In an embodiment, a continuous method of forming a bisphenol A oil comprises forming the bisphenol A oil by mixing a molten bisphenol A and water; wherein the bisphenol A oil comprises 10 to 30 wt % water based on a total weight of the bisphenol A oil and is at a temperature of 100 to 140° C.; flowing at least a portion of the bisphenol A oil through an inline densitometer and measuring a real-time density and a real-time temperature of the bisphenol A oil; determining a real-time concentration of the bisphenol A oil based on said real-time density and said real-time temperature.