Similarly, amido-derivatives can be obtained from sulphur trioxide. The action of ammonia on that compound yields ammonium sulphamate, Amides Of Sulphur Acids 177 , or, if less ammonia be used, sulphamic acid, HO-(SO2)-NH2; they are both crystalline, soluble compounds.

The action of sulphur dioxide on ammonia is accompanied by the production of the analogous compounds, ammonium sulphurosamate and sulnhurosa/mie acid, the latter of which has the formula Amides Of Sulphur Acids 178

These compounds may be taken as instances of bodies analogous to acids, in which the hydroxyl is replaced by the amido-group. They are, as a rule, stable in presence of water, and they do not generally unite with acids, the acidic nature of the oxygen which they contain counteracting the basic nature of the amido-group. Many compounds are however known, in which the amido-group replaces hydroxyl, and which, having no acidic oxygen present, are known only as salts in combination with acids. Some of these will now be described.