3Iarch 18,1871.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
743 
tf&ajltcra for Stotoitts. 
CHEMICAL NOTES TO THE PHARMACOPOEIA. 
BY WILLIAM A. TILDEN, B.SC. LOND. 
DEMONSTRATOR OF PRACTICAL CHEMISTRY TO THE 
PHARMACEUTICAL SOCIETY. 
Ferri et Ammonl® Citras. —Solution of persul¬ 
phate of iron is precipitated by pouring it into an 
excess of solution of ammonia— 
Fe 2 3S0 4 + 6 NH 4 HO 
= Fe 2 6 H O -f- 3 (NH 4 ) 2 S0 4 . 
The ferric hydrate thus thrown down is collected on 
a calico filter, and washed with distilled water until 
the filtered liquid gives no indication of sulphate of 
ammonium when tested by solution of chloride of 
barium. The hydrated oxide of iron is then dis¬ 
solved in a solution of citric acid, and ammonia 
added in slight excess. The filtered liquid, evapo¬ 
rated by a very gentle heat to a syrupy consistence, 
and spread thinly on plates, forms scales which 
should readily shake off on drying. 
There are several little points in this process 
which are deserving of attention, as students often 
fail to obtain a satisfactory product. In the first 
place it is essential to pour the solution of iron into 
the solution of ammonia, not vice versa. The object 
of this device is that the ferric sulphate, by coming 
into the presence of considerable excess of ammonia, 
may really undergo the decomposition expressed in 
the equation above ; that is, that it may be trans¬ 
formed into pure ferric hydrate. If the ammonia is 
poured into the solution of iron, the ferric sulphate 
undergoes a decomposition which is incomplete, for 
the precipitate contains a very appreciable quantity 
of sulphate, carried down in the form of an insoluble 
oxysulpliate of iron. The composition of the preci¬ 
pitate is, of course, very variable, but the general 
nature of the change is shown by this equation— 
Fe 2 3S0 4 + 4 NH 4 HO 
= Fe 2 S 0 4 4H0 + 2 (NH 4 ) 2 S0 4 . 
Hydrate of iron mixed with such impurity, when 
dissolved in citric acid and ammonia, furnishes a 
granular semi-crystalline product, not the usual bril¬ 
liant scales. The proportion of citric acid must also 
be adhered to, or the solution, on evaporation, will 
often become turbid and yield a compound only par¬ 
tially soluble in water. 
Several combinations of citric and tartaric acid with 
peroxide of iron have been employed for a long 
time in medicine. They are, however, inferior to 
the ammonio-citrate in richness and brilliancy of 
colour, and in solubility. Nevertheless, it is ob¬ 
viously improper to substitute this, or any other 
salt, when ferri citras or ferri tartras is ordered in a 
prescription. Any little difficulty in effecting solu¬ 
tion, if it should occur (which is, however, unlikely), 
may be got over as recommended by a correspon¬ 
dent of tliis Journal (“Notes and Queries,” p. 437), 
by warming the salt with distilled water in a test- 
tube. 
[§ Heated with solution of potash, it evolves am¬ 
monia and deposits peroxide of iron. The alkaline 
solution from which the iron has separated does not, 
when slightly supersaturated with acetic acid, give 
any crystalline deposit. When incinerated with ex¬ 
posure to air, it leaves not less than 27 iier cent, of 
peroxide of iron, which is not alkaline to litmus.] 
The former of these tests serves to detect the fraud 
when tartaric has been substituted for citric acid, 
and the latter shows that the preparation contains 
no potash. 
Ferri et Quinle Citras. —Solution of persulphate 
of iron is precipitated by excess of solution of am¬ 
monia, and the washed precipitate is dissolved in 
solution of citric acid, employing the same precau¬ 
tions as in making ferri et ammoniae citras. Similarly, 
sulphate of quinine, previously dissolved in a little 
dilute sulphuric acid, is mixed with solution of am¬ 
monia in excess, and the precipitated hydrate of qui¬ 
nine collected and washed. It is then dissolved in the 
solution of citrate of iron already prepared. A little 
ammonia is then added to the solution, not, however, 
sufficient to precipitate the quinine, but leaving the 
solution slightly acid. Finally, the liquid is evapo¬ 
rated down to a consistence suitable for scaling on 
plates. 
[§ Thin scales, of a greenish golden-yellow colour, 
somewhat deliquescent and entirely soluble in cold 
water. The solution is very slightly acid, and is 
precipitated reddish-brown by solution of soda (a 
mixture of the hydrates of iron and quinine), white 
by solution of ammonia (hydrate of quinine), blue 
by the yellow and red prussiates of potash, and 
greyish-black by tannic acid.] 
This compound contains both ferrous and ferric 
salt, since it gives a deep blue precipitate with red 
as well as with yellow prussiate of potash. Part of' 
the citric acid, in fact, reduces some of the iron to the- 
ferrous state, becoming itself converted into a mix¬ 
ture of acids which have not been closely examined. 
Without this reduction the scales are not of the usual 
greenish-golden colour. The addition of a very small 
quantity of potash is said to favour it, though tliis is 
not recognized by the Pharmacopoeia, and is pre¬ 
cluded by the test there given. [§ When burned 
with exposure to ah*, it leaves a residue which, when 
moistened with water, is not alkaline to test-paper.] 
It should contain 16 per cent, of quinia, unmixed 
with cinclionia and quinidia. [§ 50 grains, dissolved 
in a fluid ounce of water and treated with a slight 
excess of ammonia, give a white precipitate, which, 
when collected on a filter and dried, weighs 8 grains. 
The precipitate is almost entirely soluble in pure 
ether, and, when burned, leaves but a minute re¬ 
sidue.] This quantitative test as indicated in the 
Pharmacopoeia is defective, because it does not give 
sufficient detail. No mention is made of washing 
the precipitate, nor of the temperature at which it 
should be dried. Both these points should be clearly 
defined, or very untrustworthy results will be arrived 
at. The temperature at which hydrate of quinine 
gives up the whole of its combined water, and be¬ 
comes anhydrous, C 20 H 24 N 2 O 2 , is about 260° F.; 
the precipitate should be dried at tliis temperature. 
From recent analyses of the commercial salt sup¬ 
plied by different makers, it appears that the amount 
of quinia introduced varies very considerably, in some 
cases not exceeding one-fourth of the official propor¬ 
tion. As stated already, great injustice may be done 
in such analyses unless conducted with due precau¬ 
tions. 
Ferri Iodidum, — [§ Iodide of Iron, Fel 2 , with 
about 18 per cent, of water of crystallization and 
a little oxide of iron.] 
Iron wire, iodine and distilled water are digested 
