C. Remigius Fresenius.

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perforated caoutchouc stopper. The stopper carries a thermometer
and two short glass tubes, one of which joins it to the burette, and
the other has attached a short bit of caoutchouc tubing and a pinch-
coc-k, e. The weighed ammonium salt (not more than O'tt grm.) is
placed in the tube, /', with 10 c c. of water, and 50 c. c. of the
bromized hypochlorite. solution are brought into the bottle, a.
The cock, <?, being open, the stopper is firmly fixed in its place, and
the burette is depressed in the mercury un-
til its uppermost degree exactly coincides
with the surface of the metal. The cock is
then closed, and the bottle is inclined to
bring the two substances in contact. The
ammonium salt is speedily decomposed.
When no further evolution of gas takes
place the burette is so adjusted that the
level of the mercury without and within it
shall nearly coincide, and the operator waits
10-20 minutes, or until the thermometer in
a indicates the same temperature as the sur-
rounding air. Then the adjustment of the
burette to exact coincidence of the mercury
level, within and without, is effected, and
the volume of the gas is read off. The stand
of the thermometer and barometer are also
noted, and the recorded volume of nitrogen
is corrected by use of the tables on pp. 259-
261, arranged by DIETRICH.

The first table gives a correction for the
nitrogen which is absorbed by the 60 c. c. of liquid in the bottle a.
The amount varies with the relative volumes of air and nitrogen,
and is determined empirically by decomposing known quantities of
ammonia and noting the difference between the obtained and the
theoretical volume of nitrogen. The correction holds strictly, of
course, only for a solution of such strength as that employed by
DIETRICH and at the mean temperatures.

The second table serves to spare the labor of calculation. The
weight of 1 c. c. of nitrogen, measured e. g. at 75-1 mm, of barome-




Fig. 82.



258 DETERMINATION. [ 100.

tcr and 15, is found at the intersection of the vertical column
754 with the horizontal column 15, is, viz., 1-16187.

To the observed volume of nitrogen add the amount absorbed
as per Table I., and correct the total by Table II. It scarcely
requires to be mentioned that good results can only be obtained in
an apartment where the temperature is uniform, and when care is
exercised to avoid warming the apparatus in handling. See DIET-
RICH'S papers.*

100.

Supplement to the First Group.
LITHIUM.

In the absence of other bases, lithium may, like potassium
and sodium, be converted into anhydrous SULPHATE, and weighed
in that form (Li a SO 4 ). As lithium forms no acid sulphate, the
excess of sulphuric acid may be readily removed by simple igni-
tion. LITHIUM CARBONATE also, which is difficultly soluble in
water, and fuses at a red heat without suffering decomposition, is
well suited for weighing ; whilst lithium chloride, which deliquesces
in the air, and is by ignition in moist air converted into hydro-
chloric acid and lithium oxide, is unfit for the estimation of
lithium.

In presence of other alkali metals, lithium is best converted
into LITHIUM PHOSPHATE (Li 8 PO 4 ), and weighed in that form. This is
effected by the following process : add to the solution a sufficient
quantity of sodium phosphate (which must be perfectly free from
phosphates of the alkali-earth metals), and enough soda to keep the
reaction alkaline, and evaporate the mixture to dry ness ; pour
water over the residue, in sufficient quantity to dissolve the soluble
salts with the aid of a gentle heat, add an equal volume of solution
of ammonia, digest at a gentle heat, filter after twelve hours, and
wash the precipitate with a mixture of equal volumes of water and
solution of ammonia. Evaporate the filtrate and first washings to
dryness, and treat the residue in the same way as- before. If some
more lithium phosphate is thereby obtained, add this to the prin-
cipal quantity. The process gives, on an average, 99*61 for 100
parts of lithium oxide (



Fres. Zeit., in, 162 ; rv, 141, and v, 36.
Ann. d. Chem. u. Pharm., xcvm, 213.



99.]



TABLE OF ABSORPTION OF NITROGEN GAS.



259



GO



a !


8

TH


g 3


S 8

<M


g s?

^ csi


a 1


2


a.


e 1


i


2 $




8 S




8 2


e s


8 1


5 5




1


- 2


- ;.


