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1. 970 669 3050 On the Worldwide Web www hach com E mail techhelp hach com FAX 970 669 2932 Hach Company 2005 All rights reserved Printed in Germany Updated April 05 Edition 1
2. After completing the sequence press GRAPH to view the best fit line through the standard additions data points accounting for matrix interferences Press IDEAL LINE to view the relationship between the sample spikes and the Ideal Line of 100 recovery See Optional Reagents and Apparatus on page 7 Silver Page 4 of 8 Silver_8120_PP fm Silver 0 005 to 0 700 mg L Standard Solution Method Prepare a 0 5 mg L silver standard solution as follows 1 Pipet 0 50 mL of Silver Standard Solution 1000 mg L into a 1000 mL volumetric flask using a Class A volumetric pipet Dilute to the mark with deionized water Prepare this solution daily Perform the silver procedure as described above 2 To adjust the calibration curve using the reading obtained with the 0 5 mg L silver standard solution press OPTIONS gt MORE on the current program menu Press STANDARD ADJUST 3 Press ON Press OK to accept the displayed concentration If an alternate concentration is used press the number to enter the actual concentration Press OK Press ADJUST Method Performance Precision Standard 0 500 mg L Ag Program 95 Confidence Limits of Distribution 660 0 488 0 512 mg L Ag Sensitivity Portion of Curve AAbs AConcentration Entire range 0 010 0 005 mg L Ag Digestion This digestion is for samples containing organic matter thiosulfate or cyanide Possible sources for these compounds are wastewater si
3. Silver Method 8120 Colorimetric Method Powder Pillows 0 005 to 0 700 mg L Scope and Application For water and wastewater Before starting the test Digestion is required for samples with interferences See Digestion on page 5 For more accurate results determine a reagent blank value for each new lot of reagent Follow the procedure using deionized water instead of the sample Subtract the reagent blank value from the final results or perform a reagent blank adjust The graduated cylinder must be completely dry before beginning the test If the Silver 1 Powder becomes moist it will not dissolve completely which will inhibit color development The sample pH for this test must be between 9 and 10 Do not use a pH meter to adjust the sample pH as it will cause contamination See Digestion on page 5 for the procedure to adjust pH Generate a blank for each sample Collect the following items Quantity Silver 1 Reagent Powder Pillow Silver 2 Reagent Powder Pillow Sodium Thiosulfate Powder Pillow Clippers Cylinder graduated 50 mL Cylinder graduated mixing 50 mL po a i l Sample Cells 10 mL square 1 inch Note Reorder information for consumables and replacement items is on page 7 Silver Silver_8120_PP fm Page 1 of 8 Silver 0 005 to 0 700 mg L Stored Programs 660 Silver Start 1 Select the test 5 Use a50 mL graduated cylinder to add 50 mL of sample to the 50 mL graduated
4. ium Thiosulfate Powder Pillow 1 50 pkg 22937 66 Required Apparatus Description Quantity Test Unit Cat No Clippers 1 each 968 00 Cylinder graduated 50 mL 1 each 21179 41 Cylinder graduated mixing 50 mL 1 each 1896 41 Sample Cells 1 inch square 10 mL matched pair 2 2 pkg 24954 02 Digestion Reagents and Apparatus Description Unit Cat No Hydrogen Peroxide 50 490 mL 21196 49 Phenolphthalein Indicator Solution 1 g L 15 mL SCDB 1897 36 Sodium Hydroxide Solution 50 500 mL 2180 49 Sodium Hydroxide Solution 1 00 N 100 mL MDB 1045 32 Sulfuric Acid ACS concentrated 2 5L 979 09 Thymolphthalein Indicator Solution 1 g L 15 mL SCDB 21853 36 Water deionized 4L 272 56 Boiling Chips silicon carbide 500 g 20557 34 Digesdahl Digestion Apparatus 115 V ac 50 60 Hz each 23130 20 Digesdahl Digestion Apparatus 230 V ac 50 60 Hz each 23130 21 Safety Shield for Digesdahl each 50030 00 Recommended Standards Description Unit Cat No Silver Standard Solution 1000 mg L Ag 100 mL 14613 42 Water deionized 4L 272 56 Optional Reagents and Apparatus Description Unit Cat No Cylinder mixing 50 mL 1896 41 Nitric Acid concentrated ACS 500 mL 152 49 Sodium Hydroxide 5 0 N 100 mL 2450 32 Silver Silver_8120_PP fm Page 7 of 8 FOR TECHNICAL ASSISTANCE PRICE INFORMATION AND ORDERING HACH COMPANY In the U S A Call toll free 800 227 4224 WORLD HEADQUARTERS Outside the U S A Contact the HACH office or distributor serving you Telephone
