7.3.
ALKALINE LEAD HYDROXIDE STAINS
223
Watson (1958) wisely precautioned anyone who would use lead salts
as stains to regard these as potentially highly dangerous substances. If
old solutions are allowed to dry, or stains are spilled, very fine powders
are apt to result that all too easily can spread contamination that can be
picked up on the hands, and from there be transferred to the mouth.
Aerosols might even be inhaled. Lead, of course, accumulates in the body
and easily can reach toxic levels.
Reynolds'
(1963) lead citrate.
This stain uses citrate as a chelating
agent in sufficient excess to sequester all of the lead present, and thus
quite effectively prevents it from combining with carbonate. Tissue bonding sites, on the other hand, fortunately have a greater affinity for the
lead cation than citrate, and thus are dramatically stained. It is remarkable that fresh surfaces of alkaline lead citrate solutions need not become
contaminated even if left exposed for periods of ^ hour or more if reasonable precautions are taken.
Reynolds prepares lead citrate by placing 1.33 gm of lead nitrate,
1.76 gm of sodium citrate, and about 30 ml of distilled water in a 50 ml
volumetric flask. The resultant suspension is shaken vigorously for a full
minute, and allowed to stand with intermittent shaking for 30 minutes
in order to insure the complete conversion of the lead nitrate to lead
citrate. Then 8 ml of 1 iV sodium hydroxide are added. This should be
as carbonate-free as possible, and therefore should have been reasonably
freshly prepared from sodium hydroxide of recent manufacture. The
suspension is diluted to 50 ml with distilled water, and mixed by inversion. The lead citrate dissolves and the staining solution is now ready
for use. It should have a pH of approximately 12, and should be clear.
Residual turbidity suggests either that old lead salts were used which
may have partly decomposed to produce lead oxides, or that carbonate
was introduced in substantial quantity. Faint turbidity, if present, usually
can be removed by centrifugation. The staining solution can be stored
in glass or polyethylene bottles for periods of up to 6 months, although
old solutions may require centrifuging before use.
Grids with sections are stained by floating them upside down on single
drops of staining solution. A Petri dish makes an almost ideal moist
ing solution, slightly larger than supporting grids, are placed upon a piece of a sheet
of dental wax.
(b) Grids are floated, section side down, upon the drops of stain, subsequently to be
flushed
briefly with extremely dilute alkali and pure water.
ALKALINE LEAD HYDROXIDE STAINS
223
Watson (1958) wisely precautioned anyone who would use lead salts
as stains to regard these as potentially highly dangerous substances. If
old solutions are allowed to dry, or stains are spilled, very fine powders
are apt to result that all too easily can spread contamination that can be
picked up on the hands, and from there be transferred to the mouth.
Aerosols might even be inhaled. Lead, of course, accumulates in the body
and easily can reach toxic levels.
Reynolds'
(1963) lead citrate.
This stain uses citrate as a chelating
agent in sufficient excess to sequester all of the lead present, and thus
quite effectively prevents it from combining with carbonate. Tissue bonding sites, on the other hand, fortunately have a greater affinity for the
lead cation than citrate, and thus are dramatically stained. It is remarkable that fresh surfaces of alkaline lead citrate solutions need not become
contaminated even if left exposed for periods of ^ hour or more if reasonable precautions are taken.
Reynolds prepares lead citrate by placing 1.33 gm of lead nitrate,
1.76 gm of sodium citrate, and about 30 ml of distilled water in a 50 ml
volumetric flask. The resultant suspension is shaken vigorously for a full
minute, and allowed to stand with intermittent shaking for 30 minutes
in order to insure the complete conversion of the lead nitrate to lead
citrate. Then 8 ml of 1 iV sodium hydroxide are added. This should be
as carbonate-free as possible, and therefore should have been reasonably
freshly prepared from sodium hydroxide of recent manufacture. The
suspension is diluted to 50 ml with distilled water, and mixed by inversion. The lead citrate dissolves and the staining solution is now ready
for use. It should have a pH of approximately 12, and should be clear.
Residual turbidity suggests either that old lead salts were used which
may have partly decomposed to produce lead oxides, or that carbonate
was introduced in substantial quantity. Faint turbidity, if present, usually
can be removed by centrifugation. The staining solution can be stored
in glass or polyethylene bottles for periods of up to 6 months, although
old solutions may require centrifuging before use.
Grids with sections are stained by floating them upside down on single
drops of staining solution. A Petri dish makes an almost ideal moist
ing solution, slightly larger than supporting grids, are placed upon a piece of a sheet
of dental wax.
(b) Grids are floated, section side down, upon the drops of stain, subsequently to be
flushed
briefly with extremely dilute alkali and pure water.