CHAPTER VII_Chlorination of Water

LIQUID CHLORINE

The use of liquefied chlorine for the disinfection of water was first

proposed by Lieutenant Nesfield[1] of the Indian Medical Service. He

stated that: "It occurred to me that chlorine gas might be found

satisfactory ... if suitable means could be found for using it.... The

next important question was how to render the gas portable. This might

be accomplished in two ways: By liquefying it, and storing it in

lead-lined iron vessels, having a jet with a very fine capillary canal,

and fitted with a tap or a screw cap. The tap is turned on, and the

cylinder placed in the amount of water required. The chlorine bubbles

out, and in ten to fifteen minutes the water is absolutely safe, and has

only to be rendered tasteless by the addition of sodium sulphite made

into a cake or tablet.... The cylinders could, of course, be refilled.

This method would be of use on a large scale, as for service water

carts."

The first _practical_ demonstration of the possibilities of this method

was made by Major Darnall[2] of the Medical Corps, United States Army,

in 1910. Chlorine was taken from steel cylinders and passed through

automatic reducing valves which provided a uniform flow of gas for the

water requiring treatment. A uniform flow of water was maintained

through the mixing pipe and so secured a uniform dosage. This apparatus

might be considered as the forerunner of the various commercial types of

machines that were developed later and which are being so extensively

used at the present time.

A working model, having a capacity of 500 gallons per hour, was erected

at Fort Myer, Va., and was operated on water that had been treated with

alum but had received no further purification. Despite the presence of

the flocculated organic matter, satisfactory purification was obtained

with 0.5 to 1.0 p.p.m. of available chlorine and no taste or odour was

imparted to the supply.

From the results obtained at Fort Myer, and Washington, D.C., Darnall

concluded that "In general, it may be said that with an average

unfiltered river water such as that of the Potomac, about one-half of

one part (by weight) of chlorine gas per million of water will be

required. For clear lake waters three-tenths to four-tenths of a part

per million will be sufficient."

A Board of Officers of the War Department examined the results and

reported (June, 1911) "That the apparatus is as efficient as

purification by ozone or hypochlorite and is more reliable in operation

than either.... That it could be installed at a very low cost and that

the cost of operation would be very slight."

In June, 1912, Ornstein experimented with chlorine gas, obtained from

the liquefied gas in cylinders, for sewage and water disinfection but

his method differed from Darnall's in first dissolving the gas in water

and feeding the solution to the liquid to be treated.

Kienle[3] made experiments at Wilmington, Del., in November, 1912, and

obtained a constant flow of gas by means of high- and low-pressure

valves; the gas was dissolved in water in an absorption tower and

afterwards fed to the water to be treated.

Van Loan and Thomas of Philadelphia experimented with liquid chlorine on

a large scale at the Belmont Filter Plant in September, 1912. The

chlorine was fed into the filtered water basin in the gaseous state and

the quantity was regulated by the loss in weight of the containers. The

dosage was approximately 0.14 p.p.m. (West[4]).

Jackson, of Brooklyn, made similar experiments about the same time at

the Ridgewood Reservoir, Brooklyn, and his type of apparatus was shortly

afterwards put on the market as the Leavitt-Jackson Liquid Chlorine

Machine. The regulation of the flow in this machine was determined by

the loss in weight of the gas cylinder which was suspended from a

sensitive scale beam. By moving the counterbalancing weight on the beam

at a constant rate, a uniform flow of gas was obtained, the area of the

orifice being kept constant by the equilibrium in the balance operating

controlling valves through a system of levers.

This type of apparatus was tried at several places but it was found that

the adjustment of the regulating mechanism was too sensitive and

produced considerable irregularities in the flow of gas.

The type used by Ornstein and Kienle were combined and commercially

developed by the Electric Bleaching Gas Co. of New York.[A] In this

combined type the gas was collected from one or more cylinders by means

of a manifold which delivered it to the regulating mechanism at the

pressure indicated by a gauge attached to the inlet pipe. Beyond this

gauge were two pressure-regulating devices, the first being used

primarily to reduce the initial pressure to about 15 pounds per square

inch, and the second for controlling the pressure through a range

sufficient to give the desired discharge of gas. The gas from the second

regulator passed through an orifice in a plate at a pressure indicated

by a suitable gauge which was calibrated in terms of weight of chlorine

per unit of time. The gas, on leaving the regulating apparatus, passed

up an absorption tower of hard rubber, where it met a descending stream

of water. The solution was carried by suitable piping to the point of

application. This type was modified in some cases by the substitution of

a flow meter of the float type for the inferential pressure meter.

