Determination of thiosulphate and other related residual chemicals in processed Photographic materials－Iodine-amylose, methylene blue and silver sulphide densitometric methods
Some standard content:
National Standard of the People's Republic of China
Deterxinatian nf thiosulphate and other related residual chemicals in processed photographic materials-lodinc-amyluse,methylenc blue and silver sulphide densitometric methods
GB/T 12938-91
This standard adopts the international standard IS0417--1977 "Determination of thiosulfate and other chemical residues in processed photographic materials--methylenc blue and silver sulphide densitometric methods". This standard is one of the specifications of the photoprocessing series. The determination of residual thiosulfate and its decomposition products can be used to evaluate the degree of sufficient washing of photographic materials and the durability of image preservation. 1 Subject content and applicable scope
This standard specifies a method for determining the total amount of residual thiosulfate and its decomposition products in processed photographic materials. The sensitivity of the thiosulfate content determination is greater than 0.1/cm. The determination range of the three methods is referred to Appendix B. This standard is only applicable to gelatin window silver photosensitive materials that are fixed with thiosulfate during processing and finally washed with water. This standard does not apply to black-and-white products that have not been fixed but stabilized. 2 Reference standards
GB 9019 Storage technology for the total glue ratio of processed films 3 Iodine-amylose method
This method must be used for RC photographic paper containing developer. This method can be used for all gelatin silver halide products that meet the requirements of this standard. The sample should be determined within two weeks after processing, and the detection range is 0.1~40 μE/cm\thiosulfate. 3.1 Method summary and principle
Take a certain area of sample and put it into the elution solution containing iodide ions to extract thiosulfate. AgS.0, + +21---2Ag+ +S,0
NalAg(S,O,J+I-AgI++S,O-+ Na+The solubility product of silver iodide is smaller than that of thiosulfate. The reaction proceeds to the right. Add a certain amount of formaldehyde and formic acid to the extraction solution containing thiosulfate. Prepare a solution A with a certain amount of formaldehyde and formic acid. Mix a certain amount of formaldehyde ions with excess iodide ions and starch solution. Add neutral acid to prepare a blue solution 13.IO:+5I-+6H+3I+3H,0
1,+starch→blue
After pouring solution A into solution B, thiosulfate ions reduce iodine molecules to iodide ions, causing the solution H to turn blue. The density decreases proportionally with the increase of the rolling degree of thiosulfate. I+25.0 $,02 +21
CB/T 12938—91
Use a spectrophotometer to determine the difference in optical density of the reduced blue color, and use this optical density difference to calculate the content of thiosulfate in the corresponding sample from the standard curve.
3.2 Reagents
3.2. 1 Formaldehyde (IICHIO); 236% (m/m) 3. 2. 2 Sodium hydroxide solution: c (NaOH)--1 tr1ol/L, slowly add 20. 0 g of sodium hydroxide into about 30 ml of water while stirring, and dilute to 50 ml with water after cooling.
3. 2. 3 Sulfuric acid solution: (H,50,)=0. 1 mal/L, transfer 0. 55 ml. of concentrated sulfuric acid into about 70 ml of water while stirring, and dilute to 100 ml with water.
