The other results were:--
"Ferrocyanide"
required.
With nothing added. 20.3 c.c.
" 0.050 gram lead (as chloride) 20.9 "
" 0.050 " manganese (as sulphate) 25.5 "
" 0.050 " cadmium (as sulphate) 23.5 "
" 0.050 " nickel (as sulphate) 26.2 "
~Effect of Varying Zinc.~--These were titrated under the usual
conditions, and gave the following results:--
Zinc added 1.0 c.c. 10.0 c.c. 20.0 c.c. 50.0 c.c. 100.0 c.c.
"Ferrocyanide"
required 1.1 " 10.2 " 20.3 " 50.6 " 101.0 "
~Determination of Zinc in a Sample of Brass.~--Take the solution from
which the copper has been separated by electrolysis and pass
sulphuretted hydrogen until the remaining traces of copper and the lead
are precipitated, filter, boil the solution free from sulphuretted
hydrogen, put in a piece of litmus paper, and add sodic hydrate solution
in slight excess; add 10 c.c. of dilute hydrochloric acid (which should
render the solution acid and clear); warm, and titrate.
A sample of 0.5 gram of brass treated in this manner required 16.4 c.c.
of "ferrocyanide" (standard 100 c.c. = 0.9909 zinc), which equals 0.1625
gram of zinc or 32.
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