regard to the chemical nature of the earthy salt present in the water.
It serves only to indicate the _presence_ or _absence_ of those kinds of
substances which occasion that quality in water which is usually called
_hardness_, and which is always owing to salts with an earthy base.
If we wish to know the nature of the different acids and earths
contained in the water, the following test may be employed.[15]
EXPERIMENT.
Add about twenty drops of a solution of oxalate of ammonia, to half a
wine-glass of the water; if a white precipitate ensues, we conclude that
the water contains lime.
By means of this test, one grain of lime may be detected in 24,250 of
water.
If this test occasion a white precipitate in water taken fresh from the
pump or spring, and not after the water has been boiled and suffered to
grow cold, the lime is dissolved in the water by an excess of carbonic
acid; and if it continues to produce a precipitate in the water which
has been concentrated by boiling, we then are sure that the lime is
combined with a fixed acid.
EXPERIMENT.
To detect the presence of iron, add to a wine-glassful of the water a
few drops of an infusion of nut-galls; or better, suffer a nut-gall to
be suspended in it for twenty-four hours, which will cause the water to
acquire a blueish black colour, if iron be present.
EXPERIMENT.
Add a few grains of muriate of barytes, to half a wine-glass of the
water to be examined; if it produces a turbidness which does not
disappear by the admixture of a few drops of muriatic acid, the presence
of sulphuric acid is rendered obvious.
EXPERIMENT.
If a few drops of a solution of nitrate of silver occasions a milkiness
with the water, which vanishes again by the copious addition of liquid
ammonia, we have reason to believe that the water contains a salt, one
of the constituent parts of which is muriatic acid.
EXPERIMENT.
If lime water or barytic water occasions a precipitate which again
vanishes by the admixture of muriatic acid, then carbonic acid is
present in the water.
EXPERIMENT.
If a solution of phosphate of soda produces a milkiness with the water,
after a previous addition to it of a similar quantity of neutral
carbonate of ammonia, we may then expect magnesia. The application of
this test is best made in the following manner:
Concentrate a quantity of the water to be examined to about 1/20 part of
its bulk, and drop into about half a wine-glassful, about five grains of
neutral carbonate of ammonia. No magnesia becomes yet precipitated if
this earth be present; but on adding a like quantity of phosphate of
soda, the magnesia falls down, as an insoluble salt. It is essential
that the carbonate of ammonia be neutral.
This test was first pointed out by Dr. Wollaston.
The presence of oxygen gas loosely combined in water may readily be
discovered in the following manner.
EXPERIMENT.
Fill a vial with water, and add to it a small quantity of green sulphate
of iron. If the water be entirely free of oxygen, and if the vessel be
well stopped and completely filled, the solution is transparent; but if
otherwise, it soon becomes slightly turbid, from the oxide of iron
attracting the oxygen, and a small portion of it, in this more highly
oxidated state, leaving the acid and being precipitated. Or, according
to a method pointed out by Driessen, the water is to be boiled for two
hours in a flask filled with it, and immersed in a vessel of water kept
boiling, with the mouth of the flask under the surface of the water: it
is to be inverted in quicksilver, taking care that no air-bubble adheres
to the side of the flask, and being tinged with infusion of litmus, a
little nitrous gas is to be introduced: if the oxygen gas has been
sufficiently expelled from the water, the purple colour of the litmus
does not change; while, if oxygen be present, it immediately becomes
red.[16]
If we examine the different waters which are used for the ordinary
purposes of life, and judge of them by the above tests, we shall find
them to differ considerably from each other. Some contain a large
quantity of saline and earthy matters, whilst others are nearly pure.
The differences are produced by the great solvent power which water
exercises upon most substances. Wells should never be lined with bricks,
which render soft water hard; or, if bricks be employed, they should be
bedded in and covered with cement.
METHOD OF ASCERTAINING THE RELATIVE QUANTITY OF EACH OF THE DIFFERENT
SUBSTANCES USUALLY CONTAINED IN COMMON WATER.
To ascertain the quantity of earthy and saline matter contained in
water, the following is the most simple and easy method.
EXPERIMENT.
