Intelligence and Miscellaneous Articles, 311 



does not precipitate with chloride of sodium ; on the contrary, chlo- 

 ride of silver, which is insoluble in potash, dissolves in it very readily 

 when arsenite of potash is added. 



M. Reynoso took advantage of these two properties of arsenite of 

 silver to effect the reduction of the salts of palladium by means of 

 silver. The experiment is performed as follows : chloride of palla- 

 dium, to which arsenite of potash is previously added, is poured into 

 a solution of arsenite of silver in potash. A black powder is readily 

 precipitated, which contains metallic silver and palladium. Chloride 

 of platina is much more readily reduced than that of palladium. 

 It is to be observed that, in these reactions, arsenite of silver decom- 

 poses much more quickly than when it is alone. 



The arsenites of cobalt, nickel and uranium, dissolve completely 

 in potash and soda, only in the nascent state. For this purpose it 

 is necessary to employ arsenite of potash with a great excess of pot- 

 ash, and to pour this solution into a soluble salt of cobalt, nickel or 

 uranium. 



These reactions will be readily understood, by admitting that 

 arsenite of potash is capable of forming a double soluble salt with 

 the compound of potash and these oxides, and that it is under this 

 influence that their solution is effected. When potash is made to 

 act upon an insoluble salt, the oxide of which is itself soluble in an 

 excess of potash, a solution can only occur on the condition of the 

 formation of a soluble double salt. Thus, for example, the author 

 has stated that arsenite of lead is insoluble in potash. The proof that 

 these reactions depend upon the nature of the salt formed is, that 

 arsenite of lead, which is insoluble in potash, is completely soluble 

 in soda. 



When potash is added to an insoluble salt, it first combines with 

 the acid, and the oxide set free will remain without acting upon the 

 salt formed ; but if excess of potash be added, and the oxide is so- 

 luble in it, then if the compound of this oxide with potash cannot 

 unite with the supernatant salt, two soluble salts will be present, 

 which, being able to form an insoluble salt by their decomposition, 

 will regenerate the primary salts. This, however, is a very rare 

 case ; for experiment has proved that almost all the salts of potash 

 have the property of forming a soluble double salt with the oxides 

 soluble in potash. 



With respect to ammonia, the author has stated the solubility 

 therein of arsenite of sesquioxide of iron. 



In concluding, M. Reynoso observes that four cases of the action 

 of potash on insoluble salts may occur : — 



1 . In the case of certain oxides, which, when uncombined, are 

 soluble in potash, and which form soluble double salts with all the 

 salts of potash, the solution maybe observed under all circumstances. 



2. In some cases, uncombined oxides, which are soluble in potash, 

 will form salts insoluble in potash when the acid is not such as yields 

 a soluble double salt with the compound of the oxide and potash. 



3. Some other uncombined oxides, insoluble in potash, may ne- 

 vertheless sometimes form a soluble double salt, and they will con- 



