GB 5490-1985 General rules for inspection of grains, oilseeds and vegetable fats
Some standard content:
National Standard of the People's Republic of China
General rules of inspection grain, oilseeds and vegetable oils
This standard applies to the quality inspection of commercial grain, oilseeds and vegetable oils. 1 Grain and oil samples
UDC (633.1+633.85
+ 664.33).001.4
GB5490--85
A certain number of representative parts of the grain and oil to be inspected are called samples according to regulations. Samples are the main basis for determining the quality of a batch of grain and oil.
1.1 Original samples: The samples first taken from a batch of grain and oil to be inspected are called original samples. The number of original samples is determined according to the number of a batch of grain and oil and the requirements for quality inspection. The original samples of grain and oil are generally not less than 2kg. The original samples of oils are not less than 1kg. The number of samples of grain and oil collected and paid sporadically may be reduced as appropriate. 1.2 Average sample: The original sample is mixed and averaged according to the prescribed method, and a portion is evenly divided out, which is called the average sample. The average sample is generally not less than 1kg.
1.3 Test sample: The average sample is mixed and sampled, and a portion is weighed out as needed as a test sample, which is called the test sample, or test sample for short. The amount of test samples shall be implemented in accordance with the provisions of Chapter 7. 1.4 Sample registration: The samples taken must be registered. Registration items include: sampling date, sample number, name of grain or oil, representative quantity, place of origin, production year, sampling location (vehicle, ship, warehouse, stack number), packaging or bulk, name of sampler, etc. 1.5 Sample preservation: For grain and oil transferred and exported, original samples of no less than 1kg shall be preserved. After registration, sealing, official seal and signature of the person in charge, they shall be properly preserved in a dry and low temperature place (the moisture content shall be below 15℃ for those exceeding the safe moisture content, and the oil and fat samples shall be protected from light) for one month for re-inspection.
2 Arbitration method
There is only one inspection method for an inspection item, or the first method of two or more methods shall be the arbitration method unless otherwise specified. The arbitration method shall prevail during arbitration inspection.
3 Original records and inspection sheets
After each batch of grain and oil is inspected, there must be complete original records, and the quality inspection sheet shall be accurately filled in according to the inspection results. 4 Water and reagents for chemical analysis
The water for chemical analysis in each inspection item is distilled water. The reagents used for chemical analysis, except for the reference material and the reagent purity requirements specially specified, are all chemically pure reagents. The instruments used shall use standardized products as much as possible, and non-standard instruments shall meet the error requirements. 5 Calculation of test results
After the significant figures are determined, the remaining data shall be rounded up according to the rule of "rounding up the odd numbers and rounding down the even numbers".
Promulgated by the National Bureau of Standards on November 2, 1985
Implementation on July 1, 1986
Safety measures
GB5490—85
When analyzing the sample, if toxic and harmful gases are generated, it should be carried out in a fume hood to ensure safety. 7 Provisions on the inspection procedures and sample quantities for grains and oils See the figure below for the inspection procedures and sample quantities for grains and oils: Preserved samples
Original samples
2000g or moreSub-samples
30100g500g
Fermentation test
400 grains
1000 grains
Average sampleWww.bzxZ.net
1000g or more
Large sampleImpurities
500~1000g
Small sampleImpurities, minerals
Other impurities
10~200g
Color, odor, flavor
Incomplete grains
Processing degree
A.1 Error
GB 5490—85
Appendix A
Error and Data Processing
(Reference)
The difference between the measured value and the true value is called error, which is used to judge the accuracy of the measured value. According to its source, it can be divided into systematic error and accidental error.
A.1.1 Systematic error
Errors caused by instruments, reagents, analytical methods and operations are all systematic errors, which can be tested and corrected by the following methods.
A. 1.11 Calibrate the measuring instruments and instruments used. A, 1.1.2 Control test: Use standard methods or classical methods, or use standard substances with known contents, or perform recovery rate control tests to test the size of the error.
Recovery rate (%) = -
-3-×100-
W—weight of the substance to be measured after adding the standard substance to the sample, x2——weight of the substance to be measured in the sample,
W—weight of the standard substance added to the sample. (A1)
A.1.1.3 Blank test: no sample is added during the operation procedure, and the blank test value is subtracted from the measured value of the sample at the end to check the error caused by the reagent.
