THE PERIODIC LAW 151 



maximum valency of the elements toward oxygen is indicated 

 throughout by the Roman numeral of each group, omitting 

 the "peroxides," in which the oxygen appears to be linked in 

 a different manner. 



Maximum valency toward hydrogen in stable volatile compounds: 



Univalent: VII; 2, 3, 5, 7; powerfully acid hydrogen compounds. 



Divalent: VI; 2, 3, 5, 7; faintly acid hydrogen compounds. 



Trivalent: V; 2, 3, 5, 7; basic acid hydrogen compounds. 



Quadrivalent: IV; 2, 3, 5; neutral acid hydrogen compounds. 

 Maximum number of hydroxyls in basic compounds : 



One: I; 1, 2, 3, 6, 8. Ill; 11. VIH; 6 (c and d). 



Two: II; 2, 4, 6, 8, 3, 5, 7, 11. IV; 11. VIII; 4 (bed). 



Three: III; 3, 4, 5, 6, 7, 8, 10, 12. V; 11. VII; 4. VIII; 4a. 

 Minimum valency in oxygen acids: 



One: VII; 3, 5, 7. 



Three: V; 2, 3, 5, 7. VI; 3, 5, 7. 



Four: IV; 2, 4, 3, 5, 7, 11. 



Five: V; 4, 6, 10. 



Six: VI; 4, 6, 10. VH; 4. VIII; 4a. 

 Tendency to liberate hydrogen from water below red heat: 



I; 2, 3, 4, 6, 8. II; 2, 3, 4, 6, 8. VIH; 4a. 

 Tendency to liberate oxygen from water: 



VII; 2, 3, 5. 

 Elements whose chlorides are unstable toward water: 



V; 3, 5, 7, 11, 4, 6, 10, 12. VI; 10, 6, 4. 



Elements whose sulphides can be precipitated from dilute acid solu- 

 tion : 



VHI; 4d, 6 (abed), 10 (abed). II; 11, 7. HI; 11, 7. IV; 11, 7, 5. 



V; 11, 7, 5. VI; 12, 10, 6. 

 Ability to form alums with the sulphates of I; 2, 4, 6, 8: 



III; 2, 4, 6, 10. VI; 4. VII; 4. VIII; 4a. 

 Ability to form volatile compounds with organic radicles : 



With one methyl group: I; 3. VII; 2, 3, 5, 7. 



With two methyl groups: H; 3, 5, 7, 11. VI; 2, 3, 5, 7. 



With three methyl groups: HI; 2, 3, 5, 7, 11. V; 2, 3, 5, 7, 11. 



With four methyl groups: IV; 2, 3, 5, 7, 11. 

 Ability to form complex bases with ammonia: 



VIII; 4 (cd), 6 (abed), 10 (abed). VI; 4. II; 3, 11. 

 Consult: Newlands, On the Discovery of the Periodic Law and on Rela- 

 tions Among the Atomic Weights (London, 1884) ; Huth, Das periodische 

 Gesetz der Atomgewichte und das naturliche System der Elemente (Frankfurt 

 a. O., 1884) ; Belar, Das periodische Gesetz und das naturliche System der 

 Elemente (Laibach, 1897); Mendeleeff, "The Principles of Chemistry," in 

 A Library of Universal Literature (New York, 1901); Venable, The Develop- 

 ment of the Periodic Law (Easton, Pa., 1896). 



