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A critical study of the analytical separation of Beryllium from the rar-earth elements

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A critical study of the analytical separation of Beryllium from the rar-earth elements

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Content A CRITICAL STUDY
OF THE ANALYTICAL SEPARATION OF BERYLLIUM
FROM THE RARE-EARTH ELEMENTS
A Thesis
Presented to
the Department of Chemistry
University of Southern California
In Partial Fulfillment
of the Requirements for the Degree
Master of Arts
CE
IS
031^
by
May 1955
UMI Number: EP41462
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a ll its members, has been presented to and ac
cepted by the C ouncil on Graduate Study and
Research in p a rtia l fu lfillm e n t of the require
ments fo r the degree of
\ I
ms'mR QEnAm
Faculty Committee
Chair ma\
K.i.
TABLE OF CONTENTS
PAGE
INTRODUCTION ............................................. 1
MATERIALS AND APPARATUS................................... 9
EXPERIMENTAL WORK .................... 11
Standardization of solutions ........ 11
Rare-earth solutions ............. ..... 11
Beryllium solutions 12
Preliminary experiments ........................ IS
Determination of beryllium and beryllium hydroxide. 14
Decomposition of oxalic acid .................. 16
Solvent effect of oxalic acid on the determination
of beryllium as beryllium hydroxide with ammonium
hydroxide. ........... . 18
CONCLUSIONS............................................... 25
BIBLIOGRAPHY ............................................. 27
INTRODUCTION
Beryllium is a relatively rare metal comprising between .01 and
.001 per cent of the earth’s crust. It occurs in several types of ores,
beryl, Be Al_(SiO ) being the most important and only source of the ele-
2 £ 3 6
ment commercially. In several minerals containing beryllium elements of
the rare earth group are also present. Among these may be mentioned
gadolinite, BegFe(lO)g(SiQ4)2.
Because beryl has been the only ore of commercial importance
from which beryllium is obtained, the extraction of beryllium from it is
of great interest in the analytical chemistry of the metal. For this
reason, the quantitative separation of aluminum and SiOg from beryllium
has been thoroughly investigated.
At present, the importance of beryllium is not such as to make
practical its commercial extraction from ores other than beryl. Conse
quently, in analyses of rare-earth minerals containing beryllium, the
rare-earth elements are quantitatively extracted, while recovery of the
beryllium is ordinarily neglected.
Many investigations are being carried on involving the use of
beryllium in alloys. Having an atomic weight of only 9.02, beryllium
is almost twice as light as aluminum and may be invaluable in future
development of aircraft. With an increasing demand for beryllium, its
extraction from rare-earth minerals may become of commercial importance
so that an investigation of methods involving the quantitative separa
tion of beryllium from the rare-earths is of interest. Moreover, for
purposes of geological research it is necessary to have chemical analyses
of the highest accuracy, and some doubt has arisen as to the reliability
of current methods of determining rare-earths and beryllium in the pre
sence of each other*
The rare-earths are a group of elements so closely related that
the isolation of individual elements from others of the group is a pro
blem involving most tedious crystallization processes. As the chemical
properties are so much alike, the rare-earths may be separated as a group
from other elements with which they may be contaminated.
According to Hildebrand and Lundell (1929), beryllium can be se
parated from the cerium group of rare-earths by precipitation of the lat
ter with sodium sulphate, and from the yttrium group by precipitation
with oxalic acid in a .5n solution of the chlorides. No further infor
mation regarding the subsequent determination of the beryllium or the
reliability of the method is given.
Gibbs (18 ) mentions a separation of cerium from aluminum, beryl
lium and uranium by means of sodium sulphate, but does not suggest any
quantitative method for the separation of beryllium from the yttrium
group.
C. James and H. G. Holden (1913) give a quantitative separation
of beryllium from neodymium, a member of the cerium group of rare-earths,
using oxalic acid. Standard solutions of neodymium and beryllium were
mixed, heated to boiling, and a slight excess of oxalic acid added. The
precipitate of neodymium oxalate was washed with water, ignited and weigh
ed as NdpOe. Results obtained were as follows:
3
G. BeO MgOg (taken) KdgOg (found)
.0956
.1912
.2868
.1438
.1438
.1438
.1438
.1436
.1438
Although this data seems to indicate that a complete separation of
neodymium and beryllium had been obtained by the use of oxalic acid, no
procedure nor data for the analytical determination of the beryllium re
maining in the filtrate is suggested by the authors.
A thorough investigation of the analytical chemistry of beryllium
has been carried on by Hellmut Fisher working at the Siemens Konzem in
Germany. He has developed a method for the calorimetric determination of
beryllium, using quinalizarin (1-2-5-8 tetra hydroxianthraquinone) as an
indicator. According to a recent report by A. S. Komarowski and I. M.
Karenman (1933), however, this method cannot be used in the presence of
rare-earths, as these elements interfere with the color reaction.
