200 Mr, Vivian on the Process of Amalgamation [March, 



barrow on two wheels, in which it is taken to a convenient place 

 to cool ; and the process is repeated on another portion of ore, 

 as before described. 



This preparatory operation is altogether of such importance 

 in an amalgamation work, that I cannot too strongly impress 

 the necessity of the strictest attention to it ; and a few observa- 

 tions, in addition to those I have before made, may not be super- 

 fluous. 



The chemical changes that take place during the process are 

 the following. In the first part of the operation, the sulphur 

 becomes acidified, and from there being no fuel to be decom- 

 posed during the burning process, the whole of the atmospheric 

 air that passes through the furnace is available for that purpose. 

 A portion of the acid thus formed, unites with the metals in the 

 ore, and forms sulphates. These are again decomposed on the 

 heat being increased, when the sulphuric acid unites with the base 

 of the salt, and forms a sulphate of soda, or Glauber salt ; whilst 

 the muriatic acid thus liberated attaches itself to the silver, for 

 which it possesses a strong affinity, and forms muriate of silver. 

 By this means, the silver contained in the ore is detached from 

 its natural combinations, and instead of being in the state of a 

 sulphuret, as in the raw ore, it is, by being exposed to the fire 

 in conjunction with salt, converted into a muriate. 



The necessity of attention to the quantity of sulphur contained 

 in the ores mixed as I have before described, is easily under- 

 stood, on considering the nature of the chemical change to be 

 effected : for it is evident, that if there should not be a sufficient 

 portion of sulphur to form the quantity of acid necessary to 

 decompose the common salt, the silver will not be converted 

 into a muriate, and consequently it will not be suited to the 

 process of amalgamation. On the other hand, it is most mate- 

 rial that the whole of the sulphur contained in the ore should be 

 acidified, or expelled ; for if any portion of it remained in com- 

 bination with the silver, the union of that metal with the mercuiy 

 would not take place. 



The calcined ore, as I shall call it by way of distinction, is 

 filled from the depositing place, into small wooden boxes, each 

 containing 1 cwt. Six of these are placed in a square case, and 

 raised to the upper story, through an inclosed shaft, by means 

 of a windlass placed under the roof of the building. The ore is 

 here passed through riddles or screens, in order to separate any 

 pieces that may have been imperfectly calcined, from its having 

 caked together. 



The workmen carry the ore in boxes up the steps, and at the 

 landing place empty them into the opening, which is furnished 

 with a cover; from whence it rolls down over two inclined 

 screens placed right and left, the holes of which are about half 



