Monsanto Company

John F Freeman

Mark A Hochwalt

David O Fisher

Macaulay S Feld

Leonard F Laskowski

Gregory J Gervasio

Evan E Thomsen

There is disclosed an improved process for the preparation of phosphorus trichloride wherein elemental phosphorus is caused to react with chlorine. The improvement comprises continuous, high speed analysis of the contents of the reactor whereby the reaction is controlled to produce less phosphorus pentachloride and other by-products. The analysis is performed by a laser Raman spectrometer associated with an optrode having a remotely located probe head and a circulating sampling system to continuously provide fresh sample to the probe head continuously. Also disclosed is apparatus for the automatic control of the reaction by control of the reactant feed to the reactor in response to the on-line, continuous analysis of the reactor contents.

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Webster Groves, MO, United States of America

John F Freeman