preparations of articles (GB/T 603-2002, ISO 6353-1 with. 1982,
NEQ)
GB/T 609 chemical reagent - General method for determination of total nitrogen (GB/T 609-2006, ISO 6353-1. 1982, NEQ)
GB/T 6682 analytical laboratory use specifications and test methods (GB/T 6682-2008, ISO 3696. 1987, MOD)
GB/T 9723-2007 Chemicals flame atomic absorption spectrometry General
GB/T 9728 General method for determination of chemical reagents sulfate (GB/T 9728-2007, ISO 6353-1. 1982, NEQ)
GB/T 9729 General method for determination of chloride Chemicals (GB/T 9729-2007, ISO 6353-1. 1982, NEQ)
GB/T 9734-2008 Determination of aluminum Chemicals general method (ISO 6353-1. 1982, NEQ)
GB/T 9738 Chemicals water insoluble determination General method (GB/T 9738-2008, ISO 6353-1. 1982, NEQ)
GB/T 9739 General method for determination of iron chemical reagents (GB/T 9739-2006, ISO 6353-1. 1982, NEQ)
GB 15346 chemical reagent packaging and marking
HG/T 3484 standard chemical reagents glass emulsion and clarity standards
JJG99 weight
JJG116 standard resistor
JJG119-2005 Laboratory pH (acidity) meter
JJG153 standard battery
JJG1006 a standard material specification
3 Characters
This reagent as a white powder, water is exposed to air gradually become a hydrate, soluble in water, soluble in ethanol.
4 Specification
Anhydrous sodium carbonate as shown in Table 1.
Table 1
Name the first reference
Content (Na2CO3), /% 99.98 ~ 100.02
Clarity test/number ≤2
Water-insoluble, /% ≤0.005
Chloride (Cl), /% ≤0.001
Sulfur compounds (of SO4), /% ≤0.003
Total nitrogen (N), /% ≤0.001
Phosphate and silicate (SiO3 to count), /% ≤0.0025
Magnesium (Mg), /% ≤0.0005
Aluminum (Al), /% ≤0.001
Potassium (K), /% ≤0.005
Calcium (Ca), /% ≤0.005
Iron (Fe), /% ≤0.0003
Heavy metals (Pb), /% ≤0.0005
5 Test
5.1 Warning
Reagents used in this test method are toxic or corrosive, some of the testing process can lead to dangerous situations, the operator should take
Appropriate safety and health practices.
5.2 General Provisions
Unless specified otherwise in this chapter, the use of reagent purity should be more analytical, standard solution, preparations and products, according to GB/T 602,
GB/T 603 provisions of preparation, test water should be consistent with GB/T 6682 specifications in two water samples according to precise weighing 0.01g, used
Solution "%" are represented by the mass fraction. High purity nitrogen gas should be used.
5.3 Content
5.3.1 Principle of the method
Coulomb analysis is performed by measuring a quantitative analysis of material from one electrode reaction, or a substance to be analyzed and the electrode reaction
Charge (coulombs) chemical reaction product was quantitatively consumed to quantitative analysis. Coulometry principle is based on the law
Where.
Molar mass M --- material in units of grams per mole (g/mol);
--- Like the number of electron transfer;
F --- Faraday constant ampere seconds per mole of (A · s/mol);
I --- the current solution by electrolysis, in amperes (A);
Constant current precision coulometric titration method is based on a constant current through the electrolytic cell, so that the working electrode electrolysis to produce a titrant with cell
The test substance quantitative reaction, electrochemical method to indicate the end of the reaction, the consumption of electricity by electrolysis calculated according to Faraday's law
The amount of titrant to calculate the content of the test substance.
This method uses a platinum mesh electrode (surface area 60cm2) as the anode using the anode
4OH- -4e 2H2O + O2 ↑
Determination of electrode reaction of anhydrous sodium carbonate, indicating the end of the reaction with a pH meter.
5.3.2 instruments and devices
5.3.2.1 pH meter. meet JJG119-2005 Chapter 4 "0.001" requirements.
5.3.2.2 Weight. meet JJG99 verification requirements. G group, the annual variation of less than 10μg; mg group, the annual variation of less than 4μg.
5.3.2.3 heated fuel tank. temperature control accuracy of ± 0.01 ℃.
