| The refractive index (RI) and diffusion coefficient (DC) of liquids are the fundamental data in Physics, Chemistry, Chemical Engineering and Biology Engineering. The dissertation aims at the study on the new measurement methods of the RI and DC of liquids. A new method for measuring the RI of micro-quantity liquid by using transparent capillary is elaborated, which is characterized by a micro-quantity liquid and spatial resolution. To measure the RI of liquid more accurately, a symmetric liquid-core-zoom cylindrical lens has been fabricated, with the sensitivity of RI of the measurement system further improving. Based on the method for measuring RI of liquid with a capillary, the approach of measuring the RI of a capillary wall without destruction is introduced by filling a standard liquid in the capillary, of which the accuracy of measurement under paraxial and non-paraxial conditions are analyzed, and which makes up the blank of this field. The spatially resolving ability of the capillary in measuring RI of liquid is utilized to observe and record diffusive process directly, the transparency capillary is used as both diffusive pool and imaging element, a novel method for measuring the DC of liquid is successfully invented. In order to measure the DC more accurately, an asymmetric liquid-core zoom cylindrical lens has been designed and fabricated, in which the spherical aberration can be ignored, and which has been achieved the measurement of DC of liquid with slight range of RI.The main research contents and results of the dissertation are consisted of five aspects as following:First of all, the measurement of RI of micro-quantity liquid is realized by using a capillary. Based on imaging principle of a coaxial spherical surface optical system, the function between the focal length of optical system and the RI of the liquid is deduced, and two methods, i.e. the focusing method and imaging method of capillary, have been designed to measure the RIs of some kinds of liquid are measured at room temperature. The measurement accuracy of0.001is achieved, and the liquid amount is less than0.0015ml, which is one percent of the amount with the common instrument (Abbe Refractometer). In order to improve the accuracy of the measuring system and the stability of the measured data, virtual-real imaging method is presented, which reduced the errors of the system caused by shaking. The relationship between depth of field and sensitivity and the relationship between radii of capillary and the accuracy of RI are analyzed.Secondly, a symmetric liquid-core zoom cylindrical lens has been designed and fabricated to measure RI of liquid more accurately, which solves two problems in capillary imaging method, i.e. the sensitivity of RI is not so higher (the minimum resolved RI～0.001) due to a short focal length (≤2.35mm), and the depth of field is large caused by a narrow light source width (limited in the range of capillary diameter). Due to an improved sensitivity in measuring RI and a short depth of field in the measurement system, a high accuracy in measurement of RI is ensued, which is better than0.0002.Thirdly, a method for measuring the RI of transparency capillary without destruction is invented, which calibrated the position of the axis of capillary by using the standard liquid samples. The capillaries with same material and different diameter size have been measured and the influence on measurement accuracy of the size of capillary is analyzed. The measurement accuracy of RI is better than0.005, which can meet the request of general scientific research and experiment. To make the calculative method for RI of capillary tube more convenient and accurate, reduce the effects of the spherical aberration and the depth of field on the measurement results, we developed the method in non-paraxial condition.Fourthly, a new technology for measuring the DC of liquid is invented by using a transparent capillary, which is characterized by faster measurement (～1h) and observing diffusion process directly. The analytical solution of DC has been expressed as Gauss error function based on the Fick second law. Two methods, i.e."equivalent the RI of thin layer" and "fixed an observation height" are presented, the diffusion process of pure glycerol in water is investigated by using the two methods.Finally, the DC has been measured accurately by using an asymmetric liquid-core zoom cylindrical lens. When water is filled within the core area of the lens, the spherical aberration of the used measurement system is less than0.02jum and the measurement accuracy is1.7×10-5RIU. In the method of "equivalent the RI of thin layer", we get the DC from recording the position of layer with fixed RI as time increases, and verify that the selection of RI of the thin layer is unrelated to the measurement result of DC. In the method of "fixed an observation height", we have discussed the relationship between the height and the calculation error of DC. Through measuring the DC values in different ethylene glycol (EG) concentrations, finding the simulated formula between DC values and EG concentrations, making a limit of the concentration to zero from the formula, the DC value (1.069×10-5cm2/s) of EG at infinite dilution solution at25℃is obtained with the relative error8.6%. This method may open a new way to measure DC of liquid quickly at the condition of infinite dilution solution. |
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