5. lphthalein Indicator Solution Add 2 drops of 1 g L Thymolphthalein Indicator Solution 14 Using sodium hydroxide adjust the pH of the solution to 9 10 The solution will be pink in this pH range Note A purple color indicates a pH greater than 10 If this occurs add a drop of sulfuric acid and 2 drops of each indicator repeat pH adjustment Initially use 50 sodium hydroxide then 1 N sodium hydroxide as the end point is approached 15 Filter turbid digestates Quantitatively transfer the filtrate or unfiltered sample to a clean 100 mL volumetric flask Dilute to the mark with deionized water The sample is ready for analysis Summary of Method Silver ions in basic solution react with cadion 2B to form a green to brown to red purple complex The sodium thiosulfate acts as a decolorizing agent for the blank The Silver 1 and Silver 2 reagents contain the buffer indicator and masking agents Organic extractions are not necessary and this method does not have as many interferences as the traditional dithizone method Test results are measured at 560 nm Silver Page 6 of 8 Silver_8120_PP fm Silver 0 005 to 0 700 mg L Consumables and Replacement Items Required Reagents Description Quantity Test Unit Cat No Silver Reagent Set 50 tests includes 22966 00 Silver 1 Reagent Powder Pillow 1 50 pkg 22935 66 Silver 2 Reagent Solution Pillow 1 50 pkg 22936 66 Sod
6. lver electroplating baths and silver strike solutions Digestion should be done with a Digesdahl Digestion Apparatus DANGER Perform this digestion under a fume hood Poisonous hydrogen cyanide gas may be generated a CAUTION Always wear safety glasses and use a safety shield or operate the Digesdahl within a closed fume hood Follow the additional safety precautions in the Digesdahl Digestion Apparatus Manual 1 Add an appropriate size sample to the 100 mL digestion flask for use with the Digesdahl Add several boiling chips to prevent bumping Note Appropriate sample size is determined experimentally The final sample concentration after dilution to 100 mL should be 0 0 6 mg L Larger dilutions may be necessary for electroplating baths and silver strike solutions Do not exceed the maximum sample volume of 25 mL Several 25 mL aliquots may be digested in succession to concentrate a very dilute sample 2 Turn on the water aspirator and make sure there is suction in the fractionating head 3 Add 3 mL of concentrated sulfuric acid to the sample in the volumetric flask Immediately place the head on the digestion flask Never use less than 3 mL of acid Silver Silver_8120_PP fm Page 5 of 8 Silver 0 005 to 0 700 mg L 4 Place the digestion flask on the heater Turn the temperature dial to 440 C 825 F 5 After the sample begins to char or the sulfuric acid reflux line becomes visible wait 3 5 minutes 6 Visuall
7. mixing cylinder Stopper and invert repeatedly for one minute Silver Page 2 of 8 2 Insert the Multi cell Adapter with the 1 inch square cell holder facing the user 6 Prepared Sample Fill a square sample cell to the 10 mL mark with the mixture 3 Add the contents of one Silver 1 Powder Pillow to a dry 50 mL graduated mixing cylinder If the Silver 1 Powder becomes wet at this point the powder will not dissolve completely which will inhibit color development 7 Blank Preparation Discard all but 25 mL of the sample from step 5 4 Add the contents of one Silver 2 Reagent Solution Pillow to the cylinder Swirl to completely wet the powder If clumps of dry powder are present when the sample is poured in the powder will not dissolve completely which will inhibit color development 8 Add the contents of one Sodium Thiosulfate Reagent Powder Pillow to the remaining 25 mL of sample Stopper and invert to mix Silver_8120_PP fm Silver 0 005 to 0 700 mg L Ooo Zero OK 10 mL 02 00 9 Press TIMER gt OK 10 Pour 10 mL of the 11 When the timer 12 Press ZERO f f blank into a second square expires insert the blank oe oe sample cell into the cell holder with the Me display will show p gin fill line facing the user 0 000 mg L Ag 13 insert the prepared sample into the cell holder with the fill line facing the user Results are in mg L Ag Interfere
