W. Gibbs—Contributions to Chemistry. 213 
hate is then added, and the crucible is to be again carefully 
eated until the contents run to a clear fused mass. On cooling 
the mass usually separates readily from the crucible which is 
not attacked, and on solution the iron and copper are found com: 
pletely converted into sulphates. This process has been tried 
successfully with a great variety of ores. The whole operation 
Tequires about an hour. In the case of ores containing much 
bisulphid of iron it is best to heat the powdered ore first as long 
as sulphur is given off, and afterward to add the oxydizing mix- 
ure and heat as above. The sulphids of lead, zine and anti- 
mony are completely oxydized by the same process. 
$3. On the precipitation of copper and nickel by alkaline ear- 
bonates. 
The precipitation of copper by zine or by the electrolytic 
method requires that the metal should be present in the form 
of sulphate or chlorid and, does not succeed with the nitrate. 
As stated above the employment of the hypophosphites is lim- 
accurate for all the conditions under which the experiment may 
dilute. Mr. E. R. Taylor, who has made a careful study of this 
method of determining copper, has arrived at the following as 
the best method of conducting the process. The solution of 
ydrogen, and the copper weighed 
48 metal; it will be found to be free from alkali. In this manner 
13884 ; etallic copper 
"* 8T. pure sulphate of co ve 0°4688 gr. m ppe 
ae gr. e metallic cop. disnlved i in aqua regia gave Bip gr. se 
ak . i pe as pe “ 14670 ‘ “e =100-09 “ 
i‘ ic = ss zs nitric acid . ite ga pt 
* Handbuch der Analytischen Chemie, ii, 175. Sechste Auflage. 
