90 



Presents. 



[May 9, 



thus far be considered as proved that a decigramme of silver con- 

 taining TooWokh °^ g°ld gives a distinctive deposit of this metal, 

 which is recognised by its colour, and that silver as pure as that 

 obtained by the process of M. Stas which. I have described gives no 

 such decisive indication, though it does not yield films which can be 

 considered as absolutely free from gold. Furthermore, this test for 

 gold is more sensitive than that depending upon the employment of 

 the spectroscope. Many specimens of copper and silver have been 

 tested, and in each of them there appears to be a trace of gold. 



Gold of the fineness of 9, 12, 15, 18, and 22 carats has been shown 

 to yield films each with distinctive characters. 



The various deposits of oxides and of some metals are easily treated 

 with such acid and other reagents as are gaseous or capable of being 

 volatilised, and the colour reactions of the sulphides may be obtained 

 as definite rings of larger or smaller diameter, corresponding with the 

 volatility of the metals. 



The application of this method may ultimately be made to lead to 

 valuable results, but most of the large number of films already pre- 

 pared have yet to be examined, and their properties described ; it is 

 therefore proposed to deal exhaustively with the subject in a future 

 communication. 



Presents, May 9, 1889. 



Transactions. 



Alnwick : — Berwickshire Naturalists' Club. Proceedings. Vol. 

 XII. Part 1. 8vo. [Alnwick 1888.] The Club. 



Baltimore : — Johns Hopkins University. Circular. Yol. VIII* 

 No. 72. 4to. Baltimore 1889 ; Studies in Historical and 

 Political Science. Ser. 7. No. 4. 8vo. Baltimore 1889 ; Notes 

 Supplementary to the Studies. Nos. 2-3. 8vo. Baltimore 1889. 



The University. 



Berlin: — K. Preuss. Akademie der "Wissenschaften. Sitzungs- 

 berichte. Jahrgang 1888. Nr. 38-52. 8vo. Berlin. 



The Academy. 



Catania: — Accademia Gioenia di Scienze Naturali. Bullettino 

 Mensile 1889. Fasc. 4-5. 8vo. Catania 1889. 



The Academy. 



Emden: — Naturforschende Gesellschaft. Jahresbericht 72-73. 

 8vo. Emden 1889. The Society. 



Kew : — Royal Gardens. Bulletin of Miscellaneous Information. 

 No. 28. 8vo. London 1889. The Director. 



Leipsic : — Astronomische Gesellschaft. Vierteljahrsschrift. Jahr- 

 gang XXIV. Heft 1. 8vo. Leipzig 1889. The Society. 



