Determination of Antimony in White Metals J
A Volumetric Semimicromethod C. W. ANDERSON, Continental Can Company, Inc., Chicago, Ill.
T
HE present method is an application of a dilute bromate solution, 0.005 N , for the determination of antimony in
tory varies over a narrow range; in tin it is seldom greater than 0.02 per cent and in lead often less than 0.01 per cent. A semimicrotip attached to the 10-ml. buret is used for titrating in the analysis of lead samples, and is an aid to attaining greater accuracy. A piece of glass tubing, 5 to 6 mm. in diameter, is drawn out to nearly capillary size, is attached to the buret by rubber tubing, and should deliver about 4 drops for 0.05 ml. of bromate solution. Antimony determinations on tin samples, and tin-antimony and lead-antimony alloys can be performed in less than 1 hour; on lead and solder samples in 1.5 to 2 hours.
tin and lead and in alloys of the metals with antimony. The procedure has grown out of previous work ( I ) , in which a more concentrated bromate solution was used on 1.5-gram samples. The method may be used in the analysis of alloys such as hard lead, containing about 1 per cent of antimony, and tinbase bearing alloys, containing about 7 to 11 per cent of antimony. The procedure is usually applied to quantities of antimony in the range from 0.01 to 0.10 per cent in tin and lead and in solder made with the metals, and is identical in principle with that employed in the conventional method. T o enabIe the application of 0.005 N bromate solution, the quantities of the reagents used have been greatly decreased. The use of pure arsenic trioxide for standardizing the bromate solution is an aid to the attainment of accurate results. The degree of precision of which the method is capable is shown by Table I, presenting data obtained in determining antimony in Bureau of Standards tin-base bearing metal, containing 7.32 per cent of antimony, and another tin-antimony alloy found to contain 10.60 per cent of antimony. The antimony content of tin and lead tested in this labora-
Reference Standards
Bureau of Standards samples 42b and 54A were used as reference standards in the development of this method. The antimony content of the tin sample, No. 42b (Table 11),is 0.018 per cent. This is in close agreement with the value, 0.02 per cent, assigned to the sample when the former work was in progress. The tin-base bearing alloy, No. 54A, contains tin 88.61, antimony 7.32, copper 3.75, lead 0.21, iron 0.041, arsenic 0.039, and bismuth 0.019 per cent. Experimental analyses with this sample (Table I) show the antimony content to be 7.31 per cent. TABLEI. DETERMINATIONS ON TIN-ANTIMONY AND LEAD-ANTIMONY ALLOYS Bureau of Standards arsenic Antimony Total trioxide, sample 83, with a Weight 0.005 N Originally Antimony Antimony Antimony purity of 99.98 per cent, is Sample of Sample KBrOs Present Added Present Found Error Recovery used for standardizing the Grana M1. Mg. Mg. Mg. W. M9. % Bureau of Standards 0.01 2.40 0.732 ... 