5.3.2.4 Coulomb constant current device diagram (see Figure 1).
1 --- high precision timing constant current source;
2 --- 7½-Meter;
3 --- electrolytic cell;
4 --- end indicator (pH meter);
5 --- dummy load resistor;
6 --- Standard resistance;
7 --- galvanometer;
8 --- temperature standard battery pack;
. 9 --- step switch;
10 --- heated fuel tank.
Figure 1 Schematic diagram of the constant current coulometric
a) high-precision timing constant current source. stability is better than one hundred thousandth of the dynamic characteristics of a good steady flow DC power supply, with 1.0186 ×
1.0186 × 10mA and 100mA two output current, the current value is determined by the compensation method; the minimum timing resolution 0.1ms, electricity
Flow and timing synchronization is less than 0.1ms.
b) temperature control standard battery pack. should meet the requirements of JJG153. Range 1V, annual variation of less than 5μV.
c) Standard resistance. should meet the requirements JJG116 of. Relative uncertainty is generally not more than 3 × 10-6.
d) direct radiation galvanometer. resistance < 100Ω, critical external resistance < 1000Ω, dividing the value of < 3 × 10-9A.
5.3.2.5 electrolytic cell apparatus (see Figure 2).
An anode compartment (left) and a cathode chamber (right side) is made of quartz glass with a diameter of 50mm, 125mm high cylindrical. With between two chambers
Diameter 20mm, length 80mm quartz glass tube level connections in the tube melting inside back cover sheet respectively No. 2,2,3 glass sand core, thus formed
Two intermediate chambers each with a branch of the piston, and the pressure by pumping nitrogen gas pressurization method the electrolyte solution out of the intermediate chamber. Two small rooms
The distance between the sand core distance 20mm, two large chamber between the sand core is 40mm. Tight pre-treated with a good white port on the anode chamber
A rubber plug, the plug is inserted through a glass electrode 2, respectively, a saturated calomel electrode 3, 4 nitrogen inlet, nitrogen outlet pipe 5, a surface area of about
60cm2 platinum mesh anodes 6, the bottom of the anode compartment has a 20mm long was stirred in a sealed Teflon tube about the magnet 9, a polyethylene cover
10 placed in a platinum mesh anode on top. A cathode chamber having a 50mm × 75mm copper as the cathode 8, the bottom agar casting a rubber stopper 7.
Electrolytic cell unit on magnetic stirrer workbench.
Note. Preparation of agar rubber stopper
Weigh agar 3g, was added 50mL of water, boiling, etc. is added a solution of sodium sulfate (1mol/L) Volume boiled, mixed, cast in the hot cathode chamber
bottom.
1 --- white rubber plug;
2 --- glass electrode;
3 --- saturated calomel electrode;
4 --- nitrogen inlet;
5 --- nitrogen outlet pipe;
6 --- platinum mesh anode;
7 --- agar stopper;
8 --- copper cathode;
. 9 --- stirring;
10 --- polyethylene cover;
. 11 --- piston 1;
12 --- piston 2.
2 cell apparatus of FIG.
5.3.3 Determination
5.3.3.1 Preparation of formulations
Weighed 322.2g sodium sulfate (Na2SO4 · 10H2O) (excellent pure), was dissolved in water and diluted to 1000mL.
Weigh 79.8g copper sulfate pentahydrate, soluble in water, dilute to 1000mL.
5.3.3.2 said sample
The sample was placed in a platinum crucible at (270 ± 10) ℃ drying 4h, cooled to room temperature in a desiccator.
PTFE sample is placed in a small cup, weighing alternative method to the nearest 0.00001g. The quality of the sample shall be corrected for buoyancy,
Correction method in Appendix A.
