Abstract: Disclosed is an apparatus and method for verifying the treatment of molten metal wherein a sensing device detects an in situ response resulting from the treatment of the molten metal. The in situ response is compared to a pre-set limit or condition in order to determine whether or not proper treatment of the molten metal has occurred. In particular, the sensing device detects an in situ response resulting from the mixture of a molten metal addition to a molten metal. An electronic transformation device can be used to transform the in situ response into a response data set. The response data set can be transmitted to and received by a microprocessor. The microprocessor can manipulate the response data set. The in situ response to the treatment of the molten metal can be in the form of heat, light intensity, light wavelength, density of smoke particles, composition of smoke particles, mechanical vibration and combinations thereof.