These include calomel (mercurous chloride), and mercuric chloride. There was some controversy over the sublimation of calomel. Precipitation also tended to form very pure calomel salts. Most of the calomel ingested will be excreted through urine and stool. Depending on how calomel was administered, it affected the body in different ways. They learned how calomel worked through trial and error. The reference electrode may be a silver chloride electrode or a calomel electrode. Anecdotal evidence indicates calomel was more effective than bleeding. Opponents believed that the repeated sublimation made calomel lose some of its therapeutic ability. Many argued that the more times calomel was sublimed, the purer it got. For environmental reasons it has widely replaced the saturated calomel electrode. Reference electrodes generally used are hydrogen electrodes, calomel electrodes, and silver chloride electrodes. When calomel first started being manufactured it was done through sublimation. In 1788 pharmacist Carl Wilhelm Scheele came up with the mechanism to make precipitated calomel. Powdered forms of calomel were much more toxic, as their vapors damaged the brain.