# An Analytical Method for Gas Flow Measurement Using Conservative Chemical Elements
## 1 Introduction  
The qualitative and quantitative analyses of gas components generated during chemical reactions provide information for estimating the reaction mechanism [1; 2; 3]. However, previous studies have not reliably determined the flow rate, but rather have estimated the reaction mechanism through simple concentration analysis [2]. Although various types of flow meters can be applied to determine the gas flow rate, obtaining more reliable information is limited due to the issue of gas composition change following the generation of various types of gases during the reaction process.  
In general, gas flow rates are measured by utilizing the differences in volume, pressure, and mass while taking into account the characteristics of each fluid. Although the volumetric method is simple, obtaining precise measurements is difficult because physical properties of the fluid may change depending on the density, temperature, and pressure. Temperature or pressure correction may be applied as necessary, but additional devices required for correction may complicate the system and increase the number of variables for the measurement. Flow measurement based on mass uses direct measurement of the mass of the target gas, which does not require complex calculations and can be applied without correction for changes in fluid properties. For this reason, a mass flow meter (MFM) is universal throughout the industry. An MFM provides a calculated value based on the mass of the target gas, and for gas mixtures made up of two or more gases. Reliable flow rate information can be obtained only when corrected with the known gas compositions and mixing ratio. However, it is practically impossible to estimate the change in the gas mixingratio because of the amount of byproduct gas generated in the actual chemical reaction. Because the composition of the byproduct gas changes depending on the degree of reaction, it is difficult to obtain reliable information on the flow rate in the mass value of the target gas using an MFM.  
A conservative element is a stable chemical species that does not participate and undergo a chemical change during a reaction [4; 5]. In the gas phase, the species are collectively referred to as inert gases, which are nitrogen (N\({}_{2}\)), argon (Ar), and helium (He). For this reason, we can use the species as a tracer for the reaction process. Many tracer studies using conservative chemicals have been conducted intensively in the area of water quality [6; 7; 8; 9]. Regarding Reference [8], stream flows were calculated by utilizing water quality data, and it was confirmed that the estimation of the stream flows with an error range of within \(\pm\)9% was possible compared with the physical method based on Cl\({}^{-}\), which has conservative behavior in the water. In addition, [PERSON] and [PERSON] [7] and [PERSON] et al. [9] also estimated the degree of freshwater influence in river mouth regions using dissolved aluminum and salt. Although studies on the applicability of conservative chemical species to measure flow rate and pollutants in water environments have been reported, no tracer studies have been conducted using these chemical species in the gas phase.  
In the chemical reaction, the concentration of these conservative gases is determined only by dilution with the byproduct gas produced during the reaction process. In this study, an accurate gas flow method was applied by monitoring the concentration of the conservative gas emitted during the reaction process. From the results of this study, we intend to suggest a new method to provide reliable flow rate information by overcoming the limitations of the mechanical flowmeters. Using this method, we aim to (i) reliably measure the flow rate regardless of the number of byproduct gas components and gas composition ratio; (ii) measure the flow rate in a wide range regardless of the flow rate of the gas generated; and (iii) build a simple process by calculating the gas flow rate without applying an MFM.