MoRUow — Spectra of Manganese, Lead, Gofper, and Lithium. 281 



Lead. 



The standard solution of lead chloride was prepared by dissolving 1-342 

 grammes of pure lead cliloride in hot distilled water. Oae drop of strong 

 hydrochloric acid had to be added in order to clear the solution, which was 

 then diluted, before cooling, witli distilled water, and when cold was made 

 up accurately to 1 litre. The quantity of tliis solution (O'l o.c.) which was 

 then put into tiie vacuum tube contained therefore 0-0001 gramme of lead. 



As soon as the water had been driven off when the soluliou was being 

 evaporated to dryness in tlie vacuum tube, the solid suddenly volatilized and 

 condensed in the capillary portion of the tube, rendering it opaque ; but it did 

 not remain so wliilst tiie current was passing, so that the spectrum was 

 obtained quite well, there being a bluish colour for about 30 seconds, which 

 appeared again at intervals for about a second. Wlieu taking the third 

 photograph of the lead spectrum, the colour in the tube was pink, probably 

 mainly due to the presence of hydrogen. 



Many lines show in the first spectrum of lead, using 0-0001 grammes of 

 the metal, and a broad band appears from A 4068-2 to A 4058-0, which pro- 

 bably consists of the Hues A 4068-2, A 4062-3, and A 4058-0. In the second 

 photograph the band has disappeared, a strong line A 4068-2 remains, which 

 line appears again strongly in Plate XXIV., No. Ill, as one of the ultimate 

 lines of lead. 



