Abstract: A process for the preparation of an aqueous slurry of a water-insoluble azo compound which comprises continuously mixing together, in a reaction zone from which the slurry is continuously removed, a first stream containing a diazonium compound resulting from the diazotization of a heterocyclic or weakly basic benzenoid amine in an acid medium, hereinafter referred to as the diazo component, and a second stream containing a compound capable of coupling with the diazo component under the conditions existing in the reaction zone to form a water-insoluble azo compound hereinafter referred to as the coupling component.

Abstract: A process for the diazotization of a heterocyclic or a weakly basic benzenoid amine which comprises reacting together in a continuous manner, in a reaction zone from which a product stream containing diazotized amine is continuously removed, the amine and an aqueous solution of nitrite ions in the presence of sulphuric acid, the proportions and concentrations of the amine, the aqueous solution of nitrite ions and the sulphuric acid being so arranged as to provide a working acid concentration in the reaction zone in which the diazotized amine is stable.

Abstract: Method for detecting the presence of a substance contained in a fluid medium, which medium also contains particulate matter therein, comprising the addition of at least a portion of the fluid medium to a leaf material capable of separating by diffusion the fluid medium from the particulate matter and examination, using instrumental detection means, for the presence of the substance contained in the fluid medium in a detection area on the leaf material to which the fluid medium has diffused away from the particulate matter. Apparatus for performing the method where the fluid is a liquid is also described.