C. Remigius Fresenius.

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the case of the chloride by the action of water and lithium
carbonate by attraction of carbonic acid ; in that case it is neces-
sary, therefore, to add a few drops of nitric or, as the case may

* Other methods are given by STOLBA (ZeitscTir. f. analyt. Chem., n, 397}
and MOHB (Ib., yn, 173).

606 SEPARATION. [ 152.

be, hydrochloric acid, in the process of digestion. The separa-
tion of the alkali chlorides by means of ether- alcohol was first
proposed by EAMMELSBERG* and later on recommended by
jENZscH.f This method, however, can yield only approximate
results, as the lithium salt obtained on evaporating the alcoholic
extract is found by spectroscopic examination to be always im-
pure (DlEHL:f).

If we have to separate the sulphates, they must be converted
into nitrates or chlorides before they can be subjected to the
above method. This conversion is best effected by means of
lead salts, see 2. Ignition with ammonium chloride does not
answer for lithium sulphate, nor can the sulphuric acid be
removed by barium, or strontium, as the precipitated sulphates
would contain lithium (DIEHL).

J. "Weigh the mixed alkalies, best in form of sulphates, and 8
then determine the lithium as phosphate according to 100.
If the quantity of lithium is relatively very small, convert the
weighed sulphates into chlorides (7), separate, in the first place,
the principal amount of the potassa and soda by means of alco-
hol ( 100), and then determine the lithium (MAYER ||).

c. When exact results are required, the indirect method is 9
to be preferred. Proceed first according to #, evaporate the
spirituous solution of the lithium chloride containing the remain-
der of the other chlorides to dryness, heat moderately, weigh,
dissolve in water, estimate the chlorine, and calculate therefrom
the lithium and sodium or potassium. BUNSEN ^f also applied
the method to the indirect estimation of lithium in presence of
potassium and sodium by removing the silver from the filtrate,
and separating tlu> potassium with platinum. But I must here
point out, that according to JENZSCH** the potassium double salt
will contain lithium apparently in the form of the plat inn-
chloride of potassium and lithium.

The sulphuric acid in weighed quantities of the sulphates
of lithium, and of potassium and sodium, cannot be determined
as barium sulphate (see end of 7).

* Pogg. Annal., LXVI, 79. f Jb. t civ, 105.

J Annal. d. Chem. u. Pharm., cxxi, 97. lb., cxxi, 98.

I lb., xcvin, 193.

1 Annal. d. Chem. u. Pharm., cxxn, 348. ** Pogg. Annal., civ, 102.

153.] BASES or GROUP n. 607

The separation of lithium from ammonium may be effected
like that of potassium and sodium from ammonium (4 and 5).

Second Group.





INDEX. (The numbers refer to those in the margin.)
Barium from potassium and sodium, 10, 12.

ammonium, 11.
Strontium from potassium and sodium, 10, 13.

" ammonium, 11.

Calcium from potassium and sodium, 10, 14.

" ammonium, 11.

Magnesium from potassium and sodium, 15-26.
" ammonium, 11.

A. General Method.


Principle, on which the method is based : Ammonium car- 10
bonate precipitates, from a solution containing ammonium
chloride, only barium, strontium, and calcium.

Mix the solution, in which the metals are assumed to be
contained in the form of chlorides, with a sufficient quantity of
ammonium chloride to prevent the precipitation of the magne-
sium by ammonia ; dilute rather considerably, add some ammo-
nia, then ammonium carbonate in slight excess, let the mixture
stand covered for an hour in a moderately warm place, filter,
and wash the precipitate with water to which a few drops of
ammonia have been added.

The precipitate contains the barium, strontium, and cal-
cium; the filtrate the magnesium and the alkalies. So at
least we may assume in cases where the highest degree of
accuracy is not required. Strictly speaking, however, the
solution still contains exceedingly minute traces of calcium
and somewhat more considerable traces of barium, as the car-

608 SEPARATION. [ 1.03.

bonates of these two metals are not absolutely insoluble in
a fluid containing ammonium chloride; the precipitate also
may contain possibly a little ammonium magnesium carbonate.
Treat the precipitate according to 154, and the filtrate in
rigorous analyses as follows : Add 3 or 4 drops (but not much
more) of dilute sulphuric acid, then ammonium oxalate, and
let the fluid stand again for 12 hours in a warm place. If a
precipitate forms, collect this on a small filter, wash, and treat
on the filter with some dilute hydrochloric acid, which dis-
solves the calcium oxalate, and leaves the barium sulphate
undissolved. Since a little magnesium oxalate may have sepa-
rated with the former, add some ammonia to the hydrochloric
solution, filter after the precipitate has settled, and mix the
filtrate with the principal filtrate.

