806 PRINCIPLES OF CHEMISTRY 



district of the Government of Kutais and at Nicopol on the Dnieper 

 are particularly rich. A large quantity of the ore (as much as 100,000 

 tons yearly) is exported from these localities. 



Thus manganese gives oxides of the following forms MnO, 

 manganous oxide, and manganous salts, MnX 2 , corresponding with the 

 base, which resembles magnesia and ferrous oxide in many respects ; 

 Mn 2 3 , a very feeble base, giving salts, MnX 3 , analogous to the 

 aluminium and ferric salts, easily reduced to MnX 2 ; MnO 2 , dioxide, 

 generally called peroxide, an almost indifferent Oxide, or feebly acid ; 18 

 MnO 3 , manganic anhydride, which forms salts resembling potassium 

 sulphate ; I8dis Mn 2 O 7 , permanganic anhydride, giving salts analogous 

 to the perchlorates. 



All the oxides of manganese when heated with acids give salts, MnX 2 , 

 corresponding with the lower grade of oxidation, manganous oxide, 

 MnO. Manganic oxide, Mn. 2 O 3 , is a feebly energetic base ; it is true 

 that it dissolves in hydrochloric acid and gives a dark solution con- 

 taining the salt MnCl,, but the latter when heated evolves chlorine 

 and gives a salt corresponding with manganous oxide MnCl 2 i.e. at 

 first: Mn 2 O 3 + 6HCl==3H 2 O + Mn 2 Cl 6 , and then the- Mn 2 Cl 6 decom- 

 poses into 2MnCl 2 -rCl 2 . None of the remaining higher grades of 

 oxidation have a basic character, but act as oxidising agents in the 

 presence of aiids, disengaging oxygen and passing into salts of the lower 

 grade of oxidation of 'manganese, MnO. Owing to this circumstance, 

 the manganous salts are often obtained ; they are, for instance, left in 

 the residue when the dioxide is used for the preparation of oxygen and 

 chlorine. 19 



18 The name 'peroxide' should only be retained for those highest oxides (and MnO 2 

 stands between MnO and MnOs) which either by a direct method of double decomposition 

 are able to give hydrogen peroxide or contain a larger proportion of oxygen than the 

 base or the acid, just as hydrogen peroxide contains more oxygen than water. Their 

 type will be H 2 O 2 , and they are exemplified by barium peroxide, BaO 2 , and sulphur 

 peroxide, S 2 O 7> &c. Such a dioxide as MnO 2 is, in all probability, a salt that is, a 

 manganous manganate, MnO 3 MnO, and also, as a basic salt of a feeble base, capable of 

 combining with alkalis and acids. Hence the name of manganese peroxide should 

 be abandoned, and replaced by manganese dioxide. PbO 2 is better termed lead dioxide 

 than peroxide. Bisulphide of manganese, MnS 2 , corresponding to iron pyrites, FeS.j, 

 sometimes occurs in nature in fine octahedra (and cube combinations), for instance, in 

 Sicily ; it is called Hauerite. 



18 bis On comparing the manganates with the permanganates for example, K 2 MnO.j 

 with KMnO 4 we find that they differ in composition by the abstraction of on<* equivalent 

 of the metal. Such a relation in composition produced by oxidation is of frequent 

 occurrence for instance, K 4 Fe(CN) 6 in oxidising gives K 3 Fe(CN) 6 ; H 2 S0 4 in oxidising 

 gives persulphuric acid, HSO 4 , or H 2 S 7 O 8 ; H^O forms HO or H 2 O 2 , &c. 



w In the preparation of oxygen from the dioxide by means of H 2 S0 4 , MnSO 4 is 

 formed ; in the preparation of chlorine from HC1 and MnO a , MnClj is obtained. These 

 two manganous salts may be taken as examples of compounds MnX-z. Manganoua 

 sulphate generally contains various impurities, and also a large amount of iron salt 



