A NEW MODE OF RENDERING CERTAIN. WATERS (THE WATER OF THE THAMES, BEING AMONGST THE. NUMBER) LESS IMPURE AND LESS HARD, FOR. THE SUPPLY. AND USE OF MANUFACTORIES, VILLAGES, TOWNS; AND CITIES
Year: 1841

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I THOMAS
CLARK, Professor of Chemistry, in; Marschal College, University of Aberdeen,
send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Eighth day of March, in the fourth year of Her reign, did,
for Herself, Her heirs. and successors, give and grant unto me; the
said Thomas Clark; Her: especial; licence, full, sole privilege and authority,
that I, the said Thomas Clark, my exors, admors, and assigns, 'or'.such
others as I, the said Thomas Clark, my exors, adññiors, or assigns; should
at any time agree with, and no others, from time to time and at all timės
during the term of years therein expressed, should and lawfully might make,
use, exercise, andi vend, within England; Wales, and the Town of Berwick-
upon-Tweed, my Invention of "A NEW MODE OF RENDERING CERTAIN. WATERS
(THE WATER OF THE THAMES, BEING AMONGST THE. NUMBER) LESS IMPURE AND
LESS HARD, FOR. THE SUPPLY. AND USE OF MANUFACTORIES, VILLAGES, TOWNS;
AND CITIES;" in which said Letters Patent is contained a proviso that. 1;
the said "Thomas Clark; shall cause'n particular description of the nature
of my said Invention, and in, what manner the same is to be performed, to
be inrolled in Her said Majesty's High Court of Chancery within six calendar
months next and immediately after the .date of the said in part recited
Letters Patent, as in and by the same, reference being thereunto had, will
more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Thomas Clark, do hereby declare the nature of the said Invention, and in
what manner the same is to be performed, are fully described and ascer-
tained in and by' the following description thereof, that is to say:-
My Invention relates to a mode of rendering certain waters less impure
and less hard by the application oflime in suitable proportions, as herein-after
'explained; and in order that the Invention may be most fully understood and
readily carried into effect, I will proceed to describe the means pursued by me,
and which I have found fully to answer. As, in orderto regulate the working of
this Invention, I prefer to employ certain chemical agents, tests, and standard
solutions, I shall, preparatory to giving a particular account of the said
Invention, begin with describing the said chemical agents, tests, and standard
solutions, and shall afterwards explain the use of the same, as applicable to
the said Invention. I premise, that when I use the word gallon, I mean an
imperial gallon, and when I mention a lest measure, I mean one seventh'
thousandth part of such gallon. By test paper, I mean reddened litmus
paper; I prefer that the aciḍ employed in reddening litmus be a very dilute
nitricacid. Irecommend that the said test paper be not so red nor so free from
a blueish tint, but that it shall present a distinct red when acted upon by a
very dilute solution of an acid, and present a distinct blue or deepened blueish
tint by a very. dilute solution of unneutralized alkali or alkaline earth. The
said test paper should undergo no similar change on being allowed to remain
for half an hour in distilled water. By distilled water, I mean pure water;
and for the better assurance of possessing such water, I recommend that no
water be used as distilled unless it have been redistilled at least once, the first
eighth part that comes over of the quantity distilled being rejected in each
distillation. I employ sixteen standard solutions for the purpose of ascertaining
the degree of the hardness of waters by comparison with such standard
solutions. The following is the mode of preparing the said sixteen standard
solutions, beginning with the strongest:-Sixteen grains of pure Iceland-spar,
otherwise called calcareous spar, being what chemists call a carbonate of lime,
are to be put into a Florence flask with a short neck of about an inch in width
thereto; pure muriatic acid, of specific gravity approaching to one and a tenth
is added; I prefer a muriatic acid of this strength that has been distilled a
second.time, the first eighth part that comes over of the quantity distilled
being rejected in each distillation. A solution of the Iceland spar by the acid
will take place with effervescence. The solution, when completed, is to'be
evaporated cautiously, by placing a flask on a heated sand bath, taking care to
avoid too high a temperature, and as far as possible to evaporate the matter

page_text: as a measure.
