1888.) 105 [Davis. 
oxygen being set free, he further states that heat has the effect of decom- 
posing such solution with the same results;’? should gold be present, it 
will be precipitated in proportion to the disappearance of free chlorine.* 
” 
When it thus appeared that the recited conditions alone were sufficient 
for the deposition of gold from its solution, then was Rumford’s discovery 
consigned to the limbus of useless speculations. This remarkable property 
of carbon is casually mentioned by a few authors ; but it is nowhere taught 
that carbon is distinguished by any remarkable energy, or as differing 
from the crowd of organic substances with which it was classed. 
Neither is it anywhere suggested that such deposition was of any com- 
mercial value, and no use has ever before been made in the metallurgic 
separation of gold from its solution, nor has carbon been employed in 
obtaining gold from its ores except as a fuel. 
Just the opposite has been the case, for when the attention of experts 
was called to the claims of this process, they generally agreed that there 
was nothing in chemical laws or scientific principles to sustain the assump- 
tion, and at this moment well informed minds are at a loss to account for 
the remarkable energy of this new agent in reducing gold from a solution 
to a metallic state, and the additional fact, that it is inert towards other 
earthy and metallic constituents of the solution. Thus serving as a refining 
agent also. 
As sustaining the claim of novelty, for the hypothesis of the conversion 
of chlorine into ClH, by carbon, allusion may be made to the contrary 
opinion of many chemists, as expressed in correspondence with the writer. 
Several incline to the opinion that the reduction is simply a mechanical at- 
traction of the carbon for the gold (corresponding to the action of animal 
carbon on the impurities in sugar) ; this opinion has been. held regardless 
of the disappearance of large volumes of chlorine, and the formation of its 
equivalent of CLIT. 
Others ascribe the action to the defective carbonization of the wood, and 
seek explanation in the ‘oils, resins, or partially changed wood fibre,’’ 
which are known to precipitate gold. 
Some claim that the action is due to the presence of hydrogen in the 
gaseous ammonia, which charcoal absorbs with avidity from the air. If 
such were the case, the action would be of short duration in the presence 
of highly charged chlorine solutions ; but, that such is not the case, may 
be experimentally shown, by submitting a perfectly prepared piece of 
charcoal to a high heat, and, while in a state of ignition, quenching it in 
distilled water (simply for the purpose of cooling), then immediately 
transfer it in the dark to a cold surcharged chlorine solution carrying gold 
and copper ; the effect will be the disappearance of the free chlorine, the 
*In the quantitative investigation of this subject by Dr. G. A. Kanig of the 
Pennsylvania University, as published in Journal of Franklin Institute, May 8, 
1882, this property of heat, to decompose a gold solution was overlooked, and 
his conclusions are invalidated by his employing heat in the digestion of the 
carbon in the gold solution. 
PROG, AMER. PHILOS. SOC. XXI. 114, N. PRINTED JUNE 23, 1883. 
