In the preparation of syrups it is of great importance to employ as little heat as possible, as a solution of sugar, even when kept at the temperature of boiling water, undergoes slow decomposition. The plan which we adopt is to pour the water (cold) over the sugar, and to allow the two to lie together for a few hours, in a covered vessel, occasionally stirring, and then to apply a gentle heat (preferably that of steam or water bath) to finish the solution. Some persons (falsely) deem a syrup ill prepared unless it has been allowed to boil well; but if this method be adopted, the ebullition should be only of the gentlest kind
(‘simmering’), and should be checked after the lapse of 1 or 2 minutes.
Mr Orynski recommends the preparation of all syrups without the application of heat, as follows:
Introduce 30 or 32 oz. of sugar (according to the temperature) into a percolator, in which has been previously introduced a piece of lint or sponge, well adjusted, and gradually pour on 16 ounces of liquid, so as to make the percolate (syrup) pass drop by drop. If the first liquid is turbid pour it back into the percolator till the syrup passes clear.
The advantages claimed for this process are: First, the syrups are clear; and there is no necessity for purifying them.
Secondly, they possess their medicinal properties unaltered; since many drugs may be injured by heat, more especially aromatics, and those containing readily volatile substances; and—
Thirdly, the syrups will neither crystallise nor ferment; and may be prepared in large quantity, provided the vessels or bottles are clean before filling them with syrup.
When it is necessary to thicken a syrup by boiling, a few fragments of glass should be introduced, in order to lower the boiling point.
To make highly transparent syrups, the sugar should be in a single lump, and, by preference, taken from the bottom or broad end of the loaf, as, when taken from the smaller end, or if it be powdered or bruised, the syrup will be more or less cloudy.
Syrups are judged, by the laboratory man, to be sufficiently boiled when some taken up in a spoon, pours out like oil, or a drop cooled on the thumb-nail gives a proper ‘thread’ when touched. When a thin skin appears on blowing upon the syrup, it is judged, by the same party, to be completely saturated. These rude tests often lead to errors, which might be easily prevented by employing the proper proportions, or determining the sp. gr.