1904.] WHARTON — PALLADIUM (Pd). S'-H 



appeared afterward as beta-rays. Query : If so, why should the 

 electro-scale require charging with hydrogen to enable it to indicate 

 radio-activity ? 



Sir William Ramsay, to whom I mentioned this experiment and 

 surmise, suggested the possibility that the original ore might have 

 contained a trace of radium, which persisted with the palladium 

 until the final fusion vaporized it or passed it to the slag. 



Among the chemical characteristics of palladium may be men- 

 tioned these, not of course as novelties but as practically useful : 



1. It is completely precipitated from an acid solution as sulphide 

 by hydrogen-sulphide. 



2. It is thrown down as a black precipitate from even a dilute 

 solution by potassium-iodide. This very sensitive reaction is 

 important in practical treatment of material containing palladium. 



3. It is precipitated by mercury-cyanide as white slimy palla- 

 dium-cyanide : a property useful for quantitative determination in 

 laboratory. 



Among the uses hitherto of palladium are : 



1. For the mechanism of delicate instruments such as chronome- 

 ters, and for verniers, etc., of astronomical instruments. 



2. For surgical instruments. 



3. For plating searchlight mirrors. Why not for the mirrors of 

 reflecting telescopes ? 



4. For alloying with silver to make dental plates, etc., instead of 

 the -| silver, i platinum hitherto used in Europe. Also as palladium 

 amalgam for fillings in cavities of teeth/ 



Other uses will naturally arise as men's minds are turned toward 

 this metal, which, while in many respects equal to platinum, sells 

 for no more than the price by weight of that metal, and of course 



1 Palladium amalgam has been used to but very small extent for tooth fillings, 

 though well adapted for that use except for its dark color, arising apparently from 

 palladium black being used to form the amalgam, which is made by the dentist 

 at the iroment he wishes to use it, by triturating palladium black with mercury. 

 That darkness of color might probably be obviated by using fine palladium filings 

 instead of palladium black. 



Dr. Joseph Pettit, a careful observer, told me that he had found this amalgam 

 so made to become too hot to be comfortably held in the hand. Dr. W. Storer 

 How, of the S. S. White Dental Co , informed me that he had noticed some 

 warmth evolved in the making of the amalgam. I observed very little heat, no 

 more in fict than I thought referable to the triction of trituration. 



PKOC. AMER. PHILOS. SOC. XLIII. V. PRINTED OCT. 17, 1904. 