Evaporate the fluid containing the magnesium and the alka-
lies to dryness, and remove the ammonium salts by gentle igni-
tion in a covered crucible, or in a small covered dish of platinum
or porcelain.* In the residue, separate the magnesium from
the alkalies by one of the methods given 15 24.

MONIUM. The same principle and the same process as in the
separation of potassium and sodium from ammonium (4 and 5).

B. Special Methods.



Precipitate the barium with dilute sulphuric acid ( 101, 1, a\ 12
evaporate the filtrate to dryness, and ignite the residue, with
addition towards the end of ammonium carbonate ( 97, 1 and
98, 1). Take care to add a sufficient quantity of sulphuric
acid to convert tin 1 alkalies also completely into sulphates. In
exact analyses, in order to save the alkali salts adhering to the

*This (.ju-ration effects also the removal of the small quantity of sulphuric
acid added t> preeipiiate the traces of barium, as sulphates of the alkalies are
converted into chlorides upon ignition in presence of a large proportion qf

a i) inn .11 iu in chloride.

153.] BASES OF GKOUP II. 609

barium sulphate, remove the dry barium sulphate from the
filter, heat it with a sufficient quantity of pure strong sulphu-
ric acid to dissolve it completely, allow to cool, dilute largely,
collect the barium sulphate (now almost absolutely pure) on the
first filter, ignite, and weigh. Evaporate the filtrate in a plati-
num dish, drive off the sulphuric acid, and estimate the traces
of the alkalies.

This method is, on account of its greater accuracy, prefer-
able to the one in A, in cases where the barium has to be sepa-
rated only from one of the two fixed alkalies ; but if both alka-
lies are present, the other method is more convenient, since the
alkalies are then obtained as chlorides.


Strontium may be separated from the alkalies like barium, 13
oy means of sulphuric acid ( 102, 1, a) ; but this method is
not preferable to the one in 10, in cases where the choice is
permitted (comp. 102).


Precipitate the calcium with ammonium oxalate ( 103, 2, 14
Z, or), evaporate the filtrate to dry ness, and determine the alka-
lies in the ignited residue. In determining the alkalies, dis-
solve the residue, freed by ignition from the ammonium salts,
in water, filter if necessary, acidify the filtrate, according to cir-
cumstances, with hydrochloric acid or sulphuric acid, and then
evaporate to dryness ; this treatment of the residue is neces-
sary, because ammonium oxalate partially decomposes chlorides
of the alkali metals upon ignition with formation of alkali car-
bonates, except in presence of a large proportion of ammonium
chloride. The results are still more accurate than in A, except
where ammonium oxalate has been used, after the precipitation
by ammonium carbonate, to rejnove the minute traces of lime
from the filtrate.

610 SEPARATION. [ 135.

a. Methods based upon the sparing solubility ofMagnetwm

///,>// /,.//,/, ;// i! ',

a. Make the solution as neutral as possible, and free from 15
ammonium salts (it is a matter of indifference whether the mag-
nesium and alkali metals are present as sulphates, chlorides, or
nitrates), add baryta-water as long as a precipitate forms, heat
to boiling, filter, and wash the precipitate with boiling water.
The precipitate contains the magnesium as hydroxide. Dis-
solve it in hydrochloric, acid, precipitate the barium with sul-
phuric acid, and then the magnesium as ammonium-magnesium
phosphate ( 104, 2). The alkalies, which are contained in the
solution, according to circumstances, as chlorides, nitrates, or
caustic alkalies, are separated from the barium as directed in
10 or 12. LIEBIG, who was the first to employ this method,
proposes crystallized barium sulphide as precipitant. The
method is not very exact, as magnesium is somewhat more
soluble in solutions of alkali salts than in water. On this
account the weighed alkali salt must always be tested for
magnesium, and the latter determined if required.

ft. Precipitate the solution with a little pure milk of lime, 16
boil, filter, and wash. Separate the calcium and magnesium in
the precipitate according to 36; the calcium and the alkalies in
the filtrate according to 10 or 14. This method may be em-
ployed when magnesium has to be removed from a fluid con-
taining calcium and alkalies, provided the alkalies alone are
to be determined. Minute quantities of magnesium also in this
case remain with the alkali salt from the cause mentioned in t*.

y. Evaporate the solution of the chlorides (which must 17
contain no other acids) to dryings, and it' ammonium chloride
i> present, ignite: warm the residue with a little water (this
will dissolve it with the exception of some magnesinun oxide,
which separates). Add mercuric oxide shaken up with water,
evaporate to dryness on the water-bath with frequent stirring,
dry thoroughly, ignite with increasing temperature till all the
resulting mercuric chloride is volatilized, proceeding exactly as
detailed in 104, 3, 1. (Avoid inhaling the fumes.) There is

