ON THE PRESERVATION OF SYRUP OF IODIDE OF IRON. 
261 
absorbed. Indeed I have found by direct experiment on various organic sub¬ 
stances,—sugar, mannite, wood-spirit, etc.,—that oxidation may be produced in 
this manner. A mixture of iodine and a metallic oxide, e. g. oxide of zinc, ap¬ 
pears to act the part of a very convenient and manageable agent of oxidation. 
The only idea which suggests itself for preserving the syrup is to prevent the 
access of the air. This is sometimes done by filling small bottles to the stopper, 
and keeping them well closed ; but I think it may be effected more conveniently 
by covering the syrup with a stratum of oil. This plan is commonly pursued 
with various articles of food. It may be easily carried out as follows:— 
The syrup is first prepared, then the solution of iodide of iron is filtered into 
it, taking care not to stir till the last moment, and to form as few bubbles as 
possible. This is then poured through a funnel into the bottle previously made 
hot, and containing sufficient olive oil to form a layer of from ^ to inch deep. 
It is important to recognize this order, as the oil then coats the interior of the 
bottle, and prevents the syrup wetting the sides. Store it in the dark. 
A convenient receptacle for large quantities to be kept in this manner would 
be a jar with a small tap or stopcock at the bottom. Better than the tap would 
be a piece of india-rubber tubing, closed by a Mohr’s compression-clamp. It 
would be less liable to obstruction by crystallization of the syrup. For general 
dispensing purposes, an arrangement similar to that of an ordinary washing- 
bottle would be more easily applied. Two tubes are passed through the cork, 
one proceeding to the bottom of the bottle, aud bending over so that the ex¬ 
ternal extremity is directed downwards, the other just penetrates the cork. 
By applying the mouth to the short tube, and increasing the pressure upon 
the surface of the liquid within, the latter is made to issue from the point of the 
longer tube. This last may be kept closed by a stopper, consisting of a morsel 
of india-rubber tubing, into which a little bit of glass rod is inserted. 
Dr. Eedwood thought the subject introduced by Mr.Tilden was both interest¬ 
ing and important. Pharmaceutists often complained of the difficulty of preserv¬ 
ing solutions of iodide of iron free from change, and, although this difficulty was 
experienced with the aqueous solution more than with the syrup, even the 
latter preparation sometimes became coloured. The plan of putting a coil of iron 
wire into the solutions had, he believed, been introduced by Mr. Squire, and 
had been to some extent adopted; but he thought, although the colour of the 
solution might be thus preserved, that the method was not a satisfactory one, 
as a portion of iodine was removed from the solution by the formation of an in¬ 
soluble subsalt, and the strength of the solution was thus altered. The method 
proposed by Mr. Tilden was ingenious, and would not be subject to the objec¬ 
tion which attached to the method previously alluded to. When it had been 
first mentioned to him, he thought there were some practical difficulties in the 
way of its application, but these seemed to have been met and provided for to a 
great extent. 
Dr. Attfield asked if Mr. Tilden had noticed whether syrup of iodide of 
iron, when kept beneath the surface of oil, had exhibited any acidity. The 
alteration which occurred in the syrup had been generally looked upon as simply 
a case of oxidation, in which oxide of iron was .formed, and perhaps after a 
time a higher iodide of iron. But he believed that some years ago Mr. Phillips, 
in a paper read before the Society, gave it as his opinion that the alteration 
took place through the decomposition of the iodide of iron by water, hydriodic 
acid being thus formed. He had himself applied some tests which seemed to 
show that hydriodic acid was produced, but he had not estimated the amount. 
If the syrup kept under oil gave an acid reaction after a time, it would tend to 
corroborate Mr. Phillips’s observation. 
