10 THE ATOMIC WEIGHTS. 



conveniently take up the percentage of potassium chloride 

 obtainable from the chlorate. 



The first reliable series of experiments to determine this 

 percentage was made by Berzelius.* All the earlier estima- 

 tions were vitiated by the fact that when potassium chlo- 

 rate is ignited under ordinary circumstances a little solid 

 material is mechanically carried away with the oxygen gas. 

 Minute portions of the substance may even be actually vol- 

 atilized. These sources of loss were avoided by Berzelius, 

 who devised means for collecting and weighing this trace 

 of potassium chloride. All the successors of Berzelius in 

 this work have benefitted b3^his example; although for the 

 methods by which loss has been prevented we must refer to 

 the original papers of the several investigators. In short, 

 then, Berzelius ignited potassium chlorate, and determined 

 the percentage of chloride which remained. Four experi- 

 ments gave the following results : 



60.854 

 60.850 

 60.850 

 60.851 



Mean, 60.851, with a probable error of dr .0006 



The next series was made by Penny,t in England, who 

 worked after a somewhat different method. He treated po- 

 tassium chlorate with strong hydrochloric acid in a weighed 

 flask, evaporated to dryness over a sand bath, and then 

 found the weight of the chloride thus obtained. His results 

 are as follows, in six trials : 



60.825 

 60.822 

 60.815 

 60.820 

 60.823 

 60.830 



Mean, 60.8225, i .0014 



*Poggend. Annalen, 1826, bd. 8, s. i. 

 t Phil. Transactions, 1839, p. 20. 



