Adsorption of silver ion by insoluble compounds of the metaJ, with the production of complex ions of the type Ag~C1 + (a result of the property that characterizes all silver precipitates, tendency to adsorb its own ions) is of great importance in the consideration of possible errors occurring in quantitative precipitations? In the case of the halides of this univalent ion, the precipitating anion is adsorbed under certain conditions.
While little has been accomplished in the way of determining the exact structure of these so-called" solid solutions," the crystalline compound, AgNO3 -AgC1 has been isolated? The author has directed attention in previous work 3, 4 to the disastrous effects of occlusion upon the quantitative estimation of some compounds, and made suggestions as to how this source of inaccuracy may be removed. Of far greater significance, however, is the phenomenon of adsorption, so frequently encountered in analytical procedure. Kolthoff ~ is authority for the statement that very fine precipitates adsorb more strongly than crystalline ones. Barium sulfate is an exception, showing a pronounced inclination to adsorb foreign ions during its precipitation.
The observation that an excess of barium chloride in the