1、INTERNATIONAL STANDARD IS0 10348 First edition 1993-02-01 Photography - Processing wastes - Determination of silver content Photographie - Effluents de traitement - D it encompasses the field of analysis of silver in photographic effluents. Analysis for silver in photographic products and effluents
2、presents unique problems in sampling, handling and treatment. These problems are not always adequately covered in standard references. It is the purpose of this International Standard to provide methodology both for sample handling and for the analysis of silver in effluents. Some of the chemicals s
3、pecified in the test procedures are caustic, toxic or otherwise hazardous. Specific warning, caution and danger notices are noted for particularly hazardous materials but normal precautions required during the performance of any chemical procedure shall be exercised at all times. In the case of effl
4、uents, the photographic laboratory can best establish its conformity to regulations by appropriate chemical analysis. In some cases, in-house analyses will be possible; often the use of an outside laboratory will be required. Silver in photographic processing wastes originates as a soluble thiosulfa
5、te or other complex. Other waste components, however, may interact, re- sulting in an unstable system containing varying amounts of soluble forms of silver. Waste samples to be analysed for heavy metals are normally stabilized by acidification with nitric acid. This treatment is unsatisfactory for s
6、ilver in effluents containing photographic processing wastes. Since thiosulfate is unstable in acid solutions, the conventional treatment can actually promote the formation of insoluble silver. Cyanogen iodide (CNI) solution is the effective preservative for silver in these effluents.) This Internat
7、ional Standard includes flame atomic absorption spectroscopy (AAS) and two potentiometric iodide titration (PT) methods of analysis. The method employed will dictate the way in which the sample is preserved and treated. Samples to be analysed by the AAS method are normally ready for analysis, once s
8、tabilized with CNI solution. The iodide titration methods, however, require a digestion to solubilize the silver and remove interfering species followed by a boiling step (for Digestion A) to concen- trate the sample. The standard digestion methods for AAS, which rec- ommend the use of hydrochloric
9、acid, are not suitable for the preparation of samples for silver analysis, I) Owerbach, D. The use of cyanogen iodide (CNI) as a stabilizing agent for silver in photographic processing effluents. Journal of Applied Photographic Engineering, 4(l), pp. 2-24, 1978. V INTERNATIONAL STANDARD IS0 10348:19
10、93(E) Photography - Processing wastes - Determination of silver content 1 Scope This International Standard gives methods for deter- mining the silver content in photographic effluents from photographic processing wastes. Sampling, sample preservation and analytical methodology are included. Three a
11、nalytical procedures are given with two sup- porting sample treatment methodologies: a) a flame atomic absorption spectroscopy (AAS) method; b) two potentiometric iodide titration (PT) methods. The choice of treatment is dependent on the analysis method and form of sample. Where AAS is the cho- sen
12、method for analysis, cyanogen iodide-treated or preserved samples may be analysed directly. For the PT method, two digestion procedures are given: Di- gestion A for effluents with low salt content, and Di- gestion B for samples with high solids content. 2 Normative references The following standards
13、 contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to in
14、vestigate the possibility of applying the most re- cent editions of the standards indicated below. Members of IEC and IS0 maintain registers of cur- rently valid International Standards. IS0 385-l :I 984, Laboratory glassware - Burettes - Part I: General requirements. IS0 648: 1977, Laboratory glass
15、ware - One-mark pipettes. 2) To be published. (Revision of IS0 56673:1985) IS0 835-l :1981, Laboratory g/assware - Graduated pipettes - Pat-t 1: Genera/ requirements. IS0 835-2:1981, Laboratory g/assware - Graduated pipettes - Part 2: Pipettes for which no waiting time is specified. IS0 835-3:1981,
16、Laboratory glassware - Graduated pipettes - Part 3: Pipettes for which a waiting time of 15 s is specified. IS0 835-4:1981, Laboratory glassware - Graduated pipettes - Part 4: Blow-out pipettes. IS0 1042:1983, Laboratory glassware - One-mark volumetric f/asks. IS0 3696:1987, Water for analytical lab
