Biomedical Engineering Reference
In-Depth Information
8.12 Mixture Rule
If a diluted solution shall be made from a higher concentrated
solution and a lower concentrated one, or if you want to know which
concentration a substance has after mixture of two solutions, the
mixture rule is a simple and fast method to calculate the required
data.
If the difference of densities of the solution is relatively high,
you obtain better results if using densities of participating solutions
instead of concentrations.
The mixture rule expressed as an equation is:
=
=
V
1
F−S
2
and
V
2
S
1
−F
S
1
: starting concentration of the more concentrated solution; S
2
:
starting concentration of the less concentrated solution; F: wanted
final concentration; V
1
: needed volume of the more concentrated
solution; V
2
: needed volume of the less concentrated solution
How many volumes of a 37% hydrochloric acid (starting con-
Example
centration S
1
HCl = [HCl] = 37%) have to be mixed with volumes
of water (starting concentration S
2
[HCl] = 0%) to get a 10% hy-
drochloric acid? (It is more precise to take the densities instead of
concentrations, especially when there is a high difference in specific
gravity as shown in this example.)
Result
37
10
10
1.180
0.047
1.047
and
0
27
1.000
0.133
concentration
density
Ten volumes of 37% HCl (V
1
)havetobemixedwith27vol.ofwater
(V
2
) (from density: 28.3 vol.).