A.1.2 Accidental error
Errors mainly caused by temperature, humidity, air pressure and various accidental factors can be controlled within a certain range by repeated measurements.
A.2 Significant figures
Significant figures are the reliability of the numbers in the data, and one suspicious number can be retained in the data. For example, if the weight of an object is 12.3g, it cannot be written as 12.30g because its weighing accuracy is 0.1g and has three significant figures. The "0" in the data, such as the "0" in 0.0003, is not a significant figure. The "0" at the end of the data, such as 35600, should be written as 3.56×104 when there are three significant figures.
When adding, subtracting, multiplying or dividing values, the number of decimal places retained should be the same as the one with the least decimal places. After the significant figures are determined, the remaining figures are rounded up or down (when the number is five, the first digit is "rounded up to the odd and even to the left") according to the rules.
A.3 Accuracy and Precision
A.3.1 Accuracy: It is the degree of closeness between the measured value and the true value. The degree of difference between two values is expressed by absolute error and relative error.
Absolute error (R) = -
In the formula. x——measured value,
μtrue value.
Relative error is the percentage error of absolute error to true value: (A2)
Wherein, R—absolute error,
μtrue value.
GB 5490-85
Relative error (%)
Accuracy can also be expressed by relative error. When the true value is not easy to obtain, accuracy is usually not used, but precision is used. (A3)
A, 8.2 Precision: Precision indicates the degree of agreement between a group of measured values. High precision means that the reproducibility of each measured value is good. Precision is usually expressed by standard deviation (S). The smaller S is, the smaller the variation of the measured value is. Assume that n represents the number of measurements, 1, ×2, α\… represent the measured values of each group, and wen (read as xbar) represents the average value of each measured value. The difference between each measured value and wen is called deviation (d). Wen and S can be calculated using formulas (A4) and (A5). M
In the formula, x-
the average value of each measured value,
a product plus symbol, read as Sigmaz
≥the sum of each measured value s
—the number of measurements.
In the formula, S-standard deviation,
(xx)2-
the square of the difference between the measured value and the average value, d 2---the square of the deviation.
Example: Use the relevant values in Table A1 below to calculate S: Substitute into formula (A5) to get
The standard deviation S has the following four uses:
A.8.2.1 Determine the degree of dispersion of the measured value distribution. A large S indicates that the distribution of the measured values around the average value is more discrete and the average value is less representative. On the contrary, a small S indicates that the average value is more representative. A,8,2.2 Estimate the distribution of the measured value frequency. The application is combined with the calculation of S, and according to the area distribution law under the normal curve, the probability of each measured value appearing in the S interval can be estimated. The percentage of the results of five determinations of wheat protein content (in dry matter) is shown in Table A1: Table A1
(unique)
Ela1=0.44
Square deviation
Zdr= 0.0520
Ea2=643.03
A.3.2.3 Use S to calculate the coefficient of variation. When the units of the two groups of measured values are different or the average values of the two groups differ greatly, the S of the two groups can be converted into the coefficient of variation (CV) to determine their degree of variation. The group with a small CV indicates that its degree of variation is small. Calculated according to formula (A6): 200
GB5490—85
A.3.2.4 Use S to calculate the standard error. The standard deviation of the sample mean, called the standard error (S), can be used to determine how close the sample mean is to the population mean. A small S indicates that the sample mean is highly reliable in representing the population mean. Conversely, a large Sx indicates that its reliability is low.
A.4 Normal distribution
Normal distribution is mainly used for statistics where it is necessary to understand the distribution of each measured value around the mean. The normal curve is a bell-shaped curve with a peak in the middle, gradually decreasing at both ends and symmetrical, and never intersecting the horizontal axis. The distribution of the area under the curve has a certain regularity (as shown in the figure). In the figure, x is used as the estimated value of the population mean μ, S is used as the estimated value of the population standard deviation α (lowercase sigma), and the total area under the curve is taken as 100%. If the group of measured values conforms to the normal distribution, the area of X±S accounts for 68.26% of the total area, the area of X±2S accounts for 95.4% of the total area, and the area of x±3S accounts for 99.73% of the total area. In statistics, 1.96S is often used to represent 2S, and 2.58S is used to represent 3S as the calculation of the theoretical frequency of the normal distribution.