The most common method for the gravimetric determination of beryl
lium is by precipitation with ammonium hydroxide and ignition of the
Be(OH) precipitate to the oxide, BeO. Such a precipitation of beryllium,
however, offers difficulties, as the properties of beryllium hydroxide
vary greatly with its preparation.. According to J. M. van Bemmeln, two
forms of beryllium hydroxide exist. The first, known as << beryllium
hydroxide, is granular, while the other, 0 beryllium hydroxide, is gela
tinous. oC beryllium hydroxide is regarded as a chemical compound of
definite composition, and behaves like gelatinous aluminum hydroxide and
ferric hydroxide. 0 beryllium hydroxide is regarded as colloidal beryl
lium oxide, as there is little to show that the water is other than ab-
4
sorbed or mechanically held.
Bleyer and Boshart (1912) found that 3 beryllium hydroxide can be
changed into the ^ form by heating. This change is not complete unless
ammonium salts, either the chloride or the nitrate are present. The
determination of beryllium from < * - beryllium hydroxide is difficult to
perform in actual practice without a loss of beryllium. The main source
of error seems to be caused by a dissociation of the ammonium salts by
heating. This causes the solution to become more acid, resulting in the
dissolving of some beryllium hydroxide. Low results are therefore ob
tained by this method.
The precipitation of 3 beryllium hydroxide results if excess am
monia is added to a cold solution of beryllium salts. This precipitation
is complete, according to Bleyer and Boshart (1912) in the presence of
ammonium chloride if an excess of ammonium hydroxide is avoided. Beryl
lium hydroxide has, however, like other colloidal hydroxides, a tendency
to occlude other substances which may be present during its precipitation.
Ley, 1899.
Because of this adsorbing power of the precipitate, results are
apt to be high. It is almost impossible to remove these substances by
washing, as the hydroxide passes through the filter paper while the ab
sorbed salts are washed. According to J. M. van Bemmeln (1882, 1898),
the power of absorbing salts from aqueous solution is possessed by the
0 beryllium hydroxide but not by the modification.
Due to the difficulties involved in the determination of beryllium
with ammonium hydroxide, guanidine carbonate and hydrazine carbonate have
5
been suggested recently as more advantageous precipitants for beryllium.
The use of tannic acid, ammonium nitrite and methyl alcohol, or diammon-
iumhydrogenphosphate likewise have been proposed as suitable precipitants
for beryllium.
G. Krfiss and H. Moraht (1890) proposed a separation of the rare-
earths from beryllium by the following method: the beryllium was first
dissolved in hydrochloric acid, neutralized with ammonium hydroxide, and
an excess ammonium oxalate was added. Sufficient dilute hydrochloric
acid was then added to dissolve the flocculent precipitate of beryllium
oxalate, the oxalates of the rare-earths remaining insoluble. The filtrate
was then dropped into an ammoniacal solution of ammonium carbonate contain
ing an excess of ammonium oxalate, and the filtrate was treated with steam
for the precipitation of basic beryllium carbonate.
From the above survey it is clear that a quantitative separation of
beryllium from the rare-earths by the oxalate method seems possible, but
the variations in the directions given suggest questions in the minds of
some investigators. Furthermore, these investigators seem to have content
ed themselves with the determination of the rare-earths, and have not given
data as to the completeness of the recovery of beryllium from the oxalate
filtrate. It is well known that beryllium tends to enter complex molecul
ar formations with organic acids, and for this reason, special attention
has been given in this investigation to the determination of beryllium in
the filtrate from the rare-earth oxalate precipitation.
As ammonium hydroxide is the precipitant most commonly used in the
regular determinations of beryllium, the beryllium remaining in the fil-
trate after precipitation of the rare-earth oxalates is to be determined
by precipitation with ammonium hydroxide and ignition of the hydroxide
to the oxide, BeO. The precipitation of beryllium is complicated in this
case by the presence of excess oxalic acid necessary for the precipita
tion of the rare-earths. According to L. A. Sarver and-P. H. M-P. Brin-
ton (1927), who studied the solubilities of lanthanum, cerium, praseo
dymium, neodymium, samarium, etc., in hydrochloric,..nitric, sulfuric and
oxalic acids, the solubilities of the oxalates in solutions saturated
with oxalic acid and containing very little hydrochloric acid decrease
in the order given. For pur© solutions, a concentration of .5 N. oxalic
acid for the other rare-earth elements. Consequently, the effect of the
excess oxalic acid in the filtrate from such a precipitation must be con
sidered in the determination of the beryllium.
The possibility of a complete separation of beryllium by ammonium
hydroxide in the presence of oxalic acid is open to question. A. Rosen
heim and P. Hoge (1897) say that beryllium hydroxide is completely pre
cipitated from a solution of beryllium oxalate by ammonium hydroxide, but
that the hydroxide in such a precipitation contains appreciable oxalate.
N. V. Sidgwick and M. B. Lewis (1926), however, in a study of the beryllium
oxalate-oxalic acid-water system, state that beryllium is only partially
precipitated with ammonium hydroxide from a solution containing oxalate.
The solubility curve plotted from experimental data showed a possibility
of the existence of a solid equilibrium in which BeCgO^ SHgO and HgCgO^
2HgO exist as mixed crystals.
