316 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



(2) The weight of potassium chloride was determined 

 which was required to precipitate (as silver chloride) a known 

 weight of silver dissolved in nitric acid. It was found that 

 74-592 parts of potassium chloride would precipitate 107 '943 

 parts of silver ; this number is the equivalent of silver, 



(3) By a variety of methods it was found that 100 parts 

 of silver combined with 32*845 parts of chlorine to form 

 132*845 parts of silver chloride ; since in these 

 experiments 107-943 parts of silver combined with 



.g x 107-943 = 35454 parts of chlorine, this number 



was the equivalent of chlorine. 



(4) Subtracting 35-454 (the equivalent of chlorine) from 

 74-592 (the equivalent of potassium chloride) the equivalent 

 of potassium is found to be 39138. 



At the close of his work Stas had determined the 

 equivalents of ten elements, as follows : 



Nitrogen .' . 14-055 Lithium . . 7-022 



Sulphur . . 16-037 Sodium . . 23*0455 



Chlorine . . 35'457 Potassium . 39-1425 



Bromine . . 79 -955 Lead . . 103-456 



Iodine . . 126*848 Silver . . 107-930 



A comparison with the list of equivalents given in the table 

 above (p. 313) will show that Stas's final values (which differ 

 slightly from those worked out in the four preceding para- 

 graphs) are almost identical with those accepted at the 

 present time. 



Accuracy of the law of reciprocal proportions. Perhaps 

 the best proof of the accuracy of the law of reciprocal pro- 

 portions is the existence of tables of atomic weights, which 

 chemists everywhere use to calculate the composition of their 

 compounds, rather than trust to even the best of their own 

 analytical data. Further evidence is afforded by the main- 

 tenance of neutrality when neutral salts interact, as noticed 

 first by Richter (p. 310). The question was, however, tested 



