16 C. E. FAWMTT. 



of Ferrous and Ferric ions as noticed by wetway tests is 

 quite as great as, perhaps greater than, the difference 

 between the properties of two different elements such as 

 barium and strontium in their compounds. We cannot 

 gradually alter the properties of ferrous ion when trans- 

 forming it into ferric ion. The change involves a trans- 

 ference of a unit of electricity and nothing less than a 

 whole unit (96540 coulombs for 56 grams of iron). 



When the properties of an atom are altered as in ionic 

 creations, the change is a sudden one. In producing ions 

 from the uncharged atom the number of electrons in the 

 outer ring alters; in radioactive changes the inner nucleus 

 disintegrates and either a positive particle or electron is 

 ejected. 



Change from Passive to Active State. 

 A very interesting case of alteration, sometimes also 

 believed to be a case of allotropism, is noticed in the change 

 between the active and passive state in certain metals like 

 iron. The change whether judged by the eye or by elec- 

 trical tests is usually very sudden. A piece of passive iron 

 lying in 1*2 spec. grav. nitric acid (7) or in concentrated 

 sulphuric acid (8) becomes suddenly active on account of 

 causes which have so far remained obscure. 



In the production of compounds from elements, addition 

 of any element to another or to a compound produces a 

 fairly definite change in many of its properties. In these 

 cases we look for continuity in the sense that chemical 

 composition and constitution have an intimate relation to 

 the physical properties. 



The closeness of this correspondence is well shown, for 

 instance by the following Table (III) taken from Smiles' (9) 

 Text Book which gives the correspondence between Mole- 

 cular Volume and Composition in the case of the members 

 of the paraffin series. 



