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BRITISH PHARMACEUTICAL CONFERENCE. 
\{d) Two "bottles (blue and green) were balf-filled with syrup, and placed 
ifacing the window as before. 
Both these had changed into a reddish-brown colour, and had thrown 
down a precipitate which, on examination, proved to be phosphate of 
iron. Oxidation had taken place to the extent of 61 per cent., but in the 
blue to 23 per cent. only. Having noted the change in this latter syrup, 
an-d seeing that it had altered to such a great extent, whilst the others 
had only so slightly, I attributed it to the effect the atmospheric oxygen, 
had upon the iron, as the bottles were only half-filled when placed for 
observation. To confirm this— 
(e) A small quantity of syrup was put into a bottle, and the bottle filled 
with oxygen. 
After seven days had elapsed, it was as dark in colour as the previous 
syrup exposed for five months. To confirm this by taking its opposite— 
(f) A bottle containing a small quantity of syrup was filled with carbonic 
acid. 
This prevented the oxidation to a very great extent. I had then 
clearly made out one cause at least of change. I then sought to deter¬ 
mine whether the phosphoric acid exerted any action upon the sugar. 
(y) A syrup of the phosphoric acid and sugar was made without the iron, 
and bottles were filled and placed under similar influences as with the iron 
syrup previously remarked upon. 
These I found had not only gained colour, but an action had set up 
such as I anticipated, namely, grape sugar had been formed by the action 
of the phosphoric acid upon the sugar. The bottles, however, of this 
syrup which were half-filled, corresponded in colour to those filled to the 
cork. It was therefore evident that air had not produced the change in 
colour. 
(7^) A syrup of iron, acid, and grape sugar was made, and bottles placed in 
the various positions as before. 
These remained unchanged, or at least nearly so, except in those half- 
fulL 
(i) A solution of phosphate of iron in the phosphoric acid was also made 
without the addition of sugar. 
This merely deposited phosphate of iron, but did not gain colour. 
(7;) The same series of experiments were also tried upon a compound of 
iron, acid, and glycerine. 
This apparently was less liable to change than any of the preceding 
syrups, whether of cane or grape sugar, either with or without the iron. 
These experiments prove:—that the main cause of change in syr. ferri 
phosph. from a white to a reddish colour, is chiefly due to exposure to air 
(exp. d, e,f) ; or, in other words, to being kept in bottles only partially fitted; 
that this effect is somewhat influenced by light (exp. a, d), apparent from 
the syrup in the green bottle having become oxidized 38 per cent, more than 
that in the dark blue bottle, and that oxidation is promoted, colour produced, 
and no doubt with it chemical action upon the iron effected, by the conversion 
of the cane into grape sugar (exp. g). 
This may be seen from the fact that the liquor of acid and iron only de¬ 
composes hut slightly (exp. i), depositing a small quantity of phosphate of 
iron ; it does not, however, gain colour even in nine or twelve months. 
To entirely prevent change is a difficult task, as it has been shown that the 
bodies themselves forming the syrup, even when placed under the most 
favourable circumstances, act upon each other, viz. the acid upon the sugar, 
and the air, sugar, and light upon the iron. 
For the better preservation of this syrup, I should suggest that it be kept 
