Concentration (ρ) = mass (m)  ÷  volume (V)                [g/cm³ = kg/dm³ = t/m³]

Statements concerning the concentration of chemicals must always go together with statements of temperature (ρ20 = concentration at 20°C).

Textile fibres absorb certain amounts of humidity depending on air moisture. For accurate determination of density it is therefore necessary to indicate the absorbed amount of moisture. 

fibrous material concntration in kg/dm³
at 0% humidity at 65% humidity
Polyacrylonitrile (PAC) 1,17  1,15 
Wool (Wo) 1,30  1,31 
Silk (Ms) 1,34  1,34 
Polyvinyl chloride (PVC) 1,40  1,38 
Viscose (CV) 1,52  1,49 
Cotton (Co) 1,55  1,53 

Source: SI - Systeme