3. 2.4 Potassium iodate solution: c(K10,: 0.000 1 mol/L., transfer 1.0 mL of potassium iodate solution (K10,) = 0.100 0 mol/L) into a 1.0 L volumetric flask and dilute to the mark with water. Note: If there is no commercially available c(K10,) C.100 01 nuL/L drop solution, weigh 5.35 = 0.000 2R of potassium iodate and drop it into about 120 ml. water, transfer 25cml. to the remaining bottle, dilute to the mark with water, that is (K10,) = 0.1000moL/L liquid. 3.2.5pH = 2.0 formic acid solution: measure 110mL of formic acid 88%~90% (m/m) and transfer to about 600ml water in the 11. mother bottle, dilute to the mark, add sodium chloride (3.2.2) at 21℃ and use a pH meter to adjust the pH to 2.0 ± 0.1. Note: Formic acid is flammable. Keep away from heat sources, sparks and open flames, and use exhaust equipment. Formic acid is corrosive and can cause burns: prevent contact with eyes, skin and clothes, and thoroughly wash after operation. 3.2.6pH = 2.8 formic acid solution: transfer 10.0ml pH-2.0 formic acid solution (3.2.5) to the 11. mother bottle and dilute to the mark: 3. 2.7 Zinc iodide amylose solution: Dissolve 0.1g zinc iodide 1 in 600ml water, boil for 15 minutes, add 5.0g amylose reagent 2 dissolved in 200ml water slowly while stirring, keep boiling and stirring for 5 minutes, then slowly add 50g acid washing analysis filter aid (diatomaceous earth) while stirring, keep boiling and stirring for 5 minutes. Then vacuum filter while hot, pad filter paper with Buchner funnel, and filter with 1L vacuum bottle. Transfer the filtered solution to 11.0 volumetric bottle, rinse the vacuum bottle with water, pour it into the volumetric flask, and dilute with water to 1L scale
Note: 1) If there is no zinc iodide, 0.1g potassium iodide (KI) can be used instead of 10.0, and the preparation method remains unchanged. However, the storage performance of the reagents using potassium iodide is not as good as that containing zinc. They should be stored in small bottles under low temperature conditions. If bacterial growth (appearance) and a lighter color (light absorption) are found, they should be discarded and cannot be used again.
2) If there is no amylose reagent, soluble starch of the same weight can be used instead. Its storage performance is not as good as amylose. Please pay attention to the precautions when using it.
3.2.8 Eluent
Dissolve 1.0±0.1 g iodide (KI) and 1.0±0.1 h potassium dihydrogen phosphate trihydrate (K,HP0, -3H,O) in 6 (1 L water, and transfer to a 1 L volumetric flask and dilute to the scale with water. At 21C, add sulfuric acid solution (3.2, 3) dropwise. Use a pH meter to adjust the pH to 8. 5;3.2.9 Sodium thiosulfate standard solution c(Na.50,)=0.100Umol/L. See (Appendix A) for preparation method. 3.3 Instruments and equipment
3.3.1 Visible light photometer or spectrophotometer, calibrated to 590nm, with 5cm colorimetric cell; 3.3.2 pH meter;
3.3. 3.3.4 Pretreatment of glassware: All glassware should be free of reducing substances or oxidizing substances and rinsed with iodide-starch solution. The method is as follows: 2 mL potassium iodate solution (3.2.4), 5 mL formic acid (3.2.5) with pH = 2.0, 5 mL zinc iodide-amylose solution (3.2.7), and about 100 ml of water are mixed to make a rinse solution. Rinse the container with this solution and then rinse with water; 3.3.5 Filter and 1 [vacuum bottle!
3.3.6 Buchner funnel and medium-speed filter paper,
3.3.7 Pipette: .0 mL, 3.0 ml. 5.0 ml. 10.0 ml. 1 GB/T 1293891
3. 3.8 Volumetric flask: 50 mL, 100 mL, 250 mL, 1 000 mL3. 3.9 Volumetric flask: 100 mL, 250 mL#
3.3. 10 Beaker: 50 ml., 100 ml.. 500 ml, 1 000 mL3.3.11 Glass shallow dish: Select according to the size of the dry plate. 3.4 Sample
The sample should be cut within two weeks after processing. Cut a 10 cm strip sample from the non-image area or low-density area (if it is a film, it should not contain the right film hole).
