The value of various phenomenological coefficients and conversion maxima for oxalic acid/urinary bladder membrane are given in table I & II. The various physical properties are mentioned in table III.

Table I – Values of different phenomenological coefficients, degree of coupling and conversion efficiency for aqueous oxalic acid solution (1991)¹⁰.

(b) Temperature of the system = 35⁰C 0.1⁰C

Table II – Values of different phenomenological coefficients for urine – oxalic acid mixture systems (1992)¹⁵.

(b) Temperature of the system = 35⁰C 0.1⁰C

Table III – Values of various physical properties of urine-oxalic acid mixture

system (1999)¹⁷.

From the tables,  I, II and III following conclusion can be drawn-

1. As the concentration increases, the phenomenological coefficient relating pressure (i.e. I,₁₁) decreases whereas the phenomenological coefficients relating potential gradient (i.e. L₂₂ and L₁₂ and L₂₁) increases for oxalic acid/urinary bladder system.

2. In case of urine-oxalic acid/urinary bladder system, the hydrodynamic permeability (i.e. L₁₁) increases as the concentration of oxalic acid in urine-oxalic acid mixture solution increases; whereas coefficients relating potential gradient (i.e. L₂₂ & L₂₁) decreases with increasing concentration of oxalic acid in mixture solution.

3. The conversion efficiency maxima [n_max] and degree of coupling (q) increases with increasing concentration of oxalic acid for oxalic acid/urinary bladder membrane system. In case of urine-oxalic acid/urinary bladder membrane system, both the coefficients represent a decreasing trend as the concentration of oxalic acid in urine-oxalic acid mixture solution increases.

4. Various physical properties like surface tension, viscosity, density and pH show an increasing trend for oxalic acid system when concentration increases. For urine-oxalic acid mixture solution the surface tension, density and pH decreases with increasing concentration oxalic acid. But the viscosity of mixture solution decreases only up to the 0.004 M concentration of oxalic acid & afterward it shows an increasing trend.

The process of urination can be defined as (a) process of progressive and rapid increases of pressure (b) a period of sustained pressure and (c) return of pressure to the basal tonic pressure of the bladder⁴. In the urinary bladder, urine is collected from the kidney by ureters and this collection of urine is drop by drop. These ureters are tubular structures of smooth muscles and are to prevent back flow of urine when pressure builds up in the bladder during the micturition. As urine collects, the bladder wall gets stretched due to increased pressure. At the time of micturition the contraction of detrusor muscles empty the bladder. During the normal functioning of the bladder, there is a proper generation of micturition waves and micturition reflex. In terms of electro kinetic measurements, the process of urination may be given as follows-

As the pressure develops in the bladder, streaming potential is developed which in turns produce streaming current. The streaming current is probably responsible for micturition waves and finally micturition reflex. At the time of micturition reflex, pressure of bladder becomes almost zero and thus streaming potential and streaming current tends to at a minimum. This is a continuous process and thus phenomena are generative.

In other words, it may be stated that the electrical energy due to streaming potential and streaming current is converted into mechanical action i.e., expulsion of urine in order to overcome the effect of electrical energy on the urinary bladder. Such an action is the combined effect of pressure and electrical potential gradient acting on the membrane. The proper functioning of the bladder means maximum chances of voiding and minimum residual urine in the bladder.

The transport behavior of urine depends upon the constituents of urine. The various constituents of urine affeet the bladder membrane interface and thus proper function and normal generation of micturition waves and micturition reflex. Continuous presence of acidic urine in the bladder ruptures the bladder mucosal layer and increases the adherence of uric acid crystals¹⁶ if present in the urine and thus leads to ineffective functioning of the bladder. The sluggish flushing action of the bladder may allow time for precipitation of crystal from supersaturated urine besides the chances of infection. The proper functioning of the bladder depends upon the interaction of urinary constituents with the urinary bladder membrane. The continued presence of supersaturated urine with oxalic acid leads to its adsorption on the bladder membrane interface. As a result of which it loses its distention power. Since expulsion of urine is related with the conversion of electrical energy into mechanical work, more energy is required to expel urine saturated with stone forming material, the oxalic acid.

This fact is also supported by to values of conversion efficiency maximum [n_max] and degree of coupling (q) given in table II & I. Low values of degree of coupling (q) indicate the less tightly coupled membrane permeant system. The increase of oxalic acid in urine tends to reduce the polarization power of the urinary bladder membrane, which ultimately leads to the formation of urinary calculi in the urinary bladder itself. Although the whole process is quite complex, and urine usually undergoes changes in its composition, measurements of physical properties may be of some help in analyzing the changes taking place.

The density of urine oxalic-acid mixture solution shows a decreasing trend with increasing concentration of oxalic acid. This can be related with osmotic diureter nature of oxalic acid. The viscosity of the solution represents the interaction between solute and solvent. From table III, it is clear that the viscosity of urine-oxalic acid solution decreases only 0.004 M concentration of oxalic acid. And afterward it starts to increase with increasing concentration of oxalic acid.