56 UNIVERSITY OP COLORADO 



evaporation, or the Argall method (see page 41). The solutions 

 from one bottle would be used for determining cyanide consump- 

 tion, the duplicate being used for this assay. Apart from this it is 

 always advisable to test an occasional solution assay against the 

 corresponding tailing assay, the one giving the precious metal 

 extraction, the other the amount remaining in the tailings, and 

 they should check within the limits of experimental error. 



If the ore experimented with is to be treated by agitation, the 

 bottle tests give all the information required, if, by percolation, it 

 is necessary to establish the ratio of time between agitation and 

 percolation. It is, of course, variable, but approximates 1 for 

 agitation to 4 for percolation. ' 



PERCOLATION TESTS. 



These can be made in glass percolators holding about 4 lbs. of 

 ore. The ore, in which is thoroughly incorporated the required 

 amount of lime, should be placed evenly and carefully in the perco- 

 lator, gently pressed around the sides to prevent channeling, and 

 the solution added on top. The strength of the solution to be used 

 has been previously determined from the results of the bottle tests. 



Allow the solution to stand on the ore 4 hours, then allow to 

 percolate through. Allow the ore to drain dry every day; after 

 the second complete day's treatment turn the ore out from the 

 percolator when drained dry, and cut out a sample for assay, to 

 show the extraction, and return the remainder to the percolator. 

 Keep up this sampling, daily, until the final extraction is reached, 

 so far as one percolator is concerned. Allow the duplicate to run 

 on without being disturbed, but it must be drained dry daily. 



The percolator tests should follow the usual cyanide practice: 



1. Water, or alkaline wash, if required. 



2. Weak solution. 



3. Strong solution. 



4. Weak solution. 



5. Water wash. Finish. 



If the preliminary wash is unnecessary, add at once the strong 

 solution, followed by No. 4 and No. 5. 



Where copper or organic compounds are present, or to obtain 

 details of change in the solutions, several small-sized Working 

 Tests may be made in wooden or steel vats, holding 1,000 or 2,000 



