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自然界中存在的稳定同位素种类甚多,其分析方法除质谱法、中子活化法等外,还有晶体密度法。它能测准固体二元混合物的密度达±10~(-6)克/毫升,因此在化合物中,由于同位素取代而引起的密度相对改变,也就是在同位素质量的相对改变大于±10~(-6)的情况下,可采用晶体密度法。它对于测定轻元素的同位素组成较合适。至于在何种情况下用液体密度法,何时用晶体密度法,这取决于待分析元素有那些稳定化合物适于作为密度法的工作物。密度法一般只适用于二元混合物,其精密度并不亚于质谱计法,而且又不需要贵重复杂的仪器设备。
There are many kinds of stable isotopes in nature. In addition to mass spectrometry and neutron activation, there are crystal density methods. It measures the density of solid binary mixtures up to ± 10-6 grams per milliliter, so in compounds the relative density change due to isotopic substitution, ie the relative change in isotope mass, is greater than ± 10 to ( -6), the crystal density method can be adopted. It is more appropriate for determining the isotopic composition of light elements. As to when to use the liquid density method and when to use the crystal density method, it depends on the element to be analyzed which has stable compounds suitable as a working substance for the density method. Density method generally applies only to binary mixtures, its precision is no less than the mass spectrometry method, but does not require expensive and complicated equipment.