28 Travsactions. 



10 c.c. bleacliing-poM'der solution ; 5 c.c. cobalt-nitrate, 0-000156 N ; 

 and 5 c.c. aqueous solution of the compound investigated. 



The experiments in most cases lasted twenty minutes. Twenty-seven 

 compoimds, including acids, alkalies, oxidizing and reducing agents, and 

 salts, were tried. 



Summary of Eesults. 



1. Acids accelerate the evolution of oxygen, and this effect is proportional 

 to the concentration of the hydrogen ion. 



Example : 5 c.c. of 0-02 N hydrochloric acid added to the cobalt-nitrate 

 solution doubled the velocity (from K = 0-0063 to K = 0-0141). In case 

 of oxalic acid, 5 c.c. of 0-01 N acid had a slight retarding effect, whereas 

 5 c.c. of 0-02 N acid doubled the velocity as with other acids. This sug- 

 gests some changes in the oxalic acid at great dilution. 



2. Alkahes retard. The action is proportional to the concentration of 

 the hydroxyl ions, and is forty times as great as that of the acids. 5 c.c. of 

 0-0005 N alkali halves the velocity. 



3. Salts of the alkalies were practically without effect, even in relatively 

 strong solutions — e.g., 5 c.c. of N potassium-chloride had no very appreci- 

 able effect. 



4. Salts of the heavy metals either accelerate or retard. 



5. Copper-sulphate accelerates greatly. 5 c.c. of N copper-sulphate 

 evolves chlorine plentifully. 5 c.c. of 0-001 N solution doubles the velocity. 



5. Reagents such as sodium-sulphide, which, like the alkalies, preci- 

 pitate the cobalt, retard the evolution of oxygen. 



6. Oxidizing agents, such as ferric chloride and potassium-dichromate, 

 gave no uniformity of action ; their effects, also, were not proportional to 

 their concentrations. 



7. Nickel and iron salts are similar in their action on bleaching-powder 

 to cobalt-salts, the effect of nickel being about equal to that of cobalt, while 

 iron has only about 1 J per cent, of the effect of cobalt. 



8. It is impossible to judge from the chemical analogues of a particular 

 metal whether it will accelerate or retard the cobalt reaction. 



No record of previous quantitative work bearing on this subject could 

 be found in the " Journal of the Chemical Society," " Comptes Rendus," 

 " Zeitschrift fiir Physikalische Chemie," and " Journal of Physical 

 Chemistry." 



