426 



Prof. Odling on the Natural Groupings 



The atomic weight and specific gravity of fluorine, or 19, is 

 rather more than half that of chlorine. 



Chlorine, bromine and iodine, when in the liquid or solid 

 state, have, according to Kopp, the same atomic volume, namely 

 160, Bromine and iodine have sensibly the same atomic heat ; 

 6- 7 and 6*8 respectively. All four bodies in the free state mani- 

 fest powerful affinities. Fluorine, however, appears to be by far 

 the most energetic. Chlorine, bromine, and iodine are capable 

 of replacing hydrogen by equivalent substitution in a great variety 

 of compounds, mineral and organic ; in the latter, more espe- 

 cially, with but a slight modification in the properties of the 

 original bodies. Analogous fluorides, chlorides, bromides, and 

 iodides are for the most part isomorphous. The fluorides, chlo- 

 rides, &c. of hydrogen and the basylous metals have a great 

 tendency to unite with the protochlorides, bichlorides, and ter- 

 chlorides, &c. of the chlorous metals. The chloride, bromide, and 

 iodide of hydrogen yield a large number of corresponding oxides, 

 thus : — 



CI CI 

 CI CIO 



HCl* 



Chlorhydric acid. 



HCIO 



Hypoehlorous acid. 

 HCIO^ 



Chlorous acid. 



HBr 

 HBrO? 



>} 

 H Br03 



HI 



HI03 



HIO* 



HC103 



Chloric acid. 



HCIO^ 



Perchloric acid. 



Chlorine moreover forms a peroxide, ClO^, or rather ClO^ . ClO^ 

 = CP 0**. Neither fluorine nor fluoride of hydrogen yields oxy- 

 genized compounds. Fluorine is moreover distinguished from 

 the other three members of this group by its capability of 

 reacting upon and dissolving certain insoluble mineral acids, 

 such as the silicic, columbic, tungstic, &c., and by its greater 

 tendency to form insoluble salts. Fluoride of silver, however, 

 is very soluble. 



Iodine is possessed of metallic opacity, brilliancy and colour. 



Group II. Oxygen — Sulphur, Selenium, Tellurium. 

 An atom of each of these elements unites with two atoms of 

 hydi'Ogen to form a compound which is either neutral or feebly 



Dr. Miller in his ' Elements of Chemistry,' save that in some cases they 

 have undergone multiplication so as to coiTespond with M. Gerhardt's 

 system of formula;. 



* Laurent's 'Chemical Method/ Cavendish Society's translation, pp. 483 

 and 349. 



