G. S. Jamieson — Determination of Lead as Sulphite. 157 



Akt. XV. — On the Determination of Lead as Sulphite; by 



GrEOKGE S. JAMIESON. 



It lias been known for a long time that lead sulphite was a 

 very insoluble compound, but it remained for V. N. Ivanov* 

 to show that very small amounts of lead could be detected by 

 precipitation as the sulphite. He found a 2 per cent solu- 

 tion of acid sodium sulphite most suitable, because this reagent 

 could be employed for the detection of lead in the presence of 

 iron, nickel, silver, copper, calcium, magnesium, and aluminum. 

 Barium must not be present as it is pi*ecipi(ated under the 

 same conditions as lead. 



Since it appears that this reaction has never been used for 

 the quantitative estimation of lead, the following investigation 

 was made in order to determine the conditions under which 

 lead could be precipitated and weighed as the sulphite. It was 

 found that lead could be precipitated quantitatively from a 

 slightly acid solution with sodium or ammonium bisulphite, or 

 even with aqueous sulphurous acid, if the acidity of the solution 

 is carefully controlled. When a solution contains much acid 

 it should be almost neutralized with ammonium hydroxide 

 before attempting to precipitate the lead. 



For convenience, a solution of lead acetate was prepared 

 which contained 7 - 8320 grams of lead and 10 grams of actual 

 acetic acid in 1000 cc . Measured quantities of this solution was 

 taken in beakers and diluted to about 100 cc . To each solution 

 an excess of a 2 per cent solution of sodium bisulphite was 

 added. The solutions were thoroughly stirred and allowed to 

 settle for an hour or longer. The precipitates were filtered on 

 Gooch crucibles and thoroughly washed with cold water. It 

 is important for satisfactory washing not to allow all the liquid 

 to pass out of the crucible until the washing is completed. 

 The crucibles containing the lead sulphite were dried at about 

 150° C. for an hour. The drying is rapid and the weight very 

 constant at this temperature. 



The following results were obtained : 



No. 



cc of Pb sol. 



Pb taken 



Wt 



of PbS0 3 



Pb found 



Error 



1 



25-0 



•1958 





•2712 



•1954 



— •0004 



2 



22-0 



•1724 





•2394 



•1724 



•oooo 



3 



22-0 



•1724 





•2390 



•1723 



— •0001 



4 



30-0 



•2350 





•3262 



•2352 



+ •0002 



5 



30-0 



•2350 





•3262 



•2352 



+ •0002 



6 



20-0 



•1566 





•2175 



•1567 



+ •0001 



7 



19 95 



•1562 





•2165 



•1561 



— •0001 







* Chem. Ztg 



., xxxviii, 450, 



1913. 





