Abstract: This invention is an ethanol sensitive solid useful for the colorimetric determination of ethyl alcohol in human breath samples. The solid is prepared by wetting silica gel with an acidic solution of a chromium(VI) salt and then heating to substantially dehydrate the material. The solid so prepared will change color from a deep orange to blue-green in the presence of alcohol. By packing the solid into a transparent tube and passing a known volume of breath sample through it, the blood alcohol content of the user may be estimated by measuring the color-changed portion of the packed tube.