The preparation of saturated solution
The traditional preparation process by isothermal method is as follows [5], [6] and [7].
The cylindrical double-jacketed glass vessel was controlled to a constant temperature with continuous stirring,
in which the temperature was controlled to be constant with a precision of ±0.05 K through a thermostatic bath (Type 501 A, China).
Then, excess solute was added to the solvent.
After the temperature of the water bath was kept constant for at least 4 h,
the stirring was stopped,
and the solution was kept still for 3 h.
A portion of the upper clear solution was filtered with the membrane (0.45 μm).
In terms of this method a long dissolution time (4 h) has an increased risk of l-Gn degradation.
Therefore, an experiment to find a proper dissolution time is carried out.
Excess solute was added to the solvent, the concentration of suspension was measured by weighing method (described later) at different dissolve times.
Fig. 2 gives the concentration variation of suspension along with dissolution time.
The suspension can reach the dissolution phase equilibrium in short term,