Fig. 5. Measured viscosities for MA/sucrose particles as a function of RH with associated fit and error envelope (see Tables S1 and S2 for further information†). Data points are colour coded according to the MA mass fraction of total solute in the final droplet at coalescence (blue > 0.09, red < 0.04). The red dashed line is a fit to the aqueous sucrose data presented in ref. 22, with associated error envelope. The grey envelope (with black dashed line set to a value of 2.5 mPa s) represents the viscosity of an aqueous-MA solution at a mass fraction of 0.40.49 Black unfilled circles are measured viscosities for aqueous citric acid droplets with the associated parametrisation shown by the dashed black line. The inset (a–d) shows sequential brightfield images during coalescence of two MA/sucrose particles at an RH of 42% with a time step of 0.015 s between frames.