£ 18 Electrochemical Researches on 



Platina and gold, in specific gravity, degree of oxidability, 

 and other qualities, differ more from arsenic, iron, and tin, 

 than these last .do from barium and strontium. The phe- 

 nomena of combustion of all the oxidable metals are pre- 

 cisely analogous. In the same manner as arsenic forms an 

 acid by burning in air, potassium forms an alkali and cal- 

 cium an earth ; in a manner similar to that in which osmium 

 forms a volatile and acrid substance by the absorption of 

 oxygen, docs the amalgam of ammonium produce the vola- 

 tile alkali; and if we suppose that ammonia is metallized, 

 by being combined with hydrogen and freed from water, 

 the same reasoning will likewise apply to the other metals, 

 with this difference, that the adherence of their phlogiston 

 or hydrogen would be exactly in the inverse ratio of their 

 attraction for oxygen. In platina* it would be combined 

 with the greatest energy ; in ammonium with the least ; and 

 if it be separable from any of the metals without the aid of a 

 new combination, we may expect that this result will be af- 

 forded by the most volatile and oxidable, such as arsenic, or- 

 the metals of the fixed alkalis, submitted to intense heat, 

 under electrical polarities, and having the pressure of the at- 

 mosphere removed. 



Whatever new lights new discoveries may throw upon 

 this subject, still the facts that have been advanced, show that 

 a step nearer at least has been attained towards the true 

 knowledge of the nature of the alkalis and the earths f. 



Something 



* The common metallic oxidei r>rc lighter tlian their bases, but potash and 

 soda are heavier ; this fact may be explained on either theory; the density of 

 a compound will be proportional to the attraction of its parts. Platina, 

 having a weak affinity for oxygen, cannot be supposed to condense it in the 

 *ame degree as potassium dues; or if platina and potassium be both com- 

 pounds of hvdrogen, the hydrogen must be attracted in platina with an 

 energy infinitely greater than in potassium. Sulphuric acid is lighter than 

 sulphur : but phosphoric acid (where there is a stronger affinity) is heavier 

 than phosphorus. The oxide of tin (wood tin) is very little inferior to tin in 

 rpccilic gravity. In this instance the metallic base is comparatively light, and 

 the attraction for oxygen strong ; and u a case when the metal is much lighter 

 and the attraction for oxygen stronger, it might be expected a priori that the 

 exide would be heavier than the base. 



f Since the- facts in this paper were communicated to the Rotal Society, 



I ha v* 



