Gravimetric precipitates should be dried or ignited:

Another significant application of TG is the determination of correct drying temperature for precipitates used in gravimetry analysis. It also gives information whether a gravimetric precipitates should be dried or ignited. For familiar precipitates ignition temperature is commonly based upon practical experience of the chemical properties of the substance, like as AgCl is died at 130-150 °C and BaSO₄ is heated at 800 °C -900 °C. A better process is to make use of TG curves. It is supposed in which the horizontal portion of the TG curve provides the range of temperature over that the composition is constant and thus the mass is also constant and the precipitates could be dried in this temperature range of gravimetric analysis. The precipitate could be dried in this temperature range for gravimetric analysis. It was earlier reported that the precipitate of Al (OH)₃ should be ignited at 1200-1300 0C to get Al2O₃. But with the help of TG curve we come to know that this precipitatate might be ignited at 1030 °C in order to get Al2O₃. Aluminum oxinate [Al (C₉H₆NO) ₃] might be dried at 105- 110 °C as denoted through TG curve. TlAg₂AsO₄ furnishes a horizontal on the recording between 20 to 846 °C. It could, thus, be weighted after drying or ignition in this range of temperature. On the other hands the precipitate of calcium picolinate, Ca (C₁₀H₇ O₅N₄)_2.7H₂O starts to decompose at 300 °C, so it must be dried within a current of dust free air. Beryllium is precipitated as ammonium beryllium phosphate along with ammonium hydrogen phosphate in the presence of ammonia.

Be²⁺ + (NH₄)₂HPO₄ → Be (NH₄) PO₄.6H₂O

Its TG curve denotes the distinction within the crystal that is the elimination of water and ammonia at 30 °C so in which there is no possibility of weighing anhydrous beryllium phosphate. The thermogram displays a continuous loss in weight up to 600 °C, above this temperature the mass remains constant, this mass corresponded to the composition Be₂P₂O₇.Therefore, and ammonium beryllium phosphate decomposes simply as compared to beryllium hydoxide. Thus, this is the better method for the determination beryllium. Therefore, TG curve helps in finding the temperature at that the precipitate should be dried or ignited. If beryllium hydroxide is precipitated through ammonia with BeSO4, the precipitate is washed and ignited to provide BeO.

BeSO₄ + NH₄OH → Be (OH)₂+ (NH₄)2SO₄

Be(OH)₂   →  Be O + H₂O   at about   900 °C

Be(OH)₂   is converted to BeO only at about 900 °C .Thus, ammonium beryllium phosphate decomposes simply to Be(OH)₂. Therefore, it is better to precipitate beryllium along with ammonium hydrogen phosphate and then ignite it to 640 °C to BeP₂O₇. Therefore TG curves help in searching the temperature at that the precipitate should be dried or ignited.