Chemistry and Physics. 315 



is known of the behavior of electrotypes in solution, an entirely 

 uniform exchange of atoms when simple lead salts, such as lead 

 acetate and formate, were dissolved in water and the sparingly 

 soluble formate was allowed to crystallize by cooling the solu- 

 tion. A complete exchange was obtained also by dissolving 

 the nitrate and chloride in pyridine, as well as when plumbic 

 and plumbous acetates were dissolved in glacial acetic acid and 

 lead peroxide was precipitated by dilution. 



On the other hand, it was found that when the lead in one of 

 the compounds was firmly combined with carbon in an organic 

 substance no exchange took place. This was the- case when lead 

 chloride and tetraphenyl-lead were dissolved in pyridine, and 

 when lead nitrate and diphenyl-lead nitrate were dissolved in 

 dilute ethyl alcohol. These results were, of course, to be ex- 

 pected, but the confirmation of the expectation is interesting. 

 Bericht, 53, 410. h. l. w. 



3. The Action of Aqua- Begia on Gold-Silver Alloys in the 

 Presence of Ammonium Salts. — W. B. Pollard has found that 

 the well known difficulty of dissolving gold containing much 

 silver in aqua regia can be overcome to a large extent by the 

 addition of an ammonium salt to the reacting liquid. The 

 ammonium salt dissolves the silver chloride produced and thus 

 removes the black protecting film otherwise formed. Attention 

 is called to the fact that nitric acid and ammonium chloride were 

 used by the alchemists for dissolving gold, a method which doubt- 

 less facilitated the solution of alloys rich in silver. 



In the course of these experiments the formation of a dark 

 brown salt was observed upon cooling concentrated solutions of 

 auric, silver and ammonium chlorides. To this triple salt the 

 formula 3AgC1.4AuCl 3 .8NH 4 Cl was given, but it may be 

 observed that the investigator used very drastic operations in 

 preparing the compound for analysis, including extraction with 

 ether in a Soxhlet apparatus and heating it until ammonium 

 chloride sublimed, so that it seems possible that the salt was 

 partially decomposed by these operations, and that the rather 

 complex formula ascribed to it may be incorrect. — Jour. Chem. 

 Soc, 117, 99. 



4. The Probable Existence of Deposits of Soluble Potash Salts 

 in the United States. — It has been generally believed that the 

 German potash deposits were formed under peculiar conditions 

 in connection with rock-salt deposits, whereby the more soluble 

 constituents of the evaporated natural brines were preserved, 

 while it is supposed that in most other rock-salt deposits these 

 more soluble, potash-rich portions have been carried away in 

 solution and lost. Consequently, since no beds of potash salts 

 have been encountered in connection with the salt deposits of 

 the United States, the opinion appears to prevail that they do 

 not exist here. 



H. D. Euhm, however, takes a different view of the matter, 

 mentioning the accidental discovery of the deposits at Stassfurt, 