(frequency)
The area distribution diagram in the X±S interval under the normal distribution curve also has different ways of expressing the area in a certain interval. When u±a
is any value, the normal curve table can be used to calculate the theoretical frequency. The values in the table are not based on "", but on "O" as the center, corresponding to the single-sided area of different u values. For example, when u=1.5, the single-sided area is 0.4332, that is, 43.32%. For example, the starch content of rice (accounting for matter) is repeated 60 times, x=71.55, S=2.08, and the theoretical frequency in the range of 70.14~74.39% is calculated. Replace u with x and S with S, then u =
Substituting into the formula
t = 70.11-71.55- - 0. 68
uz = 74.39-7155=1.37
Looking up Table A2, when u1=0.68, the area on the left is equal to 0.2516, and when u2=1.37, the area on the right is equal to 0.4144. Therefore, the area of the interval -0.68 to 1.37 is 0.2516 + 0.4144 = 0.6630 = 66.60%, that is, the frequency of starch content in the range of 70.14 to 74.39% is 60 times 66.60%, which is approximately equal to 40 times (60 × 66.60% = 40). The area of a certain interval under the normal curve is shown in Table A2: Table A2
Linear regression
When the points on the standard curve deviate from the straight line, the linear regression equation can be used for calculation and then the curve can be drawn. y=a+bx.
Where: b—
slope of a straight line,
constant term of the straight line equation.
M (xy)
(Zx)(Ey)
0.4990324
0.4993129
0.4995166
0.4996631||t t||0.4997674
0.4998409
0.4998922
0.49992765
0.49995190
GB 5490-—85
Suppose n= 5.Zx= 47.2,Zy= 85.85,Z(xy) =821.266,Zx2= 459.26, (2x)2 = (47.2)2.
Substituting formula (A9) and (A10) to obtain 6 = 0.978, α = 7.884, substituting a and 6 values into formula (A8) to obtain: 3 = 7.884 + 0.978x
When x = 7, y = 14.73, x = 12, y = 19.62. The regression line can be determined by the two pairs of x and values calculated. A.6
Correlation coefficient
Correlation coefficient (r) indicates the degree of correlation between two variables. M(xy)
Assume that there are two groups of 5 pairs of measured values as shown in Table A3
Complete correlation
Incomplete correlation
(Zx)(Ey)
Take the completely correlated data in the table as an example to calculate the correlation coefficient r. ≥xy=125, Z×=15, Zy=35, Z×=55, Zy2=285.
Substituting into formula (A11), we get:
125~15×35
/(55-15
-)(285
V10×40
If the order of α in the table is reversed to 5, 4, 3, 2, 1, the relationship between × and is a completely negative correlation, and r is -1. 203
GB5490—--85
Appendix B
Preparation and calibration of several standard solutions
(reference)
B.11N, 0.5N and 0.1N sodium hydroxide standard solutions B.1.1 Preparation: Add sodium hydroxide Prepare a saturated solution of sodium, inject it into a plastic bucket and seal it until the solution is clear. Siphon the upper clear liquid with a plastic tube before use.
a. 1N sodium hydroxide standard solution: measure 52ml of saturated sodium hydroxide solution, inject it into 1000ml1 water without carbon dioxide, and shake well.
b. 0.5N sodium hydroxide standard solution: measure 26ml of saturated sodium hydroxide solution, inject it into 1000ml water without carbon dioxide, and shake well.
c.0.1N sodium hydroxide standard solution: measure 5ml of saturated sodium hydroxide solution, inject it into 1000ml water without carbon dioxide, and shake well.