C. L. Parsons and W. 0. Robinson (1906), after a survey of litera-
7
ture on complex acidic and basic beryllium oxalates, conducted experi
ments with the system BeO: H C 0.: HO, in order to determine whether
2 2 4 2
or not complex oxalates of beryllium exist. According to their research,
if a hot saturated solution of oxalic acid is treated with an excess of
basic beryllium carbonate or hydroxide, it dissolves the basic component
until a concentration of 2.85 BeO: lG^Og is reached, giving rise to a
thick syrupy solution and setting free carbon dioxide. If solutions of
oxalic acid growing less and less concentrated are used, the ratio of
base soluble in the acid grows constantly smaller. Upon dilution of a
solution containing 2.85 BeO: lCgOg, there follows a precipitation of
beryllium hydroxide until a concentration of .001 is reached, after which
the ratio of base to acid remains at a constant of 1.6: 1.
They concluded from phase rule considerations that the precipitate
obtained from various concentrations of the Be(0H)g: W 4 = HgO system
are solid solutions containing a small amount of oxalic acid in beryllium
hydroxide. They conclude that no acid oxalate of beryllium exists, and
that the so-called basic oxalate of beryllium do not exist as separate and
definite chemical compounds, but are in reality solid solutions of the
oxalate in the hydroxide. According to these authors, the presence of ex
cess base, beryllium hydroxide, or beryllium basic carbonate, will com
pletely prevent the crystallization of beryllium oxalate.
As the beryllium in this case was not determined with ammonium
hydroxide, whether or not the addition of excess ammonium hydroxide to
such a system would give a complete precipitation of beryllium cannot be
predicted, except that interference due to the formation of basic beryl-
8
Hum compounds or complexes is not to Jbe ^expected, particularly as the
authors state that no basic oxalate of beryllium has ever been made or
will ever be made where water is one of the constituents of the system.
In order to determine the effect of oxalic acid on the precipi
tation of beryllium with ammonium hydroxide, the beryllium is to be de
termined in the presence of varying amounts of oxalic acid. Other ex
periments are to be carried on in which the oxalic acid is to be destroy
ed, and the beryllium remaining determined with ammonium hydroxide.
MATERIALS AMD APPARATUS
The rare-earth solutions used in this investigation were obtained
from Dr. P. H. M-P. Brinton. The first solution contained a faintly acid
mixture of rare-earth chlorides, composed mostly of lanthanum and praseo
dymium of high purity. The second solution was made up from crystals con
taining a large percentage of neodymium and magnesium nitrates. In order
to remove the magnesium, the crystals were dissolved in distilled water,
the solution precipitated with hot concentrated oxalic acid. The oxalates
were washed with saturated oxalic acid, and ignited to the oxides in plati
num crucibles. The oxides were redissolved in concentrated hydrochloric
acid and the solution diluted to approximately two liters. The final acid
ity was approximately .23 N.
The standard beryllium solutions used for experimental work were
made up from purest beryllium basic carbonate, obtained also from Dr. P. H.
M-P. Brinton. The basic carbonate was dissolved in as small a volume of
concentrated hydrochloric acid as possible, and diluted to a definite vol
ume.
Carbonate-free ammonium hydroxide solutions vised to precipitate the
beryllium were prepared by distilling concentrated MC. P." ammonium
hydroxide, to which solid calcium oxide had been added, into distilled
water, which had been boiled to remove the carbon dioxide. Such solutions
were made up at frequent intervals to minimize sources of error due to con
tamination.
Saturated solutions of oxalic acid were prepared by heating an excess
10
of "C. P." oxalic acid crystals with distilled water, and allowing the
excess to crystallize out as the solution cooled to room temperature.
The purity of the oxalic acid was tested by igniting two 5 g. samples
of oxalic acid in sillimanite crucibles. A slight residue remained
after the ignition in each case, but its weight was negligible.
The rare-earth oxalates were washed with cold saturated oxalic
acid. Beryllium hydroxide solutions were washed with a 2 per cent am
monium nitrate solution to which a few drops of ammonium hydroxide were
added to insure alkalinity.
Except in preliminary experiments in which sillimanite erucibles
were used, all ignitions were carried out in platinum crucibles.
To obtain a uniformly high temperature during ignition, the
platinum crucibles were covered with inverted assay crucibles. Fischer
burners were also used in ignitions.
A chainomatic balance of Christian Becker make, with a sensitivi
ty of .000052 mg./scale division was used for all weighings.
All pipettes were calibrated to deliver exactly 25 ml. of solu
tion at 20° C. so that they could be used interchangeably.
Concentrated sulfuric acid was used as the drying agent in the
dessicator.
