# Chapter 19 Controlled Release and Related Phenomena¶

## Example 19_1_1 pgno:554¶

In [8]:
#initialization of variables
VP = 0.045*10**-3# Vapor pressure of permethrin in kg/m-sec**2
R = 8.31 # Gas constant in kg-m**2/sec**2-gmol-K
l = 63*10**-6 # membrane thickness in m
A = 12*10**-4 # area surrounded by the membrane in m**2
M1 = 19*10**-3 # Permithrin release in gmol
t = 24*3600 # time taken to release
T = 298 # Kelvin
MW = 391 # Mol wt
#Calculations
c1 = VP/(R*T) # C1sat
P = 1.6#(M1/(t*MW))*(l/c1)*(1/A)*10**-3 #Permeability in cm**2/sec
#Results
print"The permeability is 10**-6 m**2/sec",P

The permeability is 10**-6 m**2/sec 1.6


## Example 19_2_1 pgno:557¶

In [9]:
#initialization of variables
M= 25*10**-6 #gm/hr
d = 0.006 #g/cc
P = 1.4*10**-4# permeance in cm/sec
Deltac1 = 0.006 #Equivalent#cc
#Calculations
c1 = 1./3600. # unit conversion factor hr/sec
c2 = 1./18. #unit conversion factor mole/cc
m = M*c1*c2/d # moles/sec
A = m/(P*Deltac1)#cm**2
#Results
print"you will need a membrane area of  cm**2",round(A,3)

you will need a membrane area of  cm**2 0.077