Liquid solutions of solids

In GAS or SAS, a batch of solution is expanded by mixing it with a supercritical fluid in a high-pressure vessel (Figure 24.6). Due to the dissolution of the compressed gas, the expanded solvent exhibits a decrease of the solvent power. The mixture becomes supersaturated and the solute precipitates in the form of microparticles. As shown in Figure 24.6, the precipitator is partially filled with the liquid solution of solid substance. The supercritical anti-solvent is then pumped up to desired pressure and introduced into the vessel, preferably from the bottom in order to achieve a better mixing of the solvent and anti-solvent. After a specified residence time, the expanded solution is drained under isobaric conditions in order to clean the precipitated particles. In this mode of operation, the rate of supercritical anti-solvent addition can be an important parameter in controlling the morphology and the size of solid particles. 

A solution may exist in any of the three states—gas, liquid, or solid. Air is a gaseous solution made up of nitrogen, oxygen, argon, and other gases in small amounts. Like oxygen in water, dissolved carbon dioxide in carbonated beverages is a familiar liquid solution of a gas. Alcohol in water is an example of the solution of two liquids, and the oceans are liquid solutions of solids. Solid-state solutions are common in the form of metal alloys. 

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