The solubility of organic compounds is a topic of great importance in chemistry and of interest in several areas, such as materials, drugs and the environment. In this paper, the solubility of these species is discussed in terms of their properties, such as the predominant type of chemical bond, molecular structure, polarity and types of intermolecular interactions. Examples of biological processes fundamental for sustainability of life and related with the solubility of chemical species are presented and discussed.

The solubility of sulfides is discussed in this article based on the factors that can influence this property, such as predominant type of chemical bonds and structures formed in many compounds. For soluble sulfides, considerations are made on the thermodynamic parameters and the acid-base equilibrium, since the sulfide anion is extensively hydrolyzed in aqueous solutions. On the other hand, for the insoluble sulfides, the discussion concerned the influence of structural factors that will be determinant for the low solubility.

The solubility rules presented in the majority of introductory texts of chemistry usually do not comprise a systematic analysis of the dissolution processes, neither from a microscopic nor from a macroscopic point of view. The solubility of nitrates in aqueous solution is discussed in this article, focusing on the thermodynamic data and the properties of the nitrate ion.

The oxidation process of sulfur(IV) species by oxygen, ozone and nitrogen oxides, catalysed by trace metal ions, can play an important role in atmospheric chemistry processes like acid rain, visibility degradation and health hazard. An overview of the more relevant investigations on emissions sources, aqueous phase conversion process and environmental impact is presented.