EXPERIMENTAL WORK
STANDARDIZATION OF SOLUTIONS
Rare-earth solutions. Two rare-earth solutions were used in
the experimental work. Both were standardized by the following pro
cedure:
A 25 ml. aliquot portion of the rare-earth solution was diluted
to approximately 100 ml. with distilled water. This solution was heat-'
ed to boiling, and 50 ml. of saturated oxalic acid solution which had
been heated to boiling was added slowly with constant stirring. The
precipitate was allowed to stand for at least three hours, the oxalate
filtered, washed thoroughly with cold saturated oxalic acid, and ignit
ed wet in a platinum crucible. The ignition was carried on slowly at
first until ashing of the filter paper was almost complete. The almost
completely covered crucible was then transferred to the hottest part of
the flame, and covered with an inverted assay crucible to insure a high
and uniform temperature. After an initial ignition of one hour, the
crucible was cooled in a dessicator for a period varying from one half
to three hours, and weighed. The crucible was then ignited at twenty
minute intervals, each followed by a suitable period of cooling, until
a constant weight was obtained. The following concentrations were
found for the two standard solutions:
Solution I
Average
g. R 0_/25 ml. 0.2385 0.2386 0.2386 0.2386
2 5
12
Solution II
Average
g. Rg0^/25 ml. 0.1111 0.1111 0.1111
Beryllium solutions. Three different beryllium solutions were
used in the experimental work. All three solutions were standardized
by the following method:
A 25 ml. aliquot portion of the beryllium solution was diluted
to 100 ml. Ammonium hydroxide was added, with stirring, to-the cold
solution until the odor of ammonia showed an excess of the reagent had
been added. After half an hour, the gelatinous beryllium hydroxide pre
cipitate was filteres onto No. 41 Size 11 Whatman filter paper, washed
with 2 per cent ammonium nitrate, and ignited wet in the same manner
as were the rare-earths. Care must be taken that the ashing of the
filter paper be carried on very slowly, or a loss is apt to occur due
to splattering, caused by water occluded in the gelatinous mass. The
following concentrations were found for the three standard solutions:
Solution I
Average
g. BeO/25 ml. 0.2604 0.2601 0.2603
Solution II
g. BeO/25 ml. 0.1335 0.1335 0.1335
Solution III
g. BeO/25 ml. 0.1447 0.1446 0.1446 0.1446
15
PRELIMINARY EXPERIMENTS.
25 ml. aliquot portions of the rare-earth standard solution I were
precipitated according to the procedure given in the Standardization of
Solutions. The oxalates were ignited in platinum and sillimanite cruci
bles in order to determine if the latter could be used to ignite com
pletely the rare-earth oxalates to the oxides.
Platinum crucibles Sillimanite crucibles Error in silliman
ite crucibles
RgOg (g./25 ml.) Rg0s (g./25 ml.) (g./25 ml.)
0.2585 0.2422 +0.0037
0.2386 0.2418 +0.0032
Sillimanite crucibles are evidently not suitable for the ignition
of the rare-earth precipitates, as incomplete conversion resulted even
with prolonged heating periods. As a result, platinum crucibles were
used to ignite both the rare-earth and beryllium precipitates.
Experiments were first carried on following the same procedure
used in standardizing the rare-earth and beryllium solutions. To the
hot solutions containing mixtures of rare-earths and beryllium, varying
from 25 ml. to 50 ml. of each, 50 ml. of hot concentrated oxalic acid
were added slowly, with constant stirring. The precipitated oxalates
were allowed to stand at least three hours, filtered, washed with cold
saturated oxalic acid, and ignited wet. High results varying from
0.0006 g. to 0.0022 g. were at first obtained for the rare-earth oxides.
The residues from several such ignitions were redissolved and repreci
pitated with oxalic acid. The filtrate was tested with ammonium hydrox-
14
ide, and an appreciable amount of beryllium hydroxide was precipitated.
A more thorough washing of the oxalate precipitates was found to
be sufficient to remove completely any beryllium so occluded, apparent
ly without a loss of rare-earths.
Danger of such contamination of the rare-earths is made less if
concentrated solutions of beryllium are avoided during the precipitation
with oxalic acid.
When excess ammonium hydroxide was added to the filtrate after the
rare-earths had been removed from the mixture of rare-earths and beryl
lium, the oxalic acid seemed to interfere with the precipitation of
beryllium. It was observed that some beryllium hydroxide passed through
the filter paper, apparently in colloidal form, but was reprecipitated
in the filtrate after standing a short time. Accordingly, it was decided
to attempt a precipitation of beryllium hydroxide in the*form, in order
to obtain the hydroxide as a non-colloidal substance.
DETERMINATION OF BERYLLIUM AS c* BERYLLIUM HYDROXIDE.
Two 25 ml. aliquot portions of the beryllium solution were mixed
with an equal volume of rare-earth solution, and the mixture was diluted
to 100 ml. The beryllium remaining in the filtrate after the precipita
tion of the rare-earths with 55 ml. of hot concentrated oxalic acid was
heated to boiling, according to the procedure suggested by Hildebrand and
Lundell (1929), and ammonium hydroxide was added slowly to yellow color
ation Y/ith methyl red. According to the authors, a precipitation of *
beryllium hydroxide should result at this point. No precipitate was ap
IS
parent until much more ammonium hydroxide was added. When precipitation
seemed complete, the hot solution was filtered as suggested. As the fil
trate cooled, however, more beryllium hydroxide continuously precipitated.
This was added to the original precipitates and ignited with them. Fil
tration was much more rapid than with-the & beryllium hydroxide, as the
precipitate was flocculent, and did not adhere to the sides of the con
tainer.
