39 



jar, which is placed over a dish containing a substance called 

 Benzoic Acid. As before, vaporize the substance by heat, 

 and the hot vapour, meeting the cold leaves, is deposited on 

 them in long white silky needles imitating closely ordinary 

 hoar-frost. 



(2.) Fusion and slow cooling. 



Fragments of metallic Bismuth are crystalline, but 

 the crystals are so intermingled that no clear idea is 

 obtained of their individual form. Melt the metal down in 

 an iron ladle until the whole is well molten, and set it aside 

 until the surface metal just begins to solidify again — through 

 contact with the cold air — then quickly pierce with an iron 

 rod two holes through this crust, and turning the ladle 

 upside down, the still liquid metal from the interior is 

 poured out, leaving a crust of metal the shape of the ladle. 



On allowing this to cool, detaching it from the ladle, 

 break it with a hammer, when the inside is found to be 

 covered with beautiful and characteristic crystals of metallic 

 Bismuth. Sulphur, treated in a similar manner, leaves a 

 mass of long, yellow transparent needles. 

 (3.) Electro deposition. 



By this method, many metals may be deposited from 

 solutions containing them on a mass of metal introduced into 

 the liquid. 



In two large flasks were placed the following solutions 

 in (i) Lead Acetate (prepared by dissolving metallic Lead in 

 Acetic Acid), (2) Chloride of Tin (prepared by dissolving 

 metallic Tin in Hydrochloric Acid), and to each flask pure 

 distilled water was added. A piece of zinc was suspended by 

 means of a thread in the neck of each flask, allowing the 

 metal to rest an inch or two below the surface in each 

 case. 



An interesting change was seen to take place, for on the 

 surface of the zinc, in both instances, crystals of metal were 

 quickly deposited : on examination, the deposit in (i) proves 

 to be crystalline metallic Lead, in (2) crystalline metallic 

 Tin. The appearance of the crystals is very different, those 



