If 500 ml of mineral oil are used to prepare a liter of mineral oil emulsion, how many grams of the oil, having a specific gravity of 0.87, would be used in the preparation of 1 gallon of the emulsion?

We know that

1 gallon = 3.78541 L

1000 ml = 1.0 L

Density = mass / volume

Mass = volume * density

Therefore

(3.78541 L emulsion) x (500 mL oil / 1 L emulsion) x (0.87 g/mL oil) = 1647 g oil

Density = 0.87 g / ml

Because the density of water = 1.0 g / ml