metallic copper.

Hydrogen is included in the table, and its position should be noted
with reference to the other common elements. For a more extended
discussion of this topic the student should refer to other treatises.

POTENTIAL SERIES OF THE METALS

__________________________________________________________________
| | |
| POTENTIAL | | POTENTIAL
| IN VOLTS | | IN VOLTS
_____________________|___________|____________________|___________
| | |
Sodium Na^{+} | +2.44 | Lead Pb^{++} | -0.13
Calcium Ca^{++} | | Hydrogen H^{+} | -0.28
Magnesium Mg^{++} | | Bismuth Bi^{+++}|
Aluminum A1^{+++} | +1.00 | Antimony | -0.75
Manganese Mn^{++} | | Arsenic |
Zinc Zn^{++} | +0.49 | Copper Cu^{++} | -0.61
Cadmium Cd^{++} | +0.14 | Mercury Hg^{+} | -1.03
Iron Fe^{++} | +0.063 | Silver Ag^{+} | -1.05
Cobalt Co^{++} | -0.045 | Platinum |
Nickel Ni^{++} | -0.049 | Gold |
Tin Sn^{++} | -0.085(?) | |
_____________________|___________|____________________|__________

THE FOLDING OF A FILTER PAPER

If a filter paper is folded along its diameter, and again folded along
the radius at right angles to the original fold, a cone is formed on
opening, the angle of which is 60 deg.. Funnels for analytical use are
supposed to have the same angle, but are rarely accurate. It is
possible, however, with care, to fit a filter thus folded into a
funnel in such a way as to prevent air from passing down between the
paper and the funnel to break the column of liquid in the stem,
which aids greatly, by its gentle suction, in promoting the rate of
filtration.

Such a filter has, however, the disadvantage that there are three
thicknesses of paper back of half of its filtering surface, as a
consequence of which one half of a precipitate washes or drains more
slowly. Much time may be saved in the aggregate by learning to fold a
filter in such a way as to improve its effective filtering surface.
The directions which follow, though apparently complicated on first
reading, are easily applied and easily remembered. Use a 6-inch filter
for practice. Pla