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Nioxime : a reagent for palladium
Series Title:
United States. Atomic Energy Commission. MDDC ;
Physical Description:
4 p. : ill. ; 27 cm.
Voter, Roger C
Banks, C. V
Diehl, Harvey
Iowa State College
U.S. Atomic Energy Commission
Technical Information Division, Atomic Energy Commission
Place of Publication:
Oak Ridge, Tenn
Publication Date:


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Palladium   ( lcsh )
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )


Bibliography: p. 4.
"Date Declassified: July 9, 1947"
Statement of Responsibility:
Roger C. Voter, C.V. Banks, and Harvey Diehl.
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Manhattan District Declassified Code

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MDDC 1095



Roger C. Voter
C. V. Banks
Harvey Diehl

Iowa State Colhege

Date Declassified:

July 9, 1947

Issuance of this document does not constitute
authority for declassification of classified
copies of the same or similar content and title
and by the same authors.

Technical Information Branch, Oak Ridge, Tennessee
AEC, Oak Ridge, Tenn., 3-9-49--850-A379
Printed in U.S.A.

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Digitized by the Internet Archive
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hup: delails/nioximereagentfo00io


By Roger C. Voter, Charles V. Banks, and Harvey Diehl

The water soluble 1, 2-dioxime, 1, 2-cyclohexanedionedioxime, called Nioxime, yields a yellow pre-
cipitate with divalent palladium. This precipitate can be used as a qualitative and quantitative reagent
for this ion and offers several advantages over its analogue, dimethylglyoxime. It effectively separates
palladium from platinum with a single precipitation as well as from other cations. Palladium nioxime
can be filtered from a hot solution after a brief digestion period. Qualitatively, nioxime is a more sen-
sitive reagent for palladium than dimethylglyoxime.

The preparation of 1, 2-cyclohexanedionedioxime, Nioxime, and its use in the analytical chemistry
of nickel have already been reported (2, 5). Nioxime also yields an insoluble yellow compound with pal-
ladium which can be used for the detection and determination of this metal. This reagent offers several
advantages over dimethylglyoxime as a precipitant for palladium. Nioxime is soluble in water in con-
trast to dimethylglyoxime which must be made up in alcohol or acetone, and the possibility of contami-
nation of the palladium precipitate with excess reagent is eliminated. Palladium nioxime is very insol-
uble and may be filtered from a hot solution after a brief digestion period whereas in many procedures
it is recommended that the palladium dimethylglyoxime precipitate be allowed to cool and stand for long
periods to insure complete precipitation (3, 6). Nioxime serves to separate palladium from large a-
mounts of platinum, a feature not possessed by dimethylglyoxime (1, 6).


An 0.8 per cent, aqueous solution of nioxime was used.

A standard palladium solution was prepared from commercial palladium chloride. This salt was
purified by first precipitating out platinum as ammonium chloroplatinate (4) and then by precipitating
the palladium as palladium dimethylglyoxime. This complex was destroyed with aqua regia and the so-
lution evaporated to near dryness five times with concentrated hydrochloric acid to eliminate nitrate
ions. The palladium content of the diluted palladium chloride solution was determined by precipitating
the palladium in weighed amounts of this solution with dimethylglyoxime. These solutions were allowed
to stand overnight to insure complete precipitation of the palladium dimethylglyoxime. The results of
this standardization are given in Table 1. A portion of this solution was evaporated to dryness and the
residue spectrographically analyzed. Calcium, magnesium, aluminum, silicon, copper, chromium, bari-
um, boron, and platinum were found to be present in less than 100 ppm quantities while only traces of
manganese, silver, zinc, and nickel were found. Iridium, osmium, gold, rhodium, and ruthenium were
not detected.


Two series of five palladium solutions were made up in 100 ml volumetric flasks with concentrations
ranging from one to ten parts in ten million. To one series of solutions was added one ml of nioxime
solution and to the other, one ml of 1 per cent dimethylglyoxime in alcohol followed by vigorous shaking.

MDDC 1095

MDDC 1095

Table 1. Standardization of palladium solution with dimethylglyoxime.

Weight of palladium Weight of Weight of Gram of palladium
Trial solution taken precipitate palladium per gram of solution
Grams Gram Gram

1 20.30 0.1277 0.04044 0.001992
2 19.03 0.1197 0.03791 0.001992
3 21.70 0.1367 0.04329 0.001995

Average 0.001993

Observations made about five minutes after the addition of the reagent showed that the palladium solu-
tions of ten, seven and five parts in ten million, which contained nioxime, exhibited a slight yellow col-
oration while the corresponding concentrations of palladium with dimethylglyoxime did not. After stand-
ing several hours, precipitates were noticeable in the flasks containing the higher concentrations in each
of the series. Thus, it can be concluded that nioxime is a more sensitive qualitative reagent for palla-
dium ions than dimethylglyoxime. In making the test care should be exercised and the weakly colored
precipitate allowed to coagulate before drawing a definite conclusion.


Although palladium nioxime, Pd(CHO2N2), is formed by the union of one palladium ion with two
molecules of nioxime with the liberation of two hydrogen ions, it is precipitated from a dilute mineral
acid solution. Quantitative precipitation is obtained at pH values from 0.7 to 5 but at pH values below
0.7 quantitative precipitation is not assured.