The methods a, a, and ft are suitable for the separation of magnesium

153.] BASES OF GEOUP II. 611


no need to continue the ignition until the whole of the mer-
curic oxide is expelled ; on the contrary, part of it may be fil-
tered off together with the magnesium oxide and subsequently
volatilized upon the ignition of the latter. Treat the residue
with small quantities of hot water, filter off rapidly, and wash
the magnesium oxide with hot water, using small quantities at a
time, and not continuing the operation unnecessarily. The
solution contains the alkalies in form of chlorides. This
method, proposed by BEKZELIUS, gives satisfactory results,
and, so far as my experience goes, is the best of those given
under a. Take care to add the mercuric oxide only in proper
quantity, and always test the alkali chlorides for magnesium,
a trace of which will generally be found.

d. If the bases are present as chlorides, add as much, pure 18
oxalic acid * as may be necessary to unite with all the bases
present, viewed as potassium, to form a tetroxalate, add a
little water, evaporate to dryness in a platinum dish, and
ignite. By this operation the magnesium chloride is completely,
the alkali chlorides partially, converted into oxalates, which
on ignition yield alkali carbonates and magnesia. Treat the
residue repeatedly with small quantities of boiling water ; it
is immaterial whether the precipitate is transferred to the
filter or remains in the platinum dish. When all the alkali
salt is washed, dry the filter, incinerate it in the dish, ignite
strongly, and weigh the magnesia. Should the solution ob-
tained be slightly turbid, evaporate it to dryness, take up
the residue with water, and filter off the trifling residual
magnesia ; finally add hydrohcloric acid to the filtrate and esti-
mate the alkalies as chlorides.

If the bases are present as sulphates, add barium chloride 19
to the boiling solution until a precipitate just ceases to form,
evaporate the filtrate with excess of oxalic acid, and proceed
as in 18. Separate the slight quantity of barium carbonate
remaining with the magnesia as directed in 29.

These methods were devised by E. MITSCHEKLICH and 20
described by LASCH.| According to my experience the

* TH. SCHEREE, (Zeitschr. f. analyt. Chem., xi, 197) recommends pure
ammonium oxalate instead of oxalic acid.
\Journ.f. prakt. Chem., LXIII, 343.

612 SEfrARATIOtf. [ 153.

results are not particularly good. As a rule too little mag-
nesia is obtained ; hence the weighed alkali salt should always
be tested with sodium phosphate and ammonia for magnesia.
Not infrequently a quite weighable precipitate is obtained,
which must not be neglected.*

The method described in 18 is also applicable to nitrates,
and was recommended for these by DEVILLED During-
evaporation there are evolved carbon dioxide and nitrous acid.

J. Methods based on the Precipitation of Magnesium ~by
Ammonium Phosphate (or Ar senate).

Add ammonia in excess to the solution containing mag- 21
nesium, potassium, and sodium, and add some ammonium
chloride should this not be already present ; then precipitate
the magnesium with only a slight excess of pure ammonium
phosphate. Expel the free ammonia from the filtrate by
evaporation, and precipitate the phosphoric acid with lead
acetate as a compound of lead phosphate and lead chloride.
Remove the excess of lead oxide with ammonia and ammonium
carbonate, or with hydrogen sulphide, from the still warm
fluid, and in the filtrate determine the potassium and sodium
according to 97 and 98 (O. L. ERDMANN^:; HEINTZ).
The method is rather inconvenient, but quite accurate. If the
solution contains much ammonium chloride, the greater part
should be first removed by volatilization.

The excess of phosphoric acid may also be removed with 22
ferric oxide or silver oxide instead of with lead oxide

oc. With ferric oxide. Expel any ammonia from the
liquid with heat, neutralize if necessary with hydrochloric acid,
and add ferric-chloride solution until the liquid is yellowish ;
then add ammonium carbonate until the liquid is neutral or
only acid from the carbonic acid present, boil, filter off the
basic ferric phosphate (which, if sufficient ferric chloride has
been used, will have a reddish -brown color.), wash, evaporate

* SONNENSCHEIN'S method (boiling the chlorides with silver carbonate) 1
cannot recommend, as the filtrate always contains magnesia, and in fact more
than mere traces.

f Journf. prakt. Chem., LX, 17.

j lb. t XXXTX, 278.

%Pogg. Annul., IAMU, 119.

