42 UNIVERSITY OF COLORADO 



cupel, weigh, and part in the usual manner. The flux used consisted 

 of 42 parts potash, 84 NaHC0 8 , 2 borax-glass and 9 of flour. Should 

 copper be present in the solution, a larger proportion of flux will 

 be required, and scorification may be necessary. 



Qualitative Detection of Gold. — The presence of gold in quan- 

 tities less than 0.1 mgr. may be detected in cyanide solution by 

 acidulating, boiling till most of the HCN is expelled, then adding 

 KC10 3 and again boiling till most of the chlorous gases are driven 

 off, and finally adding stannous chloride, which gives the well- 

 known Purple of Cassius. The final solution should not be too 

 strongly acid, or the color may not appear. It frequently becomes 

 more marked on allowing to stand for some time. 



Estimation of Silver. — In the Argall method for gold we deter- 

 mine the combined weight of gold and silver, from which the silver 

 may be calculated after parting the bead with HN0 3 and weighing 

 the gold. I have not tested this method where large amounts of 

 silver were present in solution, but up to 16 oz. per ton I know it 

 gives correct results and without the formation of silver sulphates. 

 If on richer solutions this was feared, hydrochloric acid could be 

 substituted for the sulphuric. 



The following method, recommended by Alfred Chiddey*, has 

 not been tested, though it is claimed to give higher results than 

 the evaporation process in ordinary use. The proportion of silver 

 to gold in the solutions on which Mr. Chiddey used it is 10 to 1, 

 and in case of nearly pure gold solutions the addition of a known 

 quantity of silver nitrate dissolved in cyanide is suggested. Intro- 

 duce into a porcelain dish 4 assay-tons, or more, of the solution 

 to be assayed, add 10 cc. of a 10$ solution of acetate of lead, then 

 4 grams of zinc shavings; boil a minute, add 20 cc. of hydrochloric 

 acid. When the action has ceased, boil again; wash the spongy 

 lead with distilled water; transfer it with a stirring rod to a piece 

 of filter paper; squeeze into a compact lump and place in a hot 

 cupel. The mouth of the muffle should contain a piece of dry 

 pine wood, so that the muffle is filled with flame at the moment 

 of introducing the spongy lead. 



12. Estimation of Alkalies. — Generally only two determina- 

 tions are attempted: (1) What is known as the "total alkali," which 

 may be defined as the equivalent, in terms of KOH, of all the 

 ingredients which are alkaline to methyl orange. (2) What is 



* Engineering and Mining Journal, March 28, 1903, page 473. 



