1. Convert kilograms per liter to pounds per gallon:

* Kilograms to pounds: 1 kilogram = 2.20462 pounds

* Liters to gallons: 1 liter = 0.264172 gallons

2. Calculate the weight in pounds:

* Density = 1.73 kg/L

* Weight = Density * Volume

* Weight = 1.73 kg/L * 0.264172 gallons/L

* Weight = 0.457 kg/gallon

* Weight = 0.457 kg/gallon * 2.20462 pounds/kg

* Weight ≈ 1.01 pounds/gallon

Therefore, a gallon of a substance with a density of 1.73 kg per liter weighs approximately 1.01 pounds.