3.5 Iodine-amylose determination method I (measurement range 0. 1~~4μg/cm thiosulfate) 3.5.1 Blank test
Except without adding sample, follow 3.5.2~3.5, 6 steps to make three tests, and take the average value (or the group with the best repeatability) as the blank density value under the reagent conditions. If the reagent is changed or replaced, the test should be repeated. The blank density value should be between 0.7 and 0.8. Note: If the density of the blank solution is not within this range, the amount of potassium iodate solution (3.2.4) in 3.5.4 can be adjusted to about 0.8mL~1.0mL. 3.5.2 Extraction
a. Place 10mL of eluent (3.2.8) in a dry 50mL beaker. Fold the sample into a W shape and place it in the eluent. Shake the beaker until the sample is completely submerged. Shake frequently for 10 minutes. If it is medium-heavy or double-layer paper, the extraction time should be increased to 20 minutes. b. For flat plate samples, place them in a glass shallow dish slightly larger than 10 ct\, and use 1 ml. The eluent can be submerged. The extraction method is the same as that for film. After extraction, transfer as much solvent as possible into a 50mL beaker. If a larger plate is used, the ratio of eluent to plate should be kept at 1mL/cI. The most suitable container is 10 ml of the extracted liquid and put it into a 50 ml beaker.
3.5.3 Preparation of solution A
Add 1 mL of formaldehyde (3.2.1) to the 50 ml beaker (3.5.2) and shake for about 30 seconds until there are no oil droplets on the beaker wall. Then add 3 mL of formic acid (3.2,6) with a pH of 2.8 and shake for about 30 seconds until there are no oil droplets on the beaker wall. The preparation of solution A is completed. Reserve solution A for use in 3.5.5. 3.5.4 Preparation of solution B
In a 50 mL volumetric flask, transfer 1 ± 0.1 mL (see note to 3.5.1) of potassium iodate solution (3.2.4) and then transfer 5 mL of zinc iodide-amylose solution (3.2.7). Shake and mix for about 10 s. Finally, transfer 5 ml of H = 2.0 formic acid solution (3.2.5). After about 20 s of shaking, the solution turns blue and is prepared as solution B.
3.5.5 Preparation of optical density sample solution
Within 30 s after the formation of blue solution R (3.5.4), pour solution A in the beaker obtained in 3.5.3 into a 50 mL volumetric flask containing solution B (3.5.4). Rinse the sample and beaker with about 20 ml of water, pour them into the volumetric flask, and dilute to the mark with water. Cover tightly, mix thoroughly, and make a sample solution. Let it stand for 3 minutes before measuring the optical density. 3.5.6 Determination of optical density
should be completed within 15mil after the optical density sample solution (3.5.5) is prepared (otherwise the optical density value will decrease). Use a spectrophotometer to measure the optical density (ABS) value of the sample solution, with a wavelength of 590 nm, a 5cm colorimetric cell, and air as the reference zero point. Note: If the measured optical density (AJS) value of the sample solution is lower than 0.09, use method 3.6. If the test solution is the white liquor, the measured optical density is the narrow white liquor case value (AS). Calculate the optical density difference (AABS) of the sample solution. AABS - ARS type white ARS # product
3.5.7 Drawing of the standard curve of the iodine-amylose method 3.5.7.1 Preparation of sodium thiosulfate standard solution This standard solution should be used on the day of preparation. Transfer 25 ± 0.05 mL of sodium thiosulfate standard solution (3.2.9) to a 500 mL volumetric flask, dilute to the mark, stopper the flask, invert and mix for 8 to 10 times. Transfer 5 ± 0.02 mL of this solution to a 250 mL volumetric flask, and dilute to the mark with water. Stopper the flask and invert and mix for 8 to 10 times. The resulting standard solution contains 11.2 thiosulfate ions per mL. If the sodium thiosulfate standard solution of GB/T 12938-91
is the calibration concentration (Appendix A), the content of thiosulfate in each milliliter of sodium thiosulfate standard solution β is calculated by the following method. p= 112× c
wherein,
is the actual concentration of the sodium thiosulfate standard solution (Appendix A), mol/l. 3.5.7.2 Standard curve drawing steps
Use a graduated pipette to transfer the standard solution (3.5.7.1) into six 50mL beakers according to Table 1. Except for not adding samples, measure according to 3.5.2 to 3.5.6 respectively. Use the measured optical density difference (△ABS) as the ordinate and the corresponding measured thiosulfate content (Table 1) as the abscissa to draw a graph, and draw a curve similar to that in Figure 1. Table 1 Iodine-amylose method standard line sample
Beaker number
Standard solution (3.5.7.1), ml.
