[Physical and chemical properties]
Nitric acid , the molecular formula is HNO 3 , the relative molecular mass is 63.
(1) Ammonia oxidation method:
Using platinum as a catalyst, the ammonia is oxidized to nitric oxide, then air and concentrated nitric acid are all oxidized to nitrogen dioxide, and then absorbed with concentrated nitric acid to generate fuming nitric acid , which is then obtained by desorption
(2) Chinese Patent CN1113878A
This method is improved on the basis of the ammonia oxidation method
Nitric acid is a strong oxidizing acid, which is also corrosive to most metals
Table 8-3 Nitric acid cleaning process
Luo Sheng et al.
Zhan Guangquan cleans the steaming and bleaching compound scale formed on the surface of the steaming and bleaching pot and the material frame with a 3% to 5% concentration of nitric acid cleaning solution, and tests the corrosiveness of the cleaning solution at this concentration
Nitric acid is unstable and decomposes when exposed to light and heat, releasing nitrogen dioxide
Nitric acid is one of the three important strong acids and has the same properties as acids
The characteristics of using nitric acid as the cleaning medium and the matters needing attention are as follows:
(1) Because it is a strong oxidizing acid, in addition to silicate scale, it has a high reaction speed to various other rust and scale, so it dissolves quickly
(2) Nitric acid produces new ecological atomic oxygen when it is decomposed.
(3) The oxidizing property of nitric acid is beneficial to oxidizing and decomposing many organic substances in the dirt, dissolving many insoluble metal oxides and salts, and the dissolution rate is fast
(4) Nitric acid is a volatile acid, and it is easy to decompose nitrogen dioxide, nitric oxide and other gases under the action of light and heat, and its toxicity causes serious pollution to the human body and the environment
4HNO 3 →4NO 2 +2H 2 O+O 2
Therefore, in the laboratory, nitric acid should be stored in a dark container.
(5) The strong acidity, strong oxidizing properties, instability, and volatility of nitric acid have increased the risk of cleaning operations, so special attention should be paid
Nitric acid is generally used for the cleaning of passivable metal materials that are not suitable for cleaning with hydrochloric acid, such as aluminum, stainless steel and other materials
Related Links: Application of Sulfuric Acid