GOST 23859.7-79
GOST 23859.7−79 heat-resistant Bronze. Method for determination of lead (with Amendments No. 1, 2)
GOST 23859.7−79
Group B59
INTERSTATE STANDARD
BRONZE HIGH-TEMPERATURE
Method for determination of lead
Bronze fire-resistance. Method for the determination of lead
AXTU 1709
Date of introduction 1981−01−01
Resolution of the USSR State Committee for standards, dated 16 October 1979, N 3937 time of the introduction set with 01.01.81
Limitation of actions taken by Protocol No. 5−94 of the Interstate Council for standardization, Metrology and certification (ICS 11−12−94)
EDITION with Amendments No. 1, 2 approved in June 1985, March 1990 (IUS 9−85, 7−90).
This standard sets the polarographic method for the determination of lead (with a mass fraction of lead from 0.002 to 0.05%) in high-temperature copper alloys.
The method is based on the release of lead by coprecipitation with ferric hydroxide (III) ammonia in the environment and then defining it on polarography AC on the background of 1 mol/lphosphoric acid. The peak current recovery of lead is recorded at minus 0.55 V.
(Changed edition, Rev. N 1, 2).
1. General requirements for method of analysis according to GOST 25086−87 with the addition of a GOST 23859.1−79, sec. 1.
(Changed edition, Rev. N 2).
2. APPARATUS, REAGENTS AND SOLUTIONS
Polarograph AC PPT-1.
The polarographic cell (with a capacity of 40 cm), made of glass with an external electrode (saturated calomel electrode) and mercury dripping electrode.
Nitric acid GOST 4461−77 and diluted 1:1.
Hydrofluoric acid according to GOST 10484−78.
Ammonia water according to GOST 3760−79 and diluted 1:50.
Orthophosphoric acid according to GOST 6552−80, and 1 mol/DMsolution.
Iron chloride according to GOST 4147−74, a solution of 10 g/DMhydrochloric acid is diluted 5:100.
Hydrochloric acid by the GOST 3118−77, diluted 1:1 and 5:100.
The acid chloride.
Lead brands S0 according to GOST 3778−98.
Standard solutions of lead.
A. a solution of 0.1 g of lead is dissolved by heating in 30 cmof nitric acid, diluted 1:1. Nitrogen oxides are removed by boiling, the solution was cooled, poured 50 cm
of water, transferred into a measuring flask with volume capacity of 1000 cm
, made up to the mark with water and mix.
1 cmof the solution contains 0.0001 g of lead.
Solution B. 10 cmof the solution And placed in a volumetric flask with a capacity of 100 cm
, up to 4 cm
of hydrochloric acid diluted 1:1, made up to the mark with water and mix.
1 cmof solution B has the 0.00001 g of lead.
Mercury brand RO according to GOST 4658−73 that does not contain moisture.
(Changed edition, Rev. N 1).
3. ANALYSIS
3.1. For bronzes containing chromium
A sample of alloy weighing 1 g is placed in a platinum Cup, add 20 cmof concentrated nitric acid and 10 cm
hydrofluoric acid, dissolved by heating and the solution is evaporated to obtain a wet residue. After cooling, add 20 cm
of concentrated nitric acid and again evaporated to the solution until a wet residue. The operation of the evaporation with nitric acid repeated two more times.
The moist residue is dissolved in 20 cmof hydrochloric acid diluted 1:1, transfer the solution into a glass with a capacity of 250 cm
, and diluted with water to 130−150 cm
.
3.2. For bronzes not containing chromium
The sample of bronze with a weight of 1 g was placed in a beaker with a capacity of 250 cm, add 15 cm
of nitric acid, diluted 1:1, covered with a glass watch glass and dissolved under heating.
After dissolution of the alloy and removal of oxides of nitrogen by boiling, the glass and the side of the Cup then rinsed with water and the solution diluted with water to 130−150 cm.
3.3. The end of the analysis
In all cases, to the obtained solution poured 1 cmof solution of ferric chloride and ammonia is added to the transition of copper in a soluble deep blue complex and, beyond that, add another 5 cm
of ammonia. The solution is kept at a temperature of 60−70 °C for 20 min and filtered through a filter of medium density. The beaker and precipitate was washed 3−4 times with hot diluted 1:50 with aqueous ammonia. The funnel with the precipitate was placed on glass, which made the deposition, the precipitate was dissolved in 20 cm
of hot hydrochloric acid, diluted 1:1. The filter is washed with 30 cm
of hot water, the solution diluted to a volume of 130−150 cm
water and repeat the precipitation.
After three perioadele the precipitate washed with hot water in a glass and dissolve it in 5 cmof perchloric acid. The filter is washed with hot water and the resulting solution is evaporated until a white smoke of perchloric acid. Dilute the solution with water to a volume of 15 cm
, 14 cm pour the
concentrated phosphoric acid, transferred to a volumetric flask with a capacity of 50 cm
, is diluted to the mark with water and mix. Taken from the flask aliquot part of the solution (10−20 cm
) and transferred to a polarographic cell, previously washed with 1 mol/l
phosphoric acid. The solution in the cell is degassed for 5−7 min by passing nitrogen, stop the nitrogen supply and remove polarogram in the range from minus 0.3 to minus 0.7 V. the Peak recovery of lead recorded at minus 0.55 V. the Sensitivity of the recording instrument is selected so that the peak of lead was at least 15 mm.
Lead find by the method of standard additions. Aliquot part of standard solution A or B, depending on the content of lead, added to polarographically solution, mixing the solution with nitrogen 2 min. and then spend polarographically, as in the determination of lead in test solution.
The value of the standard additives is chosen so that the peak height of the lead after the introduction of the standard Supplement increased 2−3 times.
Simultaneously with the determination of lead in the alloy conduct control experience with all reagents.
(Changed edition, Rev. N 1, 2).
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of lead (a) percentage calculated by the formula
where is the peak height of lead in a control experiment, mm.
— the height of the peak lead for the test solution, mm;
— the height of the peak of the lead after the introduction of standard additives, mm;
— the concentration of a standard solution of lead, g/cm
;
— the volume of standard addition, cm
;
— the weight of the portion corresponding to the aliquot taken for polarography,
(Changed edition, Rev. N 1
).
4.2. Discrepancies in the results of three parallel definitions should not exceed the values permitted by the divergence (
the rate of convergence), calculated according to the formula
where — mass fraction of lead in the alloy, %.
4.3. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values calculated according to the formula
where — mass fraction of lead in the alloy, %.
4.4. Control of accuracy of analysis results is carried out according to State standard samples or by the method of additions or by comparison of the results obtained by atomic absorption method in accordance with GOST 25086−87.
4.3, 4.4. (Changed edition, Rev. N 2).
