Hotplate and Magnetic Stirrers
Stirring is performed to obtain homogeneous mixtures and intensifies heat and mass exchange in the mixers. In accordance with the state of aggregation of matter, there is a mixing of liquids and bulk solids. Stirring is carried out mainly in the vessels with mixing devices. The nature and intensity of mixing depend on the design of devices and mixers. Magnetic stirring can be used over a broad temperature range and with any chemical agent, as well as in open and closed systems, under pressure or vacuum. The most common mixing is carried out with the help of magnetic stirrers.
The magnetic stirrer consists of two main parts: motor with stirring mechanism and control electronics. Motor movement with a magnet on top causes rotation of stir bars which mix liquids. Control electronics supervises motor RPM, keyboard functions. Magnetic stirrers are designed for mixing fluids of different viscosity with the help of a stir that spins very quickly. They are commonly used for sample preparation and analysis, in chemistry Lab, biology lab, Pharmacy Lab and in such laboratory works as organic synthesis, extraction, oil analysis, pH measurement, dialysis, soil suspending, preparing buffer solutions where it is often needed to mix several types of liquids to get homogeneous mixtures. Magnetic stirrers have different service performance and technical parameters. The main difference is in the design which means that mixing occurs by rotating or oscillating processes. When you choose a magnetic stirrer, you should take into consideration the volume of the liquid container, the speed of rotation, the oscillation intensity, and heating if you need to raise the temperature of the mixture. A magnetic stirrer is an electromechanical device that mixes with the help of an external magnetic field that rotates a stir bar placed in the mixture. Stir bar rotates at different speeds and can mix volumes up to one litter. Since only a small magnet bar that can easily be cleaned and sterilized has to be put inside the sample, the risk of contamination is minimized. Magnetic stir bars work well in glass vessels. Glass is the material that doesn’t affect a magnetic field. The stir bar has a limited size that is why it can be used for relatively small experiments. They can have difficulties with viscous liquids and thick suspensions. The plastic case of the device serves as good isolation from spills. Magnetic stirrers have no moving parts and use a magnetic field. The housing of the most magnetic stirrers is made of polypropylene. The stir bar is made of ferrite enclosed in polypropylene.
Magnetic Stirrer with hot plates is reliable, universal, and easy to use and meet all kind of safety standards. It is necessary to consider the oscillation intensity, time, and possible heating. Modern magnetic stirrers successfully deal with these tasks and provide the right conditions. Besides, this device is a must be an instrument for consistent, reproducible mixing or mixing over a long time, for example, for multi-hour or overnight sample mixing. Magnetic stirrers have an advantage over motorized ones. They are quieter and more efficient. They have no moving external parts to break or wear out. For cleaning stir bars, you don’t need lubricants which could be the reason for contamination of the product. Sometimes magnetic stirrers include a hot plate for heating the liquid. Built-in fault diagnostics and automatic thermal shutdown ensure the safety of magnetic stirrer usage. Magnetic stirrers are easy to use and they ensure high productivity and accuracy.
Because of its small size, a stirring bar is more easily cleaned and sterilized than other stirring devices. They do not require lubricants which could contaminate the reaction vessel and the product. Magnetic stirrers may also include a hot plate or some other means for heating the liquid.
The magnetic stirrer is used in many biological labs, including microbiology labs also. A magnetic stirrer is a laboratory device consisting of either a rotating magnet or stationary electromagnets creating a rotating magnetic field. This device is used to cause a stir bar immersed in a liquid to spin very quickly, agitating, or mixing the liquid. A magnetic stirrer often includes a provision for heating the liquid. Stirrers are often used in laboratories, especially in the field of biology and microbiology. They are preferred over gear-driven motorized stirrers because they are quieter, more efficient, and have no moving external parts to break or wear out (other than the simple bar magnet itself). Due to its small size, a stirring bar is more easily cleaned and sterilized than other stirring devices. Magnetic stirrers avoid two major problems with motorized stirrers. Firstly, motorized stirrers use lubricants, which can contaminate the reaction vessel and the product. Secondly, in motorized stirrers, the sealing of the connection between the rotating shaft of the stirrer and the vessel can be problematic, especially if a closed system is needed. Magnetic stirrers also have drawbacks. For example, the limited size of the stirring bar means it can only be used for relatively small experiments. In addition, viscous liquids or thick suspensions are extremely difficult to mix using this method, although there are some stirrers with special magnets to overcome this problem.
