320 SCIENTIFIC RECREATIONS. 



COMMON METALS AND PRECIOUS METALS. 



How many invalids have swallowed magnesia without suspecting that 

 this powder contains a metal nearly as white as silver, and is malleable, and 

 capable of burning with so intense a light that it rivals even the electric 

 light in brilliancy ! If any of our readers desire to prepare magnesium them- 

 selves it can be done in the following manner : Some white magnesia must 

 be obtained from the chemist, and after having been calcined, must be sub- 

 mitted to the influence of hydrochloric acid and hydrochlorate of ammonia. 

 A clear solution will thus be obtained, which by means of evaporation under 

 the influence of heat, furnishes a double chloride, hydrated and crystallised. 

 This chloride, if heated to redness in an earthenware crucible, leaves as a 



Fig. 308. Group of alum crystals. 



residue a nacreous product, composed of micaceous, white scales, chloride of 

 anhydrous magnesium. 



If six hundred grams of this chloride of magnesium are mixed with one 

 hundred grams of chloride of sodium, or kitchen salt, and the same quantity 

 of fluoride of calcium and metallic sodium in small fragments, and the 

 mixture is put into an earthenware crucible made red-hot, and heated for a 

 quarter of an hour under a closed lid, we shall find on pouring out the fluid 

 on to a handful of earth, that we have obtained instead of scoria, forty-five 

 grams of metallic magnesium. The metal thus obtained is impure, and to 

 remove all foreign substances it must be heated in a charcoal tube, through 

 which passes a current of hydrogen. 



Magnesium is now produced in great abundance, and is very inexpen- 

 sive. It is a metal endowed with a great affinity for oxygen, and it is only 

 necessary to thrust it into the flame of a candle to produce combustion ; it 

 burns with a brightness that the eye can scarcely tolerate, and is transformed 



