PHOSPHATES. 75 



and manganese alums, in which the sulphate of alumina is replaced 

 respectively by the sulphate of iron, and the sulphate of manganese. 

 The Sulphites, Hyposulphites, and Hyposulphates are of very 

 little practical importance. 



NITRATES. 



These may be prepared by the action of nitric acid on metals, — on 

 the salifiable bases,— or on the carbonates. As they are soluble salts, 

 their acid cannot be precipitated by any reagent. They are distin- 

 guished by deflagrating with charcoal and other combustibles. When 

 exposed to a high temperature, they are decomposed with the evolu- 

 tion of oxygen gas. If subjected to the action of sulphuric acid, they 

 give off nitric acid fumes. When added to hydrochloric acid they 

 form a solvent for gold leaf, by liberating the chlorine. 



The most important nitrates are those of potassa, soda, ammonia, 

 copper, mercury, and silver. 



The Nitrites are comparatively unimportant. 



CHLORATES. 



These are very analogous to the nitrates. They are all decom- 

 posed by a red heat into metallic chlorides and oxygen gas. They 

 deflagrate with combustibles even more violently than the nitrates. 

 They are nearly all soluble in water. 



The most important salt of this class is the chlorate of potassa, 

 which is useful to the chemist in the preparation of oxygen. 



The Chlorites are chiefly remarkable for their bleaching and 

 oxidizing properties. 



The Hypochlorites may be produced by the action of chlorine gas 

 upon salifiable bases. The most important of them is the hypochlo- 

 rite of lime, the well-known bleaching powder, commonly called 

 chloride of lime. It is prepared by exposing thin strata of recently 

 slaked lime to an atmosphere of chlorine: the chloride of calcium 

 and hypochlorite of lime are formed. 



lODATES. 



These are compounds of iodic acid and a base. They bear a 

 general resemblance to the chlorates, and may be recognised by the 

 facility with which they are decomposed by deoxidizing agents, as 

 hydrochloric, sulphurous, and phosphorous acids, which unite with 

 the oxygen, setting iodine free. 



The Bromates generally resemble the iodates. 



PHOSPHATES. > 



As regards this class of salts, it is to be remembered that there 

 are three isomeric phosphoric acids, termed tribasic, hibasic, and 

 monobasic, oxpliosphoric,pyrophosphoric, and metaphosplwric dioidiS, 



