ON SYRUP OF IODIDE OF IRON. 
123 
ffucing a coil of iron wire, recommeuds for its preservation the covering of the 
syrup°with a stratum of oil and storing in the dark. Mr. F. Baden Benger, 
page 284, states that he had tried this plan “ four or five years ago,” but that 
“it failed to answer its purpose.” In what way he does not say. He then 
mentions as his practice to make a solution of the iodide and add a suitable pro¬ 
portion to simple syrup, as required. Mr. T. B. Groves, page 421, finds that 
the best method is to add “ half a fluid ounce of dilute phosphoric acid to each 
Pharmacopoeia quantity (31 fluid ounces).” I did not hear Mr. Groves s paper 
read, but I understand that his proposal was considered highly improper.. Mr. 
T. H. Holloway, of Sydenham, page 471, writes that syrup exposed in a window 
for a few hours daily to the direct light of the sun, keeps well, and that disco¬ 
loured syrup may be restored to its normal condition by the same method. 
In the discussion which followed the reading of the papers by Mr. Pilden and 
Mr. Groves, there was considerable difference of opinion as to how long the syrup 
would keep in the dark without becoming discoloured, but most of the speakers 
concurred in recommending small well- filled bottles and storing in the dark. 
Pharmacists had long ago noticed that some discoloured syrups are restored 
by being heated in bottles in a water-batli for a short time. I liis observation 
led me, on the appearance of Mr. Holloway’s letter, to try a few experiments 
based upon it. 
Small white glass bottles, some filled and stoppered, others partly filled and 
covered with muslin, were exposed to diffused light inside a window, and to direct 
sunlight outside in a yard. The specimens exposed to diffused light retained 
their original colour for a considerable time, and then became gradually bleached. 
Those exposed to the direct light of the sun retained their colour for a few days, 
the time depending upon the brightness of the weather, and the volume and 
surface of syrup exposed, and then gradually lost their colour entirely. Several 
specimens of discoloured syrup, similarly exposed to direct sunlight, were in a 
few days restored, and when the exposure was continued, became gradually 
colourless. # 
There seems to be a limit, however, to this bleaching action. Six fluid ounces 
of freshly prepared syrup were discoloured by being heated (June 11, 1869) for 
four hours in an open dish over a water-bath, with occasional stirring, and kept in 
the dark for a week. A portion has been exposed to direct sunlight without 
interruption since June 18 without sensible improvement.. Another portion was 
heated in a bottle for twenty-four hours in a water-bath, with the effect of much 
increasing the depth of colour. A little tartaric acid was now added, on the 
recommendation of M. Jeannel, Pharm. Journ. N.s. Tol. X. j this lessened t e 
colour, but did not restore it. 
The specimens exhibited comprise :— .. , , 
No. 1. Specimen of syrup made July 23, 1869, and exposed to diffused ligm 
in the open air in a bottle covered with muslin. A little of the original colour 
remains. 
No. 2. Made June 28, 1869, and exposed to bright light in a bottle covered 
with muslin. Colourless. . . ~ 7 
No. 3. Made May 11, 1868, and exposed in shop window ever since. Colour- 
l es g 
No. 4. Made April 3, 1869, discoloured by being kept in dark and afterwards 
exposed to bright light. Colourless. QA 
No. 5. Very discoloured ; heated in a water-bath for half an hour, April oO, 
1868, and since that date uninterruptedly exposed to bright light. Colourless. 
* As Mr. Holloway remarks, in a subsequent letter, Messrs. T. and H. Smith appear to have 
been the first to observe this effect upon discoloured syrup. See Pliarm. Journ. n.s. \ Qi. i- 
P* 3d3. 
