C H E M I S T R Y. 



79 



Elements of Witherite. It crystallizes in double six-sided and 

 of four-sided pyramids. It is tasteless, insoluble in wa- 

 Chemistrr. ter> but poisonous. It is not altered by exposure 

 "* to the air. When made up into a ball with char- 

 coal, and violently heated, it loses its acid. 



Sp. 8. Carbonate of Stronlian. This salt also oc- 

 curs native, usually in semi-transparent striated masses, 

 with a greenish tinge. It is tasteless, insoluble in wa- 

 ter, and not altered by exposure to the air. When 

 violently heated, it loses its acid. 



Sp. 9. Carbonate of Alumina. Water, containing 

 carbonic acid gas, dissolves a little alumina ; but when 

 the alumina is precipitated and dried, it appears, 

 from the experiments of Saussure, that it loses its 

 acid. Carbonate of alumina, then, cannot exist in a 

 dry state. 



Sp. 10. Carbonate of Yltria. A white, tasteless, 

 insoluble powder. 



Sp. 11. Carbonate of Glucina. A white, soft, 

 tasteless powder, with greasy feel. 



Sp. 1*2. Carbonate of Zirconia. A white tasteless 

 powder. 



The following Table exhibits a view of the com- 

 position of these salts, as far as it has been ascertained. 



Element* 

 of 



The subcarbonates appear to contain juat one half 

 of the acid which exists in the carbonate*. 



GENUS VII. Sulphatei. 



Sulphites. This genus of gaits has been long- known, and very 

 carefully examined. Most of the salts in it crystal- 

 lize. Their taste is usually bitter. They are inso- 

 luble in alcohol, and precipitated from water by alco- 

 hol. When heated to redness, along with charcoal, 

 they are converted into sulphurets. All their solu- 

 tions yield a white precipitate, insoluble in cold sul- 

 phuric acid, when mixed with muriate of barytes. 



Sp. 1 . Sulphate of Potash. Of this salt there are 

 two varieties. 



Variety 1. Sulphate. This salt is usually to be 

 found in considerable quantity in the potash of com- 

 merce. The crystals are small, irregular, hard, and 

 firm : usually six-sided prisms. The taste is a dis- 

 agreeable bitter. It dissolves in about 16 times its 

 weieht of cold water. It is not altered by exposure 

 to the air. In a red heat it melts, and loses about 

 14 per cent, of its weight. 



Variety 2.. Supersulphaie. This salt may be ob- 

 tained by dissolving the preceding in sulphuric acid, 

 and evaporating. Its crystals are long slender needles, 

 or six sided prism*. Its taste is acid, and it reddens 

 vegetable blues. When heated, it melts, and assumes 

 the appearance of oil. A itrong red heat is neces- 



sary to drive off the excess of acid, and convert it in 

 to sulphate. 



Sp. 2. Sulphate of Soda. This salt is often called c 

 Glauber's salt from the name of the discoverer of it. 

 There are two varieties of it, like the preceding. 



Variety 1. Sulphate. This salt crystallizes in six- 

 sided transparent prisms, terminated by dihedral sum- 

 mits. The sides of the prisms are usually channel- 

 ed. Its taste, at first, has some resemblance to that 

 of common salt, but it soon becomes disagreeably 

 bitter. It dissolves in less than thrice its weight of 

 cold water, and in less than its weight of boiling wa- 

 ter. When exposed to the air, it loses its water, ef- 

 floresces, and falls to powder. The loss of weight is 

 about 0.56 parts. When heated, it undergoes the 

 watery fusion. In a read heat it melts, and, accord- 

 ing to Kirwan, loses part of its acid. 



Variety 2. Supersitlphate. This salt may be ob- 

 tained by dissolving the preceding variety in sulphu- 

 ric acid, and evaporating the solution. It crystal-- 

 lizes in large transparent rhombs, which effloresce in 

 the air, and easily part with their excels of acid. 



Sp. 3. Sulphate of Ammonia. This salt c; 

 lizes in small six-sided prisms. It has a sharp bitter 

 taste; is soluble in twice it? weight of cold water, and 

 in its weight of boiling water. When exposed to the 

 air, it slowly attracts moisture. When heated, it de- 

 crepitates, then melts, and sublimes with some loss of 

 its alkali. When heated nearly to redness, the greatest 

 part of it is decomposed. 



Sp. 4-. SulphaJc of Magnesia. This salt was long 

 known by the name of Epsom salt, because it exists 

 in the spring at Epsom near London. It exists also 

 in sea water. It crystallizes in regular four-s;ded 

 prisms, surmounted by four-sided pyramids or dihe- 

 dral summits. The crystals refract doubly. Its taste 

 ia intensely bitter. It dissolves in its own weight of 

 cold water. In the air it effloresces. When heated, 

 it undergoes the watery fusion, and before the blow- 

 pipe melts with difficulty into an opake vitreous 

 globule. 



Sp. 5. Sulphate of Polash-and-Ammonia. This 

 salt crystallizes in brilliant plates. Its taste is bitter, 

 and it is not altered by expos\ire to the air. 



Sp. 6. Sulphate of Potash-anil- Magnesia. This 

 salt crystallizes in rhomboidal prisms, and is not al- 

 tered by exposure to the air. 



Sulphate of Soda is also capable of forming triple 

 salts with ammonia and magnesia. 



Sp. 7. Sulphate of Magneiia-and- Ammonia. This 

 salt crystallizes in octahedrons. Its taste is acrid and 

 bitter. It is decomposed by heat, and is less soluble 

 in water than either of its constituents. 



Sp. 8. Sulphate of Alumina. This salt crystal- 

 lizes in thin plate*, soft and pliant, and of a pearly 

 lustre. Its taste is astringent. It ie very soluble in 

 water, and crystallizes with difficulty. 



Sp. 9. Alum. This is a triple salt, of which there 

 are four varieties, namely, 1. Sulphate of ahimina- 

 and-potash ; 2. Sulphate of alnmina-and-amm>/ni<i ; 

 3. Supersulphate of ammonia-amt-potash ; 4t. Sttper- 

 sulphate of alumina-and-ammonia. The two last, 

 (especially the 3d,) constitute the alum of commerce ; 

 the two first have been called alum saturated Kttlt its 

 earth, or aluminated alum. 



