22 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[July 8, 1871 
filjiipfcrs for iituhuts. 
CHEMICAL NOTES TO THE PHARMACOPOEIA. 
BY WILLIAM A. TILDEN, D.SC. LOND. 
DEMONSTRATOR OF PRACTICAL CHEMISTRY TO THE 
PHARMACEUTICAL SOCIETY. 
Iodum. —[§ A non-metallic element, obtained prin¬ 
cipally from tlie ashes of sea-weeds.] 1= 127. By 
the incineration of sea-weeds a semi-fused saline 
ash is obtained called ‘ kelp.’ This is lixiviated 
with water, and the solution so obtained concen¬ 
trated till, by alternate boiling and cooling, the crys- 
tallizable salts, potassic and sodic sulphate and 
chloride, are almost completely separated.. The 
mother liquors are then mixed with sulphuric acid, 
whereby the carbonates and sulphides present are 
decomposed, and the mixture is then distilled by a 
very gentle heat with regulated quantities of black 
oxide of manganese. 
2 Nal + Mn0 2 -f 3 H () S0 4 
= 2NaHS0 4 -f MnS0 4 + 2H 2 0 +1 2 
The iodine is purified by careful resublimation. 
[§ In laminar crystals of a peculiar odour, dark 
colour and metallic lustre, which, when heated, yield 
a beautiful violet-coloured vapour, very sparingly 
soluble in water, but freely dissolved by alcohol, by 
ether and by a solution of iodide of potassium. The 
aqueous solution strikes a deep blue colour with 
starch.] The colour is destroyed by heat, and there¬ 
fore cold solutions must be emplojmd for this test. 
Iodine is also freely soluble in bisulphide of carbon 
and in benzol, minute quantities communicating to 
either of these liquids a beautiful violet tint, upon 
the production of which another very good test for 
the recognition of iodine and iodides is founded. 
For a comparison of the properties of chlorine, bro¬ 
mine and iodine, see article Bromum, p. 520, Vol. I. 
n.s. Iodine stands a little apart from the other two in 
possessing less energetic affinities, so that its com¬ 
pounds are more readily decomposed, and it exerts 
no bleaching action upon vegetable colours. 
[§ It sublimes without leaving any residue, and 
the portion that first comes over does not include 
any slender colourless prisms emitting a pungent 
odour.] By these tests non-volatile impurities, such 
as oxide of manganese or of iron, metallic iodides, 
etc. are excluded; the pungent crystalline body 
mentioned is iodide of cyanogen, an impurity com¬ 
monly met with, even to a considerable extent, in 
crude iodine. A test should be added for the detec¬ 
tion of the small quantity of chlorine which com¬ 
mercial iodine almost always contains. The follow¬ 
ing would be delicate enough for practical purposes: 
—A small quantity mixed with a slight excess of 
sulphurous acid gives a colourless solution, which, 
with nitrate of silver, strongly acidified by nitric 
acid, gives a yellowish-wliite precipitate of iodide of 
silver. This precipitate, after removal of the super¬ 
natant fluid, is insoluble in ammonia, and the am- 
moniacal liquid decanted gives no appreciable pre¬ 
cipitate upon acidification by nitric acid. 
[§ 1*27 gram dissolved in an ounce of water con¬ 
taining 20 grains of iodide of potassium requires for 
complete discoloration 100 cub. centims. of the volu¬ 
metric solution of hyposulphite of soda.] The re¬ 
action between hyposulphite of soda and iodine 
results in a colourless solution, containing iodide 
and tetrathionate of sodium. 
2Nn„S„O v 5 H 2 0 -f I, 
248'x 2 127 x 2 
= Na 2 S 4 0 6 -f 10 H 2 0 + 2 Nal. 
The volumetric solution is prepared so as to con¬ 
tain y^jth of half this quantity in a thousand parts of 
the solution, and therefore 
1000 cub. centims. contain 21*8 of hyposulphite 
and will decolorize 12*7 of iodine. 
Consequently 
100 cub. centims. will decolorize 1*27 of iodine. 
Strictly speaking, this mode of analysis is appli¬ 
cable only when chlorine and bromine are absent, 
for if present these bodies would, according to this 
method, be reckoned as iodine. 
Liquor Ammonite Fortior. —Sal-ammoniac in 
coarse powder is mixed with lime, and the ammonia 
which is evolved on heating the mixture is con¬ 
ducted first through two empty bottles, in which the 
tarry impurities of the sal-ammoniac chiefly collect, 
then into a proper quantity of water, which absorbs 
the ammonia. 
2NH 3 HC1 + CaO.IT 2 0 
= 2NH 3 + CaCl 2 + 2H 2 0. 
Ammoniacal gas is excessively soluble in water 
and also in alcohol. The B. P. solution has a spe¬ 
cific gravity — *891, and a fluid drachm of it con¬ 
tains 15*83 grains of ammonia, or upwards of 389 
times its volume of the gas. [§ When diluted with 
four times its volume of distilled water, it does not 
give precipitates with solution of lime, oxalate of am¬ 
monia, sulphide of ammonium or ammonio-sulpliate 
of copper.] These tests indicate the absence respec¬ 
tively of carbonate of ammonia, of chloride of cal¬ 
cium, of metals such as copper or zino, and of sul¬ 
phide of ammonium. [§ And when treated with an 
excess of nitric acid is not rendered turbid by nitrate 
of silver nor by chloride of barium.] The solution 
is thus shown to be free from chlorides and sul¬ 
phates. 
The liq. ammonite of commerce almost invariably 
contains small quantities of tarry matters, including 
various organio bases; when nearly neutralized by 
an acid, their odour becomes distinctly perceptible. 
Liquor Antimonii Chloridi. —Black sulphide of 
antimony, which should be finely powdered, is boiled 
with strong hydrochloric acid till dissolved; the 
solution is then strained, and duly concentrated by 
evaporation. 
This solution cannot be diluted with water to any 
great extent, as it gives a white precipitate of oxy¬ 
chloride. 
[See Antim. Oxidum.] 
The commercial article is generally coloured with 
pernitrate of iron. [§ One fluid drachm of it, mixed 
with a solution of a quarter of an ounce of tartaric 
acid in four fluid ounces of water, forms a clear 
solution, which, if treated with sulphuretted hydro¬ 
gen, gives an orange precipitate, weighing, when 
washed and dried at 212° F., at least 22 grains.] 
The best mode of performing this operation consists 
in keeping the liquid heated to near the boiling- 
point in a flask whilst the gas passes through it in 
a rapid stream. In this way, in about a quarter of 
an hour, a heavy sandy precipitate forms, which can 
be very rapidly filtered off and washed. Conducted 
in tills way, the process is fairly accurate. 
