Today in 1995, US Patent 5473161 A was issued, an invention of John A. Nix, Stephen W. Zagarola, and Louis Jolie, for their “Method for Testing Carbonation Loss from Beverage Bottles using IR Spectroscopy.” Here’s the Abstract:

A method for measuring carbonation loss in beverage bottles and predicting shelf-life thereof utilizes infrared (IR) absorption spectroscopy. The concentration of CO2 gas in a bottle being tested is measured with an infrared beam according to Beer’s Law. In one embodiment the CO2 gas measured is in the headspace of a test bottle partially filled with carbonated water. The walls of the bottle are clamped in a fixture to maintain the bottle diameter substantially constant. An IR beam is transmitted through the bottle just below the fixture, and absorption values of the beam are measured. Shelf-life is calculated from the absorption values. In another embodiment the test bottle is filled with compressed CO2 gas generated by dry ice placed in the bottle.