5.3.3.3 Pre-titration
Cathode chamber 100mL copper sulfate solution [0.5mol/L], the anode compartment was added 1.8g of recrystallized sodium sulfate, dissolved in
130mL carbon dioxide-free water. Stirring the liquid from the manifold to the anode-high purity nitrogen 40min, removal of dissolved carbon dioxide, glass insert
Glass electrode and a saturated calomel electrode. Adjust the nitrogen intake pipe into the air, maintaining a small nitrogen flow, the anode compartment electrolyte solution on the surface
Maintain a high purity nitrogen atmosphere. Open the piston 1 and the piston 2, so that the anode compartment electrolyte solution flows into the middle chamber of about 2mm deep in 10.186mA electricity
Shed, changing the polarity of the electrodes, an electrolyte solution pretreatment. Thereafter, 10.186mA current, incremental method for pre-titration curve,
After the completion of the pre-titration, the method of pressurizing and depressurizing with intermediate washing chamber several times, and washing the inner wall of the electrolytic cell with an electrolyte solution and finally the intermediate chamber
The electrolytic solution was returned to 2mm deep, the pH of the final record, the pre-titration curves plotted (see FIG. 3). The figure is the titration end point C, A
Point represents the electrolysis stop time, B point represents the final pH after completion of washing solution. More than titration end portion of the charge amount should be credited
The total charge amount. Remove the glass electrode and a saturated calomel electrode, with a teflon stopper stuffed respective two holes.
Figure 3 pre-titration curve
5.3.3.4 titration end point and seek
In order to open the piston 1 and the piston 2, so that the cathode chamber by vacuum intermediate chamber filled with electrolyte solution, close the piston 1 and the piston 2, nitrogen
Adjusted to a smaller flow rate, above the surface to blow through the intake manifold, the anode chamber to maintain a positive pressure to prevent air from entering. We will even say good sample
Put together with a small cup of pre-titration of the electrolyte solution in the anode chamber, the solution was stirred. Stirring was stopped, the dummy load resistor adjusts the current value
101.86mA, connected to two electrodes, start electrolysis. During electrolysis, every 15min observe the primary current value, if any changes tune
Section. When the desired length of time longer than 2s when electrolysis sample purity of 100%, the electrolysis is stopped, write down the time of electrolysis.
The anode chamber electrolyte solution was transferred to flat-bottomed quartz flask, chamber solution blown back anode chamber, drawing the dissolved polyethylene dropper
Polyethylene cover and rubberized mesh and washed repeatedly with platinum plugs on the washing liquid was transferred to the above flat-bottomed flask. The solution was blown back into the big room
Anode chamber, after the above washing method, the above-described washing solution and transferred to a flat-bottomed flask, boiled together 10min, carbon dioxide was removed, to be dissolved
It was cooled to room temperature, and transferred back to the electrolytic cell anode compartment, through high purity nitrogen 40min.
In 10.186mA current, incremental method to draw the end of the curve. Platinum mesh as the cathode and anode copper, each through a certain power, Hutchison
Changes recorded pH value until the checkered flag after a few do. With pre-titration as repeatedly washing the sand core connecting tube, the anode chamber wall
FIG point C is the titration end point, A point represents electrolysis stop time, B point represents the completion of the final pH value of the washing solution.
Figure 4 endpoint titration curve
5.3.4 Calculation
5.3.4.1 Calculation of the mass fraction of anhydrous sodium carbonate
Anhydrous sodium carbonate content and its value is "%" means, according to equation (2).
= QPQT ×
100 = I
(2)
Where.
--- The QP electrolytic sample charge amount actually consumed by the coulombs (the C);
Theoretical amount of charge required for electrolysis of the QT --- sample, in units of coulombs (the C);
I --- the current solution by electrolysis, in amperes (A);
--- The M values of the molar mass of anhydrous sodium carbonate units of grams per mole (g/mol);
--- Like the number of electron transfer;
F --- Faraday constant ampere seconds per mole of (A · s/mol);
E --- standard electromotive force in volts (V);
R --- standard resistor in ohms (Ω).
(2) In the formula.
I1 --- large current electrolysis current value in units of milliamperes (mA);
I2 --- pre-titration end point and seek current value, in milliamperes (mA);
Uncertainty and assay results of calculation 5.3.4.2
Expanded uncertainty assay results should generally be less than 0.02% (k = 2), the calculation method, see Appendix B.
5.4 Clarity test
Clarity Standard No. 2 Weigh 5g sample was dissolved in 100mL of water, turbidity is not greater than HG/T 3484 stipulated.
5.5 Water insoluble matter
Weigh 10g sample was dissolved in 200mL of water, determined according to the provisions of GB/T 9738's.
5.6 Chloride
Weigh 1g sample was dissolved in 10mL water, after dropping nitric acid solution (25%) and, according to the provisions of GB/T 9729 Determination. Solution
Turbidity was no larger than a standard turbidity solution.
