Patent ID: 7314582
Filing Date: 2008-01-01
Classification: G01N

Abstract:
1. Method of producing a lanthanide-halide based humidity indicator comprising: a. preparing an aqueous hydrohalide solution at least partially saturated with a free halogen; b. mixing said aqueous hydrohalide solution with lanthanide containing compound forming an acidic lanthanide-halide solution; c. evaporating the lanthanide-halide solution until it changes color forming a lanthanide-halide based humidity indicator; d. said evaporated lanthanide-halide based humidity indicator has the formula of AB e. whereby said aqueous hydrohalide is comprised of aqueous HBr and said step of preparing an aqueous hydrohalide solution comprises adding free halogen in a sufficient amount to said aqueous hydrohalide solution whereby said hydrohalide solution has an optical density between 0.1-2.0 per cm of pathlength at 500 nm; f. said lanthanide-halide solution has a pH of four or lower; and