8. nces Interference studies were conducted by preparing a known silver solution about 0 4 mg L and the potential interfering ion The ion was said to interfere when the resulting concentration changed by 10 Table 1 Interfering Substances and Levels Interfering Substance Interference Levels Aluminum Negative interference above 30 mg L Ammonia Negative interference above 750 mg L Cadmium Negative interference above 15 mg L Calcium Positive interference above 600 mg L Chloride Negative interference above 19 mg L Chromium amp Negative interference above 90 mg L Copper Negative interference above 7 mg L Iron Negative interference above 30 mg L Lead Negative interference above 13 mg L Manganese Negative interference above 19 mg L Silver Silver_8120_PP fm Page 3 of 8 Silver 0 005 to 0 700 mg L Table 1 Interfering Substances and Levels continued Interfering Substance Interference Levels Magnesium Positive interference above 2000 mg L Mercury Positive interference above 2 mg L Nickel Negative interference above 19 mg L Zinc Negative interference above 70 mg L Sample Collection Storage and Preservation Collect samples in acid cleaned glass or plastic bottles Using pH paper adjust the pH to 2 or less with concentrated Nitric Acid about 2 mL Jliter Store preserved samples at room temperature for up to 6 months If the sample contains particulates or only dis
9. solved metal content is being determined filter through a 0 45 um filter at collection After filtration adjust the pH to 2 or less as described above for storage Before analysis adjust the pH to 9 10 with 5 0 N Sodium Hydroxide See steps 13 14 of Digestion on page 5 Do not use a pH meter because of silver contamination from the electrode Accuracy Check Standard Additions Method Sample Spike 1 2 After reading test results leave the sample cell unspiked sample in the instrument Press OPTIONS gt MORE Press STANDARD ADDITIONS A summary of the standard additions procedure will appear Press OK to accept the default values for standard concentration sample volume and spike volumes Press EDIT to change these values After values are accepted the unspiked sample reading will appear in the top row See the user manual for more information Add 5 00 mL of 1000 mg L Silver Standard Solution to a 100 mL volumetric Class A flask Dilute to volume with deionized water This is a 50 0 mg L standard solution Prepare three sample spikes Fill three mixing cylinders with 50 mL of sample Use the TenSette Pipet to add 0 1 mL 0 2 mL and 0 3 mL of standard respectively to each sample and mix thoroughly Analyze each sample spike as described in the procedure above starting with the 0 1 mL sample spike Accept each standard additions reading by pressing READ Each addition should reflect approximately 100 recovery
10. y confirm the presence of acid in the flask before adding hydrogen peroxide 7 Add 10 mL of 50 hydrogen peroxide to the sample via the capillary funnel in the fractionating head 8 After the hydrogen peroxide has boiled off heat the sample until heavy white sulfuric acid fumes are present Continue heating and reduce the sample volume to near dryness Do not let the sample go completely dry at any time Note If the sample evaporates turn the Digesdahl off and cool completely Add water to flask before handling Repeat digestion from the beginning Note If only thiosulfate is present in the sample proceed to step 1 of the Colorimetric procedure 9 Add another 3 mL of sulfuric acid via the capillary funnel 10 Add another 5 mL of hydrogen peroxide Check the solution for digestion completion If digestion is not complete continue adding hydrogen peroxide in 5 to 10 mL portions Several portions may be necessary Note Digestion is complete when the digestate is colorless or the color of the digestate does not change upon addition of hydrogen peroxide Also a completely digested sample will not foam 11 After digestion is complete and all the hydrogen peroxide is boiled off reduce the volume of the digestate to near dryness Do not allow the sample to become completely dry Remove the flask from the heater Cool to room temperature 12 Slowly add about 25 mL of deionized water to the cooled flask 13 Add 2 drops of 1 g L Pheno

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