curium trioxide exists below temperatures of 800 °C, the monoclinic form between 800 °C and 1615 °C, and the hexagonal form above 1615 °C. Crystallography The lattice parameters for three of the polymorphic structures of curium sesquioxide are given below. Hexagonal: (*: No specific temperature has been stated to produce the lengths listed in the second row.) Monoclinic: (**: None of these lengths contained given uncertainties.) Cubic: Data Ever since the discovery (and isolation) of 248Cm, the most stable curium isotope, experimental work on the thermodynamic properties of curium sesquioxide (and other curium compounds) has become more prevalent. However, 248Cm can only be obtained in mg samples, so data collection for 248Cm-containing compounds takes longer than that for compounds which predominantly contain other curium isotopes. The data table below reflects a large variety of data collected specifically for curium sesquioxide, some of which is purely theoretical, but most of which have been obtained from 248Cm-compounds. (*: Different syntheses of curium trioxide have been shown to produce compounds with different experimental melting points. The melting point given in this data table is merely an average of those collected from the references.) (**: Characteristic of the monoclinic form.) (***: Various experiments have calculated different estimates of the standard molar entropy for curium trioxide: Moskin has reported a standard molar entropy of 144.3 J/molK (no given uncertainty). Westrum and Grønvold have reported a value of 160.7 J/molK (no given uncertainty), and Konings’ value is reported to be 167 +/- 5 J/molK.) Toxicology Curium metal is a radionuclide and emits alpha particles upon radioactive decay. Although it has a half life of 34 ms, many curium oxides, including curium sesquioxide, have half lives nearing thousands of years. Curium, in the form of curium sesquioxide, can be inhaled into the body, causing many biological defects. The LD50 of curium is 3 micro-Ci through ingestion and inhalation and 1 micro-Ci through absorption through the skin. In one experiment, rats were introduced to aerosolized particulates of curium(III) oxide. Although the experiment proved that inhaled 244Cm2O3 is half as carcinogenic as compared to inhaled 239PuO2, the rats still suffered from many biological deformities, such as skin lesions, malignant tumors, and lung neoplasms. A small amount of the rat population was able to clear particulate curium sesquioxide from the lungs, suggesting that curium sesquioxide is partially soluble in lung fluid. Applications Curium(III) oxide is heavily used in industrial grade-reactions