Water & Steam Tables: Understanding Specific Density

[Micko]

Hello and Happy New Year to all,

I have found one formula which uses terms I hope you'll help me understand.
It is given in the attachment, and this is l

rhoW1 specific density [kg/m3] (corresponds to table value Pa = 1 bar, liquid phase)
rhoD1 specific density [kg/m3] (corresponds to table value Pa = 1 bar, gaseous phase)

rhoM1 Specific density [kg/m3] (corresponds to table value Pa = 1 bar, reference column)

rhoW Specific density [kg/m3] (interpolated value, liquid phase)

rhoS specific density [kg/m3] (interpolated values, gaseous phase)

rhoM specific density [kg/m3] (reference water column at ambient temperature)Now, there are terminology used here I don't understand.

1. Specific density. What is that? I know about density, but not sure what specific density is.
liquid phase (steam table) means saturated water and gaseous phase (steam table) means saturated steam.
2. What would be steam density at P = 1bar?
To give you more informations, these densities are corresponding to steam and water in steam drum in boiler.
Typical values: Temperature of steam from 220 to 300 °C, pressure is about 150 bar and temperature of reference column is about 40 °C.
Now can you help me and pint to water and steam tables to figure out what would be typical values of above mentioned densities?

Thank you

 

[Chestermiller]

This looks like some sort of formula for interpolation in the steam tables, but, without additional context, it is really impossible to guess what is involved here.