IMPROVEMENTS IN PURIFYING OR DISINFECTING SEWAGE AND OTHER FOUL WATERS, AND IN THE PREPARATION OF DISINFECTANTS
Year: 1876

page_text: LETTERS PATENT to William White, of 28, London Road, Newcastle-under-
Lyme, in the County of Stafford, for the Invention of "IMPROVEMENTS IN
PURIFYING OR DISINFECTING SEWAGE AND OTHER FOUL WATERS, AND IN
THE PREPARATION OF DISINFECTANTS."
Sealed the 15th December 1876, and dated the 12th September 1876.
PROVISIONAL SPECIFICATION left by the said William White, at the
Office of the Commissioners of Patents on the 12th September 1876
WILLIAM WHITE, of 28, London Road, Newcastle-under-Lyme, in the County
of Stafford. IMPROVEMENTS IN PURIFYING OR DISINFECTING SEWAGE AND OTHER
FOUL WATERS, AND IN THE PREPARATION OF DISINFECTANTS."
This Invention has for its object improvements in purifying or disinfecting
sewage and other foul waters, and in the preparation of disinfectants.
Lime is extensively used for the purification of sewage, but with the serious dis-
advantage that it has to be employed in large excess of theoretical necessity, whereby
the deposit of sludge is increased or swept into water courses, fish are destroyed,
and corruption developed.
The reason for the use of lime in excess is its comparative insolubility. It requires
from 600 to 800 times its weight of water for solution, and the probability is that
only so far as lime is in solution is it chemically active; and therefore the value of
the milk of lime is limited by the production of lime water Hence in dealing with
sewage it has become a matter of prime importance to obtain a solvent for lime, so
that if possible little more should be used than is chemically operative. Such a
solvent have I found in chloride of calcium, which when heated with lime forms what
is known as chloroxide of calcium, yielding crystals after this formula :—
Ca C1 0+15 H2O=3 Ca O Ca Cl² x 15 H² O.
A solution of lime in chloride of calcium is readily formed by slaking quicklime
with dilute hydrochloric acid, or where chloride of calcium can be had conveniently
by slaking lime with its aqueous solution. Or hydrate or carbonate of lime
may be boiled with dilute hydrochloric acid or hydrate of lime with chloride of
calcium. The solution of chloroxide of calcium thus formed is of remarkablo
efficacy in the purification of certain varieties of sewage, especially from dye-works
and factories. The chloride of calcium is an agent in nowise inferior to its associate
lime, for it acts upon any sulphates, phosphates, and carbonates present in the

page_text: sewage, precipitating as sulphate, phosphate, and carbonate of calcium. Con-
sequently it may be employed with excellent effect in conjunction with the sulphates
of aluminum, iron, or zinc, in the treatment of sewage, liberating in reaction
chloride of aluminum, or iron, or zinc; all of which chlorides it is well known exer-
cise energetic influence in clarifying foul waters.
When sewage is strongly excrementitious or deeply coloured, I find the efficiency
of chloroxide of calcium much strengthened by the addition of more or less choride
of line or bleaching powder. Such a combination of chloroxide of calcium and
chloride of lime I propose to employ as a disinfectant after the manner of chloride
of zinc or chloride of aluminum.
I also find in some cases that the use of charcoal and of clay facilitates purifica-
tion and precipitation, and charcoal, or clay, or both together, may be advantageously
mixed up with the solution of chloroxide of calcium.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William White in the Great Seal Patent Office on the 12th
March 1877
WILLIAM WHITE, of 28, London Road, Newcastle-under-Lyme, in the County
of Stafford. "IMPROVEMENTS IN PURIFYING OR DISINFECTING SEWAGE AND OTHER
FOUL WATERS, AND IN THE PREPARATION OF DISINFECTANTS."
Among the numerous purifiers of sewage none has been so largely called into
requisition as lime That lime has a certain efficacy is unquestionable, but accom-
panied with serious drawbacks It dissolves slowly in water, requiring from 600 to
800 times its weight for complete solution, whilst the probability is that only so far
as lime is in solution is it chemically operative Hence it has to be employed in
large excess of theoretical necessity in the shape of "milk of lime," that is, lime
whipped up in water from which it settles out when the water is at rest, leaving
"lime water" proper, a clear liquor with lime in solution to the extent of about 90
grains to a gallon
What is most desirable in the treatment of sewage is the reduction of the preci
pitant to the lowest point possible, so that the precipitate which takes the form of
slush or sludge may not be unnecessarily magnified. Now when "milk of lime" is
used the precipitate is largely swollen thereby, and is not only swollen, but is made
strongly alkaline with a tendency to corruption and the evolution of ammonia in
drying. Nor does the mischief end here. The effluent water is more or less lime.
water, injurious to fish, and apt to hasten and intensify the corruption of organic
matter in its course. The mischiefs of lime as a chemical for sewage are frequently
exaggerated, but these are just grounds of complaint Were however the grounds
of complaint more serious it is questionable whether the use of lime could be dis-
pensed with
It is an essential qualification of any material for sewage precipitation
that it be cheap and abundant; whatever its efficiency an expensive precipitant
would be an impossible precipitant. Now lime is to be had every where, and in the
matter of price no other alkali is to be compared with it. Its chief defect, as ex-
plained, is its low solubility, and the question arises whether there is no remedy for
this defect
A remedy I have found in the use of chloride of calcium as a solvent for lime.
When lime is boiled with a strong solution of chloride of calcium and the liquor
filtered and allowed to cool, there appear fine needle-shaped colourless crystals of
the following constitution :-Ca, Cl, O,+15 H, O.; or otherwise-3 Ca O, Ča Cl, +
15 H, O; or to put it more plainly for those unfamiliar with chemical notation, the
needle-like crystals consist of-
Oxide of calcium or lime
-
168

