XXXVII.—On the behaviour of metallic solutions with filter paper, and on the detection of cadmium
Journal of the Chemical Society Transactions
SOME time ago, while holding a wet patch, formed by dropping a solution of silver nitrate upon filter paper, in a stream of hydrogen mixed with arseniuretted hydrogen, I noticed that the metal was contained in the centre of the blot, and that the edges for about half a centimeter inwards were entirely free from metal. After being exposed to the gas, the blot presented the appearance of a black spot surrounded by a broad ring of water. I therefore made a few experiments, in order to determine
... der to determine whether filter paper has any power of withdrawing silver salts from solntion. 7.8703 grams of silver nitrate having been dissolved in water, and diluted to 500 c.c., a quantity of this solution was placed in a beaker, and a roll of filter-paper, sufficient to absorb nearly the whole, plunged into it. After some minutes the filter-paper waa removed, and as much of the liquid as possible squeezed into the beaker. It is clear that the effect of this treatment, unless the paper possesses a power of retaining the salt, would merely be to slightly concentrate the solution by evaporation. Four experiments were made in this manner, fresh rolls of paper and fresh portions of the standard solution being used in each instance. 25 C.C. of the solution, after treatment with the paper, were mixed with hydrochloric acid, and the precipitated silver chloride dried, ignited, and weighed. The results were as follows :- Ag. found. Ag. originally present. This shows that after a roll of paper has been soaked for a, few minutes in a solution of silver nitrate, the quantity of silver has materially diminished. A few experiments made by my friend, Mr, We s ton, show that the same is true in the case of mercury salts. Drops of other metallic solutions were placed upon filter-paper, and submitted to the action of sulphuretted hydrogen. I found that in some cases the metal extends to the edge of the spot, and even seems concentrated there, while in others a water-ring surrounds the patch of sulphide.