Thiosulfate content to be measured + μB
If the concentration of the sodium thiosulfate reference solution (3.2.9> used is the calibration concentration, the volume V of the sodium thiosulfate standard solution removed in Table 1 should be calculated according to formula (2):
—the thiosulfate content to be measured in Table 1 + 8, where: m-
βThe thiosulfate content per mL of sodium thiosulfate standard solution calculated according to formula (1), pg/ml,..(2) wwW.bzxz.Net
The same reagent should be used for standard curve and sample determination. If there is a change in the sample or a new reagent is replaced, the calibration should be repeated. The standard curve should be checked regularly (e.g. once every few weeks). Figure 1 is only an example of the standard curve. Each laboratory should establish its own actual standard curve. 0. 6
GB/T 12938—91
Sgo (rg)
Figure 1 Example of standard curve of iodine-amylose method 3.6 Iodine-amylose determination method I (measurement range 1~40 g/cm2 thiosulfate) When the thiosulfate content in the sample is too high (3.5.6 method 0)), and cannot be determined by 3.5, use the extraction dilution method to expand the range. It is best not to expand the range by reducing the area of the sample to be measured to ensure accuracy. Use a measuring bottle to measure 100 triL of eluent, transfer to a 500 ml. beaker, and extract a new 10 cm sample. Stir frequently for 10 min, and increase to 20 min for medium-weight and double-image paper. If it is a sample of other area, the above ratio of eluent volume to sample area (10 ml. /cm\) should be maintained. After sufficient stirring and mixing, transfer 10 mL of the extracted solution to a clean 50 mL beaker and continue to follow steps 3.5.3 to 3.5.6. The volume increase multiple of the above extraction dilution eluent is 10 times. If the test range is not suitable, you can also choose to increase the volume increase multiple of the dilution eluent line. The volume of the eluent before extraction dilution is 10 ml.
3.7 Expression of the test results
The optical density difference (AABS) measured in 3.5.6 is used to obtain the corresponding thiosulfate content () from the standard curve. After that, it is calculated according to formula (3):
9. For single-sided emulsion layer samples
Where:
-thiosulfate content,/cm
The corresponding thiosulfate content obtained from the standard curve, ug1K,-When using method 1 (3.6) to increase the process, the volume increase multiple of the extraction dilution eluent. When using method 1 (3.5), the K value is 1; Sr is the area of the sample to be extracted, cm2.
h For the double-sided emulsion layer (or the back gelatin layer) sample, the result measured by the above method is the total amount of thiosulfate contained in both sides. To convert it to the content of one side, the measured total amount should be divided by 2. Methylene blue method
Except for RC photographic paper containing developer, all gelatin silver halide products that meet the requirements of this standard can be used. The sample should be measured within two weeks after adding GB/T 12938
. The detection range is 0.1~～45μg/cm thiosulfate. 4.1 Method and principle
Take a certain area of sample and put it into the elution solution containing iodine ion to extract thiosulfate (see 3.1 chemical equation). Potassium borohydride is added to the extracted solution to reduce thiosulfate to sulfide under alkaline conditions. 3H,0+2S.0+RH,-2HS-+2HSO,-+H,BO,+2H and then add ketone to prevent the following side reaction: Fe (S0,)s-+H,s H=2FesO,+H,SO +$+ and continue to add sulfur, high-speed iron and NNI) reagent to make the reduced sulfide participate in the oxidation reaction to produce methyl blue. H,$+2
+2Fe(SO)FeSO,+-NHHSO
-N+(CH,)
After adding ferric sulfate reagent, the liquid medium becomes acidic, and the following side reaction will occur, producing a large amount of gas: 2KBH. +6H.0+H2SO+--2H,BO, +K,S0,+8H, +HS- +H,SO, --H,$ + +IISO,
Because the overflow of hydrogen sulfide gas reduces the content of sulfur ions in the methylene blue reaction, the NN reagent should be added quickly after the addition of ferric sulfate reagent.And prevent the overflow of hydrogen peroxide gas. Use a spectrophotometer to measure the blue optical density value formed after the formation of methyl blue, and calculate the corresponding thiosulfide content from the standard curve.
