Although Quicklime & Hydrated Lime are both made from ground limestone (calcium carbonate), they are obviously not identical products. Here, we explore some of the differences between the two, using one versus the other, and why you might choose one over the other.
The first and primary difference is found in the molecular structure. Quicklime is calcium oxide, and Hydrated Lime is calcium hydroxide.
The two products also look different. Quicklime will typically appear as a more dense, BB-like product, and may be dull-white or grayer in color. Hydrated Lime is a bright white, lighter, and more ‘fluffy’ product.
Production: Quick vs Hydrated
Limestone is a type of sedimentary rock. In its raw form, it is calcium carbonate. The first step in the production process for either product is the extraction of limestone from quarries and mines. Then, the limestone is crushed, screened, and washed. By heating this crushed limestone to a high temperature, carbon dioxide is released, and calcium oxide (Quicklime) is left. To make Hydrated Lime, the production process is taken a step further, and the product is then quenched with water. This is called “slaking”, and is done in a controlled way since it does produce an exothermic reaction (it gets hot!).
Using Quicklime vs Hydrated Lime
So, which product should you use? Clearly, this depends on what you are using it for.
Quicklime and Hydrated Lime are different to work with. Quicklime reacts faster, is much more reactive, and gives off a lot of heat quickly while reacting. This is why it is called “quick”, because chemically it is ‘hotter’. Meanwhile, Hydrated Lime is less reactive and safer to handle. The safety benefits of working with Hydrated Lime are one reason why this product is more commonly used and often preferred.
Both products are alkaline and can be used for many applications, such as for pH adjustment or where calcium is needed in a chemical reaction. However, this does not mean that the two products are interchangeable. If the lime is being used for a reaction, the products are molecularly different and may not be interchangeable at all. One contains an oxygen molecule on its own, and the other contains a hydroxide molecule. These two molecules react very differently.
To compare the bonding ability of molecules using the everyday analogy of ‘hand-holding’, an oxygen molecule on its own has two hands available to hold onto other molecules; in a hydroxide molecule, the oxygen only has one hand available to hold onto other molecules- because the other one is already bonded to the hydrogen.
If you are unsure which product is best for your industrial application, get in touch with a representative. We’ll be happy to help!
Buying Lime
A useful source of alkalinity and economical source of calcium, lime is available to buy from CORECHEM in 50 lb. bags (typically supplied in pallets of bags), 2000 lb. supersacks, and bulk pneumatic tankers.
If you choose to source product elsewhere, be aware that there is a product called ‘lime’ that is sold in agricultural supply stores (or stores such as Home Depot or Lowe’s), that is actually pelletized limestone, and not the same as either of these two products. This product is unprocessed calcium carbonate, and won’t function the same as either Hydrated Lime or Quicklime. If you attempt to use it as a source of alkalinity, you will be disappointed- and it won’t work for other processes that may require either calcium oxide or calcium hydroxide, either. Check the back of the bag for more information before buying.
