64 REPORT— 1873. 



If there is still copper sulphate in the solution, this deposited zinc may in its turn 

 become coated with copper ; but if it remain exposed to water it is sure to become 

 oxidized. The black deposit often assumes a brownish colour when this is the 

 case. The copper on which zinc has been deposited gives a brassy streak when 

 rubbed in a mortar ; but the presence of oxides tend to prevent the sticking 

 together of the detached pieces of metal, and thus the formation of a streak on 

 pressure. If, however, the oxide be removed by acetic acid, the clean ramifications 

 of metal, whether black or otherwise, conglomerate of their own accord in a re- 

 markable way, and little pressure is I'equired to obtain a yellowish metallic streak ; 

 while, if hydrochloric acid be used, the zinc itself also dissolves with effervescence, 

 and the conglomerating pieces of metal when rubbed give a coppery streak. 



On a Continuous Process for Purifying Coal-gas and ohtaining Sulphur and 

 Ammonium Sulphate. By A. Veknon Harcoukt, F.B.S., and F. W. 

 Fisos, F.O.S. 



On the Spectra of certain Boric and Phosphoric Acid Blowpipe Beads. 



By Charles Hoknee. 



This memoir is intended to show the importance of studying coloured phosphoric 

 and boric acid beads with the spectroscope, and that much valuable knowledge 

 may be derived from a careful observation of the various spectra, since certain 

 constituents in complex minerals may be often recognized in the same bead. The 

 author then explains how in phosphoric acid beads didymiuni, uranium, cobalt, 

 chromium, &c. may be detected in fractional quantities bj"^ their characteristic 

 absorption-bands and lines in the presence of other substances like iron, nickel, &c., 

 which give no such positive spectra. 



The author also furnishes new tests for tungsten, molybdenum, and cadmium, 

 by which the two former more especially may be determined in infinitesimal 

 quantities of at least O'OOOl of a grain by means of their remarkable absorption- 

 spectra. To produce these results the author adopts the somewhat novel method 

 of fusing the substance along with boric acid simultaneously, at a very gentle heat, 

 until the bead is tolerably clear. Tungsten, molybdenum, vanadium, and titanium 

 oxides all yield brown beads when cold, nickel reddish purple, and cadmium a 

 bright yellow by reflected light. 



The subjoined Table gives the positions of the bands and lines according to Mr. 

 Sorby's scale and notation. 



Table of Spectea. 

 Phosjihoric acid heads. Med end. 



Uranium oxide Ill:, If, 2|, Sf, 5i, 5|, 7^. 



Chromium „ flj, 1a, 2f. 



Didymium,, 8f 4^ 6, GJ, 



Tungsten „ 8 .... 5 



Molybdenum oxide 8| 6f 



Boric acid heads. 



Tungsten oxide _ 2\ 5J 



„ with soda 1 J 8 5J 



Molybdenum oxide H 2f b^ 



Cadmium „ C| . 