4.2 Reagents
4.2.1 Acetone (CHcXOCH). 299.5% (m/m); Note: Acetone is flammable and should be kept away from heat sources, sparks and open flames. Acetone gas is harmful to the human body and should be prevented from being inhaled. An exhaust device should be used. 4.2.2 Sodium hydroxide solution, c(VaOH)=U.2mol/L. Slowly add 0.8g sodium hydroxide to about 60mL water while stirring, and dilute to 100ml with water after cooling. :
4.2.3 Eluent: Dissolve 1.0±0.1g potassium iodide (KI), 20.0+0.1g potassium bromide (KBr), 1.0+0.1g potassium dihydrogen phosphate (KH,PO,) in 1L of water. This solution is stable for at least 8 months; 4.2.4 Potassium iodide nitride solution:
Dissolve 3.0g fresh potassium borohydrideAs the ordinate, and the corresponding measured thiosulfate content (ug) (Table 2) as the abscissa, draw a graph similar to Figure 2. Table 2 Standard curve of methylene blue method Sample
Test tube number
Standard solution (4.5.4.1)
Washing solution
Measured thiosulfate content
If the thiosulfate content in the sodium thiosulfate standard solution used is not 11.2μg/mL, but is calculated according to formula (1), then the volume V, (mL) of the sodium thiosulfate standard solution transferred in Table 2 should be calculated according to formula (4): V.
Where: state. The measured thiosulfate content in Table 2.\8; (4)
P——The content of thiosulfate in each liter of sodium thiosulfate standard solution calculated by formula (1), g/mL. When changing the volume of sodium thiosulfate standard solution in Table 2, the corresponding elution volume in Table 2 should be adjusted so that the sum of the elution solution and the standard solution remains at 5ml.
The same prepared reagent should be used for standard curve and sample determination. If the drug changes or new reagents are replaced, recalibration should be performed. The standard curve should be checked regularly. Figure 2 is only an example of the standard curve. Each laboratory should establish its own actual standard curve. 0.6
S,oi (μg)
Figure 2 Example of the standard curve of the methylene blue method
GH/T12938-91
4.6 Methylene blue determination method (measurement range 0. 9~45 Fg/cm2 thiosulfate). When the sample thiosulfate content is too high and cannot be determined by the method in 4.5, the dilution method is used to expand the range. It is best not to reduce the area of the sample to expand the range to ensure accuracy. If the test range is not suitable, you can also choose the multiple of the volume increase of the extraction dilution eluent. The volume of the eluent before dilution is 5 mL4.6.1 In a clean, dry 50mL beaker, add 25mL of the eluent (4.2.3) to extract a new 10cm sample. Stir frequently for 10 minutes, center weight, double photo paper. If other area samples, the ratio of the above eluent volume to the sample area should be maintained at 2.5ml/cm2,
4.6.2 The whole range of measurement is 0.9~4.5/cm thiosulfate. Transfer 5 mL of the extracted solution (4,6.1) to a 10 mL test tube with a lid, and continue with steps 4,5.2 to 4.5.3. 4.6.3 The measuring range of 4.5 to -45 °C:tm thiosulfate is 4.5 to -45 °C. Transfer 10 mL of the extracted solution (1.6,1) to a 100 mL volumetric flask, dilute to the mark with the eluent (1.2.3) and mix well (transfer 8 to 10 times). Transfer 5 mL of this solution to a 10 mL test tube with a lid, and continue with steps 1.5.2 to 4.5.3. 4.7 Expression of measurement results
After the optical density (AB5) value measured in 4.5.3 is checked from the standard curve for the corresponding thiosulfate content (), it is calculated according to formula (5): a, for single-sided emulsion layer sample
wherein: P is the thiosulfate content, ug/cm2; m, is the corresponding thiosulfate content, which is also checked from the standard curve; K is the multiple of the volume of the diluted eluent when the measuring range is expanded by using method 1 in 4.6. If 4.6.2 is used, the K value is 55
25×100
2=50. When 4.5 force method T is used, the K value is 1;
If 4.6.3 is used, the K value is
S—the area of the extracted sample, cm
b. For samples with double-sided emulsion (or with a gelatin layer on the back), the result measured by the above method is the total amount of silver sulfide contained on both sides. To convert it to the content on one side, the measured total amount should be divided by 25. Silver density method
All gelatin silver halide products that comply with the provisions of this standard and can combine with silver ions to form yellow-brown silver sulfide (AS) under the test conditions can use this method. Method, but the density difference of the sample to be tested should be higher than 0.(3, the detection range is greater than or equal to 0.9u/cm thiosulfate. The time after the sample is processed can exceed 2 weeks, because this method can measure the derivatives and decomposition products of thiosulfate. The permissible extension time is determined by experiment. 5.1 Summary and Principle of the Method
Diffuse half of a sample into the acidified silver nitrate reagent. If thiosulfate or polythionate and other containing substances are present, a yellow-brown silver sulfide density will be produced.