Put any measured quantity of the water into a platina, or silver
evaporating basin, the weight of which is known, and evaporate the water
upon a steam bath, at a temperature of about 180°, nearly to dryness;
and, lastly, remove the basin to a sand bath, and let the mass be
evaporated to perfect dryness. The weight of the platina basin being
already known, we have only to weigh it carefully. When the solid saline
contents of the water is attached to it, the increase of weight gives
the quantity of solid matter contained in a given quantity of the water.
EXPERIMENT.
Pour upon the saline contents a quantity of distilled water equal to
that in which the obtained salts were originally dissolved. If the whole
saline matter become dissolved in this water, there is reason to believe
that the saline matter has not been altered during the evaporation of
the water. But if a portion remain undissolved, as is usually the case,
then we may conclude that some of the salts have mutually decomposed
each other, when brought into a concentrated state by the evaporation,
and that salts have been formed which did not originally exist in the
water before its evaporation.
We have already mentioned that almost the only salts contained in common
waters, are the carbonates, sulphates, and muriates, of soda, lime, and
magnesia; and sometimes a very minute portion of iron. Having determined
the different acids and bases present, in the manner stated at p. 49, we
may easily ascertain the relative weight of each.
The following formula suggested by Dr. Murray,[17] is fully as accurate
a means of analysing waters as any other, and it is easy of execution.
The weight of the saline ingredients of a given quantity of water being
determined, we may proceed to the accurate analysis of it in the
following manner.
EXPERIMENT.
Measure out a determinate volume of the water (as 500 or 1000 cubic
inches,) and evaporate it gradually, in an unglazed open vessel defended
from dust, to one third of its original bulk; then divide this
evaporated liquid into three equal portions.
EXPERIMENT.
Drop into the first portion, muriate of barytes; wash the precipitate,
collect it, dry it at a red heat upon platina foil, and weigh it; digest
it in nitric acid, dry it, and weigh it again. The loss of weight
indicates the quantity of carbonate of barytes which the precipitate
contained. The residual weight is sulphate of barytes; the carbonic acid
in the water is equivalent to 0,22 of the weight of the carbonate of
barytes; the sulphuric acid to 0,339 of the weight of the sulphate of
barytes.
EXPERIMENT.
Precipitate the second portion of the concentrated water, by the
addition of nitrate of silver; wash the precipitate, dry it, and fuse it
on a piece of foil platina, previously weighed. By weighing the foil
containing the fused chloride of silver, the weight of the precipitate
may be ascertained. The fourth part of this weight is equivalent to the
weight of the muriatic acid contained in the portion of water
precipitated.
EXPERIMENT.
Precipitate the third portion of the water by the addition of oxalate of
ammonia; wash and dry the precipitate; expose it to a red heat, on a
platina foil, or in a capsule of platina; pour on it some dilute
sulphuric acid; digest for some time, then evaporate to dryness, expose
the capsule to a pretty strong heat, and, lastly, weigh the sulphate of
lime thus produced: 0.453 of its weight indicate the quantity of lime in
the portion of water precipitated.
EXPERIMENT.
Add to the same third portion of the water thus freed from lime, a
portion of a solution of neutral carbonate of ammonia, and then add
phosphoric acid, drop by drop, as long as any precipitate falls down.
Wash the precipitate, dry it, and expose it to a red heat in a platina
capsule: it is phosphate of magnesia. 0.357 of the weight of this salt
is equivalent to the weight of the magnesia contained in the water.
EXPERIMENT.
If the water contain a minute portion of iron, a quantity of it equal to
one of the three preceding portions, must be taken and mixed with a
solution of benzoate of ammonia. The precipitate being washed, dried,
and exposed to a red heat, and weighed, nine-tenths of its weight
indicate the weight of protoxide of iron contained in the water.
In this manner the quantity of all the substances contained in the water
will be ascertained, except there be any soda. To know the amount of it,
the following method, pointed out by Dr. Murray, answers very well.
EXPERIMENT.
Evaporate a portion of the water to one third of its bulk. Precipitate
the carbonic and sulphuric acids by the addition of muriate of barytes,
taking care not to add any excess of the tests.
