import numpy
import matplotlib.pyplot as plt
import ammonia_props
amm = ammonia_props.AmmoniaProps()

0.8**20

0.011529215046068483

def bracket_p_min(x, p_low=0.002, p_high=0.2, max_iter=10):
    for i in range(max_iter):
        p = 0.5 * (p_low + p_high)
        try:
            state=amm.props2(x=x,P=p,Qu=0)
            # This p is valid, so reduce the upper bracket
            p_high = p
        except:
            # This p is invalid (too high), so set as lower bracket
            p_low = p
            
    return (p_low, p_high, state)

x_range = numpy.linspace(0,1,1001)
p_min = numpy.empty_like(x_range)
p_min.fill(numpy.nan)
t_out = p_min.copy()
for i, x in enumerate(x_range):
    p_low, p_high, state = bracket_p_min(x)
    p_min[i] = p_low
    t_out[i] = state.T

print(p_min.max())
p_above = p_min.max() * 1.1
t2 = amm.props2v(x=x_range,P=p_above,Qu=0,out='T')

0.0058671875

fig=plt.figure(figsize=(4,6))
ax1=fig.add_subplot(211)
#plt.xlabel('Ammonia mass fraction')
plt.ylabel('Minimum pressure (bar)\nbefore function fails')
plt.plot(x_range,p_min,'.')
ax2=fig.add_subplot(212,sharex=ax1)
#ax2 = ax1.twinx()
plt.xlabel('Ammonia mass fraction')
plt.ylabel('Temperature (K)\nof saturated liquid (Qu=0) ')
plt.plot(x_range,t_out,'.',label='At min pressure')
plt.plot(x_range,t2,'-',label='At p={:g} bar'.format(p_above))
plt.legend()
plt.show()

So, on my desktop, for any pressure no less than about 0.177957 bar, we can evaluate the liquid state for all x. But on the laptop, we can evaluate the function across the entire domain for any pressure down to about 0.00586719. That indicates a significant problem with evaluation on the desktop.