72 E, HAANEL ON THE APPLICATION OF 
Spectroscopic examination of, the coatings obtained by the treatment of certain substances with 
hydriodic acid in blowpipe analysis. By A. P. COLEMAN, Ph.D. 
The coatings obtained from a number of the elements by the use of hydriodic acid 
as a blowpipe reagent are so wonderfully brilliant and characteristic that, at Dr. Haanel’s 
request, I have examined most of them spectroscopically, to determine the exact composi- 
tion of the colors. A brief description of the methods employed and the results obtained 
may not be without interest. 
A holder was contrived of such a kind that the iodide fumes might sweep over a 
small plate of glass and condense on its surface. In this way a more or less transparent 
coating was obtained, which could be examined by transmitted light. The spectra thus 
produced were brighter and more distinct than those got by examining the light reflected 
from coatings made on plaster tablets. The two methods give essentially the same results, 
since the coatings on plaster are somewhat transparent, and the light penetrates the surface, 
to a greater or less depth, before being reflected. These spectra are then really formed by 
transmitted light just as in the former case. 
Although the coatings on glass give the best results, there is difficulty in preparing 
suitable ones, for the slip of glass is apt to break from unequal expansion on heating. 
Some of the coatings, too, are very opaque, even when made as thin as possible. 
A micro spectroscope à vision directe and a single-prism spectroscope of Browning's 
manufacture were used in the investigation, the sun or a gas flame serving as the source 
of light. 
The elements are taken up in the order of Mendelejeff’s periodic system, and represen- 
tations of the more striking spectra accompany this paper. 
Coloured coatings are obtained from the iodides of most substances in the 4th, 6th and 
9th periods of his system. 
ATH PERIOD. 
Copper and zinc give white coatings which simply dim the whole spectrum. 
Gallium was not at my disposal. 
The arsenic coating gives a spectrum reaching from Fraunhofer’s line A to a little 
beyond E, and including red, orange, yellow and more than half the green. The combina- 
tion of these colours gives a reddish-orange. 
The selenium coating dims all the spectrum, especially the blue and violet, and gives 
as a resultant a reddish-brown. 
6TH PERIOD. 
Silver comes first, but the slip of glass invariably cracked from the great heat necessary 
to make the coating. 
The coating of cadmium was white, and simply dimmed the whole spectrum. 
Indium was not at my disposal. 
The tin coating gives a spectrum from A to F, including red, orange, yellow and 
green. The combination colour is brownish-orange. 
The spectrum of the antimony coating extends from <A to E, covering red, orange, 
yellow and half the green, and giving as resultant orange-red. 