to dryness without boiling. When the matter has been thus evaporated to
dryness, and while the flask yet remains on the heated sand bath, the air
should be sucked out of the flask by means of a tube, so as to remove any
residue of acid fumes. After the flask has cooled, the dried matter is to be
moistened with a few drops of distilled water, and again the flask is to be
placed ou the heated sand bath, and the matter is to be evaporated with the
like precautions as before. The dried mass is then to be dissolved in about a
pint of distilled water, and the solution is to be examined by the test paper,
which, if the solution be properly prepared, will give neither an acid
nor an alkaline indication. The solution is then to be made up by addi-
tional distilled water to the bulk of precisely one gallon. The solution
thus prepared is to be called and may be labelled "standard solution of
sixteen degrees of hardness." From the standard solution of sixteen degrees
of hardness thus prepared, fifteen other standard solutions are to be made
up with distilled water as follows:-A glass bottle is to be procured, having
an accurately ground glass stopper, and being in capacity about the sixteenth
part of the bulk that is intended to be made of each standard solution. The
liquid contents of such a bottle, when the stopper is inserted, is to be taken
One such measure of the standard solution of sixteen degrees
of hardness is to be mixed with fifteen similar measures of distilled water,
being together sixteen measures, and this mixture is to be called and may be
labelled "standard solution of one degree of hardness." In like manner two
such measures of the standard solution of sixteen degrees of hardness.are to
be mixed with fourteen like measures of distilled water, being together sixteen
measures and this mixture is to be called and may be labelled "standard
solution of two degrees of hardness." After a similar manner, standard
solutions of respectively 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 degrees of
hardness are to be severally prepared, observing that the number of measures
of the standard solution of sixteen degrees of hardness and of distilled water,
when taken together, shall in each case be sixteen. By soap test, I mean
a solution prepared from the following materials, and in the following
manner: The materials are two. One material is the soap commonly
called in London white curd soap; that is to say, such white hard soap as,
having soda for a basis, is made from tallow, or from tallow chiefly. The
second material of the solution is the solvent, which is alcohol or spirit of
wine diluted with distilled water to the strength of proof spirit. As the
quality of white curd soap somewhat varies, it is necessary, in order to
prepare a soap test of nearly a uniform standard, to make a preliminary
trial solution on a small scale for the purpose of ascertaining by approxi-

page_text: mation, how much of the soap should be dissolved in the proof spirit.
Accordingly, let a small quantity of solution be made by dissolving the soap in
proof spirit, in the proportion of one ounce avoirdupois for every gallon of the
solution of soap. Now let one hundred test measures, of the standard solu-
tion of sixteen degrees of hardness, be put into a phial capable of holding
twice tliis quantity. Into the water in this phial let the prepared trial solution
of soap be gradually poured from a measure, graduated into test measures; let
the mixture be shaken after each addition of the solution of soap, and let the
operation be continued in' this manner until such time as a lather will be
'formed of sufficient consistence to remain for five minutes all over the surface
of the water when the phial is placed on its side. The number of test mea-
sures thus required will either be thirty-two or be inore or less than 32.
If the number prove to be 32, then more solution of soap may be made, in
the same proportions as in the trial solution, and the solution so made will be
the soap test. If the number be more than 32, then proportionably more of
the soap must be employed in preparing the soap test. If the number be less
than 32, then proportionally less of the soap must be used in preparing the
sop test. But in each case the soap test, after being prepared, should be
.carefully verified by a trial in the manner described, so as to ascertain whether
one hundred test measures of the standard solution of sixteen degrees of
hardness will afford a lather with exactly thirty-two test measures of the soap
test; if not, an adjustment must be made. Before making such verification
and adjustment of the soap test, it will be convenient in general to filter the
whole solution of soap by filter paper in the usual manuer, and also to
bear in mind that it is better before the final adjustment and verification to
have the prepared solution of soap rather too strong of soap then too weak,
inasınuch as it is more easy to add thereto an additional quantity of proof
spirit than it would be to dissolve therein an additional quantity of the soap.
