Use Boyle's Law and Charles' Law to work out the constant factor, then use that to solve for the volume and find the density.
Assume you have 1 L of gas. The mass of gas will therefore be 0.457 g.
652 torr = 652/760 atm, 50°C = 323.15K, and -45°C = 228.15K.
pV/T is constant. [(652/760)×1]/323.15 = 0.00265 atm L K^-1.
Now (4.75×V)/228.15 = 0.00265, so V = 0.127 L.
This will still weigh 0.457 grams. Therefore, the density will be 0.457/0.127 = 3.598 g/L