Precipitate the lime by oxalate of ammonia, and the magnesia by
carbonate of ammonia and phosphoric acid. (Page 52.) Then evaporate the
liquid thus treated to dryness. A quantity of common salt will remain:
let this be exposed to a red heat; 0.4 of its weight indicate the sodium
contained in the bulk of water employed; and 0.4 sodium are equivalent
to 0.53 of soda.
It seems hardly requisite to mention some other substances that
occasionally make their appearance in the waters used for domestic
purposes. A fine divided sand is a common constituent, which is easily
obtained in a separate state. We have only to evaporate a portion of the
water to dryness, and redissolve the saline residue in distilled water.
The silicious sand remains undissolved, and betrays itself by its
insolubility in acids, and its easy fusibility into a transparant glass,
with soda, before the blow-pipe.
DELETERIOUS EFFECTS OF KEEPING WATER FOR DOMESTIC ECONOMY IN LEADEN
RESERVOIRS.
The deleterious effect of lead, when taken into the stomach, is at
present so universally known, that it is quite unnecessary to adduce
any argument in proof of its dangerous tendency.
The ancients were, upwards of 2000 years ago, as well aware of the
pernicious quality of this metal as we are at the present day; and
indeed they appeared to have been much more apprehensive of its effects,
and scrupulous in the application of it to purposes of domestic economy.
Their precautions may have been occasionally carried to an unnecessary
length. This was the natural consequence of the imperfect state of
experimental knowledge at that period. When men were unable to detect
the poisonous matters--to be over scrupulous in the use of such water,
was an error on the right side.
The moderns, on the other hand, in part, perhaps, from an ill-founded
confidence, and inattention to a careful and continued examination of
its effects, have fallen into an opposite error.
There can be no doubt that the mode of preserving water intended for
food or drink in leaden reservoirs, is exceedingly improper; and
although pure water exercises no sensible action upon metallic lead,
provided air be excluded, the metal is certainly acted on by the water
when air is admitted: this effect is so obvious, that it cannot escape
the notice of the least attentive observer.
The white line which may be seen at the surface of the water preserved
in leaden cisterns, where the metal touches the water and where the air
is admitted, is a carbonate of lead, formed at the expense of the metal.
This substance, when taken into the stomach, is highly deleterious to
health. This was the reason which induced the ancients to condemn leaden
pipes for the conveyance of water; it having been remarked that persons
who swallowed the sediment of such water, became affected with disorders
of the bowels.[18]
Leaden water reservoirs were condemned in ancient times by Hyppocrates,
Galen, and Vitruvius, as dangerous: in addition to which, we may depend
on the observations of Van Swieten, Tronchin, and others, who have
quoted numerous unhappy examples of whole families poisoned by water
which had remained in reservoirs of lead. Dr. Johnston, Dr. Percival,
Sir George Baker, and Dr. Lamb, have likewise recorded numerous
instances where dangerous diseases ensued from the use of water
impregnated with lead.
Different potable waters have unequal solvent powers on this metal. In
some places the use of leaden pumps has been discontinued, from the
expense entailed upon the proprietors by the constant want of repair.
Dr. Lamb[19] states an instance where the proprietor of a well ordered
his plumber to make the lead of a pump of double the thickness of the
metal usually employed for pumps, to save the charge of repairs; because
he had observed that the water was so hard, as he called it, that it
corroded the lead very soon.
The following instance is related by Sir George Baker:[20]
"A gentleman was the father of a numerous offspring, having had
one-and-twenty children, of whom eight died young, and thirteen survived
their parents. During their infancy, and indeed _until they had quitted
the place of their usual residence, they were all remarkably unhealthy_;
being particularly subject to disorders of the stomach and bowels. The
father, during many years, was paralytic; the mother, for a long time,
was subject to colics and bilious obstructions.
"After the death of the parents, the family sold the house which they
had so long inhabited. The purchaser found it necessary to repair the
pump. This was made of lead; which, upon examination was found to be so
corroded, that several perforations were observed in the cylinder, in
which the bucket plays; and the cistern in the upper part was reduced to
the thinness of common brown paper, and was full of holes, like a
sieve."
