~Oxidizing properties of the permanganates.~ The permanganates are remarkable for their strong oxidizing properties. When used as an oxidizing agent the permanganate is itself reduced, the exact character of the products formed from it depending upon whether the oxidation takes place (1) in an alkaline or neutral solution, or (2) in an acid solution. 1. _Oxidation in alkaline or neutral solution._ When the solution is either alkaline or neutral the potassium and the manganese of the permanganate are both converted into hydroxides, as shown in the equation 2KMnO_{4} + 5H_{2}O = 2Mn(OH)_{4} + 2KOH + 3O. 2. _Oxidation in acid solution._ When free acid such as sulphuric is present, the potassium and the manganese are both changed into salts of the acid: 2KMnO_{4} + 3H_{2}SO_{4} = K_{2}SO_{4} + 2MnSO_{4} + 3H_{2}O + 5O. Under ordinary conditions, however, neither one of these reactions takes place except in the presence of a third substance which is capable of oxidation. The oxygen is not given off in the free state, as the equations show, but is used up in effecting oxidation. Potassium permanganate is particularly valuable as an oxidizing agent not only because it acts readily either in acid or in alkaline solution, but also because the reaction takes place so easily that often it is not even necessary to heat the solution to secure action. The substance finds many uses in the laboratory, especially in analytical work. It is also used as an antiseptic as well as a disinfectant. CHROMIUM ~Occurrence.~ The ore from which all chromium compounds are made is chromite, or chrome iron ore (FeCr_{2}O_{4}). This is found most abundantly in New Caledonia and Turkey. The element also occurs in small quantities in many other minerals, especially in crocoisite (PbCrO_{4}), in which mineral it was first discovered. ~Preparation.~ Chromium, like manganese, is very hard to reduce from its ores, owing to its great affinity for oxygen. It can, however, be made by the same methods which have proved successful with manganese. Considerable quantities of an alloy of chromium with iron, called ferrochromium, are now produced for the steel industry. ~Properties.~ Chromium is a very hard metal of about the same density as iron. It is one of the most infusible of the metals, requiring a temperature little short of 3000 deg. for fusion. At ordinary temperatures air has little action on it; at higher temperatures, however, it burns brilliantly. Nitric acid has no action on it, but hydrochloric and dilute sulphuric acids dissolve it, liberating hydrogen. ~Compounds containing chromium as a base-forming element.~ While chromium forms two series of salts, chromous salts are difficult to prepare and are of little importance. The most important of the chromic series are the following: Chromic hydroxide Cr(OH)_{3}. Chromic chloride CrCl_{3}.6H_{2}O. Chromic sulphate Cr_{2}(SO_{4})_{3}. Chrome alums