vn I he Nature and Properties of Albumen, S^x. 91 



nnd coagulated albumen will be found in the positive, and the 

 albuminates of soda and ammonia in the negative cup. 



But if the communication is made with the battery by 

 means of copper instead of platinum electrodes, a slight modi- 

 fication becomes necessary, for another agent comes into play 

 in assihiting the coagulation of albumen : I refer to the metal 

 forming the electrodes ; for on completing the connection with 

 the battery the positive vvii*e oxidizes, and the oxide of copper 

 in the nascent (?) state combines with the albumen, forming an 

 insoluble albuminate of copper, which coagulates round the 

 wire; and thus having two causes operating instead of one 

 (attraction of the oxide of copper for albumen as well as the 

 effect of the chlorine), we find the precipitation of albumen to 

 take place far more speedily and in much larger quantity when 

 copper is used instead of platinum to connect the albuminous 

 solution with the battery; and acting on this principle, when- 

 ever I have merely the detection of albumen in view, I am ac- 

 customed to use electrodes of clean copper v\'ire, connected with 

 a little battery of 5 or 6 pairs of plates (18.) excited only by 

 weak brine, which I find to be amply sufficient for the pur- 

 pose. But whatever may be the intensity of the electric cur- 

 rents, or whatever the metal forming the electrodes, we have a 

 sufficient number of facts to believe that free albumen is never 

 precipitated by the electric current itself^ but by its effects in 

 setting free chlorine, or determining the formation of an oxide 

 for which albumen has considerable affinity. 



23. It may now be asked, why in Mr. Brande's experi- 

 ments (Phil. Trans, siip. citat.) the coagulation of albumen? 

 took place as constantly at the negative, as in mine at the po- 

 sitive electrode. To this question a ready solution may be af- 

 forded, when we recollect that in Mr. Brande's experiments 

 the batteries employed were large, and excited by strong acids, 

 whereby the electric currents developed were in a state of 

 considerable tension ; in consequence of which, the albumen,, 

 rendered insoluble by the presence of chlorine at the positive 

 electrode, was mechanically conveyed by the current of positive 

 electricity towards the negative side of the battery. That the 

 passage of electricity is capable of exciting currents in liquid 

 conductors of apparenlhj considerable mechanical intensity 

 the expel iments of Sir John Herschel (Phil. Trans. 1821-, 

 p. 162,) are more than sufficient to demonstrate; whilst the 

 fact of such currents being sufficiently energetic to transfer 

 minutely divided solids from the positive tovvart^s the negative 

 electrode, even when in separate tubes, has been proved by 

 M. Becquerel, (Traite de V Electricite, tom. iii. p. 102,) wha 

 observed finely divided clay to be actually driven by the 



N2 