I have myself seen numerous instances where leaden cisterns have been
completely corroded by the action of water with which they were in
contact: and there is, perhaps, not a plumber who cannot give testimony
of having experienced numerous similar instances in the practice of his
trade.
I have been frequently called upon to examine leaden cisterns, which had
become leaky on account of the action of the water which they contained;
and I could adduce an instance of a legal controversy having taken place
to settle the disputes between the proprietors of an estate and a
plumber, originating from a similar cause--the plumber being accused of
having furnished a faulty reservoir; whereas the case was proved to be
owing to the chemical action of the water on the lead. Water containing
a large quantity of common air and carbonic acid gas, always acts very
sensibly on metallic lead.
Water, which has no sensible action, in its natural state, upon lead,
may acquire the capability of acting on it by heterogeneous matter,
which it may accidentally receive. Numerous instances have shewn that
vegetable matter, such as leaves, falling into leaden cisterns filled
with water, imparted to the water a considerable solvent power of action
on the lead, which, in its natural state it did not possess. Hence the
necessity of keeping leaden cisterns clean; and this is the more
necessary, as their situations expose them to accidental impurities. The
noted saturnine colic of Amsterdam, described by Tronchin, originated
from such a circumstance; as also the case related by Van Swieten,[21]
of a whole family afflicted with the same complaint, from such a
cistern. And it is highly probable that the case of disease recorded by
Dr. Duncan,[22] proceeded more from some foulness in the cistern, than
from the solvent power of the water. In this instance the officers of
the packet boat used water for their drink and cooking out of a leaden
cistern, whilst the sailors used the water taken from the same source,
except that theirs was kept in wooden vessels. The consequence was, that
all the officers were seized with the colic, and all the men continued
healthy.
The carelessness of the bulk of mankind, Dr. Lambe very justly observes,
to these things, "is so great, that to repeat them again and again
cannot be wholly useless."
Although the great majority of persons who daily use water kept in
leaden cisterns receive no sensible injury, yet the apparent salubrity
must be ascribed to the great slowness of its operation, and the
minuteness of the dose taken, the effects of which become modified by
different causes and different constitutions, and according to the
predisposition to diseases inherent in different individuals. The
supposed security of the multitude who use the water with impunity,
amounts to no more than presumption, in favour of any individual, which
may or may not be confirmed by experience.
Independent of the morbid susceptibility of impressions which
distinguish certain habits, there is, besides, much variety in the
original constitution of the human frame, of which we are totally
ignorant.
"The susceptibility or proneness to disease of each individual, must be
esteemed peculiar to himself. Confiding to the experience of others is a
ground of security which may prove fallacious; and the danger can with
certainty be obviated only by avoiding its source. And considering the
various and complicated changes of the human frame, under different
circumstances and at different ages, it is neither impossible nor
improbable that the substances taken into the system at one period, and
even for a series of years, with apparent impunity may, notwithstanding,
at another period, be eventually the occasion of disease and of death.
"The experience of a single person, or of many persons, however
numerous, is quite incompetent to the decision of a question of this
nature.
"The pernicious effects of an intemperate use of spiritous liquors is
not less certain because we often see habitual drunkards enjoy a state
of good health, and arrive at old age: and the same may be said of
individuals who indulge in vices of all kinds, evidently destructive to
life; many of whom, in spite of their bad habits, attain to a vigorous
old age."[23]
In confirmation of these remarks, we adduce the following account of the
effect of water contaminated by lead, given by Sir G. Baker:
"The most remarkable case on the subject that now occurs to my memory,
is that of Lord Ashburnham's family, in Sussex; to which, spring water
was supplied, from a considerable distance, in leaden pipes. In
consequence, his Lordship's servants were every year tormented with
colic, and some of them died. An eminent physician, of Battle, who
corresponded with me on the subject, sent up some gallons of that water,
which were analysed by Dr. Higgins, who reported that the water had
contained more than the common quantity of carbonic acid; and that he
found in it lead in solution, which he attributed to the carbonic acid.
In consequence of this, Lord Ashburnham substituted wooden for leaden
pipes; and from that time his family have had no particular complaints
in their bowels."
_Richmond, Sept. 27, 1802._
METHOD OF DETECTING LEAD, WHEN CONTAINED IN WATER.