BeO taken (g./25 ml.) BeO found (g./25 ml.) Error (g.)
a. 0.1556 0.1518 -0.0017
b. 0.1555 0.1556 +0.0001
The filtrate from a was evaporated to a small volume, and treated
with 10 ml. portions of fuming nitric acid until all the oxalic acid
seemed destroyed. 100 ml. of water were added, some carbonized material
was filtered off, and an excess of ammonium hydroxide was added to the
cold solution. No precipitate resulted at first, but after standing all
night, a precipitate of beryllium hydroxide was observed. This was fil
tered, washed, and ignited to the oxide. Both the filtrate and the pre
cipitate, after the decomposition of the oxalic acid with nitric acid,
seemed contaminated with- yellow. The precipitate weighed 0.0055 g.
The beryllium oxide from this ignition was redissolved in concen
trated hydrochloric acid. An insoluble residue was fused with potassium
pyro sulphate, and tested with ammonium hydroxide. A positive test for
beryllium resulted.
The manner in which the oc beryllium hydroxide was precipitated
might indicate that the presence of oxalic acid delays the precipitation
16
of beryllium hydroxide in this form, and that a complete precipitation
is not obtained in all cases even if the beryllium hydroxide which pre
cipitates on cooling is added to the original precipitate. Bleyer and
Boshart (1912), as mentioned previously, however, observed that the
quantitative determination of beryllium hydroxide in the << form is
difficultly obtained in actual practice without a loss of beryllium.
For this reason, the low results obtained in case a cannot be explained
alone as having been caused by the interference of oxalic acid.
DECOMPOSITION OF OXALIC ACID
As the presence of oxalic acid seemed to interfere with the pre
cipitation of beryllium as described, it was of interest to investigate
various acids which could be used to destroy the oxalic acid.
Accordingly, concentrated hydrochloric and sulfuric acid, as well
as mixtures of the two acids were tried, but were found to give less
satisfactory results than did fuming nitric acid.
In order to obtain the most effective decomposition of oxalic
acid by means of fuming nitric acid, it was found that beryllium solu
tions containing oxalic acid should be evaporated to a small volume, and
16 to 20 ml. of fuming nitric acid added in a fume hood. If any oxalic
acid remains after this mixture has been evaporated just to dryness, a
small volume of distilled water and 10 ml. of acid should be added and
the evaporation process repeated until all the oxalic acid is destroyed.
26 to 35 ml. of fuming nitric acid should be sufficient to destroy 55 ml.
of cold saturated oxalic acid. This method is more effective than that
17
in which the nitric acid is added to a dilute solution containing the
oxalic acid, and evaporated, or that in which only 10 ml. of nitric acid
are added at first.
Care must be taken during evaporation with nitric acid that the
solutions be removed from the fire just as they reach dryness. If this
is not done, a carbonizing of material occurs which colors the solution
after the solid impurities are filtered off, as well as the beryllium
hydroxide precipitate subsequently obtained. Splattering of the residue,
with a loss of beryllium, is also apt to occur in 3uch a case.
Two 25 ml. portions of standard beryllium solution II were mixed
with 55 ml. of saturated oxalic acid. The acid was destroyed according
to the above procedure, the residue taken up with 100 ml. distilled
water, filtered and precipitated with ammonium hydroxide.
BeO taken (g.) BeO found (g.) Error (g.)
a. 0.1355 0.1349 +0.0014
b. 0.1535 0.1363 (eontaminat- +0.0028
ed with yel
low)
Sample a was redissolved in hydroehlorie acid and reprecipitated
with ammonium hydroxide.
BeO taken (g.) BeO found (g.) Error (g.)
a. 0.1335 0.1524 -0.0011
The high results obtained after the decomposition of oxalic acid
could be explained by the existence of soluble impurities in either the
oxalic acid or the nitric acid. WC. P.1 1 fuming nitric acid was used. In
case b a slight carbonizing of material during the decomposition of the
18
oxalic acid might explain the increased error in the final result. Be
cause of the colloidal nature of the precipitate any soluble impurities
in the solution are apt to be occluded in the beryllium hydroxide and
lead to high results as Ley (1899) reported.
A reprecipitation of the beryllium oxide does not offer any solu
tion to the difficulty, as a large negative error results. It is also
difficult to redissolve beryllium oxide after ignition as the compound
is very stable.
Although the decomposition of oxalic acid could not be relied up
on to give accurate results in determinations of beryllium, such a de
struction of the acid was found to be of value in making qualitative
tests for beryllium in filtrates after an ammonium hydroxide precipita
tion, in order to determine whether or not any beryllium hydroxide had
passed through the filter paper in colloidal or dissolved form. In such
cases, the filtrates were concentrated, the oxalic acid destroyed, the
residue taken up with distilled water and excess ammonium hydroxide add
ed. A small amount of beryllium gives a floeculent precipitate which is
readily visible. It was observed, however, that the precipitation of the
hydroxide does not always occur immediately. If the solution is allowed
to stand overnight, a precipitate is often formed during that period.
SOLVENT EFFECT OF OXALIC ACID ON THE DETERMINATION OF BERYLLIUM AS
BERYLLIUM HYDROXIDE WITH AMMONIUM HYDROXIDE.
As decomposition of oxalic acid with filming nitric acid did not
lead to satisfactory quantitative results in the determination of beryl
19
lium, it was decided to make a series of analyses for beryllium in the
presence of varying.amounts of the acid in order to determine a concen
tration of oxalic acid from which beryllium might be completely preci
pitated by means of ammonium hydroxide. Besides being tedious and in
troducing sources of contamination of the beryllium precipitate, decom
position of the oxalic acid is to be avoided, if possible, as fumes from
the destruction of the acid sire particularly obnoxious if effective fume
hoods are not available.
