12 John White 



Although the above substance may be a mixture, the analyt- 

 ical results indicate the contrary, agreeing very well indeed with 

 the calculated values for a definite salt. According to the theory 

 proposed in explanation of the formation of this class of com- 

 pounds, there is no reason why one molecule of the iodid-acetate 

 should not unite with a varying number of molecules of the 

 metallic acetate, forming compounds like the above. Some re- 

 cent results obtained with another salt tend to show that this is 

 possible. 



The properties of the above salt are in general similar to those 

 described under the first sodium salt. 



The Potassium Salt. — As previously stated, Tommasi^ ob- 

 tained a potassium lead iodid-acetate to which he ascribed the 



formula 2 Pb <i ^ j^r ^ -{- KC'iHzO^. This he obtained by dis- 



solving I mol. lead iodid in a hot aqueous solution of potassium 

 acetate, containing 2 mols. This, on cooling, deposited a pa'e 

 yellow, crystalline mass, which he redissolved by heating with 

 twelve times its weight of absolute alcohol and allowed to 

 cool in a desiccator over lime. In this way he obtained a large 

 quantity of white crystal flakes. The formula assigned to the 

 compound by Tommasi differs slightly from that used here, 

 yet there is every reason to believe that the two compounds 

 are identical, for the method used was essentially the same as 

 that described in his paper, and the general appearance and 

 character of the two products were alike. Tommasi gives 

 no analytical details. The potassium salt is easier of prepara- 

 tion than the sodium compound, being much less soluble and 

 more stable than the sodium salt. Alcohol of greater dilution can 

 be used without causing decomposition ; indeed it was found that 

 imless a moderately dilute alcohol were used, very little lead 

 iodid could be brought into solution. A strong solution of 

 potassium acetate in 50 or 60 per cent alcohol was made, and 

 to this, after heating to boiling, lead iodid was added in small 

 portions at a time, until it ceased to dissolve; the addition of 



318 



