Nitric acid is a compound, its chemical formula is HNO3 and molecular weight is 63.01. Pure nitric acid is colorless liquid with pungent smell and concentrated nitric acid is a mixture. For concentrated nitric acid available in the market, its mass fraction is about 68%, density is about 1.4 g/cm³ and boiling point is 83℃, volatile and capable of dissolving in water in any proportion. Similar to sulfuric acid, it will release numerous heats during mixing and require constant stirring. Concentrated nitric acid can only be added to water, not in reversed sequence. Nitric acid with concentration of (86~97.5%) 98% is known as “Fuming nitric acid”. Pay attention to wear polythene plastic gloves and special mask because the acid is volatile, corrosive and toxic and forms white smog in case of encountering damp air. 

Concentrated and dilute nitric acid
1. After adding iron or aluminum in cold nitric acid, if there is no obvious phenomenon, it is concentrated nitric acid; if surface of iron or aluminum generates bubble, it is dilute nitric acid. 
2. Observe directly; it is concentrated nitric acid in case of white smog; it is dilute nitric acid in case of no white smog. Volatility of nitric acid is applied here (hydrochloric acid also volatile).
*Note: the method requires sealing due to fast oxidation of nitric oxide. 
In fact, concentration measurement is the most vivid method. 

Safety measures 
Never inhale fume, vapor and spray
In case it contacts your eye or skin, wash it by plenty of clear water immediately and go to see a doctor for treatment as soon as possible 
All polluted clothes must be taken off immediately
Wear proper protective clothes, protective gloves and face shield
Concentrated nitric acid shall be separated from reductive substances during its storing. 

Test Report of Tai’an Product Quality Supervision and Inspection Institute

Contact: Manager Xu

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