Sulfamic acids

White crystals melting at about 205°C with decomposition.1 

One part dissolves in about six parts water at 0°C, and in about two parts at 80°C. Sparingly soluble in alcohol slightly soluble in acetone insoluble in ether.1 

Nitrates or Nitrites. Heating with mixtures of sodium or potassium nitrates or nitrites leads to reactions that may be explosive.2 

Nitric Acid. Mixing with fuming nitric acid results in violent release of nitrous oxide.3 

Dust or solution irritates the eyes, skin, and mucous membranes. Prolonged exposure of skin to the acid may cause irritation. Avoid contact with skin and eyes.4 

Submitted by H. H, Sisler, M. Josetta Butler,and L. P. Audrieth Checked by John A. Lowbr and W. Conard Pernelius 1  

Sulfamic acid, NH2SO3H, is an ammonoaquosulfuric acid in which one of the hydroxyl groups of sulfuric acid has been replaced by the isosteric amido group. It is prepared commercially by the interaction of fuming sulfuric acid and urea. This method is not readily adaptable to laboratory preparation on a small scale. Consequently, the sulfur dioxide-hydroxylamine reaction is recom-mended.H Sulfamic acid may also be obtained by the action of sulfur dioxide upon certain compounds which yield hydroxylamine such as acetoxime. The recommended procedures are modifications of older processes and involve the use of sulfur dioxide under pressure upon aqueous solutions of hydroxylammonium salts and compounds yielding hydroxylamine. 

Since sulfamic acid has been found to be an excellent acidimetric standard of reference, detailed directions for the purification of the commercial grade of acid are also given. 

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Sulfonation under mild conditions is reported to yield thiazolyl-2-sulfamic acid, which, when heated in H2SO4. rearranges to 2-aminothiazole-5-sulfonic acid (16. 374. 390. 391). Postovskfi. however, reports exactly the opposite rearrangement (367). and spectroscopic evidence supports his conclusion (368) (see Section III.5). 

Acetamido-4-methyl-5-thiazolyl-sulfuryl chloride gives by hydrolysis the acid, which on heating with H2SO4 is reported to give the 2-sulfamic acid (337). 

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