GOST 12558.1-78
GOST 12558.1−78 Alloys palladium-silver. Method for the determination of silver (with Change No. 1)
GOST 12558.1−78
Group B59
STATE STANDARD OF THE USSR
ALLOYS PALLADIUM-SILVER
Method for the determination of silver
Palladium-silver alloys. Method of the determination of silver
AXTU 1709*
_____________
* Introduced advanced Edit. N 1.
Valid from 01.07.79
before 01.07.84*
________________________________
* Expiration removed
Protocol N 3−93 Interstate Council
for standardization, Metrology and certification
(IUS No. 5/6, 1993). — Note
manufacturer database.
DEVELOPED by Sverdlovsk factory on processing of nonferrous metals
GL. engineer A. A. Kuranov
Heads: G. S. Haak, V. T. Levin, V. D. Ponomareva
Contractor R. M. Bogdanova
INTRODUCED by the Ministry of nonferrous metallurgy of the USSR
Member Of The Board Of A. P. Snurnikov
The draft all-Union scientific research Institute of standardization (VNIIS)
Director A. V. Gichev
APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR of March 24, 1978, N 793
REPLACE GOST 12558−67 in part of sec. 2
The Change N 1, approved and put into effect by the Decree of the USSR State Committee for standards from
Change No. 1 made by the manufacturer of the database in the text IUS N 2, 1989
This standard sets the potentiometric method for the determination of silver (at a mass fraction of silver from 15 to 85.0%) using the automatic titration unit in palladium-silver alloys.
The method is based on potentiometric titration of silver ion in ammonia medium with a solution of potassium iodide to a predetermined value of the potential difference. As the electrode is used Hartley electrode. The indicator electrode is a silver wire.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 22864−83.
(Changed edition, Rev. N 1).
1.2. The numerical value of the result of the analysis must end with the digit the same category, and permissible differences.
(Added, Rev. N 1).
2. APPARATUS, REAGENTS AND SOLUTIONS
Laboratory scales lever according to GOST 24104−88*.
______________
* On the territory of the Russian Federation GOST 24104−2001. — Note the manufacturer’s database.
Glasses with a capacity of 150 cmaccording to GOST 25336−82.
Burette with automatic zero setting capacity of 50 cm.
Nitric acid GOST 4461−77 diluted 1:1.
Ammonia water according to GOST 3760−79.
Silver brand 999,9 according to GOST 6836−80*.
______________
* On the territory of the Russian Federation GOST 6836−2002. — Note the manufacturer’s database.
pH meter laboratory pH-340.
Magnetic stirrer MM-2.
The block automatic titration lab BAT-12-LM.
Potassium iodide according to GOST 4232−74, solution concentration of 0.06 mol/l; prepared as follows: 9.6 g of potassium iodide dissolved in 500 cm
of water is added 1.06 g of anhydrous sodium carbonate according to GOST 83−79, the volume was adjusted to 1000 cm
water, and stirred.
Determination of the mass concentration of the solution of potassium iodide of 0.06 mol/DM.
A portion of silver with a mass of 0.18−0.20 g, weighed with accuracy of more than 0.0001 g, placed in a beaker with a capacity of 150 cm, is dissolved by heating in 10 cm
of nitric acid, diluted 1:1, heated to remove oxides of nitrogen, dilute with water to 30−50 cm
, neutralized with ammonia to a faint smell and cool. The solution was titrated as described in sec. 4.
Mass concentration of solution of potassium iodide (), expressed in g/cm
of silver, calculated by the formula
where — weight of silver, g;
— the volume of potassium iodide solution consumed for titration, sm
.
(Changed edition, Rev. N 1).
3. PREPARATION FOR ASSAY
3.1. Chemical method of dissolution of alloys with a mass fraction of palladium of not more than 60%
The sample shall be in the form of strips or chips.
A portion of the alloy (see table) was placed in a flask with a capacity of 250 cmand dissolved in 50 cm
of nitric acid, diluted 1:1.
| Mass fraction of palladium % | The mass of the alloy, g |
| From 15 to 45 | 0,25 |
| SV. 45 «60 | 0,5 |
| «60 | 1,0 |
After dissolving, the solution was evaporated to 10 cm, is diluted with 25 cm
of water, neutralized with ammonia before formation of the colorless complex of palladium and cooled.
(Changed edition, Rev. N 1).
3.2. Method of electrolytic dissolution of alloys with a mass fraction of palladium of not more than 60%
The sample shall be in the form of two plates of length 100 cm, width 35 cm
, thickness of 0.2−0.3 mm.
To remove dirt, wipe the plates with filter paper moistened with alcohol. In the presence on the surface of the plate tint plate are reduced by hydrogen.
