78 



CHEMISTRY. 



Blementi 



GEvn V. Phosphites. 



\^r-. -_' The salts belonging to tin . ve been but lit- 



MuMphitf?. tie examined by chemists. When hcatid, they emit 

 a phosphorescent flame. Wl ly heated, they 



yield a little phosphorus, and arc converted iulo phos- 

 phate*. 



Sp. 1. Phosphite of Potash. This salt crystallizes 

 in four-sided prisms. Its taste is sharp and (aline. 

 It is soluble in three parts of cold water. It is not 

 altered by exposure to the air. 



Sp. 2. Phosphite of Soda. It crystallizes in rhom- 

 boids. Its taste is reeling and agreeable. It dissolves 

 in two parts of cold water. It effloresces in the air. 

 Before the blow-pipe, it gives out a fine yellow flame, 

 and melts into a globule which becomes opakc in 

 cooling. 



Sp. 3. Phosphite of Ammonia. It crystallizes in 

 four-sided prisms. Its taste is sharp and saline. It 

 dissolves in two parts of cold water. It deliquesces 

 a little. When heated, it loses its base ; emits phos- 

 phureted hydrogen gas, and phosphoric acid remains. 



Sp. 4. Phosphite of Ammoiiia-ti/id-Mfignesin. This 

 talt is sparingly soluble in water, and crystallizes. 



Sp. 5. Phosphite of Alumina. This salt does not 

 crystallize, but forms a glutinous mass, which dries 

 gradually, and does not afterwards attract moisture. 

 It is very soluble in water. Its taste is astringent. 



The remaining phosphites are insoluble in water. 



Sp. 6. Phosphite of Magnesia. This salt is usu- 

 ally in the state of a white powder, or of small four- 

 sided prisms. It effloresces in the air. It is said to 

 be soluble in 400 parts of cold water. 



Sp. 7. Phosphite of Lime. This is a white taste- 

 less powder, insoluble in water, but soluble in phos- 

 phorous acid, forming a superphosphite, which may 

 be obtained in prismatic crystals by evaporation. 



Sp. 8. Phosphite of Barytes, This is a white pow- 

 der, hardiy soluble in water unless there be an excess 

 of acid. 



GENUS VI. Carbonates. 



Carbo- This is one of the most important of the saline ge- 

 ates. n era. When muriatic or nitric acid is poured on them, 

 they effervesce, and give out carbonic acid. When 

 fully saturated, they do not affect vegetable blues, 

 but the alkaline subcarbonatet convert vegetable blues 

 to green. 



Sp. 1. Carbonate of Potash. Of this salt there 

 are two varieties, the carbonate and tubcarbonalc. 



Variety 1. Carbonate. This salt may be formed 

 by causing a current of carbonic acid to pass through 

 a solution of potash, till the salt crystallines. It 

 crystallizes in rhombotdal prisms, with dihedral sum- 

 mits. It has a very slight alkaline taste, and still 

 gives a green colour to vegetable blues. It is solu- 

 ble in four parts of cold water. Alcohol scarcely 

 dissolves it. Exposure to air does not alter it. 



Variety 2. Subcarbonate. This salt is obtained by 

 exposing the preceding to a strong red heat. It con- 

 tains exactly one half of the acid contained in the 

 carbonate. It is much more soluble in water ; its 

 taste is very alkaline and caustic ; and when exposed 

 to the air, it toon deliquesces and runs into a liquid. 



The potash of commerce i* always in the state of a RltmtnU 

 subcarbonate. of 



Sp. 2. Carbonate of Soda. Of thii salt, like the chtm " tr T' 

 preceding, there are two varieties. ""Y""~ 



Variety 1. Carbonate. This salt occurs native in 

 Africa, and may be formed by passing a current of 

 carbonic acid through a solution of soda, till it ceases 

 to absorb any more. It runs into a hard solid mass, 

 which is not altered by exposure to the air. 



Variety 2. Subcarbonate. What is called carbo- 

 nate of soda in commerce, is nothing else than this 

 salt. Its crystals are octahedrons, having their apexes 

 truncated, or more commonly flat rhomboidal prisms. 

 It dissolves in two parts of cold water. When ex- 

 posed to the air, it effloresces and falls to powder. 

 When heated, it undergoes the watery fusion, and 

 melts in a red heat into a transparent liquid. 



Sp. 3. Carbonate of Ammonia. Of this salt, also, 

 there are at least two varieties. 



Variety 1. Carbonate. This salt may be obtained 

 by passing a current of carbonic acid through the 

 subcarbonate dissolved in water. It crystallizes in 

 six-sided prisms ; has no smell, and much less taste 

 than the subcarbonate. When heated, it sublimes, 

 and is decomposed. 



Variety 2. Subcarbonate. This salt crystallizes, 

 but the -crystals are small and irregular. Its smell 

 and taste are similar to those of ammonia, though 

 weaker. It is lighter than water. It is soluble in 

 less than twice its weight of water. From the expe- 

 riments of Davy, it would appear that there are dif- 

 ferent varieties of this salt, containing various pro- 

 portions of acid, according to the temperatures iu 

 which it has been prepared. 



Spi 3.' Carbonate of Ammonia-and-Magnesia. This 

 salt may be formed by mixing together aqueous so- 

 lutions of its two constituents. Its properties have 

 not been examined. 



The remaining carbonates are insoluble in water. 



Sp. 5. Carbonate of Magnesia. Of this salt there 

 are likewise two varieties. 



Variety 1. Subcarbonate. This is a light white 

 powder, constituting the magnesia of commerce. 



Variety 2. Carbonate. It may be formed by dif- 

 fusing the preceding variety in water, and passing a 

 current of carbonic acid through the liquid. It cry- 

 stallizes in six-sided transparent prisms. It has little 

 taste. It dissolves, when in crystals, in 48 parts of 

 cold water. It effloresces in the air, and falls to 

 powder. 



Sp. 6. Carbonate of Lime. This salt, under the 

 names of marble, chalk, limestone, calcareous spar, 

 &c. exists in great abundance in nature. It crystal- 

 lizes in rhomboidal prisms, with angles of 101^ and 

 78j- ; and no less than 616 different varieties of form 

 have been observed and described by mineralogists. 

 It is tasteless, insoluble in water, but soluble in a 

 small proportion by means of carbonic acid. When 

 heated strongly, it loses its acid, and the escape of 

 the acid is greatly facilitated by the presence of va- 

 pour. When suddenly heated, it melts without losing 

 its acid, and assumes a form bearing some resemblance 

 to granular limestone. 



Sp. 7. Carbonate of Barytes. This salt is found 

 native, and distinguished by mineralogists by the name 



