Davis.} 1LO4 {April 6, 
samples from the receiving tanks, from the collecting tanks, from the pipe 
which carried the solution to the filter, and from the stop cock through 
which the liquid passed after the solution had been in contact with the 
charcoal. 
«The unvarying results of these repeated tests may be summed up 
briefly: 
‘‘While I never failed to get copious precipitates of gold from the solu- 
tion in the tanks, and from that taken from the faucet through which it 
flowed into the filter, I never obtained the slightest gold precipitate from 
the same liquid after it had passed through the charcoal, 
“The tests which were employed to detect gold in the liquid which had 
passed through the charcoal were varied, and entirely sufficient to be con- 
vincing. Sulphate of iron will decidedly indicate the presence of one part 
of gold to forty thousand parts of liquid. 
“Neither with this reagent, nor with any others that were used could a 
trace of gold be detected in the liquid taken from the lower spigot of the 
first barrel, containing one hundred pounds of charcoal, measuring twenty- 
eight inches vertically, after about nine hundred and sixty gallons of ter- 
chloride solution had passed through it.’’ 
This amount of solution represented about six thousand pounds of ore, 
carrying according to assays, $72 in gold. 
He continues, ‘‘ Briefly restating what has been said at greater length, I 
would repeat that the charcoal filter as here used, is entirely sufficient to 
precipitate from a terchloride solution, all the gold contained therein.”’ 
Prof. Endlich remarked on the disappearance of the chlorine from the 
solution after it had passed the filter. At this stage of the experiment the 
true cause of the deposition of the gold was not determined, on this point 
he writes ; 
“As to the chemical exchanges which take place, and produce the re- 
sult, I cannot speak positively, and have not, at present, the time at my 
command to make the requisite investigations,’’* 
It was not until operations were conducted on an enlarged scale that we 
arrived at an explanation of the reactions which occur in the contact of the 
terchloride solution with carbon. 
It was known to a few antiquarian delvers in chemical records, that 
among the multitude of substances which decompose a solution of chloride 
of gold, carbon was named by Count Rumford as possessing this property, 
but it was only under certain conditions that he observed it to act, for he 
says, ‘‘recently ignited charcoal separates gold, only in sunshine or at, 
109° ;’’ further experiment proved that under the influence of light, or 
heat, gold will separate from its solution in the absence of charcoal. 
Thus Kane teaches that, ‘‘when chlorine water is exposed to the light, 
it is gradually decomposed, chloride of hydrogen being formed, and 
*Prof, H, subsequently writes: ‘Your conclusions regarding the decom posi- 
tion of water for the formation of C1IT seem a little forced.” 
