LABORATORY NOTES. 327 



solution ; this method is A'ery exact when the solution consists of 

 pure or nearly pure sulphate of copper, but it is not satisfactory 

 when iron is present. With large quantities of iron present, as 

 frequently occurs in the case of an ore analysis, the separation of 

 the copper is unduly prolonged, sometimes more than twenty-four 

 hours being required for complete precipitation. In 1869 Luckow 

 .showed that a nitric acid solution could be used and was much 

 more advantageous than the solution of the sulphate. "With slight 

 modifications this process has been the one in general use at the 

 Wallaroo Smelting Works for the past twenty years, and has given 

 great satisfaction, and we propose to place before you the methods 

 and apparatus used for the purpose. 



Apparatus. — The battery used consists of four cells of the 

 Meidinger type, joined in series. Two siich batteries are kept 

 going for "rdinary work. The negative element in this battery is 

 a ring of rolled zinc jin. thick, 4in. high, and 4^in. outside diameter. 

 To the top edge of this ring three pieces of stout sheet copper are 

 soldered so as to project about fin., and one of these carries the 

 binding screw. These three projecting lugs serve to suspend the 

 zinc ring in the upper part of the glass jar. The po.sitive element 

 is formed of a cylinder of 4lbs. or olbs. sheet lead, 11 in. high and 

 2in. diameter. It may be formed of a piece of lead pipe, but is 

 preferably made from sheet of the weight named, the joint being 

 soldered up. The lower end of the cylinder is slit up for a distance 

 of about 2in. at four opposite points, and the tongues thus formed 

 are spread out so as to nearly fit the inside diameter of the con- 

 taining glass jar, which is SA^in. high and 4fin. diameter inside. 

 To the top of the cylinder on the outside a copper wire is soldered 

 to allow of connectms; up the cells. The zinc and lead cylinders 

 being placed in position, the cell is charged by filling up the lead 

 cylinder with crystals of copper sulphate, and by then filling up 

 the jar to \vitl\in fin. of the top with saturated solution of mag- 

 nesium sulphate. When such a battery is first made up it requires 

 to be put on closed circuit for about twenty-four hours before it 

 comes into working order. It will then be noticed that some of 

 tlie sidphate of copper has dissolved, and. passing through the 

 openings iti the lower part of the lead cylinder formed by the 

 spreading abroad of the tongues mentioned above, has formed a 

 well-defined layer of this substance at the bottom of the jar, while 

 above it rests the magnesium sulphate solution. In tui-n one cell 

 in each battei-y is cleaned up every week, i.e., the copper which 

 has deposited on the lead is removed by gentle hammering ; the 

 copper sulphate crystals and the magnesium sulphate solution 

 renewed. In this way the battery is kept very constant for any 

 length of time. Four such cells yit Id a current of -l-'lo amperes 

 ?-t 2 volts. If the battery is allowed to stand for more than twenty- 

 four hours on open circuit the two liquids commence to diffuse; 

 copper deposits on the zinc cylinder and the battery when required 



