Phosphorus to the "Poling" of Copper, 543 



addition to a permanent effect on the metal itself, the phosphorus 

 by its deoxidizing action actually poles it, thus accelerating the 

 process and rendering unnecessary much use of the ordinary 

 pole. When the experiment was first made the copper was at 

 once overpoled, and had to be exposed again to the oxidizing 

 action of the air. No attempt is made to effect the poling en- 

 tirely by phosphorus; and this does not appear so desirable as to 

 bring the metal near the tough-pitch point by its agency, and 

 then complete the process by the less rapid action of the pole, as 

 in this way the proper point at which the metal should be cast is 

 more easily reached. 



The phosphorus is added in the form of a rich compound of 

 copper and phosphorus containing about 7 per cent, of phos- 

 phorus. This is prepared by pouring melted copper upon sticks 

 of phosphorus coated with copper by immersion in a solution of 

 cupreous sulphate*, and placed at the bottom of a conical-shaped 

 iron crucible protected throughout by a lining of loam mixed 

 with powdered coke. In the cover is a funnel through which 

 the metal is poured, and a small hole for the escape of air. The 

 metal falls on to a perforated plate coated like the crucible and 

 placed midway between the bottom and cover, thus presenting a 

 body of metal to absorb the escaping vapour of phosphorus. 



The proportion of phosphorus required varies with the dryness 

 of the copper after fusion. At Chatham 1 cwt. of the phosphide 

 compound is added to a charge of 5 tons; and with this quantity 

 the copper is scarcely ever overpoled. It represents about "07 

 per cent, of phosphorus; and about half this quantity is found 

 to be permanently retained. 



The advantages of this use of phosphorus may be stated to 

 be: — 



1. Increased density of the copper, as will be seen from the 

 following determinations : Spec. grav. 



T8-835 

 Three samples of ordinary cake copper < 8-835 



[8-839 

 Copper compressed by Sir J. Whitworth 8*876 

 Copper after addition of phosphorus in'l o.^i 

 refming-furnace J 



If "1 per cent, of phosphorus be added to copper melted in a 

 crucible, its density is as great as that of compressed copper; but 

 copper at the proper pitch will only roll hot, and without over- 

 poling it, no larger addition than that stated above can be made 

 in the refming-furnace. 



2. Acceleration of the process of poling. 



3. Reduced consumption of poles. 



* At Chatham uncoated sticks of phosphorus are now used. 



