PREPARATIONS OF LEAD.
Lead, in its metallic state, is not injurious. It is, however, really
acted on by acids, exposure to the atmosphere, &c., and converted into
carbonate of lead. The chief compounds of this metal which have been
found to produce poisonous effects are the acetate, subacetate, and the
carbonate.
ACETATE OF LEAD (_Sugar of Lead_).--This is sold as a glistening white
powder, or in the form of crystalline masses resembling loaf sugar. It
is more frequently used as a poison than either of the other compounds.
It is very soluble in water and has a sweetish metallic taste. Three or
four instances are recorded in which recovery has taken place after an
ounce of this substance has been taken in solution.
Mr. Bancks, of Stourbridge, has reported the particulars of a series of
cases of poisoning by the acetate of lead (_Lancet_, 5th May, 1849). It
appears that thirty pounds of this substance were accidentally mixed at
the miller's with eighty sacks of flour. This was made into bread, from
eating which 500 persons suffered severely. The chief symptoms were a
sense of constriction in the throat and at the pit of the stomach,
crampy pains round the navel, stiffness of the abdominal muscles,
paralysis of the lower extremities, constipation, scanty urine, and the
formation of a deep blue line round the gums. Although in many cases
there was great prostration with other alarming symptoms, yet under the
use of purgatives all recovered. It was noticed that after a temporary
convalescence many of the symptoms returned in an aggravated form
without any apparent cause. Sometimes there has been vomiting and
purging, and there is great prostration, with cramps and convulsions.
_Post-mortem Appearances._--They are not usually very distinct. The
stomach and intestines have been found inflamed, and the surface of the
former softened and, in the case of animals, corroded. There may be no
characteristic signs in chronic poisoning.
SUBACETATE OF LEAD (_Goulard's Extract_).--This substance is known to
have proved fatal in three or four instances, after having caused great
agony. It is a more powerful poison than the acetate. It is found in the
shops as a whitish-colored liquid.
CARBONATE OF LEAD (_White Lead_, _Ceruse_, _&c._).--This is sold in
heavy white masses, looking like chalk. It is readily acted on by acids,
but is very insoluble in water.
Dr. Snow has reported an instance in which a child ate a portion, about
the size of a marble, mixed up with oil; it died on the fourth day.
Carbonate of lead derives its greatest interest from the chronic form of
poisoning which it produces among white lead manufacturers, painters,
&c., known as "the painters' colic," which too often terminates in "lead
palsy." In these instances the lead finds its way into the system by
absorption from the digestive canal, the lungs, or the skin; producing
its characteristic effects when a sufficient amount has been absorbed.
It is this salt which is formed by the action of air and water upon
lead.
The other preparations of this metal do not require any separate notice.
_Treatment._--The sulphates of soda or magnesia should be freely given
dissolved in water. Milk, or milk and eggs will be useful. If vomiting
is absent, an emetic of sulphate of zinc should be administered, or the
stomach-pump may be advantageously employed.
For a chemical antidote in poisoning by carbonate of lead Dr. Taylor
recommends a mixture of vinegar and sulphate of magnesia.
_Tests._--The presence of a salt of lead in solution may be thus
ascertained:--1. On passing sulphuretted hydrogen through it, or on
adding a few drops of sulphide of ammonium, a black precipitate is
given. 2. A white precipitate results from the use of liquor potassae or
liquor ammoniae. 3. Dilute sulphuric acid gives a similar precipitate,
which is insoluble in nitric acid. 4. Iodide of potassium affords a
bright yellow deposit (iodide of lead).
CHRONIC LEAD POISONING.--The chronic and insidious effects produced by
lead upon the constitution are deserving of careful attention. Water
impregnated with this metal in its passage through lead pipes or
cisterns, acquires poisonous properties. Lead-pigments are sometimes
improperly used to color cheese, lozenges, snuff, &c. The endemic colic
of Devonshire was due to the absorption of lead contained in cider,
which had been made in leaden vessels; and in the wine district of
Poictou attacks of colic were so common, from the impregnation of wine
with this metal, that we still speak of "colica Pictonum."
The pernicious influence of lead is manifested among those engaged in
the manufacture or use of lead compounds, especially painters, lead
smelters, plumbers, color grinders, shot manufacturers, workers in sugar
of lead, potters, compositors, enamellers of cards, &c. These artisans
should be advised to prevent disease by great cleanliness, by avoiding
intoxicating liquors, and by drinking freely of sulphuric acid lemonade.
The substitution of moist for dry grinding has proved useful.
The most prominent _symptoms_ of chronic poisoning by lead are as
follows: A blue line around the gums, and the liability of the latter
to bleed from any slight cause; emaciation, a pallid tint of the
complexion, poorness of blood, and a feeble quick pulse; obstinate
constipation, with attacks of colic relieved by pressure; diminution of
the renal secretion and rheumatic pains; afterwards comes weakness of
the hands, wrists, and arms, ending in paralysis of the extensors, or
"dropped wrists," creeping up the arms.
The _treatment_ of these cases must consist in the first instance in the
use of purgatives; none being better than sulphate of magnesia with the
dilute sulphuric acid. But the remedy of all others is the iodide of
potassium, in five or ten grain doses thrice daily; this agent acting
most beneficially when employed in conjunction with galvanism to the
paralysed limbs.