100 Prof. W, N. Hartley and Mr. H. Ramage. The Mineral 



and only the heavier particles remained. The contents of the dishes 

 were poured into glass cylinders, and after the heavier particles had 

 1 >een deposited the water was removed by decantation. 



Subsequently it became interesting to ascertain what substances are 

 to be found in ordinary soot and flue dust — dust from volcanic 

 eruptions, &e. TTe have tabulated the results and arranged together 

 those substances which we know to have the same origin. 



The specimens of soot required no preliminary treatment before 

 being burnt, and the analysis of each is given in the tabular statement 

 only, but the different kinds of volcanic dust and flue dust were dissolved 

 and the silica removed, after which the bases were separated into 

 groups, and the spectra of these groups were photographed : each 

 spectrum receives a detailed description preceding the tabulated 

 statement. 



Flue Dust. 



Plate 386.— Dust from the flue of Crewe gasworks. May 28, 1899. 

 The silica was removed from 1 gramme by treatment with ammo- 

 nium fluoride. 



Spectrum 1. — The insoluble residue contained — 



Ca, Sr, Xa, Pb, Fe, Cu, Ag, K. 



,, 2. — The precipitate yielded by sulphuretted hydrogen — 



Pb, Cu, Ag, Ca, Xa, Fe, K. 



„ 3. — The ammonium hydrate precipitate — 



Fe, Ga, Cu, Ag, Pb, In, Xi trace, 

 Ca, Xa, K. 



,, 4. — The ammonium sulphide precipitate — 



Mn, Xa, K, Cu, Ag, Xi, Fe. 

 ,, 5. — The less soluble sulphates — 



Ca, Sr, Cu, Xa, K. 

 6. — Magnesia and the alkalies — 



Xa, K, Ca, Sr, Xi, Eb trace. 



Plate 388. Spectra 4 and 7. — Insoluble residue after treating the dust 

 with hydrochloric acid — 



Fe, Ga, Xa, K, Ca, Cu, Ag, Xi, Mn. 



i *late 347.— Flue dust from Cleveland iron furnaces. 

 Spectrum 1. — Samuelson's samples, Xo. 6 — 

 Xa, K, Ca, Fe, Rb, Pb, Mn ; 

 traces of Cu, Ag, Xi, Ga, Tl. 



