10 Proceedings of the Royal Societi/ of Victoria. 



grains of the leached sample are then taken and assayed, and if 

 the returns show that from 2 to 4 dwts. are left in, according to 

 the richness of the original sample, then the cover of the vat is 

 raised and a spray of water under a pressure of about 20 feet 

 from a rose is allowed to fall over the surface of the ore. 



In this way most of the chlorine present is absorbed and 

 cai-ried down to the bottom of the vat. As soon as the liquid 

 reaches the bottom, the lower tap is turned on and it escapes 

 into the precipitating vat. Practically the first few gallons, 

 when washing is done in this vvay, contain most of the gold. 



When the surface of the ore, which has subsided by about a fifth 

 of its height, is again above water, another shower is sprayed 

 over it, and so on until the escaping liquid is free from gold. 



By washing in this way, it will be found that wash-water less 

 than half the bulk of the ore is sufficient to carry all soluble 

 gold out ; it also offers a further advantage : that should any 

 solid reducing agent be present accidentally — say an iron bolt — 

 almost the whole of the gold will be washed past without much 

 danger of local precipitation ; whereas, if the vat were filled in 

 the orthodox way, undesii-able secondary actions would go on 

 for a considerable distance around the metal. 



The auriferous solution is allowed to flow through an open- 

 texture canvas bag, which serves to retain any sand, sulphate or 

 chloride of lead, or other solid material which may have passed 

 through. 



The gold solution is tested with sulphate of iron in a porcelain 

 basin, the slightest discolouration being made plain against a 

 white surface. 



Many authorities recommend stannous chloride, containing a 

 small quantity of stannic chloride, as a more delicate test ; but 

 it is found in practice to fail, and is not so certain as the ferrous 

 sulphate method. 



The amount of chlorine used for each ton of ore was deter- 

 mined by weighing the cylinder before and after each operation, 

 and it was found to vary from 6 lbs. to 10 lbs. of chlorine per 

 ton of ore. On several occasions the ore was charged in hot, 

 and it was found that more chlorine was required and the 

 extraction performed in the same time as when cold. The 

 escaping liquor contained much larger quantities of base chlorides 

 than when cold. 



