COMPOUNDS OP HYDROGEN. 47 



Pro'p, — A solid of a bluish-black colour, and metallic lustre; 

 in crystalline scales; — sp, gr. 49; fuses at 225°; boils at 347° ; colour 

 of vapour a rich violet ; slowly volatile at common temperatures, 

 exhaling an odour resembling that of chlorine ; density of vapour 

 8*716, being the heaviest of all vapours; very sparingly soluble in 

 water, but soluble in alcohol. The best test for iodine is starch, with 

 which it forms a blue compound. 



The affinities of iodine are not so strong as those of chlorine, 

 since the latter always displaces iodine from its compounds. 



The non-acid compounds of iodine are called iodides. — Eq. = 126. 

 Symb. I. 



Iodine forms at least two compounds with oxygen. 



Iodic acid^ 10^, forms iodates. 



Periodic acid, 10^. 



Iodine forms a compound with chlorine, the chloride of iodine ; — 

 also with nitrogen, a very explosive compound, similar to the chloride 

 of nitrogen ; — also with phosphorus and sulphur. 



BROMINE. 



Is found in sea- water as a bromide of magnesium ; also in cer- 

 tain saline springs ; — procured from bromide of potassium by sul- 

 phuric acid and peroxide of manganese : the reaction is precisely 

 similar to that in the case of iodine. 



Prop. — A very volatile liquid, of a deep reddish-brown colour ; 

 freezes a little below 0° ; boils at 116°; odour very suffocating and 

 offensive ; slightly soluble in water ; more so in alcohol and ether. 

 The aqueous solution bleaches. It is very poisonous ; its chemical ha- 

 bitudes closely allied to those of chlorine and iodine ; it forms com- 

 pounds with oxygen, chlorine, iodine, hydrogen, sulphur, phosphorus, 

 carbon, and silicon. — Eq. = 78-4. Symb. Br. 



FLUORINE. 



Occurs in nature in combination with calcium, in the well-known 

 Jiuor spar ; has only lately been isolated, on account of its energetic 

 affinities. It is a yellowish gas, with an odour resembling chlorine; 

 — has a powerful affinity for hydrogen and the metals; — sp. gr. 

 1-289; — Eq.ii=18-68. Symb. F. Its compounds with hydrogen, 

 silicon, and boron will be described in the subsequent section. 



SECTION II. 



COMPOUNDS OF SOME OF THE FOREGOING SIMPLE 

 SUBSTANCES WITH EACH OTHER. 



COMPOUNDS OF HYDROGEN. 



Chlmineand Hydrogen; — Hydrochloric acid, Chlorohydric acid, 

 or Muriatic acid, CIH ; — prepared by the action of dilute sulphuric 

 acid on chloride of sodium, according to the following rationale : 



