Columns 7-14 contain the composition of the saline compounds of the elements, placed according to their forms, RX, RX_{2} to RX_{8} (in the 14^{th} column). If the element R has a metallic character like H, Li, Be, &c., then X represents Cl, NO_{3}, 1/2 SO_{4}, &c., haloid radicles, or (OH) if a perfect hydrate is formed (alkali, aqueous base), or 1/2 O, 1/2 S, &c. when an anhydrous oxide, sulphide, &c. is formed. For instance, NaCl, Mg(NO_{3})_{2}, Al_{2}(SO_{4})_{3}, correspond to NaX, MgX_{2}, and AlX_{3}; so also Na(OH), Mg(OH)_{2}, Al(OH)_{3}, Na_{2}O, MgO, Al_{2}O_{3}, &c. But if the element, like C or N, be of a metalloid or acid character, X must be regarded as (OH) in the formation of hydrates; (OM) in the formation of salts, where M is the equivalent of a metal, 1/2 O in the formation of an anhydride, and Cl in the formation of a chloranhydride; and in this case (_i.e._ in the acid compounds) Z is put in the place of X; for example, the formulæ COZ_{2}, NO_{2}Z, MNO_{2}Z, FeO_{2}Z_{2}, and IZ_{3} correspond to CO(NaO)_{2} = Na_{2}CO_{3}, COCl_{2}, CO_{2}, NO_{2}(NaO) = NaNO_{3}, NO_{2}Cl, NO_{2}(OH) = HNO_{3}; MnO_{3}(OK) = KMnO_{4}, ICl, &c. The 15th column gives the compositions of the peroxides of the elements, _taking them as anhydrous_. An asterisk (*) is attached to those of which the composition has not been well established, and a dash (--) shows that for a given element no peroxides have yet been obtained. The peroxides contain more oxygen than the higher saline oxides of the same elements, are powerfully oxidising, and easily give peroxide of hydrogen. This latter circumstance necessitates their being referred to the type of peroxide of hydrogen, if bases and acids are referred to the type of water (see Chapter XV., Note 7 and 11 bis). The 16th column gives the composition of the lower hydrogen compounds like N_{3}H and Na_{2}H. They may often be regarded as alloys of hydrogen, which is frequently disengaged by them at a comparatively moderate temperature. They differ greatly in their nature from the hydrogen compounds given in columns 1-4 (_see_ Note 12).