CD

a S


S 3




8 1


g 2


sj


g 5?

03


a 5


8 1


^


e 2


S cl


s 1


a 1


s g


3 2


* 1


2 8




S3 8.

O


8 S


g S

-rH




OJ


2 8




CO
CO ^


8 8


g^ 8

i i


g

0}


s




s i


S


e ^


3

Oi


s 1


8 1


00

2


e e

1 i


_. 00
Oi

oi


o> <**

i ^


8 S


?

T 1


CO

g ^

T~H


j


CO
00




* S


w

1 1


8 5


8 8.

O?


1 1
js. 07




s 5


- S


C


-i


GO
CO ^



1


o

-* ^

1 1


8 S


D 2
00 .
Oi



1O "



8 1


9 S

I I




T- J


,0 S
GO .
O^


CO

^ ^




at 1


^ s.

1 1


S 8

r-i


^ S
00
05


I I
CO TH





o


ss' s


CO S

T-J


8 2


8




1


5 8

I 1


S 8

TH


8 1


- s




a 1


55 S


s s.

TH


a 1


Evolved
Absorbed


Evolved
Absorbed


Evolved
Absorbed


Evolved
Absorbed


Evolved.
Absorbed



260



TABLE OF WEIGHTS.



L 99-



II. TABLE OF THE WEIGHT OF A

In Milligrammes for Pressures f ram 720 to 770 mm..

MILLIMETRES.





720


722


724


726


728


730


732


734


736


738


740


742


744


10


1.13380


1.13699


1.14018


1.14337


1.14656


1.14975


1.15294


1.15613


1.15932


1.16251


1.16570


1.16889


1.17208


!!


1.12881


1.13199


1.13517


1.13835


1.14153


1.14471


1.14789 1.15107


1.15424


1.15742


1.16060


1.16378


1.16696


12


1.12370


1.12693


1.13010


1.13326


1.13643


1.13960


1.14277 1.14593


1.14910


1.15227


1.15543


1.15860


1.16177


13 1.11875


1.12191


1.12506


1.12822


1.13138


1.13454


1.13769 1.14085


1.14401


1.14716


1.15032


1.15348


1.15663


14 1.11369


1.11684


1.11999


1.12313


1.12628


1.12942


1.13257 1.13572


1.13886


1.14201


1.14515


1.14830


1.15145'


15 1.10859


1.11172


1.11486


1.11799


1.12113


1.12426 1.12739 1.13053


1.13366


1.13680


1.13993


1.14306


1.14620


16


1.10346


1.10658


1.10971


1.11283


1.11596


1.11908


1.122201.12533


1.12845


1.13158


1.13470


1.13782


1.14095


17


1.09828


1.10139


1.10450


1.10761


1.11073


1.11384


1.11695 1.12006


1.12317


1.12629


1.12940


1.13251


1.135621


18


1.09304


1.09614


1.09924


1.10234


1.10544


1.10854


1.111651.11475


1.11785


1.12095


1.12405


1.12715


1.13025


19


1.08744


1.09083


1.09392


1.09702


1.10011


1.10320


1.10629 1.10938


1.11248


1.11557


1.11866


1.12175


1.12484


20


1.08246


1.08554


1.08862


1.09170


1.09478


1.09786


1.100941.10402


1.10710


1.11018


1.11327


1,11635


1.11943


21


1.07708


1.08015


1.08322


1.08629


1.08936


1.09243


1.095501.09857


1.10165


1.10472


1.10779


1.11086


1.11393


22


1.07166


1.07472


1.07778


1.08084


1.08390


1.08696


1.09002


1.09308' 1.09614


1.00881


1.10227


1.10533


1.10S39


23


1.06616


1.06921


1.07226


1.07531


1.07836


1.08141


1.08446


1.08751


1.09056


1.09361


1.09666


1.09971


1.10276


24


1.06061


1.063651.06669


1.069731.072771.07581


1.07885 1.08189 1.08493


1.08796 1.09100 1.09404


1.09708


25


1.05490


1.05801


1.06104


1.06407


1.06710 1.07013


1.07316


1.07619 1.07922 1.08225 1.08528


1.08831


1.09134




720


722


724


726


728


730


732


734


736


738


740


742


744



MILLIMETRES.



