CHEMICAL ACTION AND MAGNETISM 301 



Proper volumes of the chlorate and the acid solutions hav- 

 ing been run into the flask and sufficient water to make the 

 volume 80 cc., the solution was allowed to acquire the temper- 

 ature of the water-bath. Thereupon 20 cc. of the ferrous sul- 

 phate solution, which had been brought to the same tempera- 

 ture, were added [150] rapidly, the flask was vigorously shaken, 

 and at once replaced in the water-bath. If the magnet was to 

 be employed, its electric circuit was closed at this time. After 

 the expiration of a few minutes, 10 cc. were withdrawn from 

 the flask by means of a pipette, and were quickly run into a 

 large quantity of cold water contained in a porcelain dish, 

 the time being noted when the pipette was emptied. The titra- 

 tion was then executed as rapidly as possible. This operation 

 was repeated at suitable intervals, until the solution was ex- 

 hausted or external conditions prevented a continuation of 

 the observation. Where two reactions were to be observed 

 together, the second solution was mixed ten minutes after 

 the first, the same interval being preserved, as nearly as might 

 be, throughout. Owing to the weakness of the permanganate 

 solution and to varying conditions of illumination, my titra- 

 tions have a probable error of fully ^ to ^ cc., but this is in no 

 unfavorable proportion to the observed values; in cases of 

 over-coloration I rejected the result, rather than titrate back 

 with another solution. " 



The reaction has been proved by Hood to be subject to the 

 law 



at 



where xthe amount of substance changed, =time elapsed, 

 A and B represent the original quantities of ferrous sulphate 

 and chlorate respectively, and C is a coefficient depending on 

 external circumstances. 



