1865.] Laws of Connexion, $c. 473 



proportional quantities are destroying one another, is shown to follow from 

 a law the generality of which the authors hope to establish namely, that 

 the total amount of chemical change varies directly with the amount of 

 each of the substances partaking in it. 



In the later series of experiments the necessary condition, that the ratio 

 of the reagents should remain constant throughout the action, was fulfilled 

 by taking all but one of them in great excess as compared with that one. 

 Under these circumstances a single substance gradually disappears, all 

 around it remaining unchanged ; and according to the law above enunci- 

 ated, the total amount of change occurring at any moment is proportional 

 to the quantity of substance then remaining. It is shown that if this be 

 the case, the numbers representing the amounts of residue after equal in- 

 tervals of time should form a series in geometric progression. This relation 

 is actually exhibited by some of the experimental series ; but the greater 

 number of them do not conform to it. The reason of this is to be found 

 in the fact that more than one reaction occurs under the circumstances of 

 these experiments, and that it is only possible to measure the total effect. 

 Experiments upon the solution in which the gradual oxidation of oxalic acid 

 has taken place are adduced to show that some other oxidized product 

 besides carbonic acid is formed, and it is inferred that more than one agent 

 takes part in its oxidation. Also the facility with which hydrated peroxide 

 of manganese reacts with dilute sulphuric acid and manganous sulphate to 

 form a solution of mangano-manganic sulphate renders it probable that 

 this salt is produced in the experiment. With an excess of oxalic acid and 

 manganous sulphate the red colour of potassic permanganate disappears as 

 soon as this salt is added to the mixture. The formation of manganic bin- 

 oxide appears to be instantaneous. It finds itself in presence of two sub- 

 stances, both of which act gradually upon it oxalic acid and manganous 

 sulphate, the latter producing an intermediate oxide, probably the protoses- 

 quioxide, which is also reducible by oxalic acid. It is possible that other oxides 

 besides these may be formed ; but it is almost certain, from the experimental 

 results, that the action is not more simple than this. At the end of each expe- 

 riment both" or all of these oxides are alike instantaneously reduced by hydri- 

 odic acid and thus measured conjointly. Finally it is shown that an equation 

 may be constructed embodying this hypothesis, and that all the series of 

 experimental numbers may be expressed by equations of this form. The 

 paper concludes with a mathematical discussion, by Mr. Esson, of various 

 points in the theory of this action. An outline of his statement is here 

 appended. 



When a single substance is undergoing chemical transformation under 

 constant conditions, it is shown by experiment that the law of connexion 

 between y, the quantity of substance remaining unchanged, and x, the time 

 during which the change has been proceeding, is y=aa x ; where a is the 

 quantity of substance present at the beginning of the change, and a a con- 



VOL. XIV. 2 N 



