Equivalents of Potash^ Soda, and Silver, 325 



In the progress of discovery, however, other facts were ob- 

 served, which though at first appearing to oppose the law in 

 question, have yet been preparing the way for the removal of 

 the exceptions which opposed its general reception. Among 

 the admirable observations of Mitscherlich on the isomorphism 

 of analogous compounds was the identity of form of the sul- 

 phate and seleniate of silver with the anhydrous sulphate and 

 seleniate of soda from which the isomorphism of silver and 

 sodium was deduced; and as the same quantity of sulphuric 

 acid existed in these compounds in union with the received 

 atomic weights of the soda and oxide of silver, the opinion 

 was strengthened that these weights were correct. Professor 

 Gustav Rose more recently established the identity of form of 

 silver and gold; and though his analyses of native gold from 

 different localities did not confirm those of Boussingault, that 

 the two precious metals in native crystals replaced each other 

 in atomic proportions, yet their isomorphism connected those 

 metals by another link, and tended to strengthen the received 

 opinion in regard to the equivalent weights of both. Thus 

 far the progress of discovery was opposed to the results of 

 Dulong and Petit. 



When by the sagacity and elaborate researches of Berze- 

 lius the doctrine of the sulphur salts was established to the 

 satisfaction, at least, of the German chemists, who understood 

 it best. Professor Henry Rose entered upon the study of the 

 various compound metallic sulphurets which occur so abun- 

 dantly in the mineral kingdom. The results of this inquiry, 

 while they confirmed the beautiful doctrine of Berzelius, threw 

 an unexpected light on the nature of these sulphurets, and 

 gave a simplicity to their constitution wholly unthought of; 

 and while they made known the existence of many isomor- 

 phous relations which were to be anticipated from those al- 

 ready observed among the analogous oxygeri compounds, 

 they brought to light others also which could not even be 

 suspected to exist. To one of these only, having reference 

 to the atomic weight of silver, it is necessary at present to ad- 

 vert. 



The sulphuret, oxide, and chloride of silver are composed 

 respectively of 



Silver. Sulphur. Oxygen. Chlorine. 



1 Atom each 13*5 2-0116 1-000 4-4265 



The analogous compounds of copper consist of 



Copper. Sulphur. Oxygen. Chlorine. 



1 Atom each 7*9 2-0116 1-000 4-4265 



and the disulphuret of 1 5-8 + 2-0116. 



