C H E M I S T R Y. 



97 



Elements oxalic, Urtaric, and citric acids dissolve it readily. The 



f solutions appear to be transparent and colourless. Nei- 



Chemistry. t j jef p ruS8 j ate o f potash, nor hydrosulphuret of potash, 



occasion any precipitate in these solutions ; but infusion 



of nutgalls throws,down an orange coloured precipitate, 



provided there be no excess of acid present, but a slight 



excess of acid prevents the precipitate from appearing. 



Salts of 

 Cerium. 



GENUS XXVIF. Sails of Cerium. 



The salts of cerium have either a white or a yellow 

 colour, according to the state of oxidizement of the me- 

 tal. Their solutions in water have a sweet taste. Hydro- 

 sulphuret of potash throws down a white precipitate, 

 prussiate of potash a milk-white precipitate, and infusion 

 of nutgalls no precipitate whatever. The oxalate of am- 

 monia occasions a white precipitate, which is insoluble in 

 nitric and muriatic acids. 



Sp. 1. yilratc of Cerium. Nitric acid dissolves white 

 oxide of cerium readily : the solution is colourless, cry- 

 stallizes with difficulty, retains an excess of acid, and has 

 an austere and sweet taste. It dissolves the red oxide with 

 difficulty unless heat be applied. The solution is yellow, 

 and yields small white crystals, which deliquesce when 

 exposed to the air. Both of these salts are soluble in 

 alcohol. Heat decomposes them, leaving a red coloured 

 oxide. 



Sp. 2. Muriate of Cerium. Muriatic acid dissolves red 

 oxide of cerium when assisted by heat, oxy muriatic gas 

 is exhaled, and the solution has a yellowish red colour, 

 which becomes lighter the longer the heat is conti- 

 nued. The solution yields four-sided prismatic crystals 

 of a yellowish white colour. They are soluble in alco- 

 hol, and deliquesce when exposed to the air. Their 

 taste is astringent and sweet. Heat decomposes this 

 salt by driving off the acid and water. 



Sp. 3. Sulphate, of Cerium, Sulphuric ac:d dissolves 

 the red oxide of cerium by long digestion, an orange- 

 coloured solution is obtained, which yields sm ill octahe- 

 dral and needle- form crystals. The colour of these crys- 

 tals is partly lemon yellow, partly orange. They are 

 scarcely soluble in water. Their taste is acid and sweet. 

 When exposed to the air, they soon fall into a yellow 

 powder. 



Sulphuric acid dissolves the white oxide of cerium very 

 readily. The solution is colourless, has a sweet taste, 

 and yields crystals of sulphate of cerium. 



Sp. 4. Carbonate of Cerium. When white oxide of 

 cerium is precipitated from its solutions by an alkaline 

 carbonate, carbonate of cerium is obtained. It is a gra- 

 nular powder of a silvery whiteness, insoluble in water, 

 and composed of 23 acid, (>.5 oxide, and 12 water. 



Sp. 5. Acetate of Cerium. Acetic acid dissolves the 

 white oxide of cerium, and forms small sweet-tasted cry- 

 stals, soluble in water, but very sparingly soluble in al- 

 cohol. 



CHAP. IV. 



Of Hydrosulphurtts. 



Hydrnnil- ScLPiiritF.TED hydrogen gas possesses many of the 

 *" properties of an acid, and, like acids, it combines with 

 the salifiable bases, and forms a class of bodies called In/. 

 drosulphurets. These bodies are of considerable import- 

 ance, as they are frequently employed in chemical analy- 

 sis, and enable us to separate the metallic oxides from al- 



TOL, VI. FABT I. 



kalies and earths, because they throw down almost the 

 whole of them from their solutions in an insoluble state. 



Thehydrosulphurcts are soluble in water, and the so- 

 lution is colourless. When the solution is exposed to the 

 air, it becomes green or greenish yellow. After long 

 exposure to the air, the solution becomes again limpid 

 and colourless, and, on examination, is found only to con- 

 tain the base of hydrosulphuret combined with sulphuric 

 acid. The solution of the hydrosulphurets precipitate* 

 almost all the metallic oxides from their solutions ; 

 iron and lead, black ; antimony, orange ; arsenic, yellow, 

 &c. 



The hydrosulphurets may be formed, by dissolving or 

 diffusing the respective bases in water, and passing a cur- 

 rent of sulphureted hydrogen gas through the liquid till 

 it ceases to absorb any more. The excess of gas is then 

 driven o"ff by heat ; and the hydrosulphuret may be ob- 

 tained in a solid state if required by evaporation. The 

 yellow colour which these solutions acquire when expo- 

 sed to the air, is owing to the decomposition of the sul- 

 phureted hydrogen by the gradual absorption of oxygen 

 from the atmosphere. 



Sp. 1. Iftjdiosulphuret of Barytes. When sulphate 

 of barytes is converted into sulphuret by mixing it with 

 charcoal, and heating it red hot in a crucible, if boiling 

 water be poured upon the black mass, and filtered while 

 hot, the green coloured solution thus obtained yields, by 

 evaporation, a great number of crystals. These crystals 

 are hydrosulphuret of barytes. They are white, and 

 have a silky lustre. They have the form of scales, and 

 the shape cannot easily be distinguished. This substance 

 is soluble in water, the solution has a slight tint of green, 

 its taste is acrid and sulphureous, and when exposed to 

 the air is readily decomposed. 



Sp. 2. Hydivsiilphiircl of Slrontian. It may be pro- 

 cured by the same process as the preceding hydrosulphu- 

 ret, and its properties are nearly similar. 



Sp. 3. lli/drosulphuret of Potash. This substance is 

 formed during the solution of sulphuret of potash, and 

 may be obtained by evaporation. It is transparent and 

 colourless, and crybtallizes in large prisms, not unlike the 

 figure of sulphate of soda. Its taste is alkaline, and 

 extremely bitter. When exposed to the air it soon deli- 

 quesces into a liquor of a syrupy consistence, tinging 

 green all bodies with which it happens to come in contact. 

 The crystals have no smell at first, but when they hare 

 deliquesced they emit a fetid odour. They dissolve both 

 in water and alcohol, and during the evolution the tem- 

 peraur.e sinks considerably. Acids drive off the sul- 

 phureted hydrogen with a violent effervescence. 



Sp. -I. Hydrosulphuret (f Soda. The crystals of this 

 substance are transparent and colourless, having the fi- 

 gure of four-sided prisms terminated by quadrangular py. 

 ramids. Its taste is alkaline, and intensely bitter. It is 

 very soluble both in water and alcohol, and during the 

 solution cold is produced. When exposed to the air it 

 deliquesces, and acquires a green colour. Acids drive 

 off the sulphureted hydrogen. 



Sp. 5. Hydrosulphuret of Lime. This substance may 

 be formed, by passing sulphureted hydrogen gas through, 

 water, having lime suspended in it. The solution is co- 

 lourless, and has an acrid and bitter taste. 



Sp. 6. Hydrosulphuret of Ammonia. This compound 

 may be formed by passing sulphureted hydrpgen through 

 liquid ammonia. When equal parts of lime, sal ammo- 

 niac, and sulphur, mixed with a little water, are distilled 

 in a retort, a yellow liquid is obtained, usually distinguished 

 by the name of fuming liquor of Boyle, because first pre- 



N 



Elements 

 of 



Chemistry. 



Their pr-. 

 pcrtic? . 



How form- 

 ed. 



Hydrosul- 

 phurets of 

 barytes, 



Stroll tian, 



Potash, 



Soda, 



Lime, 



Ammonia, 