One of the most delicate tests for detecting lead, is water impregnated
with sulphuretted hydrogen gas, which instantly imparts to the fluid
containing the minutest quantity of lead, a brown or blackish tinge.
This test is so delicate that distilled water, when condensed by a
leaden pipe in a still tub, is affected by it. To shew the action of
this test, the following experiments will serve.
EXPERIMENT.
Pour into a wine-glass containing distilled water, an equal quantity of
water impregnated with sulphuretted hydrogen gas: no change will take
place; but if a 1/4 of a grain of acetate of lead (sugar of lead of
commerce), or any other preparation of lead, be added, the mixture will
instantly turn brown and dark-coloured.
To apply this test, one part of the suspected water need merely to be
mingled with a like quantity of water impregnated with sulphuretted
hydrogen. Or better, a larger quantity, a gallon for example, of the
water may be concentrated by evaporation to about half a pint, and then
submitted to the action of the test.
Another and more efficient mode of applying this test, is, to pass a
current of sulphuretted hydrogen gas through the suspected water in the
following manner.
EXPERIMENT.
[Illustration]
Take a bottle (_a_) or Florence flask, adapt to the mouth of it a cork
furnished with a glass tube (_b_), bent at right angles; let one leg of
the tube be immersed in the vial (_c_) containing the water to be
examined; as shewn in the following sketch. Then take one part of
sulphuret of antimony of commerce, break it into pieces of half the size
of split pease, put it into the flask, and pour upon it four parts of
common concentrated muriatic acid (spirit of salt of commerce).
Sulphuretted hydrogen gas will become disengaged from the materials in
abundance, and pass through the water in the vial (_c_). Let the
extrication of the gas be continued for about five minutes; and if the
minutest quantity of lead be present, the water will acquire a
dark-brown or blackish tinge. The extrication of the gas is facilitated
by the application of a gentle heat.
The action of the sulphuretted hydrogen test, when applied in this
manner, is astonishingly great; for one part of acetate of lead may be
detected by means of it, in 20000 parts of water.[24]
Another test for readily detecting lead in water, is sulphuretted
chyazate of potash, first pointed out as such by Mr. Porret. A few drops
of this re-agent, added to water containing lead, occasion a white
precipitate, consisting of small brilliant scales of a considerable
lustre.
Sulphate of potash, or sulphate of soda, is likewise a very delicate
test for detecting minute portions of lead. Dr. Thomson[25] discovered,
by means of it, one part of lead in 100000 parts of water; and this
acute Philosopher considers it as the most unequivocal test of lead that
we possess. Dr. Thomson remarks that "no other precipitate can well be
confounded with it, except sulphate of barytes; and there is no
probability of the presence of barytes existing in common water."
Carbonate of potash, or carbonate of soda, may also be used as agents to
detect the presence of lead. By means of these salts Dr. Thomson was
enabled to detect the presence of a smaller quantity of lead in
distilled water, than by the action of sulphuretted hydrogen. But the
reader must here be told, that the use of these tests cannot be
entrusted to an unskilful hand; because the alkaline carbonates throw
down also lime and magnesia, two substances which are frequently found
in common water; the former tests, namely, water impregnated with
sulphuretted hydrogen gas, and nascent sulphuretted hydrogen, are
therefore preferable.
It is absolutely essential that the water impregnated with sulphuretted
hydrogen, when employed as a test for detecting very minute quantities
of lead, be fresh prepared; and if sulphate of potash, or sulphate of
soda, be used as tests, they should be perfectly pure. Sulphate of
potash is preferable to sulphate of soda. It is likewise advisable to
act with these tests upon water concentrated by boiling. The water to
which the test has been added does sometimes appear not to undergo any
change, at first; it is therefore necessary to suffer the mixture to
stand for a few hours; after which time the action of the test will be
more evident. Mr. Silvester[26] has proposed gallic acid as a delicate
test for detecting lead.
FOOTNOTES:
[11] Dalton, Manchester Memoirs, vol. iv. p. 55.
[12] Marsden's History of Sumatra.
[13] Manchester Memoirs vol. x. 1819.