Standard preparation turbid solution is to take the ratio of 0.01mg containing chloride (Cl) standard solution was diluted to 10mL, and at the same time with the same volume of test solution
Sample processing.
5.7 sulfur compounds
Weigh 0.5g sample was dissolved in 10mL water, add 0.3mL "30% hydrogen peroxide", boiled for several minutes, cooled, washed with hydrochloric acid solution
(20%) the solution was adjusted to pH 5-6, and then boiled, cooled, diluted to 20mL, 0.5mL after adding hydrochloric acid solution (20%) acidified by
The provisions of GB/T 9728 Determination. The turbidity of the solution was not greater than the standard turbidity solution.
Standard preparation turbid solution is to take the ratio of 0.015mg containing sulfate (SO4) standard solution was diluted to 20mL, and with the same volume of test solution
When the same treatment.
5.8 total nitrogen content
Weigh 2g sample was dissolved in water and diluted to 140mL, determined according to the provisions of GB/T 609's. The yellow solution can not be deeper than the standard ratio
Color solution.
Preparation of the standard developing solution containing 0.02mg ratio is taken of nitrogen (N) standard solution, the same treatment simultaneously with the sample.
5.9 phosphates and silicates
Weigh 0.5g sample was dissolved in 50mL of water added 2.4mL of hydrochloric acid solution (20%), diluted to 80mL, heated to boiling, cooled. plus
5mL ammonium molybdate solution (100g/L), with aqueous ammonia solution (10%) or hydrochloric acid solution (20%) the solution was adjusted to pH 1.8 (pH measurement with
Set), then heated to boiling in a water bath insulation 20min, cooled. Hydrochloric acid was added 10mL, transferred to a separatory funnel with methyl-2-pentyl 25mL4-
Ketones (methyl isobutyl ketone) and extracted 2min. The organic phase was washed with 25mL of hydrochloric acid solution (0.5%). The organic phase, add 0.2mL new
Stannous chloride hydrochloric acid solution (20g/L) was prepared, add 1mL ethanol (ethanol) and shake. The organic phase was blue can not be deeper than the standard ratio
Color solution.
Preparation of the standard developing solution containing 0.012mg is to take the ratio of the silicate (Si03) standard solution, add 0.6mL hydrochloric acid solution (20%), dilute
Diluted to 80mL, with the same volume of test solution at the same time the same treatment.
5.10 Magnesium
Determined according to the provisions of GB/T 9723-2007 of.
5.10.1 Instrument Conditions
Source. magnesium hollow cathode lamp;
Wavelength. 285.2nm;
Flame. acetylene - air.
5.10.2 Determination
Weigh 10g sample is dissolved in water, adjusting the pH with hydrochloric acid test solution (20%) to a value of 5 to 6, excess 5mL, diluted to 100mL.
Take 10mL, a total of four. According to the provisions of GB/T 9723-2007 7.2.2 measurement results calculated according to the provisions of 7.2.3.
5.11 aluminum
1g sample was weighed, dissolved in water, was added dropwise a solution of hydrochloric acid (20%) the solution was adjusted to pH 5 to 6, excess 0.25mL, boiled, cooled,
Ammonia solution (10%) adjusting the pH of the solution to neutral, diluted to 10mL, measured according to GB/T 9734-2008 6.1 requirements. Solution
The red No deeper than the standard colorimetric solution.
Preparation of the standard developing solution containing 0.01mg ratio is taken of aluminum (Al) standard solution was diluted to 10mL, and at the same time with the same volume of test solution
deal with.
5.12 K
Determined according to the provisions of GB/T 9723-2007 of.
5.12.1 Instrument Conditions
Source. Potassium hollow cathode lamp;
Wavelength. 766.4nm;
Flame. acetylene - air.
5.12.2 Determination
With 5.10.2.
5.13 Calcium
Determined according to the provisions of GB/T 9723-2007 of.
5.13.1 Instrument Conditions
Source. calcium hollow cathode lamp;
Wavelength. 422.7nm;
Flame. acetylene - air.
5.13.2 Determination
Weigh 10g sample is dissolved in water, adjusting the pH with hydrochloric acid test solution (20%) to a value of 5 to 6, 2.5mL excess, dilute to 100mL.