The effect of various anions upon the determination of palladium was investigated. In the cases of
sulfate and nitrate, the chloride ions were expelled by evaporation with the respective acid before addi-
tion of the ammonium salts. A small amount of chloride was present in samples to which ammonium
acetate, ammonium tartrate and sulfosalicylic acid were added. Results obtained indicate that these an-
ions do not affect the determination, see Table 2.

Table 2. The effect of various anions upon the determination of palladium.

Anion Anion Palladium Weight of Palladium Error
present Gram taken precipitate found Mg
Gram Gram Gram

Chloride 0.5 0.0107 0.0391 0.0107 0.0
Chloride 0.5 0.0122 0.0445 0.0122 0.0
Sulfate 1.0 0.0127 0.0461 0.0127 0.0
Sulfate 1.0 0.0119 0.0437 0.0120 +0.1
Nitrate 1.0 0.0117 0.0427 0.0117 0.0
Nitrate 1.0 0.0126 0.0470 0.0129 .0.3
Acetate 1.0 0.0130 0.0483 0.0133 +0.3
Tartrate 1.0 0.0121 0.0439 0.0120 -0.1
Sulfosalicylate 1.0 0.0120 0.0438 0.0120 0.0

MDDC 1095

A series of determinations conducted in order to observe the effect of varying excesses of nioxime
indicated that as much as 150 per cent excess reagent could be added without affecting the accuracy of
results obtained. These data are shown in Table 3. The minimum excess of nioxime recommended is
thirty per cent which is 0.43 ml of reagent per milligram of palladium present.

Table 3. The effect of excess nioxime upon the determination of palladium.

Trial Excess of Palladium Weight of Palladium Error
nioxime added taken precipitate found Mg
per cent Gram Gram Gram

1 30 0.0126 0.0462 0.0127 +0.1

2 60 0.0133 0.0481 0.0132 -0.1

3 100 0.0128 0.0467 0.0128 0.0

4 150 0.0125 0.0456 0.0125 0.0

Determinations conducted on a series of different sized samples indicated that palladium could be suc-
cessfully determined over a range of 6 to 30 mg. However filtration becomes somewhat difficult with the
larger samples. Table 4 gives the data obtained.

Table 4. Determination of various amounts of palladium.

Trial Palladium Weight of Palladium Error
takeri precipitate found Mg
Gram Gram Gram

1 0.0065 0.0240 0.0065 0.0

2 0.0121 0.0444 0.0122 .0.1

3 0.0185 0.0672 0.0184 -0.1

4 0.0268 0.0970 0.0266 -0.2


Adjust the volume of the solution containing from five to twenty mg of palladium to approximately
200 mi. The pH of the solution can vary from one to five depending upon dther cations present. Heat the
solution to about 60. Add slowly from a pipet with stirring 0.43 ml of 0.8 per cent nioxime for each mg
of palladium present. Digest the solution with occasional stirring for thirty minutes at 60". Filter
through a weighed filter crucible of medium porosity and wash with live portions of hot water. Dry at
110" for one hour and weigh. The factor for palladium is 0.2743.

The determination of palladium in the presence of platinum was investigated. The separation was ef-
fected by simply using the procedure outlined above. The filtrates containing the platinum and excess
nioxime yielded a blue precipitate only upon standing more than twenty-four hours after filtration. The
data obtained is summarized in Table 5.

Palladium was determined in the presence of uranyl, beryllium, ruthenium, aluminum, lanthanum,
zinc, cadmium, alkali, and alkaline earth ions. The data obtained from these separations are shown in
Table 6. Nioxime yields a precipitate with aurous ion at 60" which is contaminated with metallic gold.

MDDC 1095

Table 5. Determination of palladium in the presence of platinum.

Pt Palladium Weight of Palladium
Trial present taken precipitate found Error
Gram Gram Gram Gram Mg

1 0.010 0.0112 0.0412 0.0113 +0.1
2 0.025 0.0118 0.0436 0.0120 +0.2
3 0.040 0.0130 0.0479 0.0131 +0.1
4 0.050 0.0132 0.0487 0.0134 +0.2
5 0.100 0.0114 0.0423 0.0116 +0.2

Table 6. Determination of palladium in the presence of various cations.

Palladium Weight of Palladium
Cation Cation taken precipitate found Error
present Gram Gram Gram Gram Mg

Uranyl 0.030 0.0127 0.0468 0.0128 +0.1
Uranyl 0.070 0.0117 0.0430 0.0118 +0.1
Ruthenium 0.010 0.0135 0.0501 0.0137 +0.2
Ruthenium 0.025 0.0125 0.0460 0.0126 +0.1
Beryllium 0.015 0.0117 0.0428 0.0117 0.0
Beryllium 0.035 0.0130 0.0472 0.0130 0.0
Lithium 0.05 ea. 0.0135 0.0494 0.0136 +0.1
ZLnth m 0.05 ea. 0.0119 0.0428 0.0121 +0.2


1. Beamish, F. E. and M. Scott, Ind. Eng. Chem., Anal. Ed., 9:462 (1937).
2. Rauh, E. G., G. F. Smith, C. V. Banks, and H. Diehl, J. Org. Chem., 10:199 (1945).
3. Scott, Standard Methods of Chemical Analysis, Vol. I, p. 724, New York, D. Van Nostrand Co., Inc.,
4. Treadwell, F. P. and W. T. Hall, Analytical Chemistry, Vol. II, p. 141, John Wiley and Sons, New
York, 1942.
5. Voter, R. C., G. V. Banks, and H. Diehl, submitted for publication.
6. Zschiegner, H. E., Ind. Eng. Chem., 17:294 (1925).


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