DRY ASSAY FOR SILVER AND GOLD. 115 



the button is '873 grains, that is, a little more than eight- 

 tenths of a grain. A rule of three sum then determines the 

 amount of precious metal per ton of ore. 



If a certain weight of ore yields eight-tenths of a grain, 

 how many grains will there be in a ton of similar ore ? 

 (N.B. There are 32 666 troy ounces in one ton.) The 

 number of ounces of precious metal in a ton will be known. 



DRY ASSAY FOR SILVER AND GOLD. 



In a gold and silver assay, the precious metals in the 

 sample, either by the scorification or " fusion in a crucible" 

 method, have to be absorbed by lead, and the resulting 

 button of lead containing the gold and silver has to be 

 cupelled in the muffle ; the final result being that the pre- 

 cious metals are left on the top of the bone-ash cupel as a 

 shining globule. 



As an assaying apparatus or " outfit" is to be obtained 

 complete in a chemical apparatus shop, there is no occasion 

 to enter into too much detail, the portable furnaces manu- 

 factured for cupellation in a muffle being made expressly for 

 prospectors and assayers. The most necessary articles are 

 the following : 



An ore and button balance with weights, two or three 

 muffles, Hessian crucibles, scorifiers, cupel mould, crucible, 

 scorification and cupel tongs, pokers and scrapers, an iron 

 pestle and mortar (or a plate and rubber), box sieve (80 

 mesh), spatula, hammer, bone-ash for making cupels, 

 litharge, borax, carbonate of soda, iron nails, nitre, coke, 

 charcoal, &c., test tubes, acids, brush for cleaning the 

 buttons. 



To light the fire. First, place some dry twigs and paper 

 or wood shavings or chips, and above this slightly larger 

 wood round about the outside of the muffle, and set light 

 to it. Then throw in pieces of charcoal, coke, or anthracite 

 coal broken into small pieces about the size of hen's eggs. 

 Shut the mouth of the muffle and the grate door. Eaise 

 the temperature as high as possible for the scorification 

 process. 



Though fusion in a crucible is very convenient for poor 

 gold and silver ores, inasmuch as a greater charge can be 



