CHEMISTET. 193 



perfectly fluid, and if subjected to the action of a galvanic current, oxygen is 

 evolved at one pole and silicium or titanium at the other. Alumina, on the other 

 hand, scarcely dissolves at all in the fluoride of sodium, and when acted on by the 

 battery, fluorine is disengaged at one pole and sodium at the other. 



Silicium may be prepared by bringing the vapor of sodium in contact with silica, 

 or even with very pure pounded glass. 



CADMIUM SALTS. 



Von Hauer has continued his researches on the double chlorides of cadmium, 

 and has described the following compounds: — The chlorobicadmiate of barium 

 with four of water ; the chlorobicadmiate of strontium and calcium, each with 

 seven of water; the chloro-hcmicadmiates (dicadmiates) of calcium and magne- 

 sium ; the chloro-bicadmiates of magnesium, manganese, iron, cobalt, and nickel, 

 with twelve, and the cldoro-monocadmiate of copper with four of water. 



BASICITY OF OXIDES. 



II. Rose has lately shewn that all oxides may be divided into two classes ac- 

 cording to their action on chloride of ammonium, (ante, January No. p. 80) — but 

 if perchloride of mercury be used, then three divisions may be established. This 

 method has the advantage that we may know immediately from the color of the 

 precipitate, to which of the three divisions the base so tested belongs. 



The first division includes the strong bases which when added in excess produce 

 a yellow precipitate of pure peroxide of mercury, even at ordinary temperatures. 

 These are potash, soda, lithia, baryta, strontia and lime, as well as solutions of al- 

 kalic silicates. 



The second section contains the weaker bases, or strong bases whose basic pro- 

 perties are somewhat obscured by combination with a weak acid. These give with 

 perchloride of mercury a precipitate of a reddish-brown color, the oxy-chloride, 

 the chloride in which cannot be converted into the oxide at the ordinary tempera- 

 ture, even by an excess of base. To this category belong the neutral alkalic 

 carbonates, the sesqui-carbonate of soda, the alkalic borates (neutral and bibo- 

 rates), the borates of the alkaline earths, magnesia, the basic carbonate of magne- 

 sia, and also the artificial neutral carbonate. Oxide and carbonate of silver seem 

 also to belong to this class. 



The third section includes the great number of bases which do not decompose 

 perchloride of mercury. The alkalic bicarbonates and the carbonates of the alka- 

 line earths also belong to it. 



Hence it follows, that in the humid way carbonic acid is a stronger acid than 

 boracic, the acid salts of which act in the same way as the neutral carbonates (on 

 alkalies), while both of them are stronger than silicic acid, which does not at all 

 obscure the basic property of the alkali with which it may be combined. 



FORMIC ACID. 



Alcohol may be represented as consisting of etherine plus water, and formic 

 acid as carbonic oxide plus water, both are resolved into their respective bodies by 

 the action of sulphuric acid. Berthelot has shewn that formic acid may be gene- 

 rated by heating carbonic oxide with caustic potassa in close vessels to a tempera- 

 ture of 212° Fahrenheit for seventy hours, water being present. 



DAT1SCINE. 



Stenhouse has examined this substance, originally found by Braconnot in the 

 leaves of the Datisca cannabina. Stenhouse obtained it from the root by extrae 



N 



