Function Description
********************

	Name: Z_amide_ph 
	Function: f(x) = 1 / (1 + Kex*T1)
	Parameters: kOH kH kH2O T1

Notes
*****

	Amide ph dependence, Olga will provide more notes here.
	This function does not seem to work right now and is
	currently only included for future development. 

C-code for the function
***********************

	b = pow(10.0,-x);
	c = a[1] * pow(10.0,-14) / b;
	d = a[2] * b;
	e = a[3];
	f = c + d + e;
	answer = 1.0 / (1.0 + f * a[0]);