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Benzalkonium chloride

Structure of Benzalkonium chloride, source: Wikipedia

Properties

 White to white-yellow powder or gelatinous yellowwhite fragments, the compound is hygroscopic, which means it easily attracts water (from f.e. the air).
When the compound gets heated, it will form a clear molten mass.
It is soluble in water and alcohol. When it is resolved in water, the H2O solution will form excessive foam.
How to identify the compound
It
- UV spectrophotometry: maxima at 257 nm, 263 nm and 269 nm.
- Using liquid chromatography
- Adding Na-tetraphenylborate and acetic acid will form a sediment of benzalkoniumtetraphenylborate. Which has a characteristic melting point of 127-133 °C.
- Bringing the compound in a NaOH solution together with BFB (bromephenol blue) and dimethylchloride will form a blue colour in the CH2Cl2 layer. This is caused by the ionpair forming with the anionic pigment (BFB) and extraction of the ionpair in the organic layer.
- Identification of Cl- ions: + AgNO3 will form a white precipitate which is soluble in NH3.
Or if you add dichromate -> chromylchloride will be formed + phenylcarbazide -> white precipitate.
Determining the content

 Adding KI in an alkaline environment -> forms benzalkoniumiodide which will be extracted to CH2Cl2 (organic layer).
The excess of the I- ions (in the water layer) will be determined using KIO3 in strong acid (H+ milieu). This is also called the method of Andrews. 

 I- + IO3- -> I+ (jodoxyl)
Intermediate = I2
Use of benzalkonium chloride

It's used as a disinfectant in concentrations of about 0,1% for hands (used in surgery), small wounds, eat and drinking disinfectant, bed sheets, etc.

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