A N A L Y T I C A L CHEMISTRY
508 Table 111.
Analysis of National Bureau of Standards Ore 25b a n d Gold Coast Ore Manganese. % Volumetric ColorimeGF
Ore
N.B.S. 25b
Av.
58.31 58.41 58.40 58.36 58.38 5 8 . 37
.I\..
56.53 56.46 56.51 56.50
58.8.5”
Gold Coast
5 6 . 4 7 * 0 05’
ACKNOWLEDGMENT
The authors express their appreciation t o David Firestone who made the measurements establishing the limits of precision attainable a t various absorbances. The authors also wish to thank Harold Hyman and Maurice Lang of the United States Electric Manufacturing Corp., for their many courtesies and helpful criticism.
value. * Certificate Determined volumetrically in course of thin research.
a
Table IV. NO. 64-44 156-47 157-47 162-47 32-48 72-48 2-49 3-49
LITERATURE CITED
Analysis of Manganese Ores
( P e r cent manganese) VoluOrigin, Supplier metric English Hydrate 53.57 Synthetic-E. J. Lavino 52.44 Synthetic-E. J. Lavino 57.38 Morocco-Bowring 59.89 Activated-Asbury Graphite 34.79 Synthetic-E. .J. Lavino 45.91 Caucasian-E. J. Lavino 56.19 Montana-E. J. Lavino 45.19
Colorimetric
It seems reasonable t o conclude, therefore, that mmganese determinations may be effected b y a procedure such as this with a precision equal t o that of the volumetric methods. I n addition, this method illustrates the high absorbance approach to colorimetry.
Difference
53.61 52.73 !7.12 39.74 54.62 46.04 56.22 45.33
f0.04 f0.29 -0.26 -0.16 -0 , 1 7 +0.13
+0.03 +0.14
with a precision of 1 part per 1000. The results obtained on these samples are given in Table 111. The data in Table I11 indicate that a precision of about 1 part in 2000 is achieved. The routine volumetric analyses of a group of rommercial pyrolusites are compared with the colorimetric method in Table
IV. I n this comparison portions of the same massive sample that had been previously ground and sieved were analyzed by the tlyo methods. There is no systematic variation between the two methods and in all probability the differences are normal to the routine analytical operations involved. It is also likely that traces of colored impurities are not contributing to the absorbtinct, of the sample since this would cause positive differences between the colorimetric and volumetric methods.
(1) Association of Official Agricultural Chemists, “Official and Tentative Methods of .halysis,” 4th ed., p. 125, Washington, D. C., 1935. 12) Bastian, R., Ax.4~.CHEY.,21, 972 (1949). (3) Bastian, R., ”Differential Spectrophotometric Determination of High Percentages of Sickel,” paper presented a t 118th Meeting of the AMERICAN CHEMICAL SOCIETY, Chicago, Ill. (4) Bastian, R., Webeding, R., and Palilla, F., ANAL.CHEM.,22, 160 (1950). (
