176 
ON THE ELECTEIC CONDUCTING POWEE OP ALLOTS. 
the iron with boiling hydrochloric acid, and fusing with nitrate of potash and a Kttle 
borax, gave — 
I. II. Mean. 
73- 63 at 13°-5 72-90 at 14°-2 73-27 at 13°-8. 
A fourth specimen, prepared exactly as the third, gave — 
I. II. Mean. 
74- 20 at 14°-8 73-78 at 15°-5 73-99 at 15°-1. 
The so-called proof-gold of the refiners gave — 
I. n. ni. 
65-57 at 23°-l 64-25 at 23°-l 65-92 at 23°-lA 
In conclusion, I give a list of the determinations of gold as found by other experi- 
menters, silver taken =100 : — 
ElESSf. LENZf. Ed. BeCQTJEEEL J. HAEEIsf. H. DAVXf. CHETSTIEt. 
59 58-5 64-9 66-6 67 73 
Matthiessbx. 
55-19 and 73-26 at 17°-8. 
On looking over these values, we find that all, except that of Cheistie, are too low. 
and the gold-silver alloys which correspond to these numbers are the alloys which con- 
tain 
99-4 per cent, gold and 0-6 per cent, silver, conducting 59, 
99-7 per cent, gold and 0-3 per cent, silver, conducting 66. 
Now the proof-gold of the refiners often contains as much as 0-5 per cent, silver, and 
the value 66 found for it would be that of the alloy 99-7 per cent, gold and 0-3 per cent, 
silver. 
Of course the value given in my paper “ On the Thermo-electric Series,” for the 
thermo-electric number of pure gold, cannot be correct, as I used the same gold for 
those determinations and for those of the conducting power. 
I am much indebted to Dr. M. Holzmaxn for the excellent manner in which he has 
carried out the greater part of the foregoing determinations. 
gold, and be reduced during the process of fusion. The following experiments prove this to be the case ; 
they were carried out in every respect in the same manner, and with the same care as those above, tlie only 
difference being in the concentration of the solution. 
Thus gold containing silver was dissolved in nitrohydrochloric acid, evaporated to dr^mess with excess of 
hydrochloric acid, dissolved in a small quantity of water and precipitated by a concentrated solution ot 
protosulphate of iron, washed alternately by boiling nitric and hydrochloric acids, redissolved in nitrohydro- 
chloric acid, reprecipitated by protosulphate of iron, washed alternately with niti'ic and hydi'ochloric acids 
and fused with nitrate of potash, and then gave 
6G-57 at 22°-0. 
Another specimen, prepared by precipitating a concentrated solution of gold by protosulphate of iron, 
washing, &c., redissolving and precipitating by sulphurous acid, washing, &c., gave — 
I. 67-87 at 22°-3. II. 67-78 at 22°-3. 
* For all the above determinations, hard-dra-wn wires were used. 
f Gmelin, vol. i. p. 289. J Ann. de Chim. et de Phys. iii. 17, 2-42. 