The rare-earths were also determined by precipitation using vary
ing amounts of oxalic acid, in order to determine the magnitude of error
such variation of oxalic acid concentration would cause in the accuracy
of their precipitation.
Accordingly, in some determinations oxalic acid was added to the
standard beryllium or rare-earth standards alone, while in others, mix
tures of the two standard solutions were used.
Volumes of staurated oxalic acid varying from 10 to 35 ml. were
used. In eases where beryllium and rare-earth solutions were mixed, the
volume of oxalic acid given represents the original volume of acid added
to precipitate the rare-earths, plus the volume added to wash the oxalate
precipitate, the volume used in the precipitation of the small amount of
rare-earths present being considered negligible. The temperature of the
saturated oxalic acid solution varied considerably, so that the volumes
of oxalic acid given are not exactly comparable. The oxalic acid is not
expressed in concentrations, as figures for the amount of oxalic acid in
a saturated solution vary according to different authorities, and the
20
oxalic acid used was not standardized by titration.
From the following table of data it is evident that the rare-earth
group is satisfactorily precipitated in the range between 15 and 50 ml.
of saturated oxalic acid. The maximum error in the determinations was - , 4
.4 per cent, this error resulting in only two samples, one containing 15
and the other 50 ml. of saturated oxalic acid to precipitate the rare-
earth group. All other determinations gave satisfactory quantitative
results. This seems to indicate that a complete separation of the rare-
earths from beryllium took place in the range of concentrations indicat
ed. At no time was there evidence that the beryllium oxide was contaminated
with rare-earth oxides.
Experimental data obtained in beryllium determinations seems contra
dictory. Unusually high results were obtained when 10 ml. of saturated
oxalic acid were added to g5 ml. of standard beryllium solution. These
samples were ignited at intense heat for two hours after constant weight
had been obtained in order to make sure a complete ignition had taken
place. At the end of this time, sample 1 weighed 0.1547 g., which still
gave a positive error of +0.0008 g., and sample 2 weighed 0.1555 g., giv
ing a positive error of +0.0020 g. Similarly, high results were obtained
with samples 1 and 2, where 25 ml. of oxalic acid and 15 ml. of wash
solution were present during precipitation, and also in sample 1, where
50 ml. of saturated oxalic acid was used. It was thought that these re
sults might be explained by the fact that the beryllium hydroxide preci
pitate had been improperly washed. Accordingly, a more thorough washing
was made with a 2 per cent ammonium nitrate solution, and results were
21
to within the limits of experimental error in samples 3,4 and 5, contain
ing 25 and 15 ml. of oxalic acid. There was a possibility, however, that
the loss occurring here was not due to a loss of occluded matter alone,
but might also be due to a loss of beryllium hydroxide particularly in
the light of experiments conducted by Ley mentioned earlier in this paper.
For this reason, filtrates from samples 3,4 and 5 containing 25 and 15
ml. oxalic acid were concentrated, the oxalic acid destroyed with fuming
nitric acid, the residue taken up with distilled water and after filtra
tion, an excess of ammonium hydroxide added. Upon standing over night,
small precipitates of beryllium hydroxide were found in all three eases.
No ignition of these precipitates was made as results of such an ignition
could not be relied upon, as before stated. It is quite possible that
the actual loss of beryllium in these cases is very small, as can be seen
from a consideration of sample 4, where 50 ml. of oxalic acid was present.
In this case, an appreciable amount of beryllium passes through the fil
ter paper and was reprecipitated in the filtrate. The precipitate was
thoroughly washed in this case,also, and the beryllium hydroxide in the
filtrate disregarded. The total loss observed was 1.7 mg. As the pre
cipitate disregarded was of much more appreciable size than that obtained
in the former cases, the amount of dissolved beryllium present could not
have been great. As a precipitate was obtained in the filtrate from sam
ple 3, where 25 and 15 ml. of oxalic acid were present after a decomposi
tion of oxalic acid, even though an error of +0.0002 g. was obtained in
the final weight of the oxide, it is evident that impurities of some sort
were absorbed by the beryllium hydroxide which caused high results, and
22
that a complete removal of the impurities was not accomplished by a
thorough washing of the precipitate, even though some beryllium itself
was lost. The possibility therefore exists that the more exact results
obtained in the presence of oxalic acid are actually somewhat low, due
to the fact that an impurity may be present which tends to bring the re
sults up to an apparently quantitative precipitation.
No visible interference with the beryllium hydroxide precipita
tion was noticed when oxalic acid varying between 10 and 40;ml. were
added originally. When SO ml. of saturated oxalic acid is present, how
ever, the beryllium precipitated appears to be in a more colloidal form,
evidenced by the fact that some passes through into the filtrate. By
the time the filtration is completed, a considerable amount of beryllium
hydroxide precipitate is visible in the filtrate. If the filtrate is
allowed to stand, a few crystals of ammonium oxalate are also visible.
