G. Williams 191 



the time. This process took about forty minutes to complete. The 

 liquid was only very faintly acid after the final addition of litharge. 

 The hot liquid was filtered, and the undissolved litharge thoroughly 

 washed. The filtrate and washings were evaporated down to dryness 

 in an evaporating basin, the pasty residue of lead salts being stirred 

 as long as this was possible. 



Weight of undissolved lead hydroxide = 136 grms. containing 



0-628 grm. of nitrogen. 

 Weight of undissolved lead oxide = 439 grms. containing 



1-598 grms. of nitrogen. 

 The lead salts were finally dried at 100° C, the weight of dry lead 

 salts obtained being 489 grms. 



Esterification of the lead salts. 



The dry lead salts were placed in a large porcelain jug, and 1500 c.c. 

 of absolute alcohol added. Dry gaseous hydrochloric acid was passed 

 in for about four hours^ and the mixture was then warmed on the water 

 bath for half an hour. A brisk evolution of hydrogen sulphide took 

 place at first during the passing in of the hydrochloric acid. The lead 

 salts soon passed into solution^ and a precipitate of lead chloride was 

 formed. Finally the liquid was saturated with dry hydrochloric acid 

 gas at 0° C. The lead chloride was filtered off (ordinary filter-paper 

 being used) and thoroughly washed with absolute alcohol. 



The weight of lead chloride was 175-7 gi-ms. containing 

 3-87 grms. of nitrogen. 



This high figure is due to the presence of the ammonia as ammonium 

 chloride in the lead chloride precipitate. The brown-coloured filtrate 

 was concentrated under reduced pressure at 40° C. By this means the 

 greater part of the hydrochloric acid and esterification water was removed. 



Removal of the remaining free hydrochloric acid. 



The thick residue in the distillation flask was diluted down with 

 absolute alcohol and cooled to 0° C. A solution of dry ammonia in 

 absolute alcohol was then carefully added until the liquid remained 

 only faintly acid to litmus. The ammonium chloride so formed was 

 filtered off and thoroughly washed. In this way the hydrochloric acid 

 was removed without any production of water which would saponify 

 the esters and lower the yield. An alcoholic solution of the ester 

 hydrochlorides was left. 



