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, - - - lOO. 



Dry quick hme, _ _ _ 19.8 



Charcoal, _ _ _ _ 4.2 



But to prevent loss the chloride must be in powder. 



3. Action of ether 011 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, Arch. t. 16, p. 126. 



4. Memoir on starch ; by M. Guibourt. — We are indebted lO' 

 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 



