Effect of the Absorbance of a Flowing Liquid on the Error of the Refractive Index Measured with a Differential Refractom
- PDF / 696,420 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 79 Downloads / 174 Views
INEAR OPTICS
Effect of the Absorbance of a Flowing Liquid on the Error of the Refractive Index Measured with a Differential Refractometer V. V. Davydova, * and A. V. Moroza aSt.
Petersburg Polytechnic University, St. Petersburg, 195251 Russia *e-mail: [email protected]
Received April 8, 2020; revised April 8, 2020; accepted May 20, 2020
Abstract—We determined the factors that affect the measurement error of the refractive index n in a flowing liquid (a change in its absorbance and temperature). When a flow-through differential refractometer is used to measure the refractive index of a flowing liquid, the error in measuring is additionally affected by the scattering of radiation in the cell converter and the wedge shape of the cell glasses. A new differential refractometer is developed designed for studying the effect of the absorbance of a flowing liquid on the measurement error of the refractive index. New results are obtained confirming this effect, and a new procedure for compensating it is proposed. Keywords: refractive index, flowing liquid, differential refractometer, measurement error DOI: 10.1134/S0030400X20090076
INTRODUCTION Monitoring of the state of liquid media flowing in pipelines of various diameters is among the most difficult tasks solved by spectroscopy [1–6]. The performed measurements should not make irreversible changes in the physical structure or chemical composition of the liquid. Therefore, noncontact methods are more preferable [5–9]. Among them, the methods based on the use of refraction [10–14] and nuclear magnetic resonance (NMR) [15–19] have the greatest advantages. The refraction method, unlike NMR, enables the monitoring of the state of both stationary and flowing liquid with one instrument, in addition to ensuring the sterility of the measuring process. The refractive index n is the main parameter by which the state of the medium is monitored. The measurement accuracy of the refractive index should be 10–4 or smaller to solve new problems in scientific research, determine the presence of impurities in the medium, or control the state of the technological process, for example, in the pharmaceutical industry [20–23]. This error value includes all adverse factors and possible measurement errors that arise for various reasons. The most difficult problem that should be solved to ensure the specified level of measurement error is to lower the effect of absorbance of the flowing liquid on the result of the determination of n. In refractometers where the liquid is in a stationary state upon measuring the refractive index, various compensation circuits are used, which makes the effect of a change in the absorbance of the liquid on the measurement error of n insignificant.
When examining a flowing liquid, compensation devices can only be used if the refractometer is built according to a differential scheme [20–25]. Depending on the design types of flow-through differential refractometers, the effect of various errors on the measurement result may either increase or decrease. In earl
Data Loading...