[A] This type has recently been withdrawn from the market.

[Illustration: FIG. 6.--Manual Control Chlorinator, Solution Feed, Type

A.]

Another type of apparatus, developed by Wallace and Tiernan,[A] is shown

in Figs. 6 and 7. The gas under the pressure indicated by the tank

pressure gauge (Fig. 6) passes into the pressure compensating chamber,

which maintains a constant drop in pressure across the chlorine control

valve, through the check valve, and into the solution jar after

measurement in the pulsating meter. The water required for dissolving

the chlorine enters the jar through the feed line and check valve and

the solution passes along the feed line after being water sealed in a

special chamber. The meter is a volumetric displacement one and is

regulated by observing the number of pulsations per minute. Each

pulsation corresponds to 100 milligrams or 0.00022 pound of chlorine;

diagrams for converting pulsations per minute into weight per

twenty-four hours are usually provided with the apparatus. This type of

meter is suitable for quantities between 0.1 and 12 pounds per day and

possesses the distinct advantage of enabling the operator to see the

actual delivery of the gas.

[A] Manufactured by Wallace and Tiernan Co. Inc. N. Y.

[Illustration: FIG. 7.--Manual Control Chlorinator, Solution Feed, Type

B.]

The quantities of gas exceeding 12 pounds per day the type shown in Fig.

7 may be used. The gas from the control valve passes through a visible

glass orifice which is connected with the manometer. This manometer, or

chlorine meter, contains carbon tetrachloride and is graduated

empirically in terms of weight of chlorine per unit of time. A suitable

gauge indicates the back pressure thrown by the check valve and

registers the same pressure as the tank gauge when the flow of gas is

stopped. The gas passes into the glass cylinder where it is dissolved in

water and passes out by the feed pipe.

The most accurate range of the orifice type is from 1-6, i.e. if the

minimum graduation on the scale is 10, the maximum is 60. If quantities

less than the minimum graduation are desired, a smaller orifice with its

corresponding scale can be substituted in a few minutes.

These types are manually controlled, but automatic control types, to

meet almost any condition, can be obtained and are in use in many

cities.

In some instances (dry-feed types) the chlorine gas is not dissolved in

water prior to addition to the water requiring treatment but is carried

to the point of application as a dry gas and enters the water through a

diffusion plate made of carborundum sponge. The sponge becomes saturated

with water because of the capillary action of the carborundum upon the

water. The pressure of the chlorine in the feed pipe forces the gas

through the diffuser in the form of minute bubbles which become

saturated with moisture. On meeting the water they immediately go into

solution and no gas escapes.

The operation of liquid chlorine machines is exceedingly simple. After

the cylinders have been connected, the cylinder valves are opened and

the joints tested for leakage by holding a swab of absorbent cotton

saturated with strong ammonia under them; a leakage is indicated by the

appearance of white fumes of ammonium chloride. The control valve is

then slightly opened and the auxiliary cylinder valves partially opened;

whilst the pressure in the apparatus is slowly increasing the remainder

of the joints are tested and if found to be tight, the cylinder valves

are fully opened and the control valve opened to the desired amount. In

the solution feed types the water required as solvent is turned on

before the control valve is opened. Once the apparatus is working, no

further attention is required, except for the regulation of the dosage

in the manual control types, until the cylinders are replaced. When the

stock of gas in the cylinders is almost depleted the pressure falls but

it is always preferable to determine the stock by standing the cylinders

on a platform scale and weighing at regular intervals. This also

provides a check on the apparatus and can be utilised to check the

operators.

The accumulation of substances that impede the flow of gas is usually

slow and is indicated by a gradual increase in the back pressure. The

orifice is calibrated at 25 pounds back pressure and any deviation from

this figure will show a discrepancy between the actual weight of

chlorine evaporated and the amount calculated from the scale reading.

Liquid chlorine is usually sent out by the manufacturers in steel

cylinders which contain about 1.1 cubic feet of liquid or approximately