B.1.2 Calibration
B.1.2.1 Determination method
a. 1N sodium hydroxide standard solution: weigh 6g of standard potassium hydrogen phthalate that has been dried at 105-110℃ to constant weight, accurate to 0.0002g. Dissolve in 80ml of water without carbon dioxide, add 2 drops of 1% phenolic acid indicator solution, and titrate with 1N sodium hydroxide solution until the pink color of the solution is the same as the standard color. Perform a blank test at the same time. b. 0.5N sodium hydroxide standard solution: weigh 3g of standard potassium hydrogen phthalate that has been dried at 105-110℃ to constant weight, accurate to 0.0002g. Dissolve in 80ml of water without carbon dioxide, add 2 Add 1% phenol indicator solution, and titrate with 0.5N sodium hydroxide solution until the pink color of the solution is the same as the standard color. Perform a blank test at the same time. C. 0.1N sodium hydroxide standard solution: weigh 0.6g of standard potassium hydrogen phthalate that has been dried at 105-110℃ to constant weight, and weigh to 0.0002g. Dissolve in 50ml of water without carbon dioxide, add 2 drops of 1% phenolic acid indicator solution, and titrate with 0.1N sodium hydroxide solution until the pink color of the solution is the same as the standard color. Perform a blank test at the same time. Note: To prepare the standard color, measure 80ml of pH 8.5 buffer solution, add 2 drops of 1% phenolphthalein indicator solution, and shake well. B.1.2.2 Calculate
The equivalent concentration of sodium hydroxide standard solution is calculated according to formula (B1): G
N=(V1-V.)×0.2042
Wherein: G—weight of potassium hydrogen phthalate, gsV——amount of sodium hydroxide solution, ml, V2—amount of sodium hydroxide solution used in blank test, ml, 0.2042—grams of potassium nitrogen per milligram equivalent of phthalate. (B1)
B.1.3 Comparison
B.1.3.1 Determination method: Measure 30.00~35.00ml of hydrochloric acid standard solution (1N, 0.5N, 0.1N), add 50ml of water without carbon dioxide and 2 drops of 1% phenolic acid indicator solution, and titrate with sodium hydroxide solution of corresponding concentration. When it is close to the end point, heat to 80℃ and continue to titrate until the solution turns pink.
B.1.3.2 Calculation: The equivalent concentration N of the sodium hydroxide standard solution is calculated according to formula (B2): N=
Wherein: V1—the amount of hydrochloric acid standard solution, ml, 204
GB 5490—-85
N,—the equivalent concentration of hydrochloric acid standard solution, N, V—the amount of sodium hydroxide solution, ml. B.21N, 0.5N and 0.1N hydrochloric acid standard solutions B.2.1 Preparation
a. 1N hydrochloric acid standard solution: measure 90ml of concentrated hydrochloric acid and inject it into 1000ml of water. b. 0.5N hydrochloric acid standard solution: measure 45ml of concentrated hydrochloric acid and inject it into 1000ml of water. c. 0.1N hydrochloric acid standard solution: measure 9ml of concentrated hydrochloric acid and inject it into 1000ml of water. B.2.2 Calibration
B.2.2.1 Determination method
a. 1N hydrochloric acid standard solution: weigh 1.6g of standard anhydrous sodium carbonate burned to constant weight at 270~~300℃, and weigh to 0.0002g. Dissolve in 50ml water, add 10 drops of bromocresol green-methyl red mixed indicator solution, titrate with 1N hydrochloric acid solution until the solution changes from green to dark red, boil for 2min, and continue to titrate until the solution is dark red after cooling. b. 0.5N hydrochloric acid standard solution: weigh 0.8g of standard anhydrous sodium carbonate burned to constant weight at 270-300℃, and weigh to 0.0002g. Dissolve in 50ml water, add 10 drops of bromocresol green-methyl red mixed indicator solution, titrate with 0.5N hydrochloric acid solution until the solution changes from green to dark red, boil for 2min, and continue to titrate until the solution is dark red after cooling. C0.1N hydrochloric acid standard solution: weigh 0.2g of standard anhydrous sodium carbonate burned to constant weight at 270-300℃, and weigh to 0.0002g. Dissolve in 50ml water, add 10 drops of bromocresol green-methyl red mixed indicator solution, titrate with 0.1N hydrochloric acid solution until the solution changes from green to dark red, boil for 2 minutes, cool and continue to titrate until the solution turns dark red. B.2.2.2 Calculate the equivalent concentration N of the hydrochloric acid standard solution according to formula (B3): G
N=(V.-VJ×0. 05299
Where: G—weight of anhydrous sodium carbonate, gs amount of hydrochloric acid solution, ml,
V---—amount of hydrochloric acid solution used in blank test, mls0.05299—grams per milligram equivalent of sodium carbonate. B.2.3 Comparison: The method is in accordance with B.1.3.
B.3 1N, 0.5N and 0.1N B.3.1 Preparation of sulfuric acid standard solution
a. 1N sulfuric acid standard solution: measure 30ml concentrated sulfuric acid, slowly inject into 1000ml water, cool, and shake. b. 0.5N sulfuric acid standard solution: measure 15ml concentrated sulfuric acid, slowly inject into 1000ml water, cool, and shake. c. 0.1N sulfuric acid standard solution: measure 3ml concentrated sulfuric acid, slowly inject into 1000ml water, cool, and shake. B.3.2 Calibration: The method is in accordance with B.2.2. | |tt||B,3.3 Comparison; Method according to B.2.3.
