Routine Analysis of Manganese Bronze EDWIN
K. BABSON AND WAYNE W. JOHNSON
Industrial Laboratory, M a r e Island Naval Shipyard, Vallejo, Calif. In a rapid method for the routine analysis of manganese bronze perchloric and nitric acids are used to dissolve the sample. The nitric acid is removed b y fuming with perchloric acid, copper, tin, and lead then being precipitated as sulfides. Tin is determined gravimetrically, copper and lead electrolytically. Iron, having been reduced by hydrogen sulfide, is titrated with permanganate) after which the aluminum is determined b y weighing the combined iron and aluminum oxides. Accepted methods are used in the determination of nickel and manganese. Results compare favorably with the certified values of two Bureau of Standards manganese bronze samples.
procedure for determining tin, copper, lead, iron, aluminum, and nickel is as follows: Transfer 1.0000 gram of sample to a 400-ml. beaker. Dissolve with 4 ml. of nitric acid (sp. gr. 1.42) and 6 ml. of perchloric acid (70'%), cover, and heat until heavy fumes of perchloric acid have been evolved for several minutes. Cool somewhat, wash the cover glass, and dilute to 200 ml, with hot wat,er. Pass hydrogen sulfide into the solut'ion for 20 minutes. Coagulate the precipitated sulfides by adding paper pulp and bringing the contents of the beaker to boiling. Filter t,hrough a Whatman No. 30 paper into a 400-ml. beaker, and wash the precipitate thoroughly with hot water, combining the washings and the filtrate. Save both the precipitate and solution. DETERYIX.~TIOX OF TIN. R r a p the precipitate and filter in another piece of filter paper, and place in a clean No. 1 porcelain crucible. Ignite completely a t 500" C., and, after allowing t,o cool carefully transfer the ignited material to a 150-ml. beaker. Pour 10 ml. of nitric acid (sp. gr. 1.42) into the crucible and heat on a hot plate for several minutes. Pour the acid into the beaker containing the major portion of the ignited oxides, and wash the crucible with 10 ml. of water, adding the washings to the beaker. Heat until the black copper oxide is dissolved. Dilute to 50 ml. with hot water, add a small amount of paper pulp, and allow to stand just below t,he boiling point for 30 minutes. Filter on a Whatman S o . 42 paper into which has been poured a small amount of paper pulp suspension. Wash the precipitate three times alternat,ely with hot water and dilute nitric acid (1 to 4). Ignite the precipitate in a tared crucible first a t 500" C. until the paper is completely charred and finally a t 900" C. unt,il fully ignited. Weigh the ignited material as SnOn,and calculate the percent,age of t i n . weight of SnOp X 0.788 Per cent tin = x 100 weight of sample
THE
fact that relatively few methods for the complete analysis of manganese bronze have appeared in the literature is perhaps evidence that the inherent difficulties have not been satisfactorily overcome. I t is known that if a sample of bronze containing considerable iron is decomposed with nitric acid the tin is incompletely precipitated, and contaminated with iron. Tin, if present in the electrolyte, will contaminate both copper and lead deposits if these elements are determined by electrolysis. Unless special precautions are taken the lead peroxide, deposited on the anode during electroplating, is contaminated with manganese dioxide. Also, the separation and determination of aluminum, a t best being time-consuming, are complicated by the presence of any tin not previously separated. While accurate methods are available, all are objectionable for one reason or another. The principal objection is the time consumed in avoiding the interferences mentioned. Results of analysis are often needed in 5 or 6 hours, and most methods fail to satisfy this requirement. Some methods involve the use of fluorides to prevent interference from tin in the electroplating of copper and lead (S), but for large numbers of samples conbiderable platinum ware is required in subsequent evaporations. Procedures which require the plating of copper and lead without prior removal of manganese result in high lead values, although in some instances ( 3 ) the amount of contamination is not excessive for routine work. One of the most acceptable methods for determining aluminum necessitates the use of the mercury cathode (2), but is somewhat slow for rapid analysis. The method described herein avoids these difficulties and is considered novel in some respects. The initial attack is made with perchloric and nitric acids, rendering soluble all constituents with the exception of a small amount of tin. Then, precipitation with hydrogen sulfide in the acid solution separates the copper, lead, and tin from the iron, aluminum, manganese, nickel, and zinc. By this means tin is removed from iron, and lead from manganese. The iron, having been reduced to the ferrous state by hydrogen sulfide, is titrated with permanganate. Later precipitation of mixed iron and aluminum hydroxides with ammonia makes the use of the mercury cathode unnecessary. The accuracy of the method is shown by values obtained with Bureau of Standards samples, and with a secondary standard which had been carefully analyzed by accepted methods (1,4 ) . Procedures for the determination of manganese and zinc are omitted because present methods (5)are satisfactory for the former, and the latter is most accurately obtained by difference.
