HOEHNEL'S REAGENT

Solution 1: 1 gram of potassium iodide dissolved in 100 cc. of water, and iodine added in excess. Solution 2: 20 cc. of glycerol are mixed with 10 cc. of water. To this cold solution are added 30 cc. of concentrated sulphuric acid. The fibre is first treated with Solution i, the excess of reagent is removed with filter paper, and after one or two minutes Solution 2 is applied.