Liquor potassae has been used in croup both locally and internally. Certainly it will dissolve fibrinous membrane outside the body, and to some, but not to a great, extent may be available in the form of spray (1/2 or 1 dr. to 1 oz. of water). It has been compared to mercury in its constitutional effect of fluidifying secretion and of promoting absorption, but it acts too slowly to be depended upon for so acute a malady as croup. Iodide of potassium is more effective, and the acetate of potash seems to have sometimes acted well. The bichromate I have occasionally used locally and internally, with excellent effect, in true membranous croup.