186 A. LIVERSIDGE. 



Some of the sandstones examined were being used at the 

 University for building purposes, in other cases the stone was 

 obtained expressly from the Pyrmont quarries. 



The amounts of gold present were determined by the ordinary 

 process of assaying 1,000 grains of the rock with red lead and 

 cupelling and correcting for the gold in the red lead. The amount 

 of silver present was neglected, it being unessential to the present 

 inquiry. The dry assay was supplemented, in some cases, by 

 extraction with potassium cyanide solution, and also by means of 

 chlorine, but the latter is not very satisfactory for small proportions 

 of gold as shown by the following experiment. 



Five pounds weight of sandstone, No. 10 in the following table, 

 was treated with chlorine water, but yielded only 1*17 grains of 

 gold per ton, although this sandstone had yielded 2*24 grains of 

 gold per ton to the potassium cyanide solution ; therefore, to test the 

 chlorine process, five fluid ounces of photographers' gold solution, 

 containing roughly two and a half grains of metallic gold was 

 added to the exhausted sandstone and left for twenty-four hours, 

 it was then extracted with fresh chlorine water and leached until 

 free from chlorine, the solution was evaporated to dryness, scorified 

 and cupelled, but only -054 grain of gold was obtained. Then, 

 since the chlorine did not remove the gold, the sandstone was 

 extracted with 1,600 c.c. of a '025% potassium cyanide solution,, 

 when 1*510 grains of gold were obtained; as the amount of gold 

 was still short, it was again extracted with 1*5 litres of *5% 

 potassium cyanide solution, when an additional "075 grain of gold 

 was obtained or, 



(1) By chlorine ... ... *054 grain of gold. 



(2) By potassium cyanide 1*510 „ 



(3) „ „ -075 



1*639 

 leaving nearly a grain of the added gold to be accounted for, as 

 well as 1*07 grains of the 2*24 grains originally present in the 

 sandstone. 