B.4 1N and 0.1N sodium carbonate standard solution
B.4.1 Preparation
a. 1N sodium carbonate standard solution: weigh 53g anhydrous sodium carbonate, dissolve in 1000ml water, shake well. b. 0.1N sodium carbonate standard solution: weigh 5.3g anhydrous sodium carbonate, dissolve in 1000ml water. Shake well. B.4.2 Calibration
B.4.2.1 Determination method
GB 5490--85
a1N sodium carbonate standard solution: Measure 30.00~35.00ml1N sodium carbonate solution, add 50ml water and 10 drops of bromocresol green-methyl red mixed indicator solution, titrate with 1N hydrochloric acid standard solution until the solution changes from green to dark red, boil for 2min, and continue to titrate until the solution turns dark red after cooling.
b.0.1N sodium carbonate standard solution: Measure 30.00~35.00ml0.1N sodium carbonate solution, add 20ml water and 10 drops of bromocresol green-methyl red mixed indicator solution, titrate with 0.1N hydrochloric acid standard solution until the solution changes from green to dark red, boil for 2min, and continue to titrate until the solution turns dark red after cooling.
B.4.2.2 Calculate the equivalent concentration N of the sodium carbonate standard solution according to Formula (B4) is used for calculation: V·N
Wherein——the amount of hydrochloric acid standard solution, mlN,—the equivalent concentration of hydrochloric acid standard solution, NV—the amount of sodium carbonate solution, ml.
B.50.1N potassium dichromate standard solution
B.5.1 Preparation: Weigh 5g potassium dichromate, dissolve it in 1000ml water, and shake it. B.5.2 Calibration
B.5.2.1 Determination method: Measure 30.00~35.00ml 0.1N potassium dichromate solution, place it in an iodine volumetric bottle, add 2g potassium iodide and 20ml 4N sulfuric acid, and shake it. Place it in a dark place for 10min. Add 150ml water and titrate with 0.1N sodium thiosulfate standard solution. When it is close to the end point, add 3ml 0.5% starch indicator solution and continue to titrate until the solution changes from blue to bright green. Perform a blank test at the same time. B.5.2.2 Calculate the equivalent concentration N of potassium dichromate standard solution according to formula (B5): Ns
(Vi-V,)ni
The amount of sodium thiosulfate standard solution, ml Where: V-
V——the amount of sodium thiosulfate standard solution used in the air test, ml, N,-the equivalent concentration of sodium thiosulfate standard solution, NV—the amount of potassium dichromate solution used, ml.
B,60. 1N Sodium thiosulfate standard solution
B.6.1 Preparation: Weigh 26g sodium thiosulfate (or 16g anhydrous sodium thiosulfate) and 3.8g borax, dissolve in 1000ml water, slowly boil for 10min, cool, and filter after standing for two weeks. B.6.2 Calibration
B.6.2.1 Determination method: Weigh 0.15g of standard potassium dichromate dried to constant weight at 120℃, accurate to 0.0002g. Place in an iodine volumetric flask, dissolve in 25ml of water, add 2g of potassium iodide and 20ml of 4N sulfuric acid, and shake well. Place in a dark place for 10min. Add 150ml of water, titrate with 0.1N sodium thiosulfate solution, add 3ml of 10.5% starch indicator solution when approaching the end point, and continue to titrate until the solution changes from blue to bright green, and perform a blank test at the same time.
B.6.2.2 Calculation
The equivalent concentration N of sodium thiosulfate standard solution is calculated according to formula (B6): G
N=(V,-V)×0. 04903
武 f: G=
-weight of potassium dichromate,
-amount of sodium thiosulfate solution used, ml,
GB 5490--85
amount of sodium thiosulfate solution used in blank test, ml, 0.04903-—grams of potassium dichromate per milligram equivalent. B.6.3 Comparison
B.6.3.1 Determination method: Accurately measure 30.00~~35.00ml of 0.1N iodine standard solution, place it in an iodine volumetric bottle, add 150ml of water, titrate with 0.1N sodium thiosulfate solution, add 3ml of 0.5% starch indicator solution when it is close to the end point, and continue to titrate until the blue color of the solution disappears. At the same time, perform a blank test of iodine consumed by water, the method is as follows: take 250ml of water, add 0.05ml of 0.1N iodine standard solution, 3ml of 0.5% starch indicator solution, and titrate with 0.1N sodium thiosulfate solution until the blue color of the solution disappears. B.6.3.2 Calculate the equivalent concentration N of sodium thiosulfate standard solution according to formula (B7): (V, - 0.05)N,
Wherein: V, — amount of iodine standard solution, ml, N, equivalent concentration of iodine standard solution, N,
V amount of sodium thiosulfate solution, mls
V, amount of sodium thiosulfate solution in blank test, ml; 0.05 — amount of iodine standard solution in blank test, ml. B.70.1N iodine standard solution
B.7.1 Preparation: Weigh 13g iodine and 35g potassium iodide, dissolve in 100ml water, dilute to 1000ml. Shake the hook and store in a brown stoppered bottle.
