244 NON-METALS AND THEIR COMBINATIONS. 



when at first iodine monochloride, IC1, and then the trichloride is formed. The 

 latter has been used as a disinfectant. 



Compounds of nitrogen with the halogens. When chlorine or iodine 

 acts on ammonia the hydrogen of the latter combines with the halogens, while 

 nitrogen is either set free or also enters into combination with the halogens, 

 thus: 



NH 3 + 3C1 = 3HC1 + N, 



NH 3 + 6C1 == 3HC1 -f NC1 3 . 



The compounds NH 2 C1 and NHC1 2 , as also the corresponding iodine com- 

 pounds, are known. All these bodies are very unstable ; nitrogen trichloride, 

 an oily liquid, is one of the most explosive substances known ; nitrogen iodide, 

 a black powder, also explodes readily. 



Fluorine, F = 18.9. This element is found in nature, chiefly as 

 fluorspar, calcium fluoride, CaF 2 ; traces of fluorine occur in many 

 minerals, in some waters, and also in the enamel of teeth, and in the 

 bones of mammals. Fluorine was, until 1887, scarcely known in the 

 elementary state, because all attempts to isolate it were frustrated by 

 the powerful affinities which this element possesses, and which render 

 it difficult to obtain any material (from which a vessel may be made) 

 which is not chemically acted upon, and, therefore, destroyed, by 

 fluorine. 'The method used now for liberating fluorine depends upon 

 the decomposition of hydrofluoric acid by a strong current of electricity 

 in an apparatus constructed of platinum with stoppers of fluorspar. 

 To prevent too rapid corrosion of the platinum vessels, the decom- 

 position is accomplished at a temperature below the freezing-point. 

 Fluorine is a gas of yellowish color, having a highly irritating and 

 suffocating odor, and possessing affinities stronger than those of any 

 other element. As a supporter of combustion, fluorine leaves oxygen 

 far behind ; it combines spontaneously even in the dark and at low 

 temperature with hydrogen; sulphur, phosphorus, lampblack, and 

 also many metals ignite readily in fluorine ; even the noble metals, 

 gold, platinum, and mercury, are converted into fluorides; from 

 sodium chloride the chlorine is liberated with the formation of 

 sodium fluoride ; organic substances, such as oil of turpentine, alco- 

 hol, ether, and even cork ignite spontaneously when brought in 

 contact with this remarkable element. 



Hydrofluoric acid, HF. A colorless gas, very irritating, soluble 

 in water. It is obtained by the action of sulphuric acid on fluorspar : 



CaF 2 + H 2 SO< = 2HF + CaSO 4 . 



Hydrofluoric acid, either in the gaseous state or its, solution in 



