Loss on ignition (LOI) is a test used in inorganic analytical chemistry and soil science, particularly in the analysis of minerals and the chemical makeup of soil. It consists of strongly heating ("igniting") a sample of the material at a specified temperature, allowing volatile substances to escape, until its mass ceases to change. This may be done in air, or in some other reactive or inert atmosphere. The simple test typically consists of placing a few grams of the material in a tared, pre-ignited crucible and determining its mass, placing it in a temperature-controlled furnace for a set time, cooling it in a controlled (e.g. water-free, CO2-free) atmosphere, and redetermining the mass. The process may be repeated to show that mass-change is complete. A variant of the test in which mass-change is continually monitored as the temperature is changed, is thermogravimetry. Theory The loss on ignition is reported as part of an elemental or oxide analysis of a mineral. The volatile materials lost usually consist of "combined water" (hydrates and labile hydroxy-compounds) and carbon dioxide from carbonates. It may be used as a quality test, commonly carried out for minerals such as iron ore. For example, the loss on ignition of fly ash consists of contaminant unburnt fuel. In pyroprocessing industries such as lime, calcined bauxite, refractories or cement manufacture, the loss on ignition of the raw material is roughly equivalent to the loss in mass that it will undergo in a kiln. Similarly, for minerals, the loss on ignition represents the actual material lost during smelting or refining in a furnace or smelter. The loss on ignition of the product indicates the extent to which the pyroprocessing was incomplete. ASTM tests are defined for limestone and lime and cement among others. Procedure Soil is composed of living organisms, water, carbonates, carbon containing material, decomposing matter and much more. To determine how much one of these soil components make up the entire soil mass, the LOI procedure is implemented. Initially, the researcher will take the mass of the sample prior to LOI and then place the sample into a heating device. Depending on what the researcher is trying to determine in the soil, the temperature of the device can be set to the corresponding temperature. The soil sample is kept at this temperature for an extended period of time after which it is removed and allowed to cool down before