0.731 -0.001 99.9 bromate solution. Metallic Sample 64A, tin0.01 5.60 0.732 1.00 1:732 1.705 -0.027 98.4 a n t i m o n y , o f t e n used f o r base bearing metal 0.01 5.05 0.732 0.80 1.532 1.537 -0.005 100.3 0.02 4.80 1.464 ... ... 1.461 -0.003 99.8 standardizing solutions of the 0.02 4.75 1.464 1.446 -0.018 98.7 salt, is difficult to obtain in 0.02 7.65 1.464 0:8+5 2:339 2.329 -0.01 99.6 0.02 7.75 1.464 0.90 2.364 2.359 -0.005 99.8 the pure form. Samples of Another tin-antimony 0.01 3.50 ... ... ... ..... .... antimony tested show the presalloy 0.01 3.45 ... ... . . 0.01 3.50 ... . . . ... ence of arsenic and silica. 0.01 3.50 ... ... ... Potassium bromate is obtain0.02 6.95 ... ... ... 0.02 6.95 2.116 ..... .... able in a highly purified form. 0.02 8.35 2:ii6 o:iia 2:i41 2.542 +o.ooi 100.04 8.95 0.02 2.116 0.625 When solutions of the salt 2.741 2.724 -0,017 99.4 0.02 9.25 2.116 0.70 2.816 2.815 -0.001 99.96 have been standardized by Lead-antimony alloy 0.20 8.00 *. . . 2.435 ..... ... means of arsenic trioxide, the 0.10 4.15 .... .. 1.263 ..... ,.. 0.10 4.10 values obtained have always . . 1.248 ..... ... 0.10 4.10 ,. .. 1.248 ..... ... been in very close agreement 0.10 4.10 ... 1.248 ..... .... 0.10 7.35 1:2& 1.00 21248 2.237 -0.011 99.5 with the theoretical, making 0.10 6.55 1.248 0.75 1.998 1.994 -0.004 99.8 0.10 8.95 1.248 1.50 2.748 2.724 -0.024 99.1 the application of a correction r factor unnecessary. 224
APRIL 15, 1939
ANALYTICAL EDITION
225 J
TABLE 11. ANALYSES OF TIN AND SOLDER
Sample
(Using 0.6-gram samples) Antimony Total 0.005 N Originally Antimony Antimony Antimony KBrOa Present Added Present Found
MZ. Antimony
4.90 4.95 3.90
Bureau of Standards tin sample 42b
0.35 2.50 3.30
Tin sample Cempure from Internationh Tin Rksearch & Development Council, London Continental Can Co. No. 1 No. 2
0.35 3.00 4.45 0.25 2.30 0.40 0.50 3.10
No. 3 Solder samples from Mount Royal Metal Co., Canada No. 2
No.3
2.85
0.15 2.10 1.05 3.85 1.35 2.10
Me.
Me.
%
... ...
1.492 1.507 1.187
-0.008 10.007 -0.013
99.5 100.5 98.9
0:$67 1.007
0.107 0.761 1.005
10.004 -0.002
...
Mg.
... ...
1.50 1.50 1.20
...
o:i07 0.107
0.65 0.90
0 : it17
0.107
0.80 1.25
0 967 1.357
0:0?6
0.63
0 : 706
iiz o:ih
0.75
0 si2
0.80
0:9b2
0:046
...
0.60
...
0:6iS
0.32
0.85
i:ii
o:4ii
0:225
01636
0:
... ...
... ...
...
...
Recovery
Error
Me*
Mg.
: :
Solutions and Reagents Required Bromine Solution. Dissolve 12 ml. of pure bromine in 100 ml. of concentrated hydrochloric acid by shaking vigorously in a glassstoppered bottle. Methyl Orange Indicator. Dissolve 0.10 gram of methyl orange powder in 100 ml. of hot water and filter. Anhydrous Sodium Sulfite. Potassium Bromate Solution, 0.005 N ; 1 ml. = 0.3044 mg. of antimony. Weigh 0.1392 gram of the salt, dissolve in water, and make up to volume in a liter flask. Standardize against pure arsenic trioxide. Weigh a quantity of the trioxide, 4.95 mg., then dissolve in 1 dro of a saturated solution of sodium hydroxide. Add a few millihers of water and 1 ml. of concentrated sulfuric acid, and titrate as in the regular analysis. The quantity of bromate required in this titration is 20 mi. after deducting the reagent blank correction, 0.15 ml.
