Liviana et al. used three experimental measurement techniques and various theoretical calculation methods to quantify the viscosity of the ammonium nitrate-sucrose-water ternary aerosol systems and estimate the characteristic internal mixing times of such systems. Overall, the study data is comprehensive, the research methods are abundant, the discussions are detailed, and the scientific reliability is high. However, some discussion can be added:

1. Lines 249-253: The discussion in the manuscript attributed the differences in viscosity measurement to the volatilization of NH4NO3. While this is a possible reason, the volatilization of ammonium nitrate at room temperature causing changes in the OIR is unlikely to generate such a significant viscosity error (the OIR may increase from 1:1 to close to 2:1, but is unlikely to increase to 4:1 as in the experimental conditions in Figure 4). It is suggested to add a discussion on systematic errors between optical tweezers and the measurement methods in the manuscript, as well as the influences of suspension droplets and bulk phase solutions on viscosity measurements in this part of the discussion.
2. Line 365-371: Based on the data presented in the manuscript, the method of estimating the viscosity of mixed particles using a mole-fraction-based mixing rule is indeed more reliable. Furthermore, it is expected that the authors will add a discussion on the following topics in the conclusion section: The current measurement and estimation methods for aerosol viscosity are actually showing quite large uncertainty (especially the poke-flow method), as shown in Fig. 3 and Fig. 5, where the differences under the same water activity conditions can reach two orders of magnitude. So, does the authors have any recommended measurement and prediction methods in the conclusion section? Or discuss the tolerance levels for quantifying aerosol viscosity?
3. Line 14-17: The authors emphasized that throughout the mid-latitude troposphere, the viscosity of inorganic-organic mixed aerosols is relatively low, and the kinetic limitations of gas-particle partitioning can be ignored. However, the work of this study seems insufficient to support this point of view: First, as the authors have mentioned, if the particle is in the form of an organic coating, the timescale of gas-particle partitioning on a high-viscosity coating is likely to be considered, and such organic-coating particles may be ubiquitous in the troposphere; Secondly, the quantification work of this study is mainly based on nitrate particles, and it can be known from previous viscosity measurement data that nitrate could significantly reduce the viscosity of the mixing system, while other major inorganic salts of aerosols, such as sulfates, may not have such large reducing effect on viscosity (it is recommended that the authors compare the viscosity of nitrate and sulfate aqueous solutions at different water activities). In a word, the results of this study may not represent the actual atmospheric aerosols of various inorganic salts and organic compounds mixtures. It is suggested to soften the statement in the abstract section, which may be too categorical.