78 THE MONTHLY BULLETIN. 



able to conclude that this drip is essentially the condensed steam which 

 is produced in passage through the cool hose. This also evidently 

 carries with it a very small quantity of the residue by mechanical 

 action, but not in sufficient quantity to cause any alarm. 



The Residue. 



The residue from the machine contains a large excess of sulfuric acid 

 so that several charges of the cyanide solution are acted upon if poured 

 into the residue. Experiments would indicate that the proportion of 

 acid in the usual formula may with advantage be cut do^m from 1^ 

 ounces to 1} ounces without affecting the results. This view is also held 

 by Mr. R. S. Woglum. 



Upon recommendation, the Limoneira machines are now being oper- 

 ated on this basis with satisfactory results. 



Metal Solution Tanks. 



Some trouble has been experienced by the users of the machines in 

 finding the most suitable containers for dissolving the cyanide. Cyanide 

 .solutions are very efficient solvents for many of the metals ; in fact, the 

 extended use in the extraction of low grade gold and silver ores is 

 dependent upon its ability to readily dissolve these metals from their 

 ores. Galvanized iron tanks have been used, but the zinc plating was 

 quickly eaten away from the iron and from between the joints of the 

 tanks with a result that while the tanks were not affected beyond the 

 iron beneath the zinc coating, leaks were developed at the joints. 

 "Wooden barrels were used, but in a short time the solution seeped 

 through the wood and the wood was also eventually disintegrated. Old 

 oil barrels were used with some better success at first, but the oil was 

 soon saponified by the action of the cyanide and then the barrels were 

 no better than untreated ones. 



Some simple experiments were therefore made to determine the 

 most suitable material for the construction of solution tanks. Strips 

 of various metals 1 centimeter wide and 15 centimeters long were cut 

 out. A piece of block tin pipe was split open, flattened and a strip cut 

 out of the same dimensions as the above. Some "1-2 and 1-2" Selby 

 solder was melted and also made into a strip as above. These strips 

 were placed in a 1 to 2 cyanide solution at a uniform depth of 6 centi- 

 meters, thus exposing a total surface of 12 square centimeters to the 

 solution. At intervals, the metals were removed, washed off, dried and 

 weighed and the loss in weight noted. The practical results of this 

 experiment are as follows : 



Sheet Iron — This material was found to be the most resistant of any 

 of the metals used. The strip of iron, weighing about 8 grams, showed 

 a loss of only 2| milligrams during a period of 88 days' exposure, being 

 an average daily loss of 0.00002841 grams. 



Sheet Lead — The strip of lead, weighing about 40 grams, lost 0.1867 

 grams over a period of 88 days' exposure, being an average daily loss of 

 0.002122 grams. 



Block Tin — The strip of tin, weighing about 17 grams, lost 0.1566 

 grams over a period of 88 days' exposure, being an average daily loss 

 of 0.00178, 