~
DETERMINATION OF COPPER AND LEAD. The filtrate from the tin determination contains the copper and lead. Dilute to 200 ml., and add 2 ml. of dilute sulfuric acid (1 to 1) and a small amount of urea or sulfamic acid. Place on an electroplater and deposit the copper and lead simultaneously. Using the customary gauze cathodes and rotating gauze anodes complete deposition will be obtained in about 60 minutes a t 2.5 amperes. Weigh the previously tared electrodes and calculate the percentage of copper and lead. Discard the electrolyte. Per cent copper = Per cent lead =
weight of Cu deposited weight of sample
x
weight of PbOz deposited X 0.864 weight of sample
100
x
100
DETERMINATION OF IROX. T o the filtrate from the sulfide precipitation add a few glass beads, and boil the solution vigorously for 30 minutes to expel the hydrogen sulfide. Cool the solution in ice water, add 10 ml. of dilute sulfuric acid (1 to l ) , and t,itrate with 0.05 N potassium permanganate to a faint pink color that should persist for 10 to 15 seconds. Reserve the solution for the determination of aluminum. Per cent iron = ml. of titration X 0.05584 X normality of KRlnOl weight of sample
x
100
DETERMINATION OF ALUMISUM. To the solution from the iron determination add 10 grams of ammonium chloride and make just alkaline to methyl red with ammonium hydroxide (sp. gr. 0.90). Add a small amount of paper pulp, bring to a boil, add 3 drops more ammonium hydroxide (sp. gr. 0.91)), and allow to settle for 5 minutes. Filter the hydroxides on a Whatman S o . 31 paper, washing three times with hot ammoniacal ammonium nitrate solution (10% ammonium nitrate made just ammoniacal to methyl red). Remove the beaker containing t'he filtrate and washings, reserving these for the nickel determination. Dissolve the hydr xjdes from the paper by pouring hot dilute hydrochloric acid (1 to 1) through the filter into the original beaker. Wash the filt,er well with cold water and discard. Add 2 grams of ammonium chloride to the solution in the beaker and reprecipitate the iron and aluminum hydroxides as described above. After
PROCEDURE
All elements except zinc and manganese are determined from a single weighed sample. After the initial solution and sulfide separation, the precipitate and filtrate are treated simultaneously, in this way decreasing the total time of analysis. The complete 292
May,
Table
I. Results of Analysis of NBS Samples
Found Copper
Tin
Lead
Sample 62aa Averaee Certified
Found
Sample 62bb Averaee Certified I
%
5%
%
%
%
%
61.47 61.51 61.47 61.43 61.46
61 47
61.51
57.36 57.35 67.31 57.39 57.34
57.35
57.40
0.84 0.84 0.83 0.83 0.84
0.84
0.84
1.02
1.01
0.97
0.51
0.52
0.50
0.28 0.29 0.30 0.29 0.26
0.28
0.27
1.03 0.99 1.00 1.02
0.52
0.52 0.51 0.53
Iron
1.02 1.02 1.02 1.03 1.04
1 03
1.01
0.80 0.80 0.82 0.80 0.82
0.81
0.81
Aluminum
0.94 0.91 0.93 0.93 0.93
0 93
0.92
0.98 0.97 1.02 0.99 1.02
1.00
0.97
0 62
0.61
0.29 0.27 0.29 0.29
0.28
0.27
Xickel
a
293
ANALYTICAL EDITION
1946
0.61 0.62 0.61 0.62 0.62 Manganese 1.51%
0.28 b
Manganese 1.28%.
