196 MESSES. A. V. HAECOURT AND W. ESSON ON THE LAWS OF CONNEXION 



Table II. 



K2 Mn2 Og+SHa Cg O4+IOH2 S O^+a^Mn S O^. 



Volume of solution 330 cub. centims. Temperature 16° C. Time 4 mins. 



It appears from these experiments, the results of which are depicted (Plate XVII. 

 fig. 2), that the eifect of increasing the amount of manganous sulphate in the solution 

 is to accelerate the action to a small extent only when the quantity added is small, but 

 rapidly when it exceeds one molecule, until at the point where three moleciiles are 

 taken, a rate is attained which is hardly increased by any further addition. This maxi- 

 mum rate is first reached with that quantity of manganous sulphate which is capable of 

 reacting with the potassic permanganate to form binoxide of manganese, 



K2Mn2 08+3MnS04+2H2 = K2S04+2H2S04+5Mn02. 

 In the succeeding experiments at least three molecules of manganous sulphate were 

 always introduced into the solution, that the gradual formation of this salt as the 

 reduction of the permanganate proceeds might not complicate the result. As to the 

 manner in which manganous sulphate acts, the gradual changes which took place in the 

 appearance of the fluid bore conclusive testimony. Though the final result, whenever 

 not less than three molecules of this salt were present, was nearly the same, the liquid 

 passed from a pink to a brown colour more rapidly as the quantity was increased, and 

 with the largest proportion it became first turbid, and then comparatively clear again, 

 before the four minutes had elapsed. 



C. Variation of Oxalic Acid. 



Two series of experiments were made in order to determine the effect of varying the 

 proportion of oxalic acid which takes part in the reaction. In one of these only 

 potassic permanganate, manganous sulphate, and oxalic acid were employed; in the 