If the beryllium hydroxide in the filtrate is added to the original pre
cipitate, it is apparently retained by the filter paper. The first three
analyses made with 50 ml. of oxalic acid present show that 1 gave high
results, while 2 and 2 are within the limits of experimental error. As
stated before, the beryllium hydroxide passing through the filter paper
in ease 4 was neglected, which gave results 1.7 mg. too low.
When 75 ml. of saturated oxalic acid are added to a beryllium
solution having a total volume of between 175 and 200 ml., after the addi
tion of excess ammonium hydroxide, most unsatisfactory results are ob
tained. A great deal of ammonium oxalate is precipitated before the beryl-
23
Hum hydroxide precipitation is complete, and very little beryllium
hydroxide remains on the filter paper. The oxalic acid here evidently
has a definite solvent effect on the beryllium hydroxide and hinders its
precipitation. The ammonium hydroxide was added very slowly, with con
stant stirring to make certain that all oxalic acid was neutralized, let
the addition of ammonium hydroxide to the filtrate caused a further pre
cipitation of beryllium hydroxide. The presence of ammonium oxalate be
fore filtration might have prevented the beryllium hydroxide from preci
pitating. Attempts were made to determine the amount of beryllium hydrox
ide actually precipitated, but ignitions were never completed as the am
monium oxalate intermixed with the beryllium hydroxide decrepitated upon
heating and caused such a splattering of the precipitate that no reliance
could be placed on results.
Literature on the formation of complex oxalates was studied, but
no evidence for the existence of a basic complex was found except in the
early work of Woge and Rosenheim, which was later disproved. The possi
bility that beryllium oxalate was precipitated in the last case discussed
is not probable, as it was stated earlier in the paper that beryllium
oxalate is never precipitated in the presence of a base.
TABLE I
Vol. sat. T. oxalic Vol. soln. Vol. soln. I
oxalic (°G)
after after Be.
(ml.) R. E. pption. taken
pption. (ml.)
(ml.)
1
10 27.5 150
2
25 1
26.5 160
2
15 1 25 115 175 .1111
KL5 wash.)
1 .1111
2 .1111
35 3 .1111
4 25 135 .1111
6 24.5 175 .1111
5 24.5 140 200 .1111
4 24.5 140 200 .1111
25 3 27.5 125 180 .2222
(+15 2 28.5 125 180 .1111
wash) 1 28.5 125 180 .1111
1 25 140
40 2 25 140
3 26 140
1 26.2 175 250 .3333
2 26.2 175 250 .3333
50 3 25.5 150
4 150
E. oxides BeO
(g«)
found error taken
(g*)
found error
.1335 .1354 +.0019
.1335 .1363 +.0028
.1335 .1332 -.0003
.1335 .1335 ±.0000
.1115 +.0004 .1446 .1447 +.0001
.1112
.1113
.1112
.1109
+.0001
+.0002
+.0001
-.0002
.1113
.1112
.1111
.2219
.1109
.1108
+.0002
+.0001
+.0000
-.0003
-.0002
-.0003
.1446
.1446
.1446
.1446
.1446
.1443
.1441
.1448
.1463
.1467
-.0003
-.0005
+.0002
+.0017
+.0021
.1135
.1335
.1335
.1136
.1332
.1451
+.0001
-.0003
+.0006
.3336
.3320
+.0003
-.0013
.1446
.1446
.2603
.2603
.1459
.1446
.2599
.2586
+.0014
+.0000
-.0004
-.0017
Vol. sat. T. oxalic Vol. soln. Vol. soln. E. E. oxides BeO
oxalic (°G) after after Be. (g.) (g.)
(ml.) R. E. pption taken found error taken found error
pption. (ml.)
(ml.)
In the above experiment using 50 ml., the Be(QH)g is partially colloidal. NH^ oxalate preci
pitates on standing. Some Be(0H)g comes through while filtering and is reprecipitated in the fil
trate. Above results except 4 had this Be in filtrate added to the precipitate before ignition.
75 150-250
A great deal of EH, oxalate comes down before the Be(0H)g is completely precipitat
ed. A great deal ofi 'Be(OH)g goes through into filtrate. Decrepitation of the ammonium
oxalate in the Be(0H)g precipitate during ignition makes quantitative determinations im
possible.
CONCLUSIONS
The precipitation of the rare-earths by oxalic acid gives a satis
factory method for a complete separation of the rare-earths from beryl
lium. The rare-earths can be quantitatively determined by such a proce
dure, but a satisfactory method for the quantitative determination of
beryllium by ammonium hydroxide was not obtained.
Investigation showed that fuming nitric acid could not be used to
destroy the oxalic acid remaining in the filtrate after the precipitation
of the rare-earths with excess oxalic acid, but that beryllium determina
tions after such a decomposition of the acid are apt to be contaminated
and give high results. Reprecipitation gave results too low for quanti
tative analysis.
Reprecipitation of beryllium hydroxide in the form seemed to be
delayed by the presence of oxalic acid. When all beryllium hydroxide pre
cipitating from the cooling solution was added to the original precipitates,
both low and quantitative results were obtained. Due to the many sources
of error involved in this method, it is not recommended.
