HYDRIODIC ACID AS A BLOWPIPE REAGENT. 73 
Tellurium, like selenium, gives a coating which dims the whole spectrum, especially 
the blue. A purplish-brown results. 
9TH PERIOD. 
The gold coating requires too great a heat to be obtained on glass. 
Mercury gives two coatings, an evanescent yellow one aiid a more permanent red one. 
An examination of the latter shows a spectrum of red and orange, reaching from A to 
slightly beyond D, and giving as colour a very pure scarlet. * 
The thallium coating consists of yellow and black. The yellow is very opaque, the 
black is more transparent, and uniformly dims the whole spectrum. 
The lead coating gives a spectrum from A to a point halfway between E and F, in- 
cluding red, orange, yellow and most of the green ; yellow, however, largely predominating. 
The combination results in a strong chrome yellow. 
Bismuth gives two coatings, one brown and the other red, the latter coming out under 
the influence of ammonia. The brown coating dims the whole spectrum, particularly the 
green, blue and violet—the resultant colour being reddish or chocolate-brown. The red coat- 
ing shows red, orange and yellow in its spectrum, which reaches from A to a point beyond 
D. The resultant red is more orange than that of mercury. 
Molybdenum which does not belong to either of the three periods mentioned, gives a 
deep ultramarine-blue coating of oxide, f with a spectrum in which only the blue and violet 
come out distinctly. 
It is worthy of note that the spectra (except that of the molybdenum coating, which 
is an oxide, not an iodide) just described all contain red and orange, most of them also 
yellow, many of them more or less green, but none of them blue or violet except those 
obtained from white coatings. They all give colours belonging to the less refrangible end 
of the spectrum. 

* The red iodide of mercury is even a more brilliant scarlet than vermilion, and hence dealers are tempted 
to sell it as a pigment. Artists should beware of it, as, unlike vermilion, it is very fugitive when moist and mixed 
with other colours. 
+ This oxide is apparently quite permanent, and, if its place were not so fully supplied by ultramarine, might 
be used as a violet-blue pigment. 
Sec. III., 1883. 10. 
