S24 Dr. Stenhouse's Examination of Purree, the substance 



soluble, and washed with hot alcohol till all excess of acetate 

 of lead was removed. When highly heated the salt melts and 

 gives off vapours, which condense in long bright yellow cry- 

 stals on the edge of the crucible. These crystals constitute a 

 substance which will presently be described. 



I. 0-4835 salt, dried at 212^ F., gave 0-128 oxide and 0-036 

 lead =34--34; per cent, of oxide. 



Per cent. 



II. 0-4-395 gave 0'125 oxide and 0-0235 lead =34-21 



III. 0-522 gave 0-152 oxide and 0-0240 lead =34-00 



IV. 0-4395 gave 0'125 oxide and 0-0235 lead =34-09 



Mean 34-16 



These determinations were made with three different quan- 

 tities of the lead salt. 



I. 0-5332 substance burned with chromate of lead gave 

 0-700 carbonic acid and 0-142 water. 



II. 0'541 substance gave 0-716 carbonic acid and 0*15 

 water. Calculated numbers. 



100-00 lOO'OO 4106 100-0 



From these analyses it is evident that the oxide of lead has 

 united with the acid without removing an atom of water, as is 

 usually the case, unless with very feeble acids. The calculated 

 atomic weight of the acid from this salt is 2712, and the num- 

 ber found is 2662. Purreic acid forms only one salt with 

 lead, as the same compound was also obtained when subace- 

 tate of lead was employed. 



When purreic acid is heated considerably above 212° F. it 

 melts, and if the heat is still further increased it begins to sub- 

 lime. The best way of obtaining this sublimate in bright 

 yellow crystals of from 1 to 1^ inch long, is cautiously to 

 heat pretty strongly a quantity of the impure acid in Mohr's 

 subliming apparatus. A very large proportion of the acid is 

 charred, but a quantity of fine large crystals may be readily 

 procured, attached for the most part to the under side of the 

 diaphragm. These crystals are not purreic acid, but a neutral 

 body which does not redden litmus. It is but slightly soluble 

 in either acid or alkaline solutions, or in water, alcohol or 

 eether. Its alcoholic solution does not precipitate neutral ace- 

 tate of lead, nitrate of silver, or the chlorides of lime or ba- 

 rytes, but with basic acetate of lead it gives a yellow mucila- 

 ginous precipitate. 



