Least squares fit
weight = [75.94 +-0.09] + air pressure X [0.183 +- 0.005] gm
For an air pressure of 14.7 psig excess wt is 0.183 X 14.7 gm
= 2.69 gm for 2.124 liters
= 1.266 gm/liter This is fairly respectable.
Major uncertainty was the volume of the bottle.