what is magneson reagent, what is its chemical formula and name - Chemistry - Surface Chemistry

Question

what is magneson reagent, what is its chemical formula and name
?

Arti Gujrati · Accepted Answer

Chemical name: 
4-(4-NITROPHENYLAZO)RESORCINOL
<img src="http://www%20chemicalbook%20com/CAS/GIF/74-39-5%20gif"
alt="4-(4-NITROPHENYLAZO)RESORCINOL Structure">

it is used for the detection of Mg in the salt analysis

what is magneson reagent, what is its chemical formula and name ?