V O L U M E 28, NO. 11, N O V E M B E R 1 9 5 6
1761
(3) Cheng, K. L., Kurtz, T., Bray, R.R., ANAL.C H E M . 1640-1 ~~, (1952). (4) Diehl, H., Goete, C. A., Hach C. C., J . A m , Water Works Assoc. 42, 80 (1950). (5) Djurfeldt, R., Hansen, J., Samuelson, O., Svensk. Kem. Tidskr. 59, 13-8 (1947). ( 6 ) Gehrke, C. W., Affsprung, H. E., Lee, Y . C., ANAL.CHEM.26, 1944 (1954).
(7) Hahn, R.,Backer, C., Backer, R.,A d . Chim. Acta 9 , 223-5 (1953). (8) Jenness* R.1 A N A L . CHEW 251 966-8 (1953). (9) Mason, A. C., Analyst 77, 529-33 (1952).
(10) Samuelson, O., "Ion Exchangers in Analytical Chemistry," Wiley, Xew York, 1953. (11) Samuelson, O., Szensk. Kem. Tidskr. 52, 241 (1940). (12) Ibid., 54, 124 (1942). RECEIVED for review December 7, 1955. Accepted June 18, 1956.
Determination of Traces of Mercury in Mercury Ore Ash by Catalytic Action of Mercuric Ions SMILJKO ASPERGER and DUSANKA PAVLOVIC lnstitute o f Inorganic, Analytical, a n d Physical Chemistry, Faculty o f Pharmacy, University o f Z a g r e b , Croatia, Yugoslavia The determination of traces of mercury in burnt mercury ore was carried out on the basis of the cataly-tic action of mercuric ions on the reaction between potassium ferrocyanide and nitrosobenzene, in which a violet complex [Fe(CN)j(CsHjKO)]---is formed. In the range where the mercury in the ash amounted to 0.0024 to 0.0097q~the relative error of the analyses varied between 6 and Z q , and the standard deviation was approximately 0.00015.
T
HE determination of small amounts of mercury in burnt ore that remains in mercury mines serves as a control of the smelting process in industry. The well burnt ore usually contains only a few thousandths of 1 % of mercury. Such small amounts of mercury cannot be accurately determined by the classical Eschka method (3),which is accurate only when the quantity of mercury in the ore is greater than 0.1%. On the other hand, the temperature used in the Eschka method to expel mercury from the ash proved to be insufficient because of the adsorption of mercury on the ash. It appears that the other more sensitive methods for determination of mercury have not been applied to this case. Proceeding with earlier experiments on the determination of small amounts of mercury ( I ) , the authors used the catalytic action of mercuric ions on the reaction of potassium ferrocyanide and nitrosobenzene in aqueous solutions to determine traces of mercury in mercury ore residue. The reaction proceeds according to Equations 1, 2, and 3 (2): H20 Fe(CK)e----
$
[Fe(CS)j(H20)I--H?O
+
CS-
[Fe(CS)s(HzO)]---
+ CsHjKO
+ H20
-+
HCY
+ CY-
(1)
[Fe(CN)j(CsHjNO)]--violet (2)
+ OH-
(3)
The concentration of the violet reaction product [Fe(CN)j(C6HsNO)]- - - at a fixed reaction time depends on the concentration of mercuric ions present in the solution. By measuring the absorbance of the violet complex at 528 mp, as little as 2 y of mercury could be determined. The ore residue was heated to 1200' C. and the mercury vapors liberated were mixed with bromine vapors according to the procedure of Moldawskij (4,5 ) , and absorbed in bromine water, and the mercuric bromide was determined by an earlier procedure (1). EXPERI>IESTA L
The ash (0.2 to 0.6 gram) v a s heated for 1.5 hours at 1200" C. and a stream of fresh air was passed through the furnace. The
apparatus for oxidizing and absorbing mercury vapors xith bromine vapors (4,5 ) was attached to the furnace. After the liberation of mercury n7as completed, the glass tubes that connected the furnace and the absorption vessel were rinsed with bromine water, vhich was added to the bromine water of the absorption cell. The absorption solution containing traces of mercuric ions was then treated for the determination of traces of mercury in the atmosphere ( 1 ) . The concentration of the mercuric ions v a s calculated from the equation lOgioCEg++= 1.112 logmEso
- 4.427
(4)
where E30 is the absorbance of the violet reaction product at 30 minutes at 528 mp and a path length of 1 em. ( 1 ) . The table shows the results of the analysis of a sample under different conditions of burning. Temp.,
c.
Time of Heating, hlin.
Mercury Found in Ash, %
10
900
15 60 90
1000 1100
90 180 240 90
1200
90
1050
0,0025
0.0029 0.0031 0.0035 0.0041 0,0043 0,0044
0.0051 0.0051
Increase of temperature above 1200" C. and prolonged heating (over 90 minutes) caused an increase of the acidity of the otherwise slightly acid absorption solution to p H 2 or less. This is not desirable, because more sodium hydroxide would be needed for the subsequent adjustment of the p H to 3.5 before addition of potassium ferrocyanide, as required by the earlier procedure ( 1 ) . This would cause an increase of the otherwise negligible negative salt effect on the catalyzed reaction, and hence slightly lower results in the analyses. The reaction shows a negative salt effect, as the charges of ferrocyanide and mercury ions are opposite in sign. Fifty analyses on ash from the Idria mercury mine in Yugoslavia were carried out on samples containing 0.0024 to 0.0097% of mercury. The standard deviation was approximately 0.00015 in this whole range and the relative error varied between approximately 6% for the ash of low mercury content and 2% for the ash of higher mercury content. LITERATURE CITED
(1) (2) (3) (4) (5)
ASperger, S., AIurati. I.,AXAL.CHEM. 26, 543 (1954). hhperger, S., PavloviC,D., J . Chem. SOC.1955, 1449. Holloway, G. T., Analysf 31,66 (1906). RIoldawskij, B. L., Zhur. Priklad. Khim. 3 , 9 5 5 (1930). Stock, -4., Cucuel, F., Ber. deut. Chem. Ges. 71,550 (1938).
RECEIVED for review June 2 , 1956.
Accepted June 16, 1956.