The plates weighed, fixed in clamps and immersed in nitric acid diluted 1:1. The dissolution of lead with alternating current at a voltage of 12−15 V, current density of 0.65 A/cm. Dissolution time 2 h To preserve the original volume (300 cm
) in a glass from time to time, add a fresh portion of nitric acid.
After reconstitution, the current is turned off, Unscrew the plate, well washed with distilled water, dried, reduced with hydrogen and weighed.
The difference in weight of plates before and after dissolution the solution is the mass of the alloy.
The resulting solution was evaporated to 150 cm, cooled and filtered in a volumetric flask with a capacity of 250 cm
. The filter with precipitate was placed in a tared crucible, calcined at 800 °C, reduced in hydrogen and weighed. Mass of undissolved sediment is subtracted from the weight of the alloy.
The solution was adjusted to the mark with water, mix well and take three aliquote parts corresponding to the mass of alloy 0.5 g, which is placed in a flask with a capacity of 250 cm. In aliquote part added in 20 cm
of water, neutralized with ammonia to the formation of a colorless complex of palladium and cooled.
4. ANALYSIS
Included in the network of power instrument pH 340, BAT-12-LM and MM-2.
After warming up for 30 minutes check and adjust the zero control unit BAT-12-LM, which set the switch «Kind of» instrument pH 340 in position «+MV» switch «Swipe» at 1500 mV, setpoint: «Pulse flow» of the BAT-12-LM is set to the «0,2», the rotating axis of the potentiometer «Set. zero», achieve a situation in which the signal light «Titration» lights up or starts flashing. Then, the rotating axis of the potentiometer «Set. zero» in the opposite direction, to achieve a situation in which the signal light «Titration» is completely off.
Installed on the device BAT-12-LM setpoint «Set point» on the value «7» and precisely «to 0.3», which corresponds to 730 mV setpoint «exposure Time» 10 C and the setpoint «Pulse flow» zone of proportionality «in 2.0».
Attach the electrodes to the instrument pH 340. The reference electrode (Hartley) attached to the terminal «VSP», the indicator electrode (silver wire) to terminal «ISM».
To a solution of the analyzed alloy, prepared for analysis, down stirring rod and set beaker with the solution on the stirrer.
Immersed in the solution electrodes and the metering tube, which should be located close to the indicator electrode to avoid perelitsovyvat solution.
Switch the magnetic stirrer set at division 2 and at the end of the titration — division «4».
The addition of ammonia or nitric acid into the solution set the arrow of the instrument pH 340 to 1000 mV (if the arrow points to more than 1000 mV, ammonia is added).
Fill the burette with solution concentration of 0.06 mol/DMpotassium iodide and set the tap to a position at which the solution from the burette will flow.
Set the switch «works» of the BAT-12-LM to the «Titration down», when this warning light illuminates «Titration» and begins applying the solution concentration of 0.06 mol/DMof potassium iodide in a glass.
After the end of titration the indicator light «End of titration» and stops supply of the solution concentration of 0.06 mol/DMpotassium iodide. After which install switch the magnetic stirrer on the zero division, the switch «works» of the BAT-12-LM in the «Manual» position, remove the electrodes from the solution, raising the electrode holder in the upper position, and wash them with water.
The glass is removed from the magnetic stirrer is removed from the solution stirring rod and wash it with water.
(Changed edition, Rev. N 1).
5. PROCESSING OF THE RESULTS
5.1. Mass fraction of silver () in percent is calculated by the formula
where is the bulk solution concentration of 0.06 mol/DM
of potassium iodide consumed for titration, cm
;
— mass concentration of a solution of potassium iodide on silver, g/cm
;
— the mass of alloy,
5.2. The difference between the largest and smallest results of the three parallel measurements at a confidence level =0.95 does not exceed the absolute value of the admitted discrepancy
=0.15% at the mass concentration of silver from 15 to 40%
=0.25% when the mass fraction of silver in excess of 40%.
The difference between the two results of the analysis of the same sample obtained in different laboratories, should not exceed the absolute value of the admitted discrepancies =0,20% when the mass fraction of silver from 15 to 40%
=0,30% when the mass fraction of silver in excess of 40%.
5.1, 5.2. (Changed edition, Rev. N 1).
5.3. Control of the correctness of the results of determining the mass fraction of silver is playing its mass fraction in the artificial mixtures the chemical composition close to the composition of the analyzed alloy, drawn through the entire course of the analysis.
The sample analysis results are considered correct if the absolute difference between the maximum and minimum values of the mass fraction of silver in the synthetic mixture do not exceed 0.12% for the mass concentration of silver from 15 to 40% and 0.20% for the mass concentration of silver in excess of 40%.
(Added, Rev. N 1).
