tered through Whatman No. 42 paper, washed with hot water, dried, ignited, and eventually weighed as Zr02. Representative results are given in Table I. Precipitation of Zirconium in Presence of Mercury(I1). Mercury(I1) gives a white precipitate with thiomalic acid which is soluble in a n excess of t h e reagent, b u t t h e precipitate reappears slowly on standing. Therefore, in the presence of mercury(I1)
Table 1.
the precipitation is carried out as above, but the precipitate is filtered hot without allowing i t t o stand, washed with hot water, dried, ignited, and the zirconium weighed as ZrOa. Estimation of Zirconium in Presence of Thorium. Although thorium does not precipitate in acidic medium, i t is coprecipitated in t h e presence of zirconium. For analyzing a mixture of zirconium a n d thorium, therefore, t h e acidity is maintained at 0.2N with respect t o nitric acid, 50 t o 80 ml. of reagent solution are added, and the system is heated to 80” t o 90” C. for 0.5 hour. After the precipitate is allowed to stand for nearly 2 hours, i t is filtered, then washed first with 0.2N nitric acid and subsequently with hot water. The precipitate is ignited and finally weighed as Zr02. The filtrate and washings are collected and the thorium content is determined by any of the standard methods. Precipitation of zirconium in the presence of elements other than thorium and mercury is effected as described for pure zirconium solution.
Determination of Zirconium
Zr02, Gram
BY thiomalic acid
BY m-nctrobenzoic acid
0.01550 0.03860 0.07700 0.1156 0.1544 0.1930
0.01542 0.03855 0.07710 0.11565 0.1542 0.19275
Difference, Gram f0.00008
$0.00005 -0.00010 -0.00005 $0.0002 +O. 00025
known but these are usually formed from concentrated solutions. The interference study in which elements as nitrates or chlorides were deliberately added is summarized in Table 111. In a n almost neutral medium, uranyl and chromic ions are coprecipitated but the error is negligible if the precipitation is effected in the higher permissible acid concentration. Iron(II1) and cerium(1V) are reduced by thiomalic acid to the lower valence states. It is peculiar that bismuth, as such, is not precipitated by thiomalic acid, but it is coprecipitated to a considerable extent in the presence of zirconium. Use of thiourea, potassium iodide, or (ethylenedinitri1o)tetraacetic acid in eliminating the interference due to bismuth by complexation was not successful. Therefore, when present, bismuth must be removed by a suitable method-e.g., by sulfide. The composition of the zirconium complex varies somewhat but corresponds approximately to zirconyl thiomalate, which has the formula
Effect of Sulfuric Acid and Sulfate Ion on Precipitation of Zirconium by Thiomalic Acid
Table 11.
(Wt. of ZrO2 taken each time, 0.0562gram) Nitric Sulfuric ZrOl, Acid, Acid, Obtained, N N Gram
Sodium Sulfate, Grams 0.2 0.5 1.0
...
... ... ... 1.0 1 .o
... ...
0.oSSi
0.05 0.075 0.10
...
0.05 0.075 0.10
1.0
0.0563
...
...
...
...
0.0561 0.0551 0.0529 0.0468 0.0490 0.0391 0.0316
ACKNOWLEDGMENT
Difference, Gram 0.0001 0.0001 0.0001 0.0011 0.0033 0.0094 0.0072 0.0171 0.0246
The authors are indebted to Lucy W. Pickett and Philip W. West for research facilities and interest in the work. The award of a Special Skinner Fellowship to S.B.S. is gratefully acknowledged. Evans Chemetics Inc., New York, gave a gift sample of thiomalic acid. Sincere thanks are due to Fred E. Beamish for permission to carry out a few experiments in his laboratory. LITERATURE CITED
DISCUSSION
Table 111.
Determination of Zirconium in Presence of Diverse ions
(0.1 to 0.2 gram of element added as nitrate or chloride. Weight of ZrOz taken eacb time, 0.03855gram)
Ion Added Ba +) Ca +a Sr +a Mg+i”
Be Zn +a Cd +z
Hg +2 Pb + a
Mn +a
c o +z
Ni +Z Fe + 3 A1 +a
Cr + 3 Ce +4
Ti +4
Th+’
vo +z
UOz+*
380
ZrOz Obtained, Gram 0.03870 0,03870 0.03860 0,03860 0.03860 0.03860 0.03850 0.03860
n. o w 0
:
0 03850 0.03870 0.03860 0.03870 0.03870 0.03860 0.03870 0.03860 0.03850 0.03870 0.03860
Difference, Gram 0.00015 0.00015 0.00005 O.ooOo5 0.00005 0.00005 0.00005 0.00005 0.00015 0.00005 0.00015 0. o0005 0.00015 0 00015 0.00005 0.00015 0.00005 0 . oo005 O.OOO15 0.00005
ANALYTICAL CHEMISTRY
The first series of experiments revealed that, while free sulfuric acid cannot be tolerated (Table 11), nitric and hydrochloric acids can be used, provided their over-all acidity does not, exceed 0.2 and 0.1N, respectively. Zirconium can also be precipitated in ammonium acetate medium. Large amounts of sulfate, nitrate, a n a chioride ions do not affect the accuracy of the results. However, sulfate ion in the presence of nitric or hydrochloric acid has almost the same adverse effect as free sulfuric acid (Table 11). Besides the low results, the zirconium precipitate under these conditions is in a very finely divided form even after 24 hours’ standing involving loss during filtration. Zirconium has a strong wnaericy to form with sulfuric acici anionic complexes-e .g. the disulfato-oxozlrconic acid, Hz[ZrO(SO& / , which undergoes hydrolytic decomposition depending upon the experimental conditions ( 2 ) . The alkali sulfate complexes are also ~
(1) Belcher, R., Wilson, C. L
, ‘‘Sew Methods in Bnalytical Chemistry ’ I Chapman and Hall, London, 1955. (2)Remy, H., “Treatise on Inorganic. Chemistry,” Vol. 11, p. 68, Elseviei, Kew York, 1956. (3) Sant, S. B.,Sant, B. R., Anal. Chim.
Acta21,221(1959).
RECEIVEDfor review June 12, 1959 Accepted November 27,1959.
Use of Celluiosic Ion Exchangers for Deter mina t ior of Quaternary Amrnoniurr Compounds Correcti tn
-
11-tne art]-le ‘‘but‘?oi beiiu.mc lor. ExcharL,gersfo Dete.-minatic 5 Quat e r n a v Ammonium Compo :nds h A L . CHEW32, 70 t19601],on rjape 7 1 , first column, line five, Cellex cui shoula be changed to Selectocei L D. METCAXFE
