1250
J. D. KURBATOV AND A. M. SILVERSTEIN
highly sensitive not only to small amounts but to moderate variations in the quantity of carbonate present in solution. The authors are deeply indebted to Professor Edward iMack, Jr., for his discussion and support of this work. The scholarship received by one of the authors from the Ohio State University Industrial Research Foundation made this research possible and is greatly appreciated. I t is a pleasure to express our thanks to the Ohio State University Development Fund for grants which secured fundamental research instruments. REFERENCES (1) BRITTOS,H.T. S.: J. Chem. Soc. 127, 2110 (1925). J. D.,A N D KVREATOV, M . H.: J. Phys. Chem. 48,441 (1942). (2) KURBATOV, (3) KURBATOV, M.H., AKD KURBATOV, J. D.: J. Chem. Phys. 13. 208 (1945). (4) PANETH,-:Mitt. Radium Institute Wien 34, 47,55 (1913). J.: AECD 1910 (1948). Technical Information Branch, AEC, Oak Ridge, (5) SCWUBERT, Tennessee. ( 6 ) SPITZER, V. I.: J Rum. Chem. SOC. 49, 357 (1917).
COAGULATION ISOTHERM OF THORIUM J. D. KURBATOV
AND
A.
IM. SILVERSTEIN
Department of Physics, the Ohio State University, Columbus,Ohio Received .Voveniber 18, 1949 IXTRODUCTION
In previous work it has been shown that the coagulation of tetravalent thorium (3) or zirconium (2) ions in quantities of the order of IO-@ gram-atom (lo+ molar), under comparable conditions of pH, salt concentration, and nature of cations and anions present, is similar to their removal by filtration from exmolar or less. Thus, weighable quantities of thotremely dilute solutions, rium or zirconium which undergo visible coagulation exhibit behavior comparable to that of the same ions in such extreme dilution that agglomeration before filtration could not be observed. Under a given set of experimental conditions such us pH, salt concentration, etc., consecutive filtrations of the same solutions of tetravalent elements result in removal on the paper of similar fractions of the material in the solution. However, the results in a series of experiments are reproducible and if removal on the filter paper in extreme dilution were entirely due to adsorption of thorium ions by filter paper, the fraction removed by filtration should be expected to vary significantly, owing to differences in the rate of filtration and in the surface of the paper covered during filtration. I n order to establish the continuity of the process of coagulation of visible
1251
COAGULATION IGOTHERM O F THORIUM
quantities and their removal from solution by filtration with the removal of invisible quantities of the same element from solution under the same experimental conditions, a coagulation isotherm of thorium has been obtained, using quantities from 1 X le6to 1 X 10-8 gram-atom. TABLE 1 C'oagulution of thorium at p H 5.6 T = 25°C.; S H , S O r = 5 X 10-8 JV; volume = 20 d= 0.2 ml.; coagulation period = 2 hr.
-
i
TUIAL ~ O P I U N
CUACULATIOS
. .
per rcnl
grom.aloml
x x x 2 x
10-9 10-1 lo-' 10-7
x
10-7
1 1 1
4
82.3 81.4 82.3 82.2 67.5
~
'
COAGCLAIIOY
,
I O 1 . U IEORIDlil
gram-atoms
per Cent
'j
6 X lo-' 1 x 10-6 4 X 10-6 1 x 10-6
53.3 42.5 22.2 13.0
1
--I
~
;I
T : 25.C.
C O A G U L A T I O N PERIOD s 2 HOURS VOLUME. P O ? . Z m l
I I I I I 10.9
I l l l l
l l l l l l
I11111
10-8 10-7 10.6 L O G G:ATOMS T H O R I U M I N O R I G I N A L S O L U T I O N
FIG.1. Coagulation
10'5
isotherm of thorium
PROCEDURE
A purified solution of known concentration of thorium nitrate in 0.01 N nitric acid was diluted in 0.01 N nitric acid so that 1 ml. of each of the various dilutions contained the quantities of thorium listed in table 1. To 1 ml. of each of the thorium solutions 2 ml. of UX1 tracer in 0.01 N nitric acid and 15 ml. of water were added. These solutions were titrated rapidly to pH 3.5, using freshly prepared ammonia solutions, and the vessels closed and allowed to stand 2 hr. Then the solutions were filtered through Schleicher and Schull blue ribbon filter papers.
1252
J . D. KURB.4TOV AND A .
M. SILVERSTEIN
The part of the thorium remaining on the filter paper ?vas dissolved in nitric acid, the solution evaporated to dryness, and its activity measured on a Geiger counter. Known fractions of the filtrate were also evaporated to dryness and their activities measured to be certain of complete recovery of the tracer. The preparation of UX1 tracer and its measurement hare been described in a recent paper (3). EXPERIMENTAL RESULTS
Table 1 shows that the fraction of thorium removed increased with dilution down to 2 X 10-7 gram-atom/ZO ml. under the conditions given. Below this concentration the fraction removed was experimentally constant. The log-log (figure 1) plot of thorium removed vs. thorium originally present shows the continuity of behavior through the whole range of concentrations used, with the curve bending tovard the abscissa in the higher concentration range, as was observed previously ivith both yttrium (1) and zirconium. SUMMARY
The coagulation isotherm obtained under the conditions described shows that therc is no discontinuity in the removal of thorium on filter paper in the concentrations of thorium used. While the highest concentration was conventional and the lowest was 5 X 10-8 K,the process of remora1 of thorium from solution at pH 3.5 is not conceded as identical with the precipitation of hydrous oxides. The process consists in (1) adjustment of the pH of the solution to that of hydrolytic coagulation and (2) filtration. For the latter step the action of the filter paper is similar to the action of adsorbents. The authors appreciate a grant in aid from The Ohio State University Development Fund for instruments and the cosperation and support of Professor Edward Mack, Jr. HEFEHESCES (1) KURBATOV, J. D.,
KURBATOV, bl. H . : J. Phys. Chern. 46, 441 (1942). (2) KURBATOV, M. H., AHD KURBATOV, J. D . : J . Chem. Phys. 13, 238 (1945). (3) KURBATOV, M. H., WEBSTER,€1. B., ASD KURBATOV, J . D.: J. Phys. Chem 64, 1239 (1950). AND
