developed a turbidity-based technique to measure the particle size. In this technique, samples have to be taken manually. This process has been automated by a dilution system combined with a flow-through cell. [4] Because this method requires taking samples, it is an online technique.In the current literature (2015), Goldfein and Kozhevnikov [5] combine dilatometry and the turbidity spectrum method to study the kinetics and the mechanism of emulsion polymerization. Turbidity was used here for particle sizing based on the determination of the wavelength exponent in Ångstrøm's equation. They found some contradictions between their results and the classical concepts of emulsion polymerization.There are also some inline monitoring techniques, i.e., methods without sampling or by-passing, which have been described in the literature. Kühn and Tauer [6] investigated the nucleation of emulsifier-free emulsion polymerization by inline monitoring of the optical transmission. Kozempel [7] studied the monomer solution state and particle formation in emulsifier-free emulsion polymerizations. The existence of styrene aggregates in the water phase could be proven by turbidity measurements with forward scattering. Landfester and co-workers [8,9] used turbidity to investigate the emulsification during the preparation of miniemulsions by sonification. In theirThe aim of the present study is to investigate applications of inline turbidity as a tool to monitor optical properties during batch emulsion polymerization and during emulsification with high sample rates. For this purpose, an InPro 8200 turbidity probe with a Trb 8300 transmitter is used in combination with an RC1e Mettler Toledo reaction calorimeter. Reproducible turbidity inline monitoring during emulsification and polymerization is achieved. Turbidity measurements allow the observation of droplet formation as well as the determination of the time needed to reach a certain emulsion state. Therefore, turbidity can be used to optimize the duration of emulsification. Higher stirring speed and longer duration lead to smaller monomer droplets and to faster reaction. Furthermore, inline turbidity can be used to detect the start of the reaction and to identify emulsion stability problems.