The **partial specific volume** **
v
i
¯
,
** express the variation of the extensive volume of a mixture in respect to composition of the masses. It is the partial derivative of volume with respect to the mass of the component of interest.

V
=
∑
i
=
1
n
m
i
v
i
¯
,
where
v
i
¯
is the partial specific volume of a component
i
defined as:

v
i
¯
=
(
∂
V
∂
m
i
)
T
,
P
,
n
j
≠
i
.

The PSV is usually measured in milliLiters (mL) per gram (g).