99.]



TABLE OF WEIGHTS.



261



CUBIC CENTIMETRE OF NITROGEN.

of Mercury, and for Temperatures from 10 to 25 C.

MILLIMETRES.



746

1.17527


748
1.17846


750

-3BB^H

1.18165


752


754


756


758


760


762


764


766


768


770




1.184841.18803


1.19122


1.19441


1.197601.20079


1.20398 1 1.20717


1.21036


1.21355


10


1.17014


1.178S8


1.176501.171681.18286


1.18603


1.18921


1.102801. 19557 1.19875


1.201931.20511


1.20829


11














1










1.16493


1.16810 1.17127 1.17444 1.17760


1.180771.18394


1.187101.190271.193441.196601.19977


1.20294


12
















1






1.15979


1.16205


1.16611 1.169261.17212


1.17558


1.178731.18189


1.185051.18820


1.191361.19452


1.19768


13


1.15459


1.15774 1.1G088 1.1G403


i. 16718


1.17032


1.17347


1.17661


1.17976 1.18291


1.18605


1.18920


1.19234


14


1.14933


1.15247


1.15560 ! 1.15873 ! 1.16187


1.16500


1.16814


1.17127


1.174401.17754


1.18067


1.18381


1.18694


15


1.14407


1.14720


1.15032


1.15344 1.15C57


1.159691.16282


1.16594


1.16906


1.17219


1.17531


1.17844


1.18156


16


1.13873


1.14185


1.14496


1.14807


1.15118


1.15429 1.15741


1.16052


1.16363


1.16674


1.16985


1.17297


1.17608


17


1.13335


1.13G45


1.13955


1.14266 1.14576


1.14886


1.15196


1.15506


1.15816


1.16126


1.16436


1.16746


1.17056


18


1.12794


1.13103


1.134121.13721


1.14030


1.14340


1.14649


1.14958


1.152671.15576


1.15886


1.16195


1.16504


19


1.12251


1 12559


1.12867


1.13175


1.13483


1.13791


1.14099


1.14408


1.14716


1.15024


1.15332


1.15640


1.15948


20


1.11700


1.12007


1.12314


1.12621 1.12928


1.13236


1.13543


1.13850:1.14157


1.14464


1.14771


1.15078


1.15385


21
















i












1.11145


1.11451


1.11757


1.12063


1.12369


1.12675


1.12982


1.13288 1.13594


1.13900


1.14206


1.14512


1.14818


22


1.10581


1.10886


1.11191


1.11496


1.11801


1.12106


1,12411


1.12716


1.13021


1.13336


1.13631


1.13936


1.14241


23


1.10012


1.10316


1.10620' 1.10924


1.11228


1.11532


1.11835


1.12139 ! 1.12443 1.12747 1. 13051 ' 1.1 3355


1.13659


24


1.00437

(KKF

746


1.09740

! U

748


1.10043

raBBBEE

750


1.10346


1.10649


1.10952


1.11255


1.11558


1.11861


1.12164


1.12467


1.12770


1.13073


25


752


754


756


758


760


762


764


766


768


770





MILLIMETRES.



262 DETEKMI NATION. [ 101.

If the quantity of lithium present is relatively very small,
the larger portion of the potassa or soda compounds should finst be
removed by addition of absolute alcohol to the most highly con-
centrated solution of the salts (chlorides, bromides, iodides, or
nitrates, but not sulphates); since this, by lessening the amount of
water required to effect the separation of the lithium phosphate
from the soluble salts, will prevent loss of lithium (W. MAYER).*

The precipitated normal lithium phosphate has the formula
2Li,PO 4 + H a O. It dissolves in 2539 parts of pure, and
3920 parts of ammoniated water ; at 100, it completely loses itu
water ; if pure, it does not cake at a moderate red heat (MAYKR).