2Agt+5:0,-H=Ag:5<yellow-brown)++S0, then immerse the entire sample in sodium chloride melt to remove most of the adsorbed silver ions. Ag +CI-—AgCl (slightly soluble)
Then use a fixative to remove the remaining silver ions. 2Ag++Na2S,O,2Na++Ag2S,0,(male solution)AgS,Og+NaS,0, —2Na[Ag(S,O,)(micro)2NatAg(S.0.)+2Na,S,0, -..2Na.[Ag(S,O,).J(easy bath)After taking out the sample from the fixer and washing it with water, measure the density difference between the discolored area and the discolored area of the sample, and find the corresponding thiosulfate content from the standard curve,
5.2 Reagents
GB/T 12938—91
5.2.1 Silver nitrate-acetic acid solution: Dissolve 10g of silver nitrate in 750ml of water containing 30ml of glacial acetic acid L=90.5% (m/m) in a 1000mL volumetric flask. Mix and dissolve until dissolved, and dilute to the mark. Store in a brown bottle with a glass stopper and keep away from strong light. If the solution turns black, discard it.
Note: Silver nitrate is toxic. Once swallowed, it can cause blindness or death. If inhaled, the number of people recovered. If an accident occurs, medical care should be obtained immediately. 5.2.2 Sodium nitride solution: Dissolve 50g of sodium fluoride in water. , dilute to 11.; 5.2.3 Sodium thiosulfate-sodium sulfite fixer: Dissolve 19 parts sodium sulfite and 50 parts sodium thiosulfate pentahydrate in a 1000mL volumetric flask containing 750mL water, dilute to the scale, the water used should be water that has just been cooled. 5.3 Instruments and equipment
5.3.1 Ultraviolet spectrophotometer: can be calibrated to a wavelength of 320nm or 350nm; 5.3.2 Transmission densitometer that can measure ultraviolet,
5.3.3 Reflection densitometer that can measure ultraviolet region (used to measure samples for reflection viewing), 5.3.4 For 5.3.2, 5.3.3 The corresponding filter for light transmission in the ultraviolet region of the densitometer: The ideal spectral transmission state is the area under the curve in Figure 3, but in practical applications, as long as the peak of light transmittance is between 300400nm, most of it is included in the wavelength range under the curve (see Figure 3):
Figure 3 Ideal spectral transmission curve of silver sulfide density method filter 5.3.5 Beaker: 50mL.1000mL;
5.3.6 Volumetric flask: 1000mL.
5.4 Samples
Cut from the non-image area or the lowest density area Take a strip sample of about 10 m, fold it in half from the midpoint and cut it along the midline. The density of the two cut samples should be as similar as possible so that the density difference can be compared during the measurement. Do not scratch the film during the measurement. For dry plate samples, two samples should also be selected according to the requirements. When the area is too large, the ratio of the area to the solution should be maintained during the measurement, and the optical density measurement should be able to be performed.
