1911.] 



Decomposition of Organic Compounds. 



271 



the maximum voltage was gradually developed. This voltage died away by 

 degrees as the zinc was dissolved and the chemical action ceased. 



It should be noted that the zinc was not allowed to come in contact with 

 the platinum electrodes, and thus the bubbles of hydrogen escaped from the 

 zinc and not from the platinum wire. 



A similar cell, in which hydrochloric acid was used in conjunction with 

 zinc placed in the jar, gave parallel results, the voltage being 0"7. 



Other substances used to develop an E.M.F. were phosphorus, potassium, 

 and sodium. 



Phosphorus. — The cell and porous pot were charged with distilled water, 

 and a pair of platinum electrodes, one immersed in the outer and the other 

 in the inner fluid, were connected with the condenser and galvanometer. 

 The relative charge upon this pair of electrodes being determined, a stick of 

 phosphorus was suspended partially immersed in the outer fluid, the tempera- 

 ture of the water in the jar being 10° C. For a period of 28 minutes no 

 effect could be observed on the galvanometer, the constant relative charge 

 upon the pair of electrodes giving the same number of deflections, although 

 copious fumes were being given off. At the end of this period the effect of 

 the oxidation could be observed, and the voltage developed steadily increased. 

 After 11 minutes it increased to O05, after 13 minutes to - 06, and after 

 35 minutes to 01. After this time, the phosphorus, becoming dry, ignited, 

 and the E.M.F. then suddenly increased to 021 volt. It should be noted 

 that the current was in the same direction as with zinc and sulphuric acid, 

 namely, the oxidising phosphorus was zincative. 



In this experiment the comparatively long period between the introduction 

 of the phosphorus and the first signs of the development of any E.M.F. was 

 due to the low temperature of the cell (10° C), and with a higher temperature 

 it was found to be considerably reduced. 



Potassium and Sodium.— A similar cell, with water in both jar and porous 

 pot and with a pair of platinum electrodes, gave an E.M.F. when either 

 metallic potassium or sodium was introduced into the jar, the direction of the 

 current being the same as in the other cases already mentioned. 



From the curves given it will be noted that a short interval of time 

 elapses after the introduction of the zinc into the sulphuric acid before the 

 E.M.F. can be detected, although the action of the acid upon the zinc is at 

 once evidenced by the liberation of the hydrogen or the fumes given off from 

 the phosphorus. A similar time of presentation was observed with both 

 sodium and potassium. Although experiments have not been undertaken 

 with special regard to this point, it is suggested that the gradient of the 

 curve of the E.M.F. is a function of the temperature. 



