Acidic oxide Some non-metal oxides, such as nitrous oxide (NO) and carbon monoxide (CO), do not display any acid/base characteristics. Acidic oxides can also react with basic oxides to produce salts of oxoanions: Acidic oxides are environmentally relevant. Sulfur and nitrogen oxides are considered air pollutants as they react with atmospheric water vapour to produce acid rain. Although it is difficult to classify these oxides as acids, the property is manifest in reactions with bases. For example, carbon dioxide reacts with alkali. For this reason, alkali is kept in stoppered vessels to inhibit reaction with atmospheric carbon dioxide. In geochemistry complex silicates
Lower sulfur oxides has been detected in the gas phase using neutralization-reionization mass spectrometry. Both cyclic and chain structures were found. A number of monoxides SO are known where n= 5-10, where the oxygen is bonded to one sulfur. They can be prepared by oxidising the homocycles with trifluoroperoxoacetic acid: The compounds are yellow or orange-coloured and thermally unstable near room temperature. One dioxide is well characterized: the deep orange SO (m.p. 60–62 °�C with decomposition), which arises using trifluoroperoxoacetic acid. Lower sulfur oxides The lower sulfur oxides are a group of inorganic compounds with the formula SO, where m < 2n. These