153.] . BASES OF GROUP II. 613

the filtrate to dryness, expel the ammonium salt, and deter-
mine the potassium and sodium according to 97, 98. A
good and convenient method.

/?. With silver oxide. Evaporate to dry ness the fluid fil-
tered off from the ammonium- magnesium phosphate, ignite
cautiously, dissolve in water, and mix with silver nitrate and
a slight excess of silver carbonate. After filtering, remove
the excess of silver from the filtrate with hydrochloric acid,
and evaporate the solution to dry ness with an excess of hydro-
chloric acid (CHANCEL *).

The separation is somewhat shorter, if less precise and
convenient, when the magnesium is precipitated with ammo-
nium arsenate( 12T, 2) instead of ammonium phosphate, and
the liquid, with some ammonium chloride added, evaporated
to dry ness and the residue ignited under a good chimney.
By this treatment the excess of arsenate added is volatilized,
while the alkalies remain behind as chlorides (always retaining,
however, a little magnesium chloride). C. v. HAUEftf
recommended a similar method.

c. Method lased on the Precipitation of the Magnesium
as Ammonium- Magnesium Carbonate.

Mix the solution of sulphates, nitrates, or chlorides (it 23
must be very concentrated) with an excess of a concentrated
solution of sesquicarbonate of ammonia in water and ammonia
(230 grm. of the salt, 360 c. c. solution of ammonia, sp. gr.
0*96, and water to one litre). After twenty-four hours filter
off the precipitate (MgCO 3 *[]S r H 4 ], 1 CO 3 + 4H 2 O), wash it with
the solution of ammonia and ammonium carbonate used for the
precipitation, dry, ignite strongly and for a sufficient length
of time, and weigh the magnesium oxide. Evaporate the
filtrate to dry ness, keeping the heat at first under 100, expel
the ammonium salts, and determine the alkalies as chlorides
or sulphates. When sodium alone is present the results are
fairly satisfactory. In the presence of potassium the ignited
magnesium oxide must be extracted with water before weigh-
ing, as it contains an appreciable quantity of potassium carbo-

* Compt. rend., L, 94.

\ Jahrb. der k. k. geolog. Keichsanstalt, iv, 863.

614 SEPARATION. [ 153.

nate ; the washings are to be added to the principal filtrate.
This last measure is unnecessary in the absence of potassium.
The magnesium is always a little too low. Mean error 0*009


d. Method based on the Precipitation of the Alkalies as
Silicofluorides (STOLE A J).

"When a solution contains a mixture of potassium and mag- 24
nesium chlorides or potassium and magnesium nitrates, the
potassium in one aliquot portion may be precipitated and de-
termined as silicofluoride ( 97, 5), while in another the magne-
sium may be precipitated as ammonium-magnesium phosphate
( 104, 2). If it is desired to make both determinations in the
same portion of fluid, remove the excess of silicofluoric acid
from the fluid filtered off from the potassium silicofluoride, by
an alcoholic solution of potassium acetate, wash the precipitate
with a mixture of equal volumes of alcohol and water, and
determine the magnesium in the filtrate. If sulphates are pres-
ent, the method, in my opinion, is rendered so difficult as to
make it untrustworthy, because of the difficult solubility of the
magnesium sulphate in dilute alcohol.

This method is less adapted for the separation of sodium
from magnesium than for potassium from magnesium, because
sodium silicofluoride is more soluble in alcohol than is the po-
tassium salt. In the case of sulphates it is unserviceable, and
in the case of chlorides or nitrates, to obtain results of any
value, it is necessary to add 2 volumes of strong alcohol after
adding the hydrosilicofluoric acid, and to allow the precipi-
tate to settle completely before filtering.

e. Indirect methods which give simultaneously the quan-
tity of Potassium and Sodium, if loth are present.

a. Weigh the sulphates, dissolve, divide the solution into 25
two parts, and in one determine the magnesium according to
104, 2 ; in the other determine the potassium as in 2, cal-
culate the magnesium sulphate and potassium sulphate, and
from the difference find the sodium sulphate.

* Pogg. Annal, civ, 482. f VicrteljaJiresschriftf. prakt. Pharm., vin, 161
J ZeitscJir. f. analyt. Chem. , iv, 160.

154.] BASES OF GROUP II. 615

/?. With proper caution convert the bases into pure neutral 26
sulphates, weigh these, dissolve in water, determine the sul-
phuric acid present with barium chloride ( 132), precipitate
the excess of barium chloride in the filtrate with sulphuric acid,
filter again, and in the filtrate, concentrated by evaporation,
determine the magnesium as directed in 104, 2 (K. LIST*).

