Iraqi Journal of Chemical and Petroleum Engineering

The inhibitive action of Phenyl Thiourea (PTU) on the corrosion of mild steel in
strong Hydrochloric acid, HCl, has been investigated by weight loss and potentiostatic
polarization. The effect of PTU concentration, HCl concentration, and temperature on
corrosion rate of mild steel were verified using 2 levels factorial design and surface
response analysis through weight loss approach, while the electrochemical
measurements were used to study the behavior of mild steel in 5-7N HCl at
temperatures 30, 40 and 50 °C, in absence and presence of PTU. It was verified that
all variables and their interaction were statistically significant. The adsorption of
(PTU) is found to obey the Langmuir adsorption isotherm. The effect of temperature
on the adsorption process showed that the adsorption process is exothermic,
spontaneous and represents mixed chemical and physical adsorption for PTU on the
metal surface

Prediction of accurate values of residual entropy (SR
) is necessary step for the
calculation of the entropy. In this paper, different equations of state were tested for the
available 2791 experimental data points of 20 pure superheated vapor compounds (14
pure nonpolar compounds + 6 pure polar compounds). The Average Absolute
Deviation (AAD) for SR
of 2791 experimental data points of the all 20 pure
compounds (nonpolar and polar) when using equations of Lee-Kesler, PengRobinson, Virial truncated to second and to third terms, and Soave-Redlich-Kwong
were 4.0591, 4.5849, 4.9686, 5.0350, and 4.3084 J/mol.K respectively. It was found
from these results that the Lee-Kesler equation was the best (more accurate) one
compared with the others, but this equation is sometimes not very preferable. It was
noted that SRK equation was the closest one in its accuracy to that of the Lee-Kesler
equation in calculating the residual entropy SR
of superheated vapor, but it was
developed primarily for calculating vapor-liquid equilibrium and to overcome this
problem, efforts were directed toward the possibility of modifying SRK equation to
increase its accuracy in predicting the residual entropy as much as possible. The
modification was made by redefining the parameter α in SRK equation to be a
function of reduced pressure, acentric factor, and polarity factor for polar compounds
in addition to be originally function of reduced temperature and n parameter –which is
also function of acentric factor– by using statistical methods. This correlation is as
follows:
  
2
  1 n  ,    
0.34091 4 0.996932 4
0.920338 0.064049 0.370002  
  P  T   P Tr r r r
This new modified correlation decreases the deviations in the results obtained by
using SRK equation in calculating SR when comparing with the experimental data.
The AAD for 2791 experimental data points of 20 pure compounds is 4.3084 J/mol.K
while it becomes 2.4621 J/mol.K after modification. Thus SRK equation after this
modification gives more accurate results for residual entropy of superheated vapor of
pure 20 compounds than the rest of the equations mentioned above.

Poly vinyl alcohol has been studied for its ability to form crystallites by using
annealing method. Semicrystalline films of poly vinyl alcohol (PVA) were prepared
by casting 11.5 wt. % and 13 wt. % PVA aqueous solution onto glass slides at
annealing temperature range 90 -120°C and duration time 15- 60 minute. This
allowed the macromolecules to form crystallites, small regions of folded and
compacted chains separated by amorphous regions where single PVA chain may pass
through several of these crystallites. Degree of crystallinity of PVA films (hydrogels)
was determined by method of density; on the other hand the swelling behavior was
conducted by the determination of water uptake, wet degree of crystallinity, gel
fraction and solubility. The results of PVA films showed that water uptake decreased
with increasing temperature, time of annealing and PVA concentration, while degree
of crystallinity increased, and gel fraction and solubility decreased with increasing
temperature and time of annealing. The maximum dry and wet degree of crystallinity
was 64% and 36% respectively at 120°C and 60 min.

Empirical equations for estimating thickening time and compressive strength of
bentonitic - class "G" cement slurries were derived as a function of water to cement
ratio and apparent viscosity (for any ratios). How the presence of such an equations
easily extract the thickening time and compressive strength values of the oil field
saves time without reference to the untreated control laboratory tests such as
pressurized consistometer for thickening time test and Hydraulic Cement Mortars
including water bath ( 24 hours ) for compressive strength test those may have more
than one day