fooled 
XXXII. 
ON THE QUANTITATIVE SPARK-SPECTRA OF TITANIUM, 
URANIUM, AND VANADIUM. 
By JAMES H. POLLOK, D.Sc., Royal College of Science, Dublin. 
[Purates XXV.-XXYVI.] 
[Published Frspruary 25, 1909.] 
Owine to the very large number of lines in the spectra of 
titanium, uranium, and vanadium, a knowledge of their quanti- 
tative spectra is absolutely necessary for analytical purposes ; 
and as titanium is a very common constituent of minerals, its 
residuary lines are continually found in the course of spectro- 
graphic analysis. 
The quantitative spectra of those elements were determined 
by the method devised by Professor W. N. Hartley,! with the 
modifications described by Mr. A. G. G. Leonard and me, in our 
various papers on Quantitative Spark-Spectra,’? published in the 
Proceedings of this Society. Purchased samples of the metals 
and oxides were used, and in each case a weighed quantity of 
oxide was dissolved in hydrochloric acid, then diluted so as to 
contain 10 per cent., 1 per cent., ‘1 per cent., ‘01 per cent., and -001 
per cent. of the element. ‘These solutions were then successively 
sparked, using a Ruhmkorff coil, condenser, and self-induction coil 
for the removal of air-lines; and photographs were taken of the 
spectra, giving an exposure of one minute each. Photographs 
were also taken of the spectra given by the fused metals; and it 
was found that, in each of the three cases, the solutions gave 
all the lines given by the metallic electrodes. 
1 Proc. Roy. Soc., 1882, p. 81. 
2 Proc. Roy. Dub. Soc., 1907. Nos. 16,17, and 18; and 1908. Nos. 23 and 24. 
SCiENT. PROC. R.D.S., VOL. XI. NO. XXXT. PX 