Components of Magnetic Stirrer with Hot Plate:
- Base with power switch, two control knobs, and LED indicators
- Teflon-coated magnetic stir bar (1-inch length)
- Power cord
- Support stand (2-piece support rod, right-angle clamp, and thermometer holder)
How does a magnetic stirrer work (Working Principle)?
Magnetic stirrer working principle is repulsive for like charges and attractive for unlike charges. Micromotor drives magnet to generate rotating magnetic field to stir the stirring bar in a vessel, making solution conduct completely mixed reaction, stirring speed is adjustable, widely applies to solvent stirring in different viscosity. It equips with a temperature control system, which can heat and control the temperature of the sample according to experiment requirement, maintaining the needed temperature condition and guaranteeing the mixed liquid meets the experiment need.
How to maintain a magnetic stirrer with Hot Plate?
- Put the bottle on the working table.
- Switch on the power switch, the indicator will light.
- Choose to heat, turn on the heating power switch, the heating indicator will light, this means the heater is working now. Insert the sensor solution, adjust the thermostat knob to the desired temperature scale.
- Adjust the speed control knob, rose to the required speed.
- After work, set the speed control knob at the lowest speed position, the heating switch is in a non-working state, turn off the power switch, cut off the power supply.
- Clean the working surface and sensor, make sure no water and dirt on it.
Precautions when using a magnetic stirrer with Hot Plate:
- Instrument housing should be properly grounded to avoid accidents.
- When unused for long periods, should cut off the power, store a dry and ventilated place.
- The instrument should be kept clean and dry, prohibit the solution flows into the machine, to avoid damage to the machine, cut off the power when not working.
- During mixing, when find stirrer is beating or non-stirring, reduce speed or disconnect the power to check whether the flat bottom of the beaker, location is positive.
- Stirring heating time not too long, intermittent use can extend the life, not heated without stirring.
- The medium-speed operation can continuously work for 8 hours, high-speed operation can continuously work for four hours, to prevent severe vibration during operation.
Different Types of Hotplate and Magnetic Stirrers
- Magnetic Stirrers
Magnetic stirrers use a rotating magnetic field to cause a stirrer bar (of flea), immersed within a liquid, to spin and therefore stir. Most magnetic stirrers are suitable for small volumes of low viscosity. However there are some models which have been developed to handle large volumes and high viscosity.
Variations: Single plate and multiple plate options. Digital or Analogue.
- Stirrer Hotplates
Stirrer hotplates are stirrers combined with a hot plate. Either function can be use on its own on combined with each other. The main difference in the variety of stirrer hotplates are what material the top plates are made from:
Ceramic: Ceramic top plates have excellent chemical resistance, so are ideal if you are working with corrosive chemicals which may splash onto the plate surface. They can offer higher temperatures of up to around 450°C and are easy to wipe clean. Again, as with the magnetic stirrers, the white surface also means they are good for titrations or other work where clear visibility of colour is a must. Ceramic plates also have cool edges, which is useful for operator safety but may not be suitable if you need heating all over the plate surface. Ceramic hotplates must only be used to heat glassware, do not heat liquids in metal containers on a ceramic hotplate. They are also not suitable for sand baths and any vessel which will reflect heat back onto the surface causing cracking.
Aluminium: Aluminium top plates are more robust and will withstand accidental knocks better than ceramic plates. They offer a consistent temperature all over the plate and become hot right up to the edges of the plate surface. Metal top hotplates can also be used to heat metal vessels, so if you are working with stainless steel beakers or other metal containers this is the best choice.
Variations: Single plate and multiple plate options. Digital and analoue. Advanced digital (temperature presets and programs), External probe monitoring, Bath Vessel and tube mounting options.
Information required to to quote on an Autoclave
- Do you require heating?
- Do you require stirring?
- How many plate positions do you require?
- Any specific requirements for the top plate? Aluminium, Ceramic Coated?
- Do you need an external probe?