B.7.2 Calibration
B.7.2.1 Determination method: Weigh 0.15g of standard arsenic trioxide that has been dried to constant weight in a sulfuric acid dryer in advance, and weigh to 0.0002g. Place it in an iodine volumetric flask, add 4ml 1N sodium hydroxide to dissolve, add 50ml water, add 2 drops of 1% phenol indicator solution, neutralize with 1N sulfuric acid, add 3g sodium bicarbonate and 3ml 10.5% starch indicator solution, and titrate with 0.1N iodine solution until the solution turns light blue. Perform a blank test at the same time. B.7.2.2 Calculate the equivalent concentration N of the iodine standard solution according to formula (B8): G
N={V1-V)x0.04946
Where: G——weight of arsenic trioxide, g; V,——amount of iodine solution used, ml;
Va-amount of iodine solution used in a blank test, ml; 0.04946——grams of arsenic trioxide per milligram equivalent. B.7.3 Comparison: The method is in accordance with B.6.3.
B.8 0.1N potassium permanganate standard solution
B.8.1 Preparation: Weigh 3.3g potassium permanganate, dissolve in 1050ml water, boil slowly for 15min, cool and store in a dark place for two weeks. Filter with a No. 4 glass filter into a dry brown bottle. Note: The No. 4 glass filter used to filter the potassium permanganate solution should be slowly boiled for 5 minutes with the same potassium permanganate solution beforehand, and the collection bottle should also be washed 2 to 3 times with this potassium permanganate solution.
B.8.2 Calibration
B.8.2.1 Determination method: Weigh 0.2g of standard sodium oxalate dried to constant weight at 105-110℃, accurate to 0.0002g. Dissolve in 100ml of water containing 8ml of sulfuric acid, and add 0.Titrate with 1N potassium permanganate standard solution, heat to 65℃ when near the end point, and continue titrating until the solution turns 207
pink for 30s. Perform a blank test at the same time. B.8.2.2 Calculation
GB5490-85
The equivalent concentration N of potassium permanganate standard solution is calculated according to formula (B9): G
N=(V1-Vx0. 06700
Wherein. G-
Weight of sodium oxalate, g;
Amount of potassium permanganate solution used, ml;
Amount of potassium permanganate solution used in blank test, ml; 0.06700Number of grams of sodium oxalate per milligram equivalent. B.8.3 Comparative
Determination method: Measure 30.00-35.00 ml of 0.1N potassium permanganate solution, place it in an iodine volumetric flask, add 2g of potassium iodide and 20ml of 4N sulfuric acid, and shake well. Place in a dark place for 5 minutes. Add 150ml of water and titrate with 0.1N sodium thiosulfate standard solution. When it is close to the end point, add 3ml of 10.5% starch indicator solution and continue to titrate until the blue color of the solution disappears. Perform a blank test at the same time. B.8.3.2 Calculation
The equivalent concentration N of potassium permanganate standard solution is calculated according to formula (B10): N-(Vi-ve)n.
Wherein: V-
The amount of sodium thiosulfate standard solution, ml; The amount of sodium thiosulfate standard solution used in the blank test, ml: N1--The equivalent concentration of sodium thiosulfate standard solution, N; V The amount of potassium permanganate solution used, ml.
Additional remarks:
This standard was proposed by the Ministry of Commerce of the People's Republic of China. This standard was drafted by the Grain Storage and Transportation Bureau of the Ministry of Commerce. The main drafters of this standard are Gao Xiuwu, Yang Haoran, Wu Yanxia, and Lv Guifen. 208
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.