Optic method to measure the density of methane

Put forward A new optic method to measure the density of methane. That is, by using the Newton ring structure to build air chamber and chamber for methane under test, and by measuring the differences of the Newton ring interference fringes of the two rooms, the density of methane has been measured. The interference theory of Newton ring has been theoretical analyzed, and a formula which can be used to measure the refractive index of methane is put forward. The parameters of methane density, refractive index and gas thickness have been used in the formula. The results show that the method of Newton ring interference is practical to measure the density of methane.