Some Peculiar Double Salts of Lead 



19 



On heating in a vacuum bath at 77°C. for 7 hours, 0.8712 

 gram substance lost 0.0327 gram in weight, which corresponds 

 closely with the required loss for the above compound ; it was 

 impossible, however, to bring it to constant weight, for a very- 

 slow, almost imperceptible diminution of weight follows from 

 this point. This was found to be true of all compounds con- 

 taining lead acetate, and is probably caused by a gradual 

 breaking down of the lead acetate ; in air this takes place rap- 

 idly. When heated in a melting tube, the salt assumes a slight 

 yellowish tint with slight signs of sintering at i8o°C. ; at 192° 

 it becomes pasty, and melts slowly to a clear, amber colored, 

 very viscous liquid at 202-205 °C. No visible decomposition 

 takes place during the heating. 



The lead salt behaves in general like the other salts de- 

 scribed, being, however, somewhat more stable than these. 



The Action of Solvents. — It has been stated that most of 

 the substances commonly employed as solvents exert a de- 

 composing action upon these double iodid-acetates. This is 

 particularly true of water, the alcohols, and the acids ; the 

 ethereal salts, when thoroughly dry, seem to be without action 

 of any sort ; dry hydrocarbons likewise. It is unfortunate that 

 no good solvent has as yet been found, since it has not been 

 possible to settle positively the question of the structure of 

 the salts. But the action of water and alcohol is of interest, 

 nevertheless, since the decompositions resulting furnish some 

 evidence bearing upon the structure. The sodium, potassium, 

 and ammonium double salts were each pulverized and shaken 

 up in stoppered flasks with water and with absolute (96 to 98 

 per cent) alcohol respectively, the time ranging from 24 hours 

 to six days. 



325 



