you can check to see if it's really pure gas you're getting with some food coloring.
mix a small quantity of any color with water, take a small bottle of the suspect gas and add some of the coloring. agitate. when it settles, there should be a definite meniscus between the gas and colored water if it's pure gas. if it's E90 it will change color entirely, as the food color solution will absorb into the ethanol component.
sometimes you can see tiny purple fishes laughing in the deep blue ethanol