11,in preparing the trial solution of soap in the manner described, the number
of test measures necessary to form the lather shall exceed forty, the soap
should be rejected. I prefer a white curd soap, such as in the trial solution
forins the lather with less than thirty-five test measures. In preparing large
quantities of the soap test, it will be found convenient to scrape off the soap
into shavings by a straight sharp edge of glass, and to dissolve it by heat it
part of the proof spirit, mixing the solution thus formed with the rest of the
proof spirit. By acid test I mean a solution of oxalic acid in distilled water,
in such proportion as to contain in every gallon of the solution oneavoirdupois
ounce and a quarter of the acid in crystals free from external moisture. The
oxalic acid employed should be prepared by crystallizing for a third time from

page_text: solution in distilled water good commercial crystals of that acid. By silver
test I mean a solution of nitrate of silver in distilled water. Any proportion
between our thousand and four thousand grains of nitrate of silver in a gallon
of solution will be convenient. And it should be remarked, that any water
whereof one hundred test measures require more than three measures of the
soap test for producing the lather herein described, or any water causing a
milkiness to appear on having dropped into it the silver test herein mentioned,
should be rejected as not distilled water in the sense that has been defined.
By ineans of the foregoing chemical agents, tests, and standard solutions, thrée
operations of testing are perforined; one operation consists in measuring the
harduess of any water; a second consists in measuring the alkalinity of any
water; the third consists in ascertaining whether there be dissolved in water
any caustic alkaline or earthly matter, which caustic matter may be caused in
the working of this Invention by an excess or overdose of lime water.
In order to measure the hardness of water, I put one hundred test measures
of the water whose hardness is to be tried into a suitable phial, and add
thereto, with agitation, the soap test measured iii test measures until a lather
be produced of sufficiers consistence to remain all over the surface of the
water for five minutes, when the phial is placed on its side. Now, in order to
form such a lather, the measured water under trial will take thirty-two test
measures of the soap test, or less than thirty-two of such measures, or it will
take more than thirty-two. First, I shall advert to the case of the water
under trial, taking thirty-two or less than thirty-two test ineasures of the soap
test, in order to form the lather. If the quantity of soap test required be
exactly thirty-two test measures, which is the same quantity as is required by
the standard solution of sixteen degrees of hardness, then the hardness of the
water is called sixteen degrees, after the standard solution'with which it thus
corresponds. In like manner, if in order to produce the latter the water
under trial for liardness take exactly the same proportion of soap test as any
other of the standard solutions required, the hardness will be called after such
standard solution. For example, if one hundred test measures of the water
under trial for hardness take precisely the same number of test measures of
soap test as 'the standard solution of ten degrees of hardness takes, such water
would be called ten degrees of hardness. Again, if the water under trial took
precisely the same proportion of soap test'as the standard solution of eleven
degrees is found to take, such water would be called eleven degrees of hard-
ness. But if to form the lather one hundred test measures of the water under
trial require more of the soap test than what is required by the standard sölu-
tion of ten degrees, and less than what is required by the standard solution of

page_text: eleven degrees, then the water would be said to be ten and a fraction degrees
of hardness, which fraction is to be computed proportionally from the difference
in soap test measures required by the solution of eleven degrees over and
above the solution of ten degrees. Thus, in forming the lather, if one hun-
dred test measures of the standard solution of eleven degrees were found to
take 1 test measures of soap test more than what one hundred test measures
of the standard solution of ten degrees would require, and if one hundred test.
measures of the water under trial for hardness require of a test measure
over and above what the same standard solution of ten degrees would require,
then the water under trial would be said to be 10 degrees of hardness.
