THE SOLUBILITY OF LEAD SULPHIDE AXD LEAD CHROMATE 35 



An advantage of the indicator method is that, irrespective of impuri- 

 ties, only the amount of the labelled element is measured, whereas in other 

 very highly developed mieroanalytical methods of determination, e.g. 

 by employing microweighing, there is always the danger of co-deter- 

 mining invisible impurities. Apart from this, the sensitivity of the 

 radioactive indicator methods is indeed significantly greater and, assu- 

 ming the availability of adequate amounts of the radioactive substance, 

 can ])e increased almost without limit. 



Summary 



The solubility- of lead chroniate at 25° in pure water has been determined as 

 1.2 X 10~5 gm/1-; for lend sulphide at 25° in puie water and in HjS-saturated water 

 the values were 3 x 10~* and 1.5 X 10* gm/l. respectively; RaD was used as 

 a tracer for lead. 



