Quicklime

Quicklime is also known as burnt lime or unslaked lime. Its chemical name is calcium oxide. It is produced by applying intense heat to crushed limestone, often in a rotary kiln. During this process, called "calcination," the original limestone undergoes a chemical reaction resulting in quicklime and the waste product carbon dioxide.

Hydrated Lime

Hydrated lime is also called slaked lime or pickling lime. Its chemical name is calcium hydroxide. Hydrated lime is produced by subjecting the quicklime produced during calcination to another step: adding water to cause a second chemical reaction. Just enough water is used so the resulting substance is a dry powder, not a liquid.

Applications of Quicklime and Hydrated Lime

Quicklime has a number of industrial uses. It can play a role in the chemical reaction that creates the heat in self-heating soup cans, for example. Among other applications, hydrated lime is useful for the home gardener. Because it is a chemical base with a high pH, it can be added to overly acidic soil to make it more hospitable to certain varieties of garden or landscape plants.

Using Hydrated Lime for Gardening

Because hydrated lime is a powerful base, it is important to test the soil's current pH to determine if it is acidic enough to warrant the use of hydrated lime. Soil that is too basic can be as harmful to plants as soil that is very acidic. It is also important to find out the preferred pH level of the specific plants in your garden or landscaped yard, as different varieties can have widely ranging ideal pH levels.