17、oratory use - Specification and test methods. IS0 4788:1980, Laboratory glassware - Graduated measuring cylinders. IS0 5667-l :1980, Water quality - Sampling - Part 1: Guidance on the design of sampling pro- grammes. IS0 5667-2:1991, Water quality - Sampling - Part 2: Guidance on sampling techniques
18、. IS0 5667-3:-2), Water quality - Sampling - Part 3: Guidance on the preservation and handling of samples. IS0 6353-l :I 982, Reagents for chemical analysis - Part I: Genera/ test methods. IS0 6353-2:1983, Reagents for chemical analysis - Part 2: Specifications - First series. IS0 63533:1987, Reagen
19、ts for chemical analysis - Part 3: Specifications - Second series. 1 IS0 10348:1993(E) 3 Principle 3.1 Flame atomic absorption spectroscopy (AAS) methodology A silver-containing lamp, when heated to excitation, generates a spectrum which includes the ultraviolet emission bands of the silver atom. Th
20、e silver ions in a solution aspirated into a flame will absorb the silver emission bands when light from the lamp is passed through the flame, according to a Beers law relation- ship: where As T TO k is the concentration of silver ions; is the transmittance of light through the flame at the specifie
21、d wavelength aspir- ated with the sample; is the transmittance of light through the flame at the specified wavelength aspir- ated with a silver-free reference sample; is a constant. A calibration curve is normally generated to define the relationship specifically. 3.2 Potentiometric titration (PT) m
22、ethodology The titration of a solution containing silver ions with an iodide solution will form a precipitate of silver iodide in accordance with the reaction: Ag+ + I- 3 Agl(solid) A silver electrode, either prepared from a silver billet (11 .1.2) or an iodide-selective electrode, with an ap- propr
23、iate reference electrode will generate a potential in the presence of a solution containing silver ions in accordance with the Nernst equation: E = E, I- 0,023(RT/nF)40g(cAg) where E is the measured potential, in volts; EO is the base potential, including the refer- ence electrode contribution, in v
24、olts; R is the universal gas constant; T is the thermodynamic temperature; n is the number of electrons transferred; F is the Faraday constant; % is the concentration of silver ions. In the presence of an excess of iodide ions, the silver ion concentration, c Cl is the concentration of iodide ions.
25、A sharp change in potential is obtained during the titration as the solution progresses from one with sil- ver ions in excess to one with iodide ions in excess. 4 Reliability The practical lower limits (approximate) for silver analyses are the following Direct flame AAS 03 mg/l PT, Digestion A (samp
26、le 500 ml; titrant 0,001 mol/l potassium iodide) 02 w/l PT, Digestion B (sample 1,0 ml; titrant 0,001 mol/l potassium iodide) 100 mg/l The 2a confidence limits for Digestion A, as deter- mined through inter-laboratory tests, are equal to + 0,12 mg/l for samples containing 0,2 mg/l to 4,0 mg/l of sil
27、ver in effluent samples. These results are based on seventeen data points obtained from six different laboratoriesa. This value is true for both potentiometric iodide titration methods using either the manual method (pH-meter) or the automatic titrimeter method with a titrant addition rate of 0,l ml
28、/min. The 20 confidence limits for the flame AAS method are equal to & 0,007 mg/l for samples containing 0,02 mg/l to 0,05 mg/l of silver in photographic effluents, when directly aspirated after a five-fold sample volume reduction. 5 Safety and operational precautions The test procedure for silver a
29、nalysis given in this International Standard requires careful technique by an experienced operator. It requires care in sample storage and safe handling of both the sample and re- agent solutions due to the hazards and/or toxicity of the cyanogen iodide stabilizing agent and other sol- utions. Due t
30、o the vigorous agitation and possible loss by splashing in the potentiometric iodide titration, careful monitoring of the procedure is required. The unique requirements and the large number of items 3) For an explanation on how the data were treated, see the ASTM Handbook on Statistical Methods. Cop