page_text: The combination of lime and chloride of calcium is indifferently designated
chloroxide of calcium or oxychloride of calcium, and furnishes lime in the condition
most eligible for sewage, soluble, ready for action, and therefore without the necessity
of employment in excess after the manner of crude limo in milk of lime. As soon
as a solution of chloroxide of calcium is introduced to sewage the union of the oxide
and chloride of calcium is dissolved, and the lime in a state of minute division is set
free to operate.
The value of the chloride of calcium is moreover in nowise inferior to that of its
associate lime, for it reacts on any sulphates, phosphates, and carbonates prosent in
the sewage, and sulphate of phosphate and carbonate of calcium are precipitated.
Chloroxide of calcium is not an expensive chemical. As we have seen three-fifths
of it is lime, the cost of which is known. The cost of the remaining two-fifths, the
chloride of calcium, is unknown because at present there is no market for it in other
than laboratory quantities. It is a considerable bye product in a variety of chemical
manufactures, and is commonly discharged as useless. To boil it with lime or to
slake quicklime with its solution would result in the production of chloroxide of
calcium and thus turn to excellent account what now runs to waste; or where
chloride of calcium is not available it would suffice to slake quicklime with dilute
bydrochloric acid, or to boil hydrate or carbonate of lime with the same acid
The processes for the production of chloroxide of calcium which I prefer are,
where chloride of calcium can be obtained, I use a dilute solution of the salt to slake
quickline. The resulting solution of chloroxide of calcium is filtered from remain-
ing lime and is then ready for use. The solution may be made of any strength
desned. Where chloride of calcium is not readily obtained I use commercial
muriatic acid diluted with its own weight of water, and with this I slake quicklime
and proceed as already described.
Chloride of calcium lends itself with facility to operations in connection with
the sulphate of aluminum, or of iron, or zinc. Sulphate of aluminum is after lime
the most important of sewage purifiers, and when used in conjunction with chloroxide
of calcium sulphate of line is thrown down by reaction with the chloride of calcium
and chloride of aluminum or "chloralum" is liberated to exercise the numerous
virtues ascribed to it. A similar reaction occurs with either sulphate of iron or
sulphate of zinc, chloride of iron in the one case and chloride of zinc in the
other being liberated, each chloride having a special efficacy with certain kinds
of sewage.
The following compounds give good results, namely, four parts of chloroxide
of calcium to five parts of sulphate of aluminum, both being estimated as anhydrous,
or two parts of chloroxide of calcium to one part of sulphate of iron or zinc
Great expectations were formerly based on charcoal, chiefly for filtration; but it
has been discovered that sewage slimes over and destroys a filter long ere the char-
coal has rendered any service commensurate with its cost. But there are forms of
sewage the purification of which is accomplished more readily and thoroughly when
charcoal is used as a precipitant, and I prepare it for that purpose by soaking with
a solution of chloroxide of calcium, for it is hardly necessary to observe that unless
thus weighted charcoal is more likely to float than to sink. Equal weights may
conveniently be employed of charcoal and of chloroxide of calcium in crystals. In
like manner and in some cases I find that chloroxide of calcium may be ad-
vantageously mixed with more or less clay or with clay in combination with
charcoal.
When sewage is strongly excrementitious or deeply coloured I find the efficiency
of chloroxide of calcium much strengthened by the addition of more or less chloride
of lime or bleaching powder. And such a combination of chloroxide of calcium and
chloride of lime I propose to employ as a disinfectant after the manner of chloride of
Zinc or chloride of aluminum. Equal weights of chloride of lime and chloroxide of
calcium reckoned as anhydrous, put into aqueous solution, mixed, filtered, and the
liquor kept in stoppered bottles, forms a preparation which is very suitable for the
treatment of sewage and also for use as a disinfectant.

page_text: Having thus described the nature of my said Invention and the manner of per-
forming the same, I would have it understood that I claim,-
First. The use of chloroxide of calcium or lime in combination with chloride of
calcium for the purification of sewage and other foul waters substantially as
described.
Second. The use of the said chloroxide of calcium conjointly with the sulphate
of aluminum, or of iron, or zinc, for the purification of sewage and other foul waters
substantially as described.
Third. The use of charcoal saturated with chloroxide of calcium for the purifica-
tion of sewage and other foul waters substantially as described.'
Fourth. The use of chloroxide of calcium combined with chloride of lime for the
purification of sewage and other foul waters substantially as described.
Fifth. The manufacture of disinfectants by compounding chloroxide of calcium
with chloride of lime substantially as described.
In witness whereof, I, the said William White, have hereunto set my hand
and seal, this Eighth day of March, in the year of our Lord One thousand
eight hundred and seventy-seven.
WILLIAM WHITE. (L.S.)