1894.] Specific Resistance of Pure Electrolytic Copper. 



79 



250 cm. of this wire were compared with the standard ohm, 

 according to the method described. The following are the observa- 

 tions : 



Table IV. 





From the numbers in column 6 the values of the specific resistance 

 of this sample can be obtained by multiplication with the constant 

 1*6826 obtained in the same manner as the value for the hard variety, 

 the difference being due to the difference in the diameters. All the 

 other constants of the measurements were the same. The results by 

 calculation give the following values : 



Specific resistance of rocking tank A copper, annealed in C0 2 

 gas: 



At 16-8 C. = 1672-4 C.G-.S. units. 

 19-95 = 1696*0 

 48-0 = 1876-0 



The temperature coefficient, calculated from the following for- 

 mula : 



gives the value 0*00418 at ordinary temperatures. 



Applying this value of x to the amount of specific resistance at 

 16*8 C., the following is obtained as the specific resistance of this 

 special sample of annealed rocking tank A deposit : 



<T O C = 1566 C.G.S. units. 



Specific Resistance of Soft Annealed Copper Wire made from De- 

 posited Sheet Copper named -Z?, the Deposit being obtained from a 

 Solution of Rocking Tank A Copper Dissolved in Pure Diluted 

 Sulphuric Acid, using an Anode of the Tank A Copper. 



Origin of the Copper. A solution of sulphate of copper was pre- 

 pared by using a piece of rocking tank A copper, as the anode in a 



