46
a mixture of equal parts of 2N sodium citrate and 2N acetic
acid.
To each funnel,
5 ml of 0.001 per cent dithizone
(diphenylthiocarbazone) in CClqg and 5 drops of 25 per cent
(weight/volume) sodium thiosulfate solution (to complex lead)
were added.
The buffer and sodium thiosulfate solutions had
previously been extracted with dithizone to remove any zinc
which might have been present as a contaminant,
tered to remove excess dithizone.
and then fil-
Next, a 1/100 or 1/1000
aliquot
(depending upon the type and weight of the tissue
sample)
of the zinc fraction of each sample was introduced
into one of the separatory funnels and shaken vigorously for
2 minutes.
If the dithizonate
to blue or bluish purple,
tube.
(CClq phase) changed from green
it was drawn off into colorimeter
If the color remained green or turned only slightly
greenish blue,
additional aliquots of the sample were added
and shaken until a decided bluish hue was attained.
color,
If the
after the addition of the first aliquot was purple or
red after shaking,
additional 5 ml portions of dithizone solu~
tion were added and shaken until the desired bluish color was
attained in the CCl4 phase.
The per cent transmittance of monochromatic light,
wave length of 515 mu,
at a
through the mixed-colox dithizonate