Abstract: The method of making a glass diffusion cell which utilizes taking of an inner glass tube and forming an enlarged annular flange at one end of this tube and in the sidewall of this tube forming a refilling port and a sampling port. This inner glass tube is then located within an outer glass tube with the end of this outer glass tube that is located directly adjacent the enlarged annular flange being sealed to the inner glass tube. The sidewall of the outer glass tube is then spot heated which permits a refilling tube to be connected to the refilling port and a sampling tube to be connected to the sampling port establishing a fluid interconnection with the interior of the inner glass tube. Inlet and outlet tubes are connected to the sidewall of the outer glass tube which fluidly connect with the annular chamber located between the inner glass tube and the outer glass tube. The bottom wall of both the inner glass tube and the outer glass tube are then sealed.