204 INDUCTIVE AFFINITY. 



[G * for each grain of steel 



is a complete magnet. 

 It will be observed 

 also that these threads 

 diverge from each 

 other ; because while 

 unlike poles are in 

 contact in each thread which attract, like poles are in contact of 

 adjoining threads which repel. This repulsion of polar chains 

 by each other, there will be occasion again to recur to. 



Chemical polarity and induction. With these elementary 

 notions of polarity and the mode of action of a force by induc- 

 tion, we may return to the chemical phenomena of the voltaic 

 circle. It is to be assumed that the zinc and hydrochloric acid 

 are both composed of particles, or molecules, which are suscep- 

 tible of a polarized condition, like the particles of soft iron, in 

 which condition, the opposite ends of each molecule possess diffe- 

 rent and contrary attractive powers. Of hydrochloric acid, the 

 chemical atom may be taken as the polar molecule, and it will 

 therefore consist of an atom of chlorine and an atom of hydrogen 

 associated together. The polar molecule of zinc may be sup- 

 posed, for a reason which will afterwards appear, to consist of a 

 pair likewise of associated atoms, which, however, are in this body 

 both of the same element. The powers developed in a polarized 

 molecule of zinc and of hydrochloric acid are the same. One 

 pole of each molecule has the attraction, or affinity, which is 

 characteristic of zinc, or zincous attraction, and may be called the 

 zincous pole 5 while the other has the attraction, or affinity, 

 which is characteristic of chlorine, or chlorous attraction, and 

 may be called the chlorous pole. Polarity is not an ordinary 

 condition of the particles of either the zinc or acid, but is deve- 

 loped in both when brought into contact with each other. Such 

 is to be supposed the mode in which chemical affinity always acts. 

 Zinc and acid in contact may therefore be represented (Fig. 

 FIG. 10. 10.) by trains of associated 



zinc. Acid. pairs of atoms. In the mo- 



lecule of hydrochloric 'acid 

 B c D B, which is in contact with 

 zinc, the chlorous affinity is thereby developed on the side next the 

 zinc, and we have there the constituent chlorine atom forming the 

 chlorous pole, the fluidity of the acid allowing its molecule to take 



