( 733 ) 
subhaloid in both cases. In order to determine the chemical com- 
position of this subhaloid, he added at intervals to a known quantity 
of silver a chlorine solution containing */,, of the quantity required 
for the formation of Ag Cl, and then each time determined electro- 
motorically the oxidation potential of the remaining chlorine. In the 
beginning it remained constant at 0,55 Volts, but when the composi- 
tion Ag, Cl had been reached, it suddenly became 1,45 Volts, and 
after that remained fairly constant. In the synthesis of silver bromide 
he also observed a rise of the potential at Ag,Br. E. Baunr*’) con- 
firmed this in the case of Ag,Cl, and could further demonstrate a 
slight rise of the potential in proportion as the percentage of chlorine 
increased, from which he inferred that Ag,Cl forms with silver 
chloride homogeneous mixture series (absorption compounds). On the 
ground of the existence of a number of subhaloids it follows from 
this just as well that the subhaloids with an increasing amount of 
halogen show a very slight rise of the oxidation potential without 
there being any need to deny the formation of absorption compounds 
of these subhaloids with silver haloid. At the same time it appears 
that for the present a more exact determination of these subhaloids 
by this method does not promise much success. 
If, however, these results are considered in connection with series 
(I), it appears that the first subhaloid formed synthetically, and con- 
sequent poorest in halogen, is Ag,Hal, and the following improved 
photo-chemical decomposition series is obtained: 
Agon Halo, ae Agon Halas Agon Halon—o noon TE 
ar Agon Hal, Fers Agon Hal, iss 2nAg (II) 
This series is in harmony with the opinion already expressed by 
J. M. Eper '®) some time ago: “Vielleicht bilden sich auch Silber- 
subchloride, welche als Zwischenprodukte von Ag,Cl und AgCl 
aufzufassen sind.” 
One of the most prominent peculiarities of the silver subhaloids, 
by which they were even discovered, is their absorption spectrum. 
As these subhaloids have the power of rendering the whole visible 
spectrum (the subchlorides do this best of all), I have endeavoured 
to determine experimentally the colour sequence of series (II). 
‘ 
Method of Investigation. 
The method of procedure might have consisted in photographing 
the sun’s spectrum by the SerBreK process and in subsequently 
controlling the colour changes by means of a sun spectrum placed 
50 
Proceedings Royal Acad. Amsterdam. Vol. XI. 
