GB/T 9104.4-1988 Test method for industrial stearic acid - Determination of color GB/T9104.4-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test methods for industrial stearic acids-Determination of colour
Subject content and scope of application
This standard specifies the method for determining the colour of industrial stearic acid by platinum-cobalt colour number spectrophotometry. 2 Principle
UDC668.1.012
：543.06
GB 9104.4—88
Based on the similar spectral absorption characteristics of fatty acid samples and platinum-cobalt standard colour numbers, a spectrophotometer is used to measure the absorbance of a series of standard colours at a certain wavelength and draw a working curve. The absorbance of the sample is measured at the same wavelength, and the corresponding fatty acid colour value is obtained by comparing it with the drawn working curve. It is expressed in platinum-cobalt colour units (Hazen). 3 Instruments and reagents
3.1 Instruments
3.1.1 Spectrophotometer wavelength range 360~800nm. 3.1.2 Six-hole constant temperature water bath
3.1.3 Beaker 50mL, several
3.2 Reagents
3.2.1 Cobalt chloride hexahydrate CoCl2·6H,O (GB1270). 3.2.2 Potassium chloroplatinate (K,PtCl.), analytical grade. 3.2.3 Hydrochloric acid (GB622).
4 Test steps
4.1 Instrument installation and calibration
4.1.1 The spectrophotometer should be placed in a dry room, on a stable workbench. The indoor lighting should not be too strong, and it is forbidden to use an electric fan to blow air directly to the instrument.
4.1.2 Check whether the position of each adjustment knob is correct, turn on the power, and adjust the pointer of the meter to the 0\ position. 4.1.3 Turn on the power, open the cover of the colorimetric III dark box, adjust the "wavelength knob, adjust the wavelength to 420nm, and set the "amplifier sensitivity selection" knob to "2". Adjust the "zero adjustment" knob to make the meter pointer at the "0" position. Cover the colorimetric dark box, the colorimetric band is in the distilled water calibration position, so that the photoelectric tube is exposed to light, and adjust the "full scale" knob to make the meter pointer at the full scale position. 4.1.4 The principle of selecting the position of the "amplifier sensitivity" knob is: when ensuring that the "full scale" knob can be well adjusted and the meter is in the full scale state, try to adjust the sensitivity knob to a lower position as much as possible, so that the instrument has higher stability. When using it, first set it to the "1" position, and if the sensitivity is not enough, then gradually increase it. After changing the sensitivity position, you need to readjust the 0" position and full scale of the meter according to 4.1.3. 4.1.5 After the instrument is adjusted according to the provisions of 4.1.3, preheat for about 20 minutes, and then adjust it repeatedly according to the provisions of 4.1.3 several times until the pointer of the meter correctly points to the 0 position and the full scale. 4.2 Drawing of standard working curve
4.2.1 Preparation of standard color mother solution
GB 9104.4--88
In a 1000mL volumetric flask, dissolve 1.00g of cobalt chloride hexahydrate and 1.245g of potassium chloroplatinate in water, add 100mL of hydrochloric acid solution, dilute to the scale, and mix evenly. Note: The absorbance of the standard color mother solution can be checked by a spectrophotometer with a 1cm cuvette at a wavelength of 430nm. The absorbance range should be 0.110~0.120.
4.2.2 Preparation of platinum-cobalt standard colorimetric solution Transfer the standard colorimetric mother solution into 20 100mL volumetric flasks according to the volume listed in the table below, dilute to the mark with distilled water, and shake well to form the platinum-cobalt standard colorimetric solution.
Preparation of platinum-cobalt standard colorimetric solution
Platinum-cobalt colorimetric
Unit (Hazen)
Absorb standard mother solution
Platinum-cobalt colorimetric
Unit (Hazen)
Absorb standard mother solution
4.2.3 Drawing of standard working curve of platinum-cobalt colorimetric unit (Hazen)-absorbance (A) 30
Place the prepared 20 platinum-cobalt standard colorimetric solutions one by one in 10cm colorimetric blood. Use distilled water as reference and measure the absorbance (A) at a wavelength of 420nm with a spectrophotometer. Then use regression analysis to find the linear equation Y (Hazen) = a + bX absorbance (A). Using this linear equation, with platinum-cobalt color units (Hazen) as the ordinate and absorbance (A) as the abscissa, draw a standard working curve in two sections. Note: For the drawing of the standard curve and the method of finding the linear equation, please refer to Appendix A (reference). 4.3 Place the stearic acid sample in a dry and clean 50mL beaker and heat it to 75±5℃ on a water bath. After it is completely melted, immediately pour it into a pre-warmed 10cm colorimetric III, measure it, and read the absorbance value. The average value of the readings repeated three times is taken as the final measurement result.
The range of the readings of the three determinations shall not exceed 0.005. 5 Expression of the determination results
The average absorbance of the three determinations obtained in 4.3 is checked against the Hazen-absorbance (A) standard working curve to obtain the corresponding chromaticity value; or the average absorbance is substituted into the linear equation to obtain the chromaticity value, which is the color of the sample. 108
GB 9104.4—88Www.bzxZ.net
Appendix A
Regression analysis method to obtain the linear equation
Reference
For the drawing of the platinum-cobalt chromaticity unit-absorbance standard working curve and the method of obtaining the linear equation, the following steps can be followed. A1 determines the absorbance of platinum-cobalt standard colorimetric solution (wavelength 420nm, 10cm colorimetric III, measurement data of no less than twelve pieces), and the absorbance value is as follows:
(Hazen)
Absorbance (A)
Use regression analysis to obtain the equation of the straight line
The equation of the straight line is:
In the formula:
(Hazen)
Absorbance (A)
Y(Hazen)=a+b×(Absorbance A)
n.EXY - EX.ZY
n. EX2 -- (EX)2
a=— bx
The relevant values ​​in formula (2) and formula (3) are calculated using Table A2. Table A2
4. 84×10-4
1.255×10-3
2.116×10-3
4.225×10-3
7.056×10-3
9.409×10-3
Substituting the relevant values ​​in the above table into formula (2) and formula (3) we get: XY
(Hazen)
Absorbance (A)
*++.*..++++--.+-( 2)
Equation of the straight line
A3 Drawing the standard working curve
GB 9104.488
b15×.1060.6-4.51×1490
15 × 3.16 (4. 51)2
a=99.33340×0.3007~-3
Y(Hazen）= 340 ×（Absorbance A） 34
Use platinum-cobalt chromaticity unit (Hazen) as ordinate and absorbance (A) as abscissa, and draw the standard working curve in two sections according to formula (4). The division range of the two sections is based on the principle of convenient table lookup. Generally, the chromaticity value of the first section is 0～60, and the absorbance value is 0～0.19; the chromaticity value of the second section is 50～500, and the absorbance is 0.1～1.3.
Additional remarks:
This standard is proposed by the Ministry of Light Industry of the People's Republic of China. This standard is under the technical jurisdiction of the Daily Chemical Industry Science Research Institute of the Ministry of Light Industry. This standard was drafted by Shanghai Synthetic Detergent Factory. The main drafter of this standard is Xu Xingsu.
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.