Deduct the weight of the magnesium calculated as mag-
nesium sulphate from the weight of the total sulphates; the
difference will give the weight of the alkali sulphates. Further,
deduct the weight of the sulphuric acid combined with the
magnesium from the total sulphuric acid ; the difference will
give that combined with the alkalies. See 152, 3 (6).

It is, of course, evident that the indirect methods can give
accurate results only when the most painstaking care is exer-
cised. The accuracy of method ft is, besides, impaired by
the tendency of barium sulphate to carry down with it readily
soluble salts.



INDEX. (The numbers refer to those in the margin.)
Barium from strontium, 28, 31, 40.

calcium, 28, 30, 31, 35, 40.
" magnesium, 27, 29.

Strontium from barium, 28, 31, 40.
" calcium, 34, 38, 39.

" magnesium, 27, 29.

Calcium from barium, 28, 30, 31, 35, 40.
" strontium, 34, 38, 39.

magnesium, 27, 32, 33, 36, 37. f
Magnesium from barium, 27, 29.

" strontium, 27, 29.

calcium, 27, 32, 33, 36, 37. f

* Annal. d. Chem. u. Pharm., LXXXI, 117.

f Compare also the method of OEFFINGEB, Zeitschr. f. analyt. Ghem.,

616 SEPARATION. [ 154.

A. General Method.


Proceed as in 10. The magnesium is precipitated from the 27
filtrate as ammonium-magnesium phosphate (see foot-note, p.
620). The precipitated carbonates of barium, strontium, and
calcium are dissolved in hydrochloric acid, and the bases sepa-
rated as directed in 28. The traces of magnesium, which may
be present in the ammonium carbonate precipitate, are obtained
by evaporating the nitrate from the strontium or calcium sul-
phate to dryness, taking up the residue with water, and precipi-
tating the solution with sodium phosphate and ammonia.

B. Special Methods.

1. Methods ~based upon the Insolubility of Barium


Mix the neutral or slightly acid solution with hydrofluosi- 28
licic acid * in excess, add one third of the volume of alcohol of
0'81 sp. gr., let the mixture stand twelve hours, collect the pre-
cipitate of barium silicofluoride on a weighed filter, wash with
a mixture of equal parts of water and alcohol until the wash-
ings cease to show even the least trace of acid reaction (but no
longer), and dry at 100. Precipitate the strontium or calcium
from the filtrate by dilute sulphuric acid ( 102, 1, a, and !<>:;,
1). The results are satisfactory. For the properties of barium
silicofiuoride, see 71. If both strontium and calcium are pres-
ent, the sul|)li;itcs are weighed, and then separated according
to 34, or they are converted into carbonates ( 132, II., 5), and
separated according to 38 or 39.

* If not kept in a gutta-percha bottle it should be freshly prepared.

154.] BASES OF GROUP II. 617

2. Methods based upon the Insolubility of Barium
Sulphate or Strontium Sulphate, as the case may be, in
Water and in Solution of Sodium T hiosulphate.


Precipitate the barium and strontium with sulphuric acid 29
( 101, 1, a and 102, 1, a), and the magnesium from the fil-
trate with ammonia and sodium-ammonium phosphate
( 104, 2).


Mix the solution with hydrochloric acid, then with highly 30
dilute sulphuric acid (1 part acid to 300 water), as long as a pre-
cipitate forms ; allow to deposit, and determine the barium sul-
phate as directed 101, 1, a. Concentrate the washings by
evaporation and add them to the filtrate, neutralize the acid
with ammonia, and precipitate the calcium as oxalate ( 103, 2,
b, oi). The method is principally to be recommended when
small quantities of barium have to be separated from much cal-
cium. If we have to separate calcium sulphate from barium
sulphate, the salts may (in the absence of free acids) be treated
repeatedly with a solution of sodium thiosulphate at a gentle
heat. The barium sulphate remains undissolved, the calcium
sulphate dissolves. The calcium is precipitated from the fil-
trate by ammonium oxalate (DiEHL*).

3. Method based upon the different deportment with
Alkali Carbonates of Barium Sulphate on the one hand,
and Strontium and Calcium Sulphates on the other.

Digest the three precipitated sulphates for twelve hours at 31
the common temperature '(15 20), with frequent stirring,
with a solution of ammonium carbonate, decant the fluid on to
a filter, treat the residue repeatedly in the same way. wash
finally with water, and in the still moist precipitate, separate
the undecomposed barium sulphate by means of cold dilute
hydrochloric acid from the strontium and calcium carbonates
formed. To hasten the separation you may boil the sulphates
for some time with a solution of potassium (not sodium) car-

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