CHEMISTBY. 305 



MANGANESE. 



Brunner prepares this metal by the actiou of sodium on the fluoride. Its 

 specific gravity is 7 .138— Y .206, unchanged in the air, harder than steel, oxidizes on 

 the surface when heated, like iron, is non-magnetic, dissolves readily in diluted 

 sulphuric acid, and in nitric and hydrochloric acids. From its extreme hardness 

 it may probably find useful applications in the arts. 



CHROMIUM. 



Fremy obtains this metal in crystals of great brilliancy by passing the vapour of 

 sodium over the chloride. The crystals are very hard, and resist the action of 

 the strongest acids. 



SILVER IN SEA "WATER. 



It has long been known that sea water contains an appreciable quantity of silver, 

 probably in the form of chloride, dissolved in the chloride of sodium. As such a 

 solution is readily decomposed by metallic copper, Field was induced to examine 

 whether the yellow metal employed in the sheathing of vessels contained more 

 silver after long exposure to sea water than it did when first applied. One speci- 

 men from sheathing which had been used for seven years gave as much silver as 

 would amount to upwards of one pound per ton. The original yellow metal could 

 not be obtained for examination, but it undoubtedly could not have contained any- 

 thing like this quantity. Sheathing, which had been exposed for three years was 

 compared with some of the unused metal ; the latter contained about one ounce 

 of silver per ton, the former more than seven ounces. 



Various other experiments were made, and in every case a similar difference 

 observed, but in cases where the sheathing had only been exposed a short time, 

 the differences were very slight, 



MAGNESIUM. 



Deville and Caron have prepared this metal in considerable quantities and 

 examined its properties. They find that it resembles zinc in being volatile, and 

 almost at the same temperature. It fuses at about the same temperature as zinc ; 

 at a higher point it inflames, and burns like zinc, producing a brilliant flame and 

 white flakes. Specific gravity, l.wo. 



PREPARATION OF METALS. 



Deville recommends the use of lime crucibles in the preparation of chromium 

 and manganese, as thereby the presence of silicium is avoided, which i3 almost 

 always formed when earthen and porcelain crucibles are employed. Charcoal 

 vessels are equally objectionable. Cobalt and Nickel, when prepared in this way, 

 possess very different properties from those usually ascribed to them, cobalt being 

 one of the most ductile and tenacious of metals. Manganese and chromium thus 

 prepared are excessively hard; the latter, when pure, is less fusible than platinum, 

 it dissolves readily in hydrochloric acid, giving a blue solution of Peligot's proto- 

 chloride. 



OXIDE OF SILICIUM. 



Wohler found that by heating silicium to a slight red heat in a current of dry 

 hydrochloric acid gas, hydrogen is given off, and a new chloride of silicium formed. 

 It is a very mobile fuming liquid, more volatile than the ordinary chloride. 

 Water decomposes it into hydrochloric acid and the new oxide. The latter is 

 white, slightly soluble in water, easily in alkalies, even in ammonia, evolving 



