Abstract
The generation of controlled atmospheres composed of mixtures of gases and liquids from a single pressurized gas cylinder is very difficult, yet logistically desirable. An equal mixture of the hydrocarbons n-butane, isobutane, n-pentane and isopentane was pressurized to 250 p.s.i.g. with nitrogen in a gas cylinder. The four-component mixture was taken from the cylinder as a liquid to a heated microvalve where all components underwent a simultaneous liquid to gas phase change. The resultant vapor was drawn through a heated delivery line maintained at a negative partial pressure to the mixing turret of a one cubic meter inhalation chamber. In this manner, the concentrations of total hydrocarbons and the relative make-up of the components were kept constant. The functional operation of the system was confirmed during the conduct of a three-week inhalation toxicity study at target concentrations of 0.11, 1.11, and 11.11 mg/L. The actual analytical concentrations were within 9 percent of the target values with standard deviations of less than 8 percent of the means.