5.5 Measurement
5.5.1 Preparation of silver sulfide density sample
Mark one of the two samples at the corners first, immerse it in 20 mL of silver nitrate-acetic acid solution (5.2.1), and stir it frequently for 4 min.
GB/T 12938 ---91
Then carefully take out the sample and drain it, and put it into 0mL sodium chloride solution (5.2.2) together with another sample, stirring frequently for 4 min.
Then carefully take out the two samples and drain them, and then immerse them into 20IL fixer (5.2.3), stirring frequently for 4 min. Then carefully take out the two samples, rinse them with plain water for about 10 minutes, and put them in a ventilated place to dry. The sample immersed in silver nitrate is a color-changing sample, and the sample not immersed in silver nitrate is a non-color-changing sample. 5.5.2 Determination of optical density
5.5.2.1 Transmission material sample
: Use ultraviolet spectrophotometer to measure the optical density (ABS) of the color-changing sample and the non-color-changing sample. Use 320nm wavelength for measurement (if this wavelength is not available, 350nm can also be used). Put the non-color-changing sample block in the reference light path and the color-changing sample block in the measurement light path. The measured value is the optical density difference (△ABS). You can also measure the optical density of the color-changing and non-color-changing sample blocks separately and then calculate the optical density difference. If the sensitivity is not enough, use a double-layer sample for measurement.
Calculation: AABS-ABS—ABS*chromaticity.
h.If there is a transmission densitometer and corresponding filter (5.3.4) that can measure the ultraviolet region, the density meter can be used to measure and find the optical density difference. If the sensitivity is not enough, the double-lip sample can be used for measurement. 5.5.2.2 Reflection material samples
Reflection material samples can only be measured with a reflection densitometer and corresponding filter (5.3.4) that can measure the ultraviolet region to find the optical density difference.
5.5.3 Drawing of the standard curve of the silver sulfide chromaticity method 5.5.3.1 Preparation of standard curve samples
After the type of sample to be measured is determined, the unexposed silver halide material of the same type is washed according to the correct processing technology. After the shading process is carried out, it is washed according to different washing times (it can also be done by hand), such as every 30 seconds as a sample, 0.5min1min, 1.5min, *, until the washing time specified in the process is reached. The size of each sample should be no less than 20 cm. Let the sample dry and wait for determination to obtain the same thiosulfate content sample. 5.5.3.2 Steps for drawing the standard curve
Number each sample in sequence, cut off a part and use the iodine-amylose method (or methylene method) to determine the thiosulfate content (μg/cm\) of each sample as the standard value. Then re-measure it using the silver sulfide density method to determine the density difference (AHS) between the color changing area and the non-color changing area of each numbered sample. Then use the measured density difference as the ordinate and the measured thiosulfate standard value (/cm\) of the corresponding sample as the abscissa, where the abscissa uses a logarithmic coordinate to draw a standard curve (see Figure 4). .
GB/T 12938—91
Use iodine amylose method or sub-methylene blue method to determine the thiosulfate content in the sample) Figure 4: Example of calibration curve of silver sulfide density method 50
When the product to be tested has been placed for a long time, the reliability of the corresponding relationship may be reduced. Therefore, the product within two weeks after processing should be used as the sample of the standard curve. The corresponding sample should be re-measured by silver sulfide density method every period of time (such as once a month) to see if the measured silver sulfide density difference has changed. Through experimental methods, find out the test period that this product can be placed after processing, that is, within this period of time, the product will not affect the test result when measured by silver sulfide density method. Different products of each type of material in the silver sulfide density method only correspond to the standard curve determined by experiment. When changing the variety of the sample to be tested, it must be re-calibrated. Each variety should have its own calibration curve. Due to different experimental conditions and product varieties, the shape of the standard curve may also change. Each laboratory should establish its own actual standard curve.
5.6 Description of the test results
The corresponding thioate content (ug/cm\) is obtained from the silver sulfide density difference (ABS) of the sample on the standard curve. When the density difference is less than or equal to 0.03, it can be ignored.
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