Take 20mL, a total of four. According to the provisions of GB/T 9723-2007 7.2.2 measurement results calculated according to the provisions of 7.2.3.
5.14 Iron
1g sample was weighed, dissolved in water, was added dropwise a solution of hydrochloric acid (20%) the solution was adjusted to pH 5 to 6, excess 0.5mL, boiled, cooled, diluted
Diluted to 15mL, adjusting the pH with aqueous ammonia solution (10%) to the value of 2, determined according to the provisions of GB/T 9739's. The solution may not be red
Deeper than the standard colorimetric solution.
Preparation of the standard developing solution containing a ratio is taken of iron (Fe) standard solution, adding 10mL water and 0.5mL of hydrochloric acid 0.003mg
(20%), diluted to 15mL, simultaneously with the same volume of the test solution treated similarly.
5.15 Heavy Metal
6g weighed sample was dissolved in 25mL water, with a solution of nitric acid (25%) and in excess 0.5mL, evaporated on a water bath. The residue is dissolved
Water, with a solution of sodium hydroxide [Ba (NaOH) = 0.1mol/L] solution was adjusted to pH 4, diluted to 40mL. Take 30mL, add 0.2mL
Acetic acid solution (30%) of freshly prepared saturated hydrogen sulfide and water 10mL, shake, place 10min. The solution was dark No deeper than the standard
Color solution.
Preparation of standard color solution is to take over the remaining 10mL sample solution and standard solution containing 0.015mg of lead (Pb), diluted to
30mL, simultaneously with the same volume of the test solution treated similarly.
6 Inspection rules
For mass-produced products, in accordance with the requirements of uniformity JJG1006 initial inspection.
Bulk product inspection can be carried out by the preliminary dispensing, after extracting a sample formal test.
Official test sample rule. when the total number of units is less than 200, the number of shape extraction unit less than 11; When the whole is greater than the number of units 200
When less than 500, like less than 12; when the total number of more than 500 units, like no less than 15.
7 Packaging and marking
According to GB 15346 requirements for packaging, storage and transportation, and flags are given, including.
Packing unit. Class 3;
Inner packaging. NB-4, NB-5, NB-6;
Packaging forms. The specifications for the 600g/m2 of box board paper box, outer mounted electro-optical blue paper.
Appendix A
(Normative)
Substance was weighed mass air buoyancy correction
Where.
ρK --- when the density of the air weighing in grams per cubic centimeter (g/cm
3);
ρW --- density of the material to be weighed in grams per cubic centimeter (g/cm
3);
pf --- weights density in grams per cubic centimeter (g/cm
3).
Formula (A.1) in.
Air density (ρK), in grams per cubic centimeter (g/cm
3), according to equation (A.2) Calculated.
Where.
P1 --- atmospheric pressure value in units of kilopascals (kPa);
P2 --- vapor pressure of water at room temperature value in units of kilopascals (kPa);
(A.2) in the formula.
The value of water vapor pressure (P2), in units of kilopascals (kPa), according to equation (A.3) Calculated.
P2 = W × P3 (A.3)
Where.
W --- values of relative humidity of air in%;
Numerical P3 --- saturated vapor pressure of water at room temperature, measured in kilopascals (kPa).
Water vapor pressure values are shown in Table A. 1.
Table A. 1 Water vapor pressure (P Rao k)
Temperature (℃) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Appendix B
(Informative)
Calculation Determination of Uncertainty
B. Calculate 1 assay results of the Class A standard uncertainty components
A class standard uncertainty component [u A (Qin)] according to formula (B.1) Calculated.
U A (Qin) = Ju
(Qin)
槡 like
(B.1)
Where.
Standard deviation Ju (Qin) --- like second measurement results, the value of "%" means.
B. Calculation 2 assay results of Class B combined standard uncertainty components
Class B according to the relative combined standard uncertainty component assay results Chapter 5 (2) of [u cBrel (Qin)] according to formula (B.2) Calculated.
Where.
U rel (I) --- current relative standard uncertainty component;
The relative standard u rel (M) --- anhydrous sodium carbonate molar mass values of the uncertainty components;
U rel (F) and the relative standard --- Faraday constant uncertainty components;
U rel (x) --- determine the end point of the relative standard uncertainty component.
B. 2.1 Current relative standard uncertainty component computing
Current relative standard uncertainty component [u...
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