This fraction of is obtained by proportion thus-
Differences of soap test.
1
:
Difference in degrees of hardness.
: 1
:: 1
Although thestandard solution of sixteen degrees of hardness takes thirty-two
test measures of the soap test in order to form the lather as described, which
is in the proportion of two test measures for each degree, yet all the othe
standard solutions require more than two test measure for every degree, and
the proportion more increases as the degrees descend. I shall next advert
to the case where thirty-two test measures of the soap test do not suffice to
produce the lather when added to one hundred test measures of the water
under trial. By continuing the first trial farther in such a case, no final result
can be obtained, but a preliminary result, necessary in order to prepare for
obtaining a final result, may be got by continuing the first trial in the following
manner: Supposing that thirty-two test measures of the soap test have been
added toone hundred test measures of the water without producing the lather,
the next step of the preliminary trial is to add one hundred test measures of
distilled water. To the mixture I continue to add soap test as before until I
have added in all sixty test measures of the soap test, provided I have not pre-
viously added enough to produce the lather. If at 60 test measures of soap
test, or at any number of such measures between thirty-two and sixty, the
proper lather be produced, then a final trial may be made in the following
manner-One hundred test measures of the water under trial for hardness is
at the outset to be mixed with one hundred test measures of distilled water
To this mixture soap test is to be added until the lather be produced, in the
same manner as in the case of a water whereof one hundred test measures
require no more than thirty-two test measures of soap test to form the lather;
but the quantity of soap test necessary in the present case will be more
than 32 and less than 64, at the same time that it will be somewhat more
than what was required in the preliminary trial. Whatever the quantity of soap

page_text: degrees of hard-
test be within these limits, I divide the number of such test measures by 2.
The half will not exceed 32, and accordingly may be expressed in a degree
of hardness ascertained by comparison with the standard solutions in the
manner that has already been described. The double of such degree will be
the hardness of the water under trial in this particular case. For instance, if
half the soap test that has been required correspond to 10
ness, then 'the hardness of the water under trial will be 21', being double
of 10. If again in the preliminary trial, conducted as has been described,
60 test measures of the soap test have not sufficed to produce the lather, I
thereuponadd an additional hundred test measures of distilled waterand con-
tinue the preliminary trial by thereafter adding as before soap'test, but not
beyond 90 test incasures, until a proper lather be produced, if producible such
a lather be by such quantity of soap test. In the case of such a lather having
been produced, I proceed to make a final trial. I begin by adding to 100'test
measures of the water whose hardness is to be tried, 200 test measures of
distilled water. To the mixture I add (with agitation) soap test as before
until the lather be produced. The quantity of soap test thus required is to be
divided by 3, and the degree of hardness corresponding with the third part
is to be ascertained by comparison with the standard solutions in the manner
that has already been described; this degree multiplied by 3 will be the hard-
ness of the water under trial. In like manner I proceed with waters of-a
higher degree of hardness by successive additions of 100 'test measures of
distilled water and of 30 test measures of soap test followed by corresponding
final trials, and concluded by corresponding calculations.
The second operation of testing consists in measuring the alkalinity of any
water; as a preliminary, it is proper to ascertain whether the water be alkaline.
For this purpose it is enough to put into a small test glass,' such a conical wine
glass, about 20 test measures of the water to be tried, and place in this water a slip
oftest paperin order to observe whether a blueish or purplish tint be produced.
