Is this in an open vessel?

If so, you may need a hotplate with temperature probe like the photo I've attached.

You can use the hot plate with a temperature probe.

If you do not have it, what you can do is gradually heat up your solution until it reaches 95 °C and record what is the temperature of a hot plate in that moment. You do this in a separate experiment of course. For this you only need a simple thermometer.

By using hot plate

It controls the temperature and favours the reaction.

To keep your syrup mixture at 95°C during this process, especially if you're using a hot plate, you must consider both the temperature of the mixture and heat transfer between the hot plate, the pot, and the syrup. Here are a few suggestions on how to handle this:

1. Use a thermocouple or probe thermometer.

The most accurate way to monitor the temperature of the syrup is to use a thermometer that can be immersed directly into the mixture (a digital probe thermometer or a thermocouple designed for liquids). This allows you to monitor the actual temperature of the syrup, rather than just the surface of the hot plate.

Stir the syrup gently to maintain the temperature.

2. Control the heat input

Initial Heating: Because you are heating the syrup to 115°C, you can use a higher heat setting on your hot plate at first, but once you reach 115°C, reduce the heat input to avoid overshooting as the syrup cools down.

Gradual Cooling: After reaching 115°C, remove the syrup from direct heat and reduce the power of the hot plate to allow it to cool naturally. The key is to let the syrup cool to about 95°C before adding the second mixture.

3. Use a Temperature Controlled Hot Plate

You can set your hot plate's temperature control or built-in thermostat to automatically regulate the temperature. However, this may still measure the plate's surface temperature rather than the syrup, so it is not ideal on its own.

4. Stir the syrup While cooling

Stirring will help to evenly distribute heat and prevent hot spots. It will also ensure that the thermometer accurately reads the temperature of the mixture, as heat can vary slightly within the pot or pan.

5.Use a Water Bath.

A water bath can provide more consistent temperature control (a double boiler setup). Set the water bath temperature to 95°C and place your syrup mixture in a container within the bath. This indirect heating method is gentler and will help keep the syrup at a consistent temperature.

In order to maintain a temperature of 95°C for the mixture, it is necessary to heat all of the liquids to this temperature before combining them.

Dear Mohamed,

very naive question: ...are you (can you) using a magnetic stirer with temperature control? Can you stir your syrup? For our device we cannot program temperature ramps....I do not know whether you need this or whether manual operation is fine for your work.

Alfred

The best control is often inertia! Use your hot plate - preferably one with automatic temperature sensing by a probe in a large beaker of water - to maintain a water bath at 95'C. That should be fairly easy to control and pretty accurate. Then you put your syrup mixture into a vessel immersed in the water bath. Final feedback of a temperature probe in your solution mixture will let you know when the entire solution is at the equilibrium temperature of 95'C. The initial temperature of your mixture or additive and the rate of addition to the mixture will determine how much localized temperature variation you will have. Slower is more homogeneous.

mix of ethylene glycol and another co-reagent, or use electric controler rod with thermoset and thermometer on three neck round flask

Use a thermocouple and a digital probe thermometer to directly measure the temperature of the mixture, however to heat the mixture to 115°C, an oil bath must be used.