filtering and washing the precipitate, place in a tared porcelain crucible, char the paper at 500” C., and ignite a t 900” C. Cool the ignited oxides in a desiccator, and weigh the mixturf, of iron and aluminum oxide ( l ( 2 0 8 ) rapidly. From the weight of the RIOI and the percentage of iron previously determined calculate the per cent aluminum. Pcr cent aluminum = ( w i g h t of R203
overcome, S o error attributable to the presence of nitric acid was observed in the subsequent iron titrat,ions. Aluminum and tin values on sample 62b were found to be consistently high. Spectrographic analysis disclosed the presence of silicon in the ignited tin oxide and in the mixed oxides. This was due to the presence in the sample of 0.047% silicon which is not ordinarily found in manganese bronze analyzed in this laboratory. From a consideration of coprecipitation, hygroscopicit,y, and solubilities one might not expect to obtain the accuracy shown. However, it is possible that fortuitous compensat,ing errors result in slightly better values than woultl normally be expected. J17ith this method one sample of manganese bronze can he analyzed in approximately 5 hours. Six samples require approximately the same time and 12 samples can be completed hy one analyst in an 8-hour period. Experience with other method$ had indicated that, in order to obtain the same degree of accuracy, about 8 hours are required for a single sample. The equipment required is found in all nonferrous laboratories, no special apparatus or reagents being necessary. All operations are of such simplicity that little is required in the n a y of special technique and training. It has been demonstrated that a satisfactory analysis of manganese bronze can be accomplished if tin is separated from iron, if i t is not, present in the copper-lead electrolyte, and if manganese is separated from lead. The separations described in this method isolate the elements in such a manner that little intcwfcrence is encountered in each determination. It therefore appears that t’hemethod at least part,ly satisfies the requirement? for rapid analysis, and has sufficient accuracy to warrant its use in routine control and inspection Ivork. Table
-
weight of Fe X 1.429) 0.529 weight of sample
x
Found
100
=
m i g h t of NiO X 0.786 weight of sample
x
Average
Accepted Value
5
5%
70
J G 03 56,03 56.02 56 00 55.99 0.36 0 39 0.3.5 0.35 0.38
.56.01
56.01
0.37
0.3i
Iron
0.82 0.83 0.83 0.83 0.8:
0.83
0.82
Aluniinum
0 0 0 0 0
0.63
0.61
Copper
DETERMISATIOS OF SICKEI.. T o the filtrate from the first hydroxide precipitation add 15 ml. of dimethylglyoxime solution (l’%alcoholic solution). Warm until the precipitate is well coagulated and filter through a Whatman No. 41 paper, washing eight to ten times with hot water. K r a p the filter in a moistened ashless filter paper and ignit’ein a tared, covered, porcelain crucible, first a t 500” C., and finally a t 800” C. Cool in a desiccator and weigh as X O . Per cent nickel
II. Results of Analysis of Laboratory Standarda
Tin
Lead
100
E X P E R I M E N T A L RESULTS
Sational Bureau of Standards manganese bronze samples 62a and 62b wcre used to test the accuracy of the method. The results obtained are shown in Table I. Most samples analyzed in this laboratory have less tin, manganese, lead, and nickel than do the Bureau of Standards samples. A sample of more common alloy, the composition of which had been carefully established by accurate methods (1, 4 ) , was analyzed by the above method. Results are shown in Table 11.
61 63 60 fi3 fi3
Manganese 0.427,.
DISCUSSION
ACKNOWLEDGMENT
The properties of perchloric acid make it particularly suitable for this method. Its oxidizing properties when hot and concentrated and the solubility of its salts provide practically complete solution of the sample. Further, the fact that dilute solutions of the acid have no oxidizing power makes it satisfactory for the hydrogen sulfide precipitation and iron titration. I t was originally contemplated that the initial attack should be with perchloric acid alone. However, the tin values were founa to be consistently low and somewhat erratic. I t seemed possible that this might be due to volatilization of the tin during solution of the sample. By using both nitric and perchloric acids, and then evaporating to perchloric acid fumes, this difficulty was
Acknowledgment is made to bther members of the Industrial Lahorat.ory, Mare Island S a v a l Shipyard, for their helpful assistance. LITERATURE CITED
Methods of Chemical Analysis of Metals”, Philadelphia, Pa., American Society f o r Testing Materials, 1943. Holler, A. C., and Yeager, J. P., ISD. ESG. CHEM.,ANAL.ED., 14, 719-20 (1942). Ravner, Harold, Ibid., 17, 41-3 (1945). Saxer, E. T., and Minto, R. E., Ibid., 15, 261-2 (1943). Scott, “Stafidard Methods of Chemicltl .4nelysis”, 5th ed., To]. 11, p. 1358, New York, D. Van Nostrand Co., 1939.
(1) “A.S.T.M.
(2) (3)
(4) (5)
T H L views expressed in this paper are those of t h e authors and d o n o t necessarily reflect the opinion of the N a v y Department.
