394 CHEMISTEY. 



cury. It forms a magnificently crystalline amber-yellow mass. SG=2.6. Fuses at 

 39°, boils at 230° The chloride boils at 135°. The difference = 3 X 31£ which is 

 exactly the same difference as between the bromide and chloride of silicium. Ac- 

 cording to Kopp, the boiling points of the bromides differ from those of the chlo- 

 rides by 32" for every equivalent of bromine replacing chlorine. According to 

 this the formula of Titanic acid would be TiO, and the equivalent would require 

 alteration. Further experiments are required to test this hypothesis. 



Mercury. — R. Weber has examined the behaviour of sulphide of mercury to the 

 compounds of the alkalic metals, and finds that it is capable of forming a crystal- 

 line sulpho-salt with the protosulphides of potassium or sodium, which compound 

 however can only exist in presence of free alkali. According to Brunner the po- 

 tassium salt is KS+HgS+5HO. 



Silver. — Mr. Hambly has made some valuable experiments on the loss of this 

 metal, resulting during its cupellation. Plattner has also investigated the cause of 

 the loss of silver observed during the roasting of its ores, and he is inclined to be- 

 lieve from some experiments on the subject, that it results from the fact of oxide 

 of silver being formed, which is again reduced in an exceedingly finely divided 

 state, and is thus carried off by the gas of the furnace. 



Sulphur in Hop*. — It is often of importance to determine whether hops have 

 been treated with sulphurous acid. The old silver lest being of little value, 

 Heidenreich evolves hydrogen from zinc and hydrochloric acid, with which the 

 hops have been mixed ; the formation of sulphuretted hydrogen, indicated by the 

 brown color produced on passing the gas through a solution of acetate of lead, 

 proves the presence of sulphurous acid. Wagner adopts the same process, but 

 uses a pale solution of nitroprusside of sodium made slightly alkaline. The test is 

 exceedingly delicate, but will not succeed if the hops have been kept some months. 



Iodates. — Rammelsberg has carefully examined the crystalline forms of the dou- 

 ble salts formed by biniodate of potassa with chloride of potassium and sulphate of 

 potassa. The formula? are KC1+KO, 2I0 5 and KO.IO +4K0.2S0 3 the latter be- 

 ing remarkable as containing anhydrous bisulphate. — Pogg. Ann. 97, p. 92. 



Silicium. — Wohler has described the properties of the graphite modification of 

 silicium, obtained by fusing aluminium with dry silicofluoride of potassium or sodium. 

 The mass is crushed, the aluminium extracted by hydrochloric acid, the silica by 

 hydrofluoric acid, the residue washed. It forms opaque metallic crystalline leaves, 

 very similar to graphite, but with more metallic lustre ; it is harder than glass, 

 but softer than topaz. S. G. = 2.490, being less than that of its oxide. Cannot be 

 oxidized by oxygen even when heated to whiteness, infusible, like the amorphous 

 silicium, when heated with carbonate of potassa, it oxidizes and produces combus- 

 tion. Insoluble in acids, but slowly dissolved by solutions of potassa or soda. 

 Combines readily with chlorine. Pogg. Ann. 97, p. 484. 



Chromates. — Lowe has examined two chromates of bismuth, one obtained by pre- 

 cipitating nitrate of bismuth with chromate of potassa, the other by the action of 

 dilute acids on the salt so formed. The formula? are 3Bi0 3 +2Cr03 and Bi0 3 + 

 2Cr03. Jf. Pr. Ch e 67. 288. 



Solubility of Sulphate of Baryta in acids. — Mr. Noad has made some experi- 

 ments to determine the effect of dilute hydrochloric acid in rendering sulphate of 

 baryta soluble, in reference to Calvert's statements. (Vide ante, No. III., p. 311.) 