Precipitation of beryllium hydroxide in the 8 form in the presence
of oxalic acid gives high results in many cases. This error is probably
due to impurities occluded during the precipitation of the hydroxide, as
suggested by Ludwig Moser and Josef Singer (1927). A thorough washing of
the beryllium hydroxide precipitate, while bringing the results down to
a quantitative range, also allows the passage of some beryllium hydroxide
through the filter paper, H. Ley (1899) found that washing of beryllium
26
hydroxide precipitates tended to give similar results if occluded sub
stances were present in the precipitate.
The presence of saturated oxalic acid in amounts as concentrated
as 50 ml. of saturated oxalic acid /25 ml. of solution after precipita
tion with ammonium hydroxide, interferes with precipitation, although
practically all of the beryllium hydroxide may be recovered by addition
of the small amount of beryllium hydroxide appearing in the filtrate
during precipitation, to the original precipitate. Approximately 2 mg.
of beryllium hydroxide may be lost if this is not recovered. When oxalic
acid is present in amounts as concentrated as 75 ml. of the saturated
solution in a volume, after precipitation with ammonium hydroxide between
150 and 250 ml., the beryllium hydroxide is only partially precipitated.
Ammonium oxalate crystals separate out with the beryllium hydroxide and
their decrepitation causes splattering which would make an ignition un
satisfactory even though the precipitation of beryllium hydroxide was com
plete.
A fully satisfactory method for the precipitation of beryllium after
separation from rare-earth oxalates could not be developed in the time
available for this piece of research, and it is recommended that further
investigations be carried on to try and solve this difficult analytical
problem. It is believed that the whole subject of the quantitative deter
mination of beryllium in the presence of interfering substances needs to
be investigated.
BIBLIOGRAPHY
BOOKS
Gmelin, Leopold, Gmelin1s Handbuoh der Anorganischen Chemie, 8 Auflage,
Berlin: Deutsche Chemisehe Gesellschaft, 1950. 180 p.
Hillebrand, W. F., and Lundell, G. E., Applied Inorganic Analysis. New
York: J. ?Jiley and Sons, Inc., 1929. 929 p.
Hopkins, B. S., Chemistry of the Rarer Elements. New York: D. C. Heath
and Company, 1925. 576 p.
Millor, J. W., Comprehensive Treatise of Inorganic Chemistry. Vol. IV,
New York: Longman's Green-and Company, 1925. 1074 p.
Siemen-Konzern, Beryllium. Its Production and Application. Translated
by Richard Rimbach and A. J. Michael. New York: Chemical Catalog
Company, 1952. 351 p.
Spencer, J. F., The Metals of the Rarer Earths. New York: Longmans,
Green and Company, 1919. 297 p.
JOURNALS
Bleyer, B., and Boshart, K., "Die Gewichts Analytisehe Bestimmung des
Berylliums." Zeit. f. Anal. Ghem,, 51, 1912. pp. 748-755.
Gibbs, W., Amer. J. Sci., 87, 1868. pp. 354-356.
James, C., and Holden, H. C., J. Amer. Chem. Soc., 35, 1915. p. 565.
Jelek, Ant. and Kota, Jan, "Determination of Beryllium." Zeit. Ann.
Chem., 89, 1932. pp. 345-554.
Jelek, Ant. and Kota, Jan, "Gray. Determination of Beryllium with Hydro'
zine Carbonate." Coll. Czech. Chem. Comm., 2, 1950. pp. 571-583.
Komarowski, A. S., and Karenman, I. M., "Das Verhalten von Zr. Th. und
einigen seltenen Erden zu Chinalizarin." Zeit. f. Anal. Chem.,
94, 1933. 247-249.
Kriiss, G., and Moraht, H., Liebig's Annalen, 262, 1890. p. 58}
Berichte, 23, 1890, p. 2552.
Ley, H., Zeit. Phys. Chem., 30, 1899. p. 218.
28
Ludwig, Moser and Singer, "Determination and Separation of Rare Metals
from other Rare Elements. X." Monatshefte, 48, 1927. pp. 673-687.
Parsons, C. L., and Robinson, W. 0., "Equilibrium in the System BeO.
Oxalic Anhydride and Water." J. Amer. Chem. Soe., 28, 1906.
pp. 555-569.
Rosenheim, A., and Woge, P., "IJeber die Wertigkeit des Berylliums."
Zeit. Anorg. Chem., 15, 1897. p. 285.
Sarver, L. A., and Brinton, P. H. M-P., "The Solubilities of some Rare-
Earth Oxalates." J. Amer. Chem. Soc., 49, 1927. pp. 943-958.
Sidgewick, N. V., and Lewis, N. B., J. Chem. Soc., 28, 1926. pp. 1291-
1302.
Van Bemmeln, J. M., J. Prakt. Chem., (2), 26, 1882. p. 227; "Umsetzung
des Krystallinischen Hydrate in Amorphe Subs tan zen.1 1 Zeit. Anorg.
Chem., 18, 1898. p. 128.

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Creator Carrigan, M. E (author)

Core Title A critical study of the analytical separation of Beryllium from the rar-earth elements

Degree Master of Arts

Degree Program Chemistry

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag chemistry, inorganic,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor [illegible] (committee chair), Clark, Loren T. (committee member), Roberts, L.D. (committee member)

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