The objections raised by RAMMELSBERof to MAYER'S method
of estimating lithia I find to be ungrounded. Accoidhig to my
own experience, it appears that the filtrate and wash-water must
be evaporated in a platinum dish not only once, but ut least twice
in fact, till a residue is obtained which is completely soluble in
dilute ammonia. Lithium phosphate may be dried at 100, or
ignited according to 53, before being weighed. In the latter
case, care must be taken to free the filter as much as possible from
the precipitate before proceeding to incinerate it. I have thus
obtained, ^ instead of 100 parts lithium carbonate, by drying at
100, 99-84, 99-89, 100-41, by igniting 99*66 and 100-05. The
lithium phosphate obtained was free from sodium.

Second Group.

BARIUM STRONTIUM CALCIUM MAGNESIUM.

101.

1. BARIUM.
a. Solution.

Caustic baryta is soluble in water, as are many barium salts,
r.arium salts which are insoluble in water are, with almost the
single exception of the sulphate, readily dissolved by dilute hydro-
chloric :icid. The solution of the sulphate is effected by fusion
with sodium carbonate, &c. (See 132.) Barium silico-fluoride

* Ann. der Chem. u. Pharm., xcvm, 193, where Mayer has also demonstrated
the non-existence of a sodium lithium phosphate of fixed composition (Berzelius),
or of varying composition (Rammelsberg).

\Pogg. Annal., en, 448. \Zeit8c7ir.f. analyt. Chem., I, 42,



101.] BARIUM. 263

may be readily converted into barium sulphate by heating and
evaporating with moderately dilute sulphuric acid in a platinum
vessel. It may also be readily decomposed by fusing it with po-
tassium-sodium carbonate.

I). Determination.

Barium is weighed either as sulphate or as carbonate, rarely (in
the separation from strontia) as barium silico- -fluoride or barium
chromate ( 71). Barium oxide or hydroxide, also barium car-
bonate, may also be determined by the volumetric (alkalimetric)
method. Comp. 223.

"We may convert into

1. BARIUM STTLPHATE.
a. By Precipitation.

All barium compounds without exception.
~b. By Evaporation.

All barium salts of volatile acids, if no other non-volatile body
is present.

2. BARIUM CARBONATE.

a. All barium salts soluble in water.

5. Barium salts of organic acids.

Barium is both precipitated and weighed, by far the most fre-
quently as sulphate, the more so as this is the form in which it is
most conveniently separated from other bases. The determination,
by means of evaporation (1, J) is, in cases where it can be applied,
and where we are not obliged to evaporate large quantities of fluid,
very exact and convenient. Barium is determined as carbonate in
the wet way, when from any reason it is not possible or not desir-
able to precipitate it as sulphate. If a fluid or dry substance con-
tains bodies which impede the precipitation of barium as sulphate
or carbonate (alkali citrates, metaphosphoric acid, see 71, a and
&), such bodies must of course be got rid of, before proceeding to
precipitation. The precipitation of barium as a silico-fluoride or
chromate will be treated of under the separation of barium fropi
strontium, 154.

1. Determination as Barium Sulphate.

a. By Precipitation.

Heat the moderately dilute solution of barium, which must no\
contain too much free acid (and must, therefore, if necessary, first



264 DETERMINATION. [ 102.

be freed therefrom by evaporation or addition of sodium carbon-
ate), in a platinum or porcelain dish, or in a glass vessel, to incipi-
ent ebullition, add dilute sulphuric acid so long as a precipitate
forms, keep the mixture for some time at a temperature very near
the boiling point, stirring if not on a water-bath, and allow the
precipitate to subside ; decant the almost clear supernatant fluid on
a filter, boil the precipitate once with water and a little dilute sul-
phuric acid, then three or four times with water, then transfer it
to the filter, and wash with boiling water, until the filtrate is no
longer rendered turbid by barium chloride. Dry the precipitate,
and treat it as directed in 53, employing only a moderate heat.
If the precipitate lias been properly washed in the manner
here directed, it is perfectly pure. In the presence of alkali salts,
however, the precipitate will still contain small quantities of alkali
sulphate. Comp. 153.

J. By Evaporation.

Add to the solution, in a weighed platinum dish, pure sul-
phuric acid very slightly in excess, and evaporate on the water-
bath ; expel the excess of sulphuric acid by cautious application of
heat, and ignite the residue moderately.

