Sulfamic acid
[CAS# 5329-14-6]

Identification

• Classification: Organic raw materials >> Amino compound >> Sulfonic acid amino compound
• Name: Sulfamic acid
• Synonyms: Amidosulfonic acid; Amidosulfuric acid; Aminosulfonic acid
• Molecular Formula: H₃NO₃S
• Molecular Weight: 97.09
• CAS Registry Number: 5329-14-6
• EC Number: 226-218-8
• SMILES: NS(=O)(=O)O

Properties

• Density: 1.9±0.1 g/cm³, Calc.^*, 2.12 g/mL (Expl.)
• Melting point: 215-225 °C (dec.) (Expl.)
• Index of Refraction: 1.544, Calc.^*
• Water solubility: 146.8 g/L (20 °C) (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS08;GHS07 Danger
• Risk Statements: H315-H319-H412
• Safety Statements: P260-P264-P264+P265-P270-P273-P280-P302+P352-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Acute toxicity	Acute Tox.	4	H302
Serious eye damage	Eye Dam.	1	H318
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2A	H319
Skin corrosion	Skin Corr.	1C	H314
Skin corrosion	Skin Corr.	1B	H314

• Transport Information: UN 2967

Discovery and Applications

Sulfamic acid, also known as amidosulfonic acid, is an inorganic compound with the formula H₃NSO₃. This versatile chemical was first synthesized in the late 19th century when chemists were exploring sulfur-based compounds, leading to its discovery as a stable crystalline solid with unique acidic properties. Sulfamic acid quickly gained attention for its strong yet relatively safe acidic profile, making it ideal for various applications across industries. It is particularly valued for its descaling and cleaning capabilities, as it reacts with mineral deposits like calcium carbonate, effectively breaking down stubborn limescale and rust. This property has made sulfamic acid a staple in water treatment, industrial cleaning, and household cleaning products.

One of the primary uses of sulfamic acid is in water treatment systems where mineral buildup can damage pipes, boilers, and other equipment. As a descaling agent, sulfamic acid dissolves calcium and magnesium deposits, prolonging the life and efficiency of water-related systems. Compared to harsher acids, it poses fewer risks to metal surfaces and does not emit strong fumes, making it a safer choice for routine maintenance. It also plays a critical role in the maintenance of large-scale systems, such as those in power plants, where scaling can impair efficiency and lead to costly repairs. The mild corrosive nature of sulfamic acid is advantageous for industries seeking effective cleaning without damaging infrastructure.

In addition to industrial cleaning, sulfamic acid is a popular component in household cleaning products. Its ability to remove soap scum, rust stains, and mineral deposits makes it ideal for bathrooms and kitchens. Many consumer products designed for limescale removal contain sulfamic acid, as it is safe for various surfaces, including ceramics, stainless steel, and tiles. Its mild nature compared to hydrochloric acid-based cleaners means it is less likely to cause surface etching or release irritating fumes, making it suitable for regular household use.

In industrial processes, sulfamic acid is widely used as a catalyst, particularly in the production of dyes, pigments, and certain pharmaceuticals. In dye synthesis, it facilitates the formation of sulfonic acid groups, which are critical for enhancing the water solubility of dyes. In the pharmaceutical industry, sulfamic acid assists in synthesizing sulfonamides, a group of compounds with antibacterial properties. Sulfamic acid’s role as a reliable and efficient catalyst is also essential for creating other organic compounds used in industrial applications, including detergents and synthetic resins.

Sulfamic acid is also a valuable laboratory reagent. It is employed in organic synthesis, particularly in reactions involving the sulfonation of organic compounds, where it acts as a stable source of sulfonic acid groups. Its solubility and stability in various solvents make it useful in synthesizing amides and amino acids, as well as preparing sulfonic acid esters. Additionally, sulfamic acid is used in laboratory-scale reactions requiring consistent acidity and minimal side reactions, allowing chemists to control and fine-tune reactions for desired outcomes.

Handling sulfamic acid requires care due to its acidity. Direct exposure can irritate the skin, eyes, and respiratory system, so appropriate safety equipment is advised. Nevertheless, it is considerably safer than many alternative acids, especially for routine descaling and cleaning applications.

In summary, sulfamic acid’s discovery introduced a powerful, versatile agent to industries ranging from water treatment to pharmaceutical synthesis. Its non-corrosive nature, solubility, and effective acidity continue to drive its use in both commercial and industrial settings. The compound remains integral to many fields, especially those requiring safe and efficient descaling and catalytic agents, ensuring its place as a valuable resource in modern industry.

References

2018. Chitosan: A macromolecule as green corrosion inhibitor for mild steel in sulfamic acid useful for sugar industry. International Journal of Biological Macromolecules.
DOI: 10.1016/j.ijbiomac.2017.08.064

2024. Enhancing optical properties in sulphamic acid single crystals through caesium doping for advanced NLO applications. Optical and Quantum Electronics.
DOI: 10.1007/s11082-024-07748-y

2020. Maltodextrin for corrosion mitigation of zinc in sulfamic acid: Electrochemical, surface and spectroscopic studies. International Journal of Biological Macromolecules.
DOI: 10.1016/j.ijbiomac.2019.12.197