C.I.42755. Also known as acid Blue 22, China Blue, Soluble Blue B. Widely used as a counter stain, collagen stain, connective tissue stain, and in bacteriological media. Running out of a component in your MasterTech Stain Kit? Replace your used or expiring item by purchasing an individual solution. Components are available in larger sizes to fit your rate of usage. F.W. 737.74 Absorption Max.: 600 nm Visual Transition Interval: pH 10.0 (blue) to pH 13.0 (orange).