For the properties of barium sulphate, see 71.

Both methods, if properly and carefully executed, give almost
absolutely accurate results.

2. Determination as Barium Carbonate,
a. In Solutions.

Mix the moderately dilute solution of the barium salt in a
beaker with ammonia, add ammonium carbonate in slight excess,
and let the mixture stand several hours in a warm place. Filter,
wash the precipitate with water mixed with a little ammonia, dry,
and ignite moderately ( 53).

For the properties of the precipitate, see 71. This method
involves a trifling loss of substance, as barium carbonate is not
absolutely insoluble in water. The direct experiment, No. 56,
gave 99-79 instead of 100.

If the solution contains a notable quantity of ammonium salts,
the loss incurred is much more considerable, since the presence of
such salts greatly increases the solubility of barium carbonate.



102.] STRONTIUM. 265

b. In Barium Salts of Organic Acids.

Heat the salt slowly in a covered platinum crucible, until no
more fumes are evolved; place the crucible obliquely, with the
lid leaning against it, and ignite, until the whole of -the carbon is
consumed, and the residue presents a perfectly white appear-
ance ; moisten the residue with a concentrated solution of ammo-
nium carbonate, evaporate, ignite gently, and weigh. The results
obtained by this method are quite satisfactory. A direct experi-
ment, No. 57, gave 99.61 instead of 100. The loss of substance
which almost invariably attends this method is owing to particles
of the salt being carried away with the fumes evolved upon igni-
tion, and is accordingly the less considerable, the more slowly and
gradually the heat is increased. Omission of the moistening of
the residue with ammonium carbonate would involve a further loss
of substance, as the ignition of barium carbonate in contact with
carbon is attended with formation of some caustic baryta, carbon
monoxide gas being evolved.

102.

2. STRONTIUM.

a. Solution.

See the preceding paragraph ( 101, a. Solution of baryta and
barium salts); the directions there given apply equally here.
Strontium silico-fluoride is readily and completely soluble in water
acidulated with hydrochloric acid.

b. Determination.

Strontium is weighed either as strontium sulphate or as stron-
tium carbonate ( 72). Strontium in the form of oxide, hydrox-
ide, or carbonate, may be determined also by the volumetric
^alkalimetric) method. Comp. 223.

We may convert into

1. STRONTIUM SULPHATE.

a. By Precipitation.

All compounds of strontium without exception.

b. By Evaporation.

All strontium salts of volatile acids, if no other non-volatile
body is present,



266 DETERMINATION. [ 102.

2. STRONTIUM CARBONATE.

a. All strontium compounds soluble in water.

ft. Strontium salts of organic acids.

The method based on the precipitation of strontium with sul-
phuric acid yields accurate results only in cases where the fluid
from which the strontium is to be precipitated may be mixed,
without injury, with alcohol. Where this cannot be done, and
where the method based on the evaporation of the solution of
strontium with sulphuric acid is equally inapplicable, the conver-
sion into the carbonate ought to be resorted to in preference, if
admissible. As in the case of barium, so here, we have to be on
our guard against the presence of substances which would impede
precipitation (citrates of the alkalies, metaphosphoric acid, etc.),
and if necessary, these must first be removed.

1. Determination as Strontium Sulphate.

a. By Precipitation.

Mix the solution of the strontium salt (which must not be too
dilute, nor contain much free hydrochloric or nitric acid) with
dilute sulphuric acid in. excess, in a beaker, and add at least an
equal volume of alcohol; let the mixture stand twelve hours,
and filter; wash the precipitate with dilute alcohol, dry and ignite

( 53).

If the circumstances of the case prevent the use of alcohol, the
fluid must be precipitated in a tolerably concentrated state, and u
fairly large excess of sulphuric acid added (this is particularly neces-
sary if large quantities of potassium chloride, sodium chloride, or
magnesium chloride are present). The mixture is then allowed
to stand in the cold for at least twenty-four hours, filtered, and the
precipitate washed with cold water, until the last rinsings manifest
no longer an acid reaction, and leave no perceptible residue upon
evaporation. If traces of free sulphuric acid remain adhering t<
'the filter, the latter turns black on drying, and crumbles to pieces;
too protracted washing of the precipitate, on the other hand, tends
to increase the loss of substance.

