112 Dr. L. Play fair on a neiv Fat Acid. 



by igniting the salt, ascertaining the weight of the lead, and 

 oxide of lead, which remained; washing the mixture with 

 weak acetic acid by decantation, and calculating the loss as 

 oxide of lead. 



It has been shown* that both benzoate and margarate of 

 lead contain acetic acid in chemical combination, and not as 

 a mere accidental constituent arising from imperfect washing. 

 Hence it was necessary to ascertain whether or not sericate 

 of lead contained this acid. For this purpose a ^ew grains of 

 the salt were moistened with alcohol and sulphuric acid, and 

 subjected to distillation. Acetic aether passed over and was 

 easily recognized by its well-known properties. The quantity 

 of acetic acid contained in the salt, appeared to be very 

 small. 



0*985 gramme of salt left, after ignition, 0*421 gramme of 

 lead and oxide of lead ; of this 0*55 gramme was oxide of 

 lead, and 0*366 gramme metallic lead : both together are 

 equal to 45*58 per cent, of oxide of lead. 



0*456 gramme, burned with oxide of copper, gave 0*684 

 gramme carbonic acid, and 0*273 gramme water. 



We have already seen that sericine contained four atoms 

 of sericic acid, and one atom of oxide of glyceril. In the 

 sericate of lead made frona sericine, the oxide of glyceril ap- 

 pears to be displaced by one atom of basic acetate of lead 

 (Ac+3PbO). 



4 atoms of neutral sericate of lead = Ci,2 + Hj08 + O,2+ Pb04 

 1 atom of basic acetate of lead = C 4 + H g+Og+PbOg 



1 atom of sericate of lead = Cii5+Hiii + 0,5+ PbO^ 



The formula would therefore be 4 (C^g Ho^Og + Pb O) 



+ (C4H3 0,+ Pb03). 



Another salt of sericic acid and oxide of lead may be ob- 

 tained by adding acetate of lead to a solution of sericate of 

 potash. ' But from the great disposition of oxide of lead to 

 form basic salts, a mixture of salts appears, in this case, to be 



* AnnalenderCkemieundPharmacie,\\}i.v. 1. 



