Lab and Pathology
17th January 2022
Stirring and agitation are common steps in almost all research and testing labs worldwide, for blending, dissolving, or other purposes, regardless of their application. Magnetic Hot Plates & Overhead stirrers are basic lab equipment that is found in every laboratory. These are used for various heating and stirring needs depending on the application and are available in different configurations with varying capacities and functionalities. Here in this blog we will know the parameters for selecting stirring range for laboratory use.
Stirring can be combined with heating and mixing. Choosing between the type of stirrer as per your application is not always a simple task, to use a correct instrument to get the desired result there are several factors to be considered.
1. Volume of sample
2. Viscosity of sample
3. Heat requirement
4. Type of vessel
5. Type of mixing
Magnetic stirrers offer low noise, better efficiency, lesser instances of external parts breaking or wearing out. Basically a magnetic stirrer is good when dealing with small volumes from 0.4 ml to around 20L, typical lab bench models (Neuation provides magnetic stirrer up to 200liter).
A Magnetic stirrer is used in Biological, chemistry laboratories, and microbiological laboratories as it is small in size and easy to move from one place to another having various position options for wider lab application solutions to be made in one go. This type of stirrer operates with magnetic bars that work best with commonly used flat bottom glass containers for various chemical reactions. While using a magnetic stirrer, the stir bar size selection is also important. As for choosing the bar there are often suggestions for the maximum size of bar to be used as a too short bar can result in low or improper mixing.
One of the advantages of using a magnetic stirrer is there is almost no risk of contamination occurring. There are complete ranges of magnetic stirrer with or without heating capabilities. Whereas mechanical stirring devices are used for larger volumes to get expected results. Overhead stirrer can range up to from 10L to 100L for higher volumes.
Magnetic stirrer and Hot plate stirrer can be used for solutions having Viscosity close to water. But higher viscosity and larger volume mixing are where the overhead stirrers have an important role, but again it can be critical in applications where there is non-newtonian fluid, like polymerization and lotion making where viscosity increases as it cools. Refer to the overhead stirrer’s viscosity and torque specs to ensure the motor is suitable for the viscosity of your sample, and check for the ability to maintain the set rpm under changing viscosity. Hence, overhead stirrers can be used for pseudo plastics, Newtonian fluid with high volume; Thixotropic liquid after checking its viscosity to the instrument’s maximum viscosity range.
| Common Liquids | Viscosity (m Pa.s) |
|---|---|
| Water | 0.89 |
| Whole Milk (20℃) | 2.12 |
| Condensed Milk (40℃) | 40-80 |
| Sunflower oil (26℃) | 48.8 |
| Olive Oil(26℃) | 60 |
| Soap Solution (60℃) | 82 |
| Yogurt (40℃) | 152 |
| Printer Ink (38℃) | 550-2200 |
| Glycerol (20℃) | 934 |
| Common Liquids | Viscosity (m Pa.s) |
|---|---|
| Baby Food (93℃) | 1400 |
| Detergent (70℃) | 1470 |
| Shampoo (36℃) | 3000 |
| Paraffin Emulsion (18℃) | 3000 |
| Honey (20℃) | 10,000 |
| Ketchup (25℃) | 20,000 |
| Biscuit cream (18℃) | 29,200 |
| Cottage cheese (18℃) | 30,000 |
| Vaselline (20℃) | 64,000 |
Many magnetic stirrer models include a hot plate for simultaneous heating and mixing. Overhead stirrers require separate equipment for heating, whether it is a hotplate below the vessel or a heating mantle. If solutions to be autoclaved with a Magnetic bar it ensures mixing without non-sterile environment exposure.
Magnetic stirrers have their best performance in flat bottomed vessel providing unhindered rotation of stir bar and closest contact with the magnetic agitator.
This blog has been taken from Parameters To Select Your Stirring Range For Laboratory Use - Neuation
Courtesy of Neuation Technologies
