effected by Mechanical Force. 243 



any case on the metal, which preserved its full brightness in 

 the parts in contact with the material, so that the effects ob- 

 served were due to pressure only. 



Silver sulphite in platinum foil was moderately darkened by 

 two days pressure. 



Silver salicylate was rendered very dark by two days pres- 

 sure. 



Silver carbonate was moderately darkened by a somewhat 

 longer pressure. 



Silver tartrate was not affected. 



Silver oxide was thoroughly dried at 150°. A piece of 

 platinum foil was heated to redness and rapidly cooled, a por- 

 tion of oxide was folded up in it and weighed. Weight 

 found *7639. It was then subjected to very great pressure for 

 four days. Weight found to be *T639, no change. 



Ferric oxide recently precipitated and dried. No effect 

 produced by pressure, no formation of ferrous oxide. 



Potassium platinobromi.de. Where the pressure was greatest 

 the brilliant red color of this substance was blackened, not 

 superficially only, but all through. 



Ammonium platino chloride. Moderate but well marked 

 darkening. 



Potassium chlorate. When this substance was subjected to 

 pressure by itself no effect whatever was produced and not a 

 trace of chloride was formed. Rut when it was mixed with 

 silver nitrate, both in line powder, and subjected to pressure 

 there was an evident formation of silver chloride. The mate- 

 rial was no longer completely soluble in water but left an 

 abundance of white flakes which darkened when exposed to 



Mercuric oxide requires a very high pressure to produce an 

 effect upon it. It then darkens slightly but very distinctly 

 and this change seems to be accompanied by a slight loss of 

 weight requiring, however, very careful weighing to detect it. 



The darkened part as well as the rest dissolves without 

 difficulty in acetic acid and consisted therefore probably of 

 traces of mercurous oxide and not metallic mercury. 



Mereurou8 chloride showed no change. 



Mercuric chloride. Corrosive sublimate perfectly free from 

 calomel, which commercial sublimate is very apt to contain, 

 was subjected to great pressure and then treated with ammonia. 

 As no darkening took place there had evidently been no reduc- 

 tion. 



Mercuric iodide. Red mercuric iodide when subjected to 

 very great pressure darkened considerably and at points where 

 the pressure was greatest it became absolutely black. It did 



