504 Mr. Warington on the Molecular Structure of Silver. 



wards, a watchmaker resident in Shoreditch, by whom it was 

 purchased, it was without a cover, and the contents had been 

 thrown away, with the exception of some black ashes, which 

 were not preserved. Its thickness was about from 0*015 to 

 0'017 of an inch, its surface presented a dull tarnished aspect, 

 and was stained in patches with red oxide of iron. It was 

 extremely rotten and brittle, breaking by the application of 

 the slightest force ; the surfaces of fracture were uneven and 

 of a bright white metallic lustre. When examined under the 

 microscope by a power magnifying 100 diameters it presented 

 a highly crystalline structure, the facets of the crystals being 

 exceedingly bright and approaching the cubic form, but none 

 of them could be observed perfectly developed; they were 

 more analogous to the characters of grain tin in its broken 

 state as met with in commerce. It appeared also as though 

 there had been a recry stall ization of the metal, as the particles 

 looked as if they had been drawn from the central part to 

 the sides of the thin plate, leaving cavities or interstices of 

 considerable extent and depth ; the exterior surface was also 

 coated with a film of about 0*0005 of an inch thick, having 

 a grayish-olive colour, and totally different in its structure 

 from the other parts, being striated across its breadth. The 

 specific gravity of the metal in this state was found to be 

 9*937, great care having been taken to remove the air from 

 the internal cavities by means of the air-pump. 



The metal was next heated to redness in a crucible, and 

 the heat sustained for about ten minutes, after which its cha- 

 racters were found to be totally altered ; it had lost its extreme 

 brittleness, requiring to be bent several times before a fracture 

 could be effected, and then, by the aid of the microscope, 

 exhibited a close, small grained tough aspect of a dull white 

 colour, and without the previous cavernous appearances ; the 

 superficial film seemed also in places to have partially sepa- 

 rated from the substance of the thin plate of metal during the 

 bending. The specific gravity was again taken, adopting the 

 previous precautions, and was found to be 9*95, making an 

 increase of 0*013 on the gravity taken before the application 

 of a red heat. 



It was next submitted to analysis; 8*5 grains were digested 

 in dilute nitric acid, and the soluble parts (A) decanted, and 

 the residue well washed. This residue was in small thin 

 grayish-white flakes, and by exposure to the light became ra- 

 pidly of a purple tint, indicating the presence of chloride of 

 silver ; fearing that this might have arisen from some acci- 

 dental impurity in the materials employed, both the nitric 

 acid and distilled water were carefully tested and proved to 



