Sodium nitrite NaNO2 has many uses, and can be used as heat treatment agent, foaming agent, metal surface treatment agent, bleaching and dyeing agent, etc. On the construction site, the freezing point of the inorganic salt solution is used as an antifreeze agent for cement construction. Because NaNO2 is a strong oxidant, eating NaNO2 by mistake can oxidize hemoglobin containing +2 iron ions to methemoglobin with +3 iron ions, and lose the ability of hemoglobin to carry O2 to exchange CO2. Because NaNO2 has the same salty taste as table salt, there have been many incidents of migrant workers being poisoned by cooking staff on construction sites mistakenly using industrial salt NaNO2 as edible salt.
How to distinguish between NaNO2 and ordinary table salt?
(l) heating method
If it is on the construction site, the salt to be tested can be heated in an iron pot (dry burning). Since the melting point of NaCl is 801°C, which is much higher than the melting point of NaNO2 (271°C), if it melts and is accompanied by the formation of odorous gas The must be NaNO2.
(2) Acid addition method
Add a small amount of salt to be tested into the test tube, add a few drops of hydrochloric acid or dilute sulfuric acid or vinegar, if there is reddish-brown NO2 gas, it must be NaNO2.
2 NaNO2 + 2H2SO4 = 2NaHS04 + NO2 + N0 + H2O