Notes and Comments. 389 NOTES AND COMMENTS.* AN ELECTRIC ASSAY FURNACE FOR RICHARDS' METHOD OF SEPARATING GOLD AND SILVER BY VOLATILIZATION.
In the discussion of Dr. Richards' paper on the separation of silver and gold by volatilization, it was suggested that it would be advantageous in this operation to employ electric heat, for the reason that in a properly constructed furnace of this type, the temperature could be much more readily controlled than by the use of the blowpipe flame.
Commenting on this suggestion, Dr. W. Borchers, in a recent impression of the Zeilscariflfiir ElektrocAemie, describes an electric furnace devised and used by him for metallurgical work on the laboratory scale, and which he recommends as being well adapted for the special purpose above named.
' 2a2a"
Referring to the cut, Kand Kare two carbon electrodes about 4o millimeters in diameter, between which is placed a small carbon bar k, 6 to 8 millimeters thick. This bar is hollowed out to receive the test piece, and if it be dasired to avoid bringing it in contact with carbon, the hollowed portion may be given a lining of magnesia, or of some other suitable refractory ~ material.
This arrangement of parts is, as shown by the cut, enclosed within a suitable crucible C. To avoid the rapid burning out of the carbon bar, a few fragments of charcoal are thrown into the crucible. The manner of holding the bar k in position, and of introducing the current is so obvious as to need no special description. The electrode support on the left is made adjustable, so that the carbon cradle for the test piece may be firmly held in place by operating the hand-screw S.
According to Borchers, a current density of 5 amperes per square millimeter of section of k at the recessed part, will, be sufficient for the purpose of the assay.
W.