A Comprehensive Treatise on Inorganic and Theoretical Chemistry

84 INORGANIC AND THEORETICAL CHEMISTRY
wire, decomposition of a molecule AB occurs with production of two ions, A
positively and B negatively charged, A being expelled or stored up, later to be
expelled when an electric force is applied. At higher temp. B loses its electron.
It is necessary to assume the presence of at least two substances capable of so
producing ions on heating. By heating the wire in the flame of a Bunsen burner,
an increased positive emission is also obtained, probably in part due to the removal
of a surface material incapable of producing ions and in part due to the hydrogen
absorbed, owing to its affinity for electrons. Heating in carbon dioxide decreased,
if anything, the positive emission. The decay with time of the positive currents
at different temperatures showed the existence of two sources of ions, the first
source decaying according to an exponential law, and the second increasing to a
maximum before decaying. A. M. Tyndall and G. C. Grindley found that the
electrons emitted by an incandescent platinum wire, when removed from the
vicinity of the particles, attach themselves to molecules and give rise to normal
ions of the same mobility as those produced by polonium. The positive emission
is complex, and although the greater number have mobility of 1*4 cm. per sec. per
volt per cm. the mean value is of the order of 1*1. It is concluded that positive
ions are emitted either as small metallic clusters or as atoms, many of which cluster
before Teaching the observation chamber, that the uncharged particles are metallic
clusters ranging from atomic size to metallic dust, and that their growth and
subsequent coagulation are responsible for the blackening of filament lamps.
W. H. Crew studied the effect of light. The thermionic emission of positive ions
was studied by F. Horton, !L. Weissmann, H. A. Erikson, H. A. Wilson, C. Grieb,
and Li. Li. Barnes ; and G. I. Finch and A. W. Ikin found that the catalytic activity
of films of platinum is connected with electrical activity. The thermionic emission
of electrons from oxide-coated platinum was studied by Ti. H. Germer, C. Davisson
and Li. H. Germer, and H. E. Ives and T. C. Fry ; and the thermionic constants,
by H. LJ. van Velzer.
Platinum chloride yields a flame spectrum which, according to J. Formanek, 5
is of short duration. According to A. Gouy, the band spectrum of platinic chloride
in the bunsen flame stretching from the red to the violet, is due to platinous chloride.
The 16 bands form two groups : The one on the right, at the violet end, is very
striking, that on the left is very feeble ; some bands have black lines running
through them. Some bands are visible in the region above the inner cone of the
flame. W. N. Hartley observed no spectrum in the oxy-hydrogen flame ; and
W. F. Meggers and O. Laportc, and L. H. G. Clark and E. Cohen, the under-water
spark spectrum.
J. Formanek observed that platinic chloride furnishes a spark spectrum even
with a feeble spark. A. J. Angstrom first examined the spark spectrum of platinum,
and after him came D. Alter, A. Masson, V. S. M. van der Willigen, T. R. Robinson,
and W. A. Miller ; and measurements were made by G. Kirchhoff, W. Huggins,
and R. Thalen. According to J. Formanek, the principal lines are the green or
a-line 5476 ; and the green lines 5390, and 5368(c), 5302Q3), 5227(S), 5060(y) ; the
blue line 4879 ; and the indigo-blue lines 4553, 4442, 4415, 4392(-^), and 4327(C)—
illustrated in Fig. 11. The spark spectrum was also examined by W. E. Adeney,
f-r—i—i—r-»T—r-*-i 1 1 r"—i"- "t—*T r-"—J H 1 1 1—» 1 *—W •—, , ___ ^
6500 6000 5500 '5000 4500 40Q }
Fio. 13.—The Spark Spectrum of Platinum.
Li. and E. Bloch, Zi. de Boisbaudran, R. Colley, E. Demarcay, F. Exner and
E. Haschek, H. Finger, W. Gibbs, C. E. Gissing, A. Hagenbach and H. Konen'
W. N. Hartley, W. N. Hartley and H. W. Moss, H. G. Howell and G. D. Rochester'