When the alkaline matter is in very small proportion some time is necessary
in order to produce such alkaline indication, but if no degree of alkaline iudi-
cation be produced at the end of half an hour, the alkalinity of the water
may be regarded as too inconsiderable for trial. If the water be alkaline
enough for trial, a pint of it is to be measured and put into an ample evapo
rating basin, such as is used by chemists. Thereto is to be added the 'test
acid, measured in test measures, so long as any alkaline indication is produced
by the water on 'the test paper. On account of the slowness of the alkaline
action on the test paper when the alkaline'matter exists in waters in small
proportion', 'the process of neutralizing the alkaline matter in the manner

page_text: described is somewhat tedious, especially towards the end. The process may
be safely hastened by applying heat to the evaporating basin when-nearly the
neutralizing quantity of the test acid has been added, and the water may even
be made to boil. At the same time care should be taken not finally to adopt
my indication of the test paper in the water when it boils, or when it is near the
boiling temperature, for under such circumstances a fallacious appearance may
be produced on the test paper. After the water has been raised to the boiling
temperature, the application of heat should be withdrawn during the continu-
ance of the experiment. I recommend as convenient, that in order to observe,
as the successive quantities of test acid.are added, whether an alkaline or an
acid action prevail, or whether the solution be neutral, that portions of about
20 test measures be put each into a test glass with slips of test paper. The
number of test measures ascertained in this manner as necessary in order
to neutralize the alkaline matter, being divided by 2, will give the degree of
alkalinity of the water under trial.
The third operation of testing consists in ascertaining whether there be
dissolved in water any caustic, alkaline, or earthy matter.
For this pur-
pose the silver test is employed. The indication, by means of this test,
of the presence of the caustic matter will be best understood by inspec-
tion, and may be judged of by making a mixture of saturated or nearly
saturated lime water with distilled water, and also with each of the
standard solutions of one degree of hardness, of two such degrees, and
of four such degrees, in the proportion of one measure of the lime water
to 100 measures, and likewise to 200 measures of each of the others; and
by adding the silver test to a test glass of each of these mixtures, and
likewise, for the sake of comparison, to a test glass of each of the standard
solutions that have been just named, which contain no caustic matter,
but which of themselves will occasion a white precipitate by the silver
test, a yellowish or brownish-yellow appearance may be observed where the
lime water has been added. Such appearance in waters examined by the
silver test must be observed within the first ten minutes after adding the silver
test; for it is well known that with lapse of time, and especially under the
action of light, other appearances, such as might mislead, are produced in
solution to which the silver test may have been added.
My said Invention being applicable only to certain waters, I proceed to give
three indications whereby the waters alluded to may be recognized and distin-
guished; First, the water must indicate an alkaline action by test paper;
second, the water, being boiled in a glass vessel for two hours, under arrange-
ments such as allow all of the steam or the most of the steam to condense,

page_text: and the condensed water to trickle back to the body of the boiling water, will
deposit a powder which will be entirely or almost entirely soluble with effer-
vescence in muriatic acid; third, the water should be softened by such boiling
to an extent that is material for practical purposes. The degree of softening
is to beascertained by weighing the water, together with the vessel containing
it, at the outset; then, after the boiling and subsequent cooling, weighing both
again, and replacing with distilled water any loss of water that have occurred
in the form of steam, and by measuring the hardness both of the water thus
boiled and adjusted, and of the water in its original state. My Invention, in
what I regard as its most eligible form of application, consists in mixing lime
water (saturated or nearly saturated) in ascertained proportions, and so as to
guard against any excess with the certain waters above defined, and then by
subsidence, or by subsidence and filtration, to separate the precipitate con-
sequent on the mixture. The general preliminary rule for ascertaining the
proportions of the lime water proper to be used with the water intended for
purification is, to measure the alkalinity of the lime water as well as the alka-
linity of the water to be purified, and to use the lime water and the water to be
purified in the inverse proportious of their respective degress of alkalinity.
