I still cant understand why is this happening $???$ Why the volume increased When mixing ammonium format and methanol $??$ no specific condition while mixing $,$ ammonium formate as solid $($ like crystals droplets not completely solid powder$)$ and the methanol is liquid $,,$ i though mixing of two are not soluble will either not mixed $,$ or expansion of volume but both are polar $,,$ please explain $...$

also another question $,,$ if I use C$18$ column $,,$ can i use water as blank $??$ Please explain the basics