https://sci-hubtw.hkvisa.net/10.1007/s12011-007-8044-0
Sodium selenosulphite (Na2SeSO3 ) can be prepared by refluxing 5.54 gms of Sodium Sulphite (Na2SO3) with 0.214gms of Selenium powder in 50ml of distilled water for 5 hrs. at 70 ᴼC
"The solid is relatively sensitive to shock and friction. For this reason DNPH is usually handled as a wet powder.".
https://en.wikipedia.org/wiki/2,4-Dinitrophenylhydrazine