0. W. Huntington—Spectrum of Arsenic. 215 - 
and more or less diffused spectrum always accompanied the 
four principal hydrogen lines. It being then impossible to 
eliminate the diffused spectrum, we next tried alloying the 
platinum electrodes with arsenic, and experimented with these 
in a rarefied atmosphere of hydrogen, both with continuous 
discharge of Ruhmkorff coil, and with siecle tel discharge 
with Leyden jar. We now obtained very definite arsenic 
bands, apparently the same in both cases; but the effect was 
momentary, and gave no opportunity for measurement. ‘The 
spectrum while it f lasted was very striking; but, as soon as the 
arsenic on the extreme point of the electrode passed off, the . 
characteristic spectrum disappeared. 
were by this experience led to contrive the following 
apparatus, by which we obtained the desired result, and the 
same may be useful in experiments on the spectra of similar 
volatile substances. A longitudinal section of the tube, one- 
half of the — si is shown in fig. 2 of plate. e 
portions AA’ and A” of rather coarse thermometer tubing. 
BB’ is a tube left ‘pik - B, and drawn to a capillary point 
at B’. The substance to be ‘examined, after being reduced to 
powder, is introduced through the opening at B until the 
tube is about half full. Then one end ofa platinum wire is 
buried in the substance, and the other end is fused into the 
tube at B, thus closing the o ening. After the hydrogen has 
been allowed to flow throught the tube a sufficient length of 
time, the opening at A is closed by a nipper-tap, and the tube is 
exhausted at B”. Now u upon connecting B with the negative 
electrode, and C with the positive electrode, of a small induc- 
tion coil, we have the vapor of the substance in the tube BB’ 
carried in the current through the tube A’ where the spectrum 
may be observed. 
One advantage of this serdar form of tube is, that, in 
order to compare the spect of the substance with that of 
hydrogen, we have only td reverse the current, making C the 
negative pole, and shen all the lines rea fs those of hydrogen 
at once disappear 
The arsenic speckrans thus obtained is very brilliant, and 
consists of numerous well-marked sharply defined bands. The 
nds are most numerous and brilliant in the green, and these 
apart as the two D lines, In addition, there may be also a 
more or less diffused spectrum, which in some parts cannot be 
distinguished from the similar diffused spectrum of hydrogen, 
and it is worthy of remark in this connection, as indicating the 
Am. Jour. Ser. ae Series, Vou. XXII, No. 129.—Sepremeer, 1881. 