Procedure for Tin, Lead, and Solder Weigh a 0.6-gram sample of filings, SO-mesh for lead, into a 50-ml. beaker. Add a few milli0.005 N liters of concentrated hydroSample KBrOa chloric acid and about 5 ml. of Ml. the bromine-hydrochloric acid Continental Can CO. lead 0.20 solution. Heat over a small samples 0.20 3.50 flame, adding small quantities Sample 2 0.15 of bromine solution as required 2.10 Sample 3 0.10 to complete solution of the metal. 1.45 At this stage in the process, the Sample 4 0.05 solution should appear pale 2.35 yellow in color, indicating a slight excess of free bromine. The presence of any considerable amount of free bromine upon solution of the metal may prevent suitable reduction of the antimony by sodium sulfite. Add to the hot solution 20 mg. of anhydrous sodium sulfite, followed by 5 of concentrated hydrochloric acid, and evaporate to a volume of 7 to 8 ml. to expel any arsenic present. Add 1 ml. of concentrated hydrochloric acid and 5 ml. of water and place over the small flame again until gentle boiling begins. Pass a gentle current of air through the solution for 30 seconds. Remove from the burner, wash off the cover glass and sides of the beaker, and titrate with 0.005 N potassium bromate solution, using a 10-ml. buret graduated in 0.05-ml. divisions. After the addition of a drop of meth 1 orange indicator add the bromate solution drop by drop to tge disappearance of the pink color of methyl orange. During the titration keep the temperature of the solution near the boiling point. The high temperature aids in obtaining a more distinct end point. From the final buret reading deduct 0.15 ml., the amount obtained in the titration of a blank
.....
0.107 0.913 1.355 0.076 0.700 0.122
run under the conditions obtaining in this determination. It is advisable to determine the reagent blank correction occasionally. The amount of this correction may vary according to the purity of the reagents ..onA UYZiCL.
Procedure for TinAntimony and LeadAntimony Alloys
i00:5 99.8
Analyses of these alloys are performed with 0.10-gram sam..... ... ples of SO-mesh filings for lead99.1 -0:006 antimony alloys, and 0.02-gram ..... ... 0.868 samples for tin-antimony. To -0.004 99.5 0.152 ..... ... these quantities add 5 to 10 ml. 99.2 0.944 -0.008 of concentrated hydrochloric acid, using 50-ml. beakers, and 0.046 ..... ... 0.639 -0.007 99.0 heat gently over a small flame 0.32 ..... for 5 to 10 minutes. At this 1.172 -to.ooz 106:2 stage some of the antimony, 0.411 40:003 10015 separated in black Dowderv 0.639 foim, can be observed- on th"e bottom of the beaker. Add a few drops of bromine-hydrochloric acid solution which has been diluted with about 2 volumes of concentrated hydrochloric acid. Heat over the flame, adding a few drops of bromine solution as required, to complete solution of the antimony, avoiding more than a slight excess of bromine. Upon addition of 35 to 40 m . of sodium sulfite, the process is continued as in the procedurefor tin, lead, and solder. -(Q:006 -0.002
10017 99.8
the first three experimentsof Table 11, quantities of antimony, taken from a solution prepared by dissolving powdered antimony in concentrated hydrochloric acid with the addition of potassium chlorate, were carried through the regular course of analysis, In all the experimental analyses Of I1 and II1, the error is less than the antimony value of 0.05 ml. of the bromate solution.
TABLE 111. ANALYSES OF LEAD (Using 0.6-gram samples) Aqtimony Tptal Orimnally Antimony Antimony Present Added Present
Antimony Found
Error
Me.
Me.
Mo
..
Me.
0:&1
1:OO
1:OEl
0:046
...
0160
0:646
0.03
0:42
0.45
0:0i5
o:io .
o:iis
Mg.
...
...
...
0.061 0.061 1.065 0.046 0.639 0.03 0.441 0.015 0.715
9
Recovery
%
.....
...
10.004
..... .....
100:4
..... .....
... ...
.....
...
-0.007
99.2
-0.009
98.0
...
The antimony content of the second tipantimony alloy shown in Table I was found t o be 10.60 per cent, the average of several determinations. The third and fourth experiments using 0.01-gram samples, and the fifth and sixth, in which 0.02 gram was used, were carried out consecutively. The average value for the antimonycontentobtained in these four is 10.61 per cent* The average obtained in the six experimental analyses, determining the antimony content of this alloy, is 10.60 per cent,
Literature Cited (1) Anderson, C. W., IND.
ENQ.CHBIM., Anal.
Ed., 6. 456 (1934).
