20 



John White 



In each instance, the action of water was to produce an 

 almost instantaneous decomposition, yielding lead iodid, 

 shown by the orange-yellow color characteristic of this substance 

 when deposited in the amorphous state; in a very short time, 

 however, the color begins to change, turning lighter in hue. 

 The time required for completion of this change varied in length 

 with the size of the particles and, to some extent, with the salt, 

 the potassium salt usually reacting more slowly than the others. 

 The color at the end was a light sulfur-yellow. Analysis proved 

 this to consist of basic iodid of lead. In the table the sodium 

 salt is designated as A, the potassium as B, and the ammonium 

 as C. 



The action of absolute alcohol upon the three double salts 

 was in general of a character similar to that of water, but here 

 the nature of the individual salt seemed to play an important 

 part, for it was found that the potassium salt, which is the 

 easiest of the three to prepare, was scarcely acted upon at all 

 by the alcohol, there being but very slight change in color, 

 even after digesting for several days. An iodin estimation in 

 the filtered and dried residue, after prolonged extraction, 

 showed 25.74 per cent iodin, the theory requiring 25.84 per 

 cent, thus proving that there had been no action. The am- 

 monium salt, which stands next to the potassium salt in readi- 

 ness of preparation, showed, after the same time of digestion, 

 a slight decomposition ; the residue gave 30.73 per cent iodin, 

 while the original salt contains 27.00 per cent. The decompo- 

 sition in the case of the sodium salt was almost complete, giv- 

 ing 33.64 per cent iodin, while the original salt contained 25.12 

 per cent and the basic iodid 36.16 per cent. Thus it appears 

 that the degree of solubility of the salt in absolute alcohol is 

 indicative of the degree of decomposition produced by it. It 



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