Intelligence and Miscellaneous Articles, 133 



teiver along with a vessel of water, we shall be able to ascertain 

 whether it is pure sulphate of potash or mixed with sulphate of 

 soda; if it be the former it will gain no permanent weight however 

 long the experiment may be continued ; but if there be any of the 

 latter present, it will gain weight till that portion becomes of the 

 same constitution as it is of when it exists in the crystallized state. 



I 



NEW ACETATE OF LEAD. 



M. Payen produced to the Academy of Sciences a regularly cry- 

 stallized specimen of a new acetate of lead. It is composed of 

 three atoms of neutral acetate and one atom of trisacetate ; its for- 

 mula is represented by 



3 PbO, C« H« 0=»+ 3 (PbO, C« H^ O^). 

 It is distinguished from the neutral and trisacetate by its crystalliza- 

 tion in hexagonal plates, which form slowly, by exposing the solu- 

 tion, in radiating mamellated crystals; it crystallizes very abun- 

 dantly so as to become almost a mass on cooling, whilst the trisace- 

 tate crystallizes with difficulty. Its solubility in water and of alco- 

 hol of various strengths, both cold and hot, is much greater than 

 that of the two other acetates ; thus at 65° Fahr. water dissolves 

 about four times as much of it as of the neutral acetate and six 

 times as much as of the trisacetate. It has an alkaline reaction ; it 

 is more stable than the first acetate and less so than the second. 

 A saturated aqueous solution dissolves either of the other acetates, 

 and acquires by so doing the consistence of a syrup, and thus re- 

 tards or prevents all crystallization. An equal volume of anhy- 

 drous alcohol does not decompose this solution, whereas it causes 

 the other acetates to appear in their respective solutions. When 

 heated it suffers igneous fusion only, while the neutral acetate un- 

 dergoes two successive fusions and the trisacetate does not fuse at 

 all. It does not lose any of its acid in a dry vacuum, whereas the 

 neutral acetate loses a portion of it on cooling. Carbonic acid de- 

 composes an atom of the trisacetate of lead, and converts it entirely 

 into neutral acetate. This new acetate can, on the contrary, dis- 

 solve hydrated or anhydrous oxide of lead and become complete 

 trisacetate. By the addition of ammonia, according to the propor- 

 tion and temperature, the new acetate yields either trisacetate, or 

 anhydrous protoxide of lead, or crystallized hydrate. 



This acetate is prepared by dissolving three atoms of neutral ace- 

 tate in a solution of one atom of trisacetate; after due evaporation 

 the solution is to be allowed to crystallize, and this occurs in three 

 or four days after the solution has become cool ; the crystals are to 

 be drained, pressed in blotting paper, and dried in vacuo 3 a syrupy 

 solution remains. M. Payen observes that the existence of this new 

 acetate explains why several authors have stated that the subacetate 

 of lead is more soluble than the acetate, while others have shown the 

 contrary : this has happened because the former have observed the 

 solubility of the new acetate or of its mixtures, while others have 

 operated on the trisacetate. 



It also appears why the neutral acetate effloresces, and by losing 

 a portion of its acid in the air acquires an alkaline reaction, then 



