DOUBLE HALOID SALTS. 77 



former view. According to the present doctrine, when a hydracid is 

 presented to any salifiable base, both are decomposed, water and a 

 haloid salt of the metal being formed. Take hydrochloric acid and 

 potash by way of example : 



TT J , , . . J S Chlorine .^Chloride of potassium. 



Hydrochloric acid ^ Hydrogen, 



•D t u S Potassium- 



Potash . . . ^Oxygen ^- Water. 



The only hydro-salts which are now at all recognised are the 

 compounds of ammonia with a hydracid ; though even these might 

 be considered as haloid salts of the hypothetical metal am7no?iiu7ii. 

 This will be evident by the following diagram : — 



Hydrochloric acid \ ^^""^ ^^^^^"^"^ ) 



f ???°:;^"" ^^^ V Sal ammoniac. 



Ammonia . . ^-^y^'^^^'^--^:::::::^ a • \ 



f Nitrogen -—•::a5w Ammnmum ; 



The most important of the ammoniacal salts are the hydrochlorate, 

 commonly called sal ammoniac, and the hydrosulphate, formerly 

 termed the fuming liquor of Boyle. 



SECTION III. 



SULPHUR SALTS. 



The sulphur salts are double sulphurets, just as the oxy-salts are 

 double oxides ; the sulphuret of one metal acting as an acid, while 

 the sulphuret of another metal acts as a base. The sulphur salts 

 are so constituted, that if the sulphur in both the acid and base was 

 replaced by oxygen, an oxy-salt would result. 



The principal sulphur-bases are, the protosulphurets of potassium, 

 sodium, lithium, varium, strontium, calcium, and magnesium ; and 

 the principal sulphur-acids are the sulphurets of arsenic, tin, anti- 

 timony, tungsten, molybdenum, tellurium, and gold, together with 

 hydrosulphuric acid and bisulphuret of carbon. Kermes' mineral, 

 an important antimonial medicine, is an example of a sulphur salt, 

 being composed chiefly of sulphuret of antimony, united with sul- 

 phuret of potassium. 



SECTION IV. 



DOUBLE HALOID SALTS. 



These salts are composed of two simple haloid salts, one of which 

 acts as an acid, and the other as a base, in a manner analogous to 

 the double sulphurets. The principal groups consist of double 

 chlorides, double iodides, and double fluorides. 



When an oxide and chloride unite, they constitute a compound 

 known by the name of oxy-chlmide. 



7* 



