296 VINEGAR, CIDER, AND FRUIT-WINES. 



access of the carbonic acid of the air. Very remarkable is the 

 behavior of the tribasic acetate towards hydrogen dioxide; plum- 

 bic dioxide is first formed, but in a short time this exerts a de- 

 composing influence upon the hydrogen dioxide which may be 

 present in excess, so that both dioxides now lose one-half of their 

 oxygen, which evolves in the form of gas, and water and plumbic 

 oxide are formed.* Now, as freshly precipitated plumbic di- 

 oxide possesses the further property of decomposing solution of 

 potassium iodide, Schoenbein recommends tribasic acetate of lead 

 together with paper coated with paste prepared with potassium 

 iodide as the most sensitive re-agent for hydrogen dioxide. 



Lead sesquibasic acetate, triphimbic tetracetate. This salt is ob- 

 tained by heating the diacetate until it becomes a white, porous 

 mass; this is re-dissolved in water and set aside to crystallize. 

 Sesquibasic acetate is soluble in both water and alcohol ; its solu- 

 tions are alkaline. 



Tribasic acetate of lead is prepared by digesting 189.5 Ibs. of 

 sugar of lead with 223 Ibs. of plumbic oxide (pure) or 3 Ibs. of 

 sugar of lead to 4 Ibs. of litharge ; or, according to Payen, into 

 100 volumes of boiling waiter are poured 100 volumes of aqueous 

 solution of sugar of lead saturated at 86 F., and afterwards a 

 mixture of pure water at 140 F., with 20 volumes of ammonia 

 liquor free from carbonate. The vessel is then immediately 

 closed, and in a short time an abundance of the tribasic acetate 

 crystallizes out. This salt presents itself under the form of long 

 needles. It is insoluble in alcohol, very soluble in water, its so- 

 lution being alkaline. Tribasic acetate is the most stable of all 

 the subacetates of lead. It takes a leading part in the manufac- 

 ture of white-lead by the Clichy process ; it is, in point of fact, a 

 solution of this salt which is decomposed by the carbonic acid, 

 and gives rise to the carbonate of lead, being itself at the same 

 time converted into lead diacetate. In the Dutch process the 

 formation of lead carbonate is, according to Pelouze, also due to 

 the formation of tribasic acetate on the surface of the sheets of 

 lead, which is, in its turn, decomposed by the carbonic acid. 



Sexbasic acetate of lead. This body is prepared by digesting 



* Schoenbein in Wagner's Jahresbericht, 1862. 



