66 THE ATOMIC WEIGHTS. 



The general method of working upon these ratios is due to Penny.* 

 Ap]")lied to the ratio between the chloride and nitrate of potassium, it is 

 as follows: A weighed quantity of the chloride is introduced into a flask 

 which is placed upon its side and connected with a receiver. An excess 

 of pure nitric acid is added, and the transformation is gradually brought 

 about by the aid of heat. Then, upon evaporating to dryness over a 

 sand bath, the nitrate is brought into weighable form. The liquid in 

 the receiver is also evaporated, and the trace of solid matter which had 

 been mechanically carried over is recovered and also taken into account. 

 In another series of experiments the nitrate was taken, and by pure hy- 

 drochloric acid converted into chloride, the process being the same. In 

 the following columns of figures I have reduced both series to one stand- 

 ard, namely, so as to express the number of parts of nitrate correspond- 

 ing to 100 of chloride : 



First Series. — KCl treated with HNO^. 



135-639 

 135-637 

 135-640 

 135-635 

 135-630 

 135-640 

 135-630 



Mean, 135.636, ± .0011 



Second Series. — KNO^ treated with HCl. 

 135.628 



135-635 

 135-630 

 135-641 

 135 630 

 135-635 

 135-630 



Mean, 135.633, =h .0011 



Stas' t results are as follows : 



135-643 

 135-638 

 135-647 

 135.649 

 135.640 

 135-645 

 135-655 



Mean, 135.6453, =h .0014 



*Phil. Trans., 1839. 



+ Aronstein's translation, p. 270. 



