Decompofition cfthe Muriate of Soda by Lead. 471 



maulfeft contradiction. The fuperior affinity of the oxide of lead for the muriatic acid, 

 which is urged for the folutlon of the difficulty, is deftroyed by the decompofition of the 

 muriate of lead, by means of cauftic foda ; and that of the carbonic acid contained in the ' 

 litharge, to which account has been had, is equally contradided by the abfolute inaftion 

 of the carbonate of lead upon marine fait, and by minium which contains little of this acid, 

 but neverthelefs decompofes the muriate of foda. 



To avoid this difficulty, fomc authors have affirmed that the oxide of lead decompofes fea 

 fait only in part ; but this was an error naturally produced by a faulty explanation of a fadl 

 which is true in itfelf. 



I have, on the contrary, clearly afcertained that the decompofition of this fait is compleat, 

 when the quantity of oxide of lead is fufficient ; for how can this partial adion take place 

 if pure foda be obtained .' and why fiiould the procefs ftop at any determined limit, without 

 having been weakened by fome known caufe ? 



With the intention of clearing up this fubjeft I made the following experiments : 



1. I mixed feven parts of finely ground litharge, with one part of muriate of foda; I 

 fprinkled the mixture with a fufficient quantity of water, to give it the confiftence of thin 

 foup ; after which I agitated it for feveral hours, in order to renew the furfaces and facilitate 

 the a£tion of the ingredients. 



The oxide of lead loft its natural colour, and. gradually became white; its volume was 

 fingularly increafed; and in proportion as the water was abforbed the mixture acquired a 

 confiderable confiftence, fo that 1 was obliged at feveral reiterations, to add a quantity of 

 water. Laftly, at the end of four days the litharge appearing to have entirely changed its 

 nature, and no further progreffion being obfervable in the efFefts, I diluted the mafs with 

 /even or eight parts of water, and filtered. The filtered liquor had a very evident alkaline 

 tafte, and contained a fmall quantity of the muriate of lead in folution, without one atom 

 of the muriate of foda. When it was reduced to about V^th of its volume, it affijrded 

 cryftals of carbonate of foda, rendered opaque by fome traces of muriate of lead. 



2. The oxide of lead waftied and dried, had a dirty white colour, and its weight was 

 increafed about one eighth part. When gently heated, it acquired a very fine lemon 

 yellow colour, with the lofs of 0,025 °^ '^^ weight. A part of this oxide, heated with a 

 folution of cauftic foda, prefented the following phenomena : 



I. Its orange colour was converted into a dull yellow. 2. Its pulverent form was con- 

 verted into that of needles, and its bulk was greatly diminifhed ; the folution of foda had 

 not perceptibly changed its tafte, but it afForded a very abundant black precipitate,, by the 

 hydro-fulphuret of foda; a. white depofition, with the muriatic of the nitric acids ; but that 

 formed by the latter was re-diflblved in an excefs of acid. Thefe depofitions were per- 

 fectly fimilar to the portion of matter which was not diflblved by the foda. 



3. One hundred parts of the fame matter were heated with diluted nitric acid, which 

 diflblved the greateft part ; the remainder being of a white colour and cryftalline form. 

 This fubftance, feparated from th? fluid, was fufed upon ignited coals, aflumed a black 



3 P 2 colour. 