Care must be taken that the precipitate be thoroughly dry,
before proceeding to ignite it ; otherwise it will be apt to throw
off tine particles during the latter process. The filter, which is to
be burnt apart from the precipitate, must be as clean as possible,
or some loss of substance will be incurred ; as may be clearly seen



102.] STRONTIUM.

from tlje depth of the carmine tint of the flame with which the
filter burns if the precipitate has not been properly removed.

For the properties of the precipitate, see 72. When alcohol
is used and the directions given are properly adhered to, the results
are very accurate ; when the sulphate of strontium is precipitated
from an aqueous solution, on the contrary, a certain amount of loss
is unavoidable, as strontium sulphate is not absolutely insoluble in
water. The direct experiments, ISTo. 58, gave only 98*12 and 98*02
instead of 100. However, the error may be rectified, by calculat-
ing the amount of strontium sulphate dissolved in the filtrate and
the wash-water, basing the calculation upon the known degree of
solubility of strontium sulphate in pure and acidified water. See
Expt. ISTo. 59, which, with this correction, gave 99*77 instead of
100. The necessity for making the correction may be obviated by
washing with 1 part sulphuric acid mixed with 20 parts water till
all substances precipitable by alcohol are removed, then with alco-
hol till all the sulphuric acid is removed. Strontium sulphate also
carries down sulphates of other strong bases in small quantities,
and this point must not be overlooked in making accurate analy-
ses. See 153.

b. By Evaporation.

The same method as described for barium, 101, 1, 5.

2. Determination as Strontium Cat-bonate.

a. In Solutions.

The same method as described 101, 2, a. For the proper-
ties of the precipitate, see 72. The method gives very accurate
results, as strontium carbonate is nearly absolutely insoluble in
water containing ammonia and ammonium carbonate. * A direct
experiment, No. 60, gave 99'82 instead of 100. Presence of
ammonium salts exercises here a less adverse influence than the
precipitation of barium carbonate.

b. In Salts of Organic Acids.

The same method as described 101, 2, ~b. The remarks mad<?
there, respecting the accuracy of the results, apply equally here.



68 DETERMINATION. [103.

103.

3. CALCIUM.

a. Solution.

See 101, a. Solution of barium. Calcium fluoride is, by
means of sulphuric acid, converted into calcium sulphate, and the
latter again, if necessary, decomposed by boiling or fusing with
an alkali carbonate ( 132). [Calcium sulphate dissolves readily
in moderately dilute hydrochloric acid. It is much less soluble in
strong hydrochloric acid.]

b. Determination.

Calcium is weighed either as calcium sulphate, as calcium
carbonate, or calcium oxide ( 73). It may be converted into
sulphate by evaporation, as well as by precipitation ; and into
carbonate or oxide by precipitation as oxalate or carbonate, or by
ignition. Calcium, in the form of oxide, hydroxide, or carbon-
ate, may be determined also by the volumetric (alkalimetric)
method. Comp. 223. The volumetric estimation may be also
effected by precipitating the calcium as oxalate, either by a direct
or an indirect method.

We may convert into

1. CALCIUM SULPHATE.

a. By Precipitation.

All calcium salts of acids soluble in alcohol, provided no other
substance insoluble in alcohol be present.

b. By Evaporation.

All calcium salts of volatile acids, provided no non-volatile body
be present.

2. CALCIUM CARBONATE, OR CALCIUM OXIDE.

a. By Precipitation ivith Ammonium Carbonate.
All calcium salts soluble in water.

b. By Precipitation with A in ,>!>' "in Oxalate.

All calcium salts soluble in water or in hydrochloric acid with-
out exception.

c. By Ignition.

Calcium salts of organic acids.

Of these several methods, 2, b (precipitation v/ith ammonium



103.] CALCIUM. 269

oxalate) is the one most frequently resorted to. This, .and the
method"!, 5, give the most accurate results. The method, 1, #, is
usually resorted to only to effect the separation of calcium from



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