31、ies are available from ASTM, 1916 Race Street, Philadelphia, PA 19103, USA. 2 IS0 10348:1993(E) in separate categories result in the following safety and operational precautions. 5.1 Hazard warnings Some of the chemicals specified in the test pro- cedures are caustic, toxic or otherwise hazardous. S
32、afe laboratory practice for the handling of chemicals requires the use of safety glasses or goggles, rubber gloves and other protective apparel such as face masks or aprons where appropriate. Specific danger notices are given in the text and footnotes for par- ticularly dangerous materials, but norm
33、al precautions are required during the performance of any chemical procedure at all times. The first time that a hazardous material is noted in the test procedure section, the hazard will be indicated by the word “DANGER” fol- lowed by a symbol consisting of angle brackets “c ” containing a letter w
34、hich designates the spe- cific hazard. A double bracket II will be used for particularly perilous situations. In subsequent statements involving handling of these hazardous materials, only the hazard symbol consisting of the brackets and letter(s) will be displayed. Furthermore, for a given material
35、, the hazard symbols will be used only once in a single paragraph. Detailed warnings for handling chemicals and their diluted solutions are beyond the scope of this Inter- national Standard. Employers shall provide training and health and safety information in conformance with legal re- quirements.
36、The hazard symbol system used in this International Standard is intended to provide information to the users and is not meant for compliance with any legal requirements for labelling as these vary from country to country. It is strongly recommended that anyone using these chemicals obtain from the m
37、anufacturer pertinent information about the hazards, hand- ling, use and disposal of these chemicals. 5.2 Hazard information code system Harmful if inhaled. Avoid breathing dust, vapour, mist or gas. Use only with adequate ventilation. Harmful if contact occurs. Avoid contact with eyes, skin or clot
38、hing. Wash thor- oughly after handling. Harmful if swallowed. Wash thoroughly af- ter handling. If swallowed, obtain medical attention immediately. May be fatal if swallowed. If swallowed, obtain medical attention immediately. Will burn. Keep away from heat, sparks and open flame. Use with adequate
39、ventilation. Oxidizer. Contact with other material may cause fire. Do not store near combustible materials. 5.3 Safety precautions ALL PIPETTE OPERATIONS SHALL BE PER- FORMED WITH A PIPETTE BULB OR PLUNGER PIPETTE. Failure to observe this warning notice can result in cyanide poisoning. THIS IS A CRI
40、TI- CAL SAFETY WARNINGI Digestion procedures shall be performed in a fume hood. Hydrogen cyanide or other toxic substances can be evolved. Safety glasses shall be worn for all laboratory work. Cyanogen iodide may be decomposed by treat- ment with sodium hypochlorite. 5.4 Operational precautions 5.4.
41、1 The cyanogen iodide (CNI) silver solvent shall be added to the bulk sample a sufficient time before the test sample is taken, to ensure complete dissol- ution of occluded or precipitated silver. If a bulk sam- ple is acidic, it shall be neutralized before CNI is added. The minimum reaction time af
42、ter CNI addition is 1 h. CNI may be added at the bulk sampling time. The treated sample is stable indefinitely. 5.4.2 Bulk samples containing large quantities of sil- ver, to be dissolved by the addition of large volumes of CNI (up to 20 % addition), shall have the original bulk sample volumes recor
43、ded at the bulk sampling time before the addition of CNI. When tested, the di- lution factor given in 8.2.3 shall be used with the AAS value to find the true concentration of the sample. The recommended reaction time is overnight for samples with large silver concentrations resulting from particulat
44、e matter. Representative samples, including solids and particulate matter, shall be taken for true silver values. Representative sampling shall also take into account adsorption of silver or precipitation of silver species on the container walls. Appropriate treatment of the container when removing the sample is necessary. 5.4.3 Where CNI preservation is used, the sample container material is not of significant concern. In these cases, plastic containers are preferred to avoid breakage. In any event, sample containers shall be properly cleaned (see 5.4.5). 3