Forexample, suppose the alkalinity of lime water be one hundred and seventy-
five degrees, and the alkalinity of the water to be purified be twelve and a half
degrees; in this case, where the alkalinity of the lime water is fourteen times
the alkalinity of the water to be purified, the lime water being one measure,
the purified water should be fourteen measures. But the indication thus
derived from the alkalinity, although in general a sufficient guide in deter-
mining the proportions of lime water and of the water to be purified, should
be regarded only as a preliminary indication, and should be confirmed by
experimental trials; for instance, in the case supposed, where the proportion
of lime water to the water to be purified is as 1. to 14, it might be proper to
make in glass vessels five experiments on a scale where the total of each
mixture need not exceed one or two gallons in the proportions of lime water to
the water to be purified, of 1 to 12, of 1 to 13, of 1 to 14, of 1 to 15, of 1 to
16. As the waters proper to be the subject of this Invention vary much in
their characters, it will be proper for the operator to observe the characters
that manifest themselves in such experiments in all respects that may serve
for his guidance in the working of the said Invention, and in particular the
peculiarities of the water as regards the facility or slowness of substance in
the precipitate that appears after admixture. In such experiments as the
foregoing, in varied proportions, the hardness of each water, after entire subsi-
dence of the precipitate, is to be tried by means of the soap test; and-the
R

page_text: presence or absence of caustic matter is to be ascertained by the application of
the silver test, in the manner that has been described. Amongst the several
proportions used in such trials, the one is to be preferred that gives the least
degree of hardness after entire subsidence of the precipitate consequent on
mixture, at the same time that it gives by the silver test no indication of the
presence of caustic matter.in solution. The alkalinity of the water to be
purified, I have stated, will in general indicate with sufficient accuracy the
proportion of lime water required, and such I have actually found to be the
case with river water, and in some degree with spring water also; but there
are some waters, and more especially some spring waters, such as would
require a larger proportion of lime water than what would be deduced from
their alkalinity. In the case of any such water, the proper proportion may be
ascertained by experiments on the small scale, such as have been described, if
carc be taken that the mixtures be so regulated as to increase the proportions
of lime water above what is deducible from the ascertained alkalinity. The
particular kind of waters alluded to consist of such as, according to chemists,
have a larger proportion of carbonic acid than would suffice to form alkaline
or earthy bicarbonates. If such excess of carbonic acid is considerable, the
proportion of extralime water that is required, over and above what is indicated
by the alkalinity of the water, may be ascertained approximatively by an
experiment such as the following :-In a series of stoppered bottles, each
capable of containing a little more than a quart, let there be put a quart or
equal quantities of the water to be purified, and let lime water, the same as is
to be used in purification, be added to each in succession, in a series of
increasing proportions, such as 10, 20, 30, 40, 50, or more test measures, and
let the mixture be left for a day in the bottles, closed by the stoppers, it will
then be seen whether in any or in which of the bottles the lime water has been
added without producing any purification. Amongst those bottles that give
no precipitate in such experiments, the one that has had the largest proportion
of lime water will give the nearest approximation to the proportion of lime
water that should be used, over and above what lime water is indicated, by the
alkalinity of the water to be purified. One such mixture, where ten test
measures of lime water has beenadded, and another where twenty test measures
of lime water has been added, each to a quart of any water, will indicate
whether the water be such as to require any extra allowance of lime water
over and above what the alkalinity of the water may indicate. The rules and
the precautions that have been given for the regulation of the proportion of
the lime water to the water to be purified, as well as for guarding against any
excess of the lime water, are of importance, inasmuch as an excess of lime

page_text: water imparts impurity, and would restore hardness. I wish it not to escape
attention that from those rules and precautions, and more especially from the
indications of the tests, the quantity of burnt lime proper for the purification
of any water might be apportioned so as to avoid a final excess of lime water;
but I prefer apportioning the lime water as has been described. When in
accordance with the rules and precautions that have been given, the proportion
of lime water proper to be used in the purification of any given water has been
ascertained, the said liquids are to be intimately mixed together in such
portions, and the precipitate thereupon formed is to be allowed to subside.
In preparing lime water for such purpose, I prefer in the routine of working
my Invention to employ such water as has been purified thereby.
pro-
In witness whereof, I, the said Thomas Clark, have hereunto set my
hand and seal, this Eighth day of September, One thousand eight