Miscellanies. 37 1 



fectly clean, the decomposition goes on pretty rapidly of itself, but if 

 not entirely clean and fresh, it may be slow, and in that case, a little 

 muriatic or sulphuric acid must be added. This addition is, besides, 

 necessary for washing the silver and having it pure. The operation 

 is rapid and curious to observe. The reduction penetrates from the 

 surface to the center. The temperature rises, if the mass be con- 

 siderable, and contributes to accelerate the operation. It may, if too* 

 weak, be aided by artificial heat. 



The chloride of silver may be reduced also by heating it with a 

 mixture of lime and charcoal in the following proportions. 



Chloride of silver, - 100. 



Dry quick lime, ... 19 # 8 



Charcoal, - 4.2 



But to prevent loss the chloride must be in powder. 



3. Action of ether on sulphate of indigo ; by M. Cassola. — If 

 one part of indigo be dissolved in four parts of sulphuric acid and 

 diluted with twenty parts of water and an equal quantity of sulphu- 

 ric ether be added, the liquid becomes discolored in about half an 

 hour, if it is kept constantly at a temperature of 100° F. in a well 

 stopped bottle. The blue color cannot be restored by oxygen, or 

 metallic oxides. — Kartsner r Arch. t. 16, p. 126. 



M 



We 



M. Raspail for the interesting discovery that starch is not a homoge- 

 neous substance, — that each granule is a real organ, consisting, 1st 

 of a shining envelope or tegument, inattackable by water and acids 

 at common temperatures, susceptible of being highly colored by 

 iodine ; 2nd, of an interior substance, soluble in cold water, liquid, 

 even in its natural state, and when evaporated loses the property of 

 being colored by iodine, and which possesses all the properties of gum. 

 He further states, that the coloring of starch blue by iodine is owing 

 to a volatile substance, but my own experiments are contrary to this 



assertion. 



Potatoe starch is quite insoluble in cold water. When rubbed in 



a dry state on a stone, it loses its white shining appearance, and if it 



be moistened with water it forms a tenacious paste which becomes 



very hard, when dry. Pounded in a mortar, it produces a mucilage 



analogous to gum tragacanth. Starch, in mass, acquires a sky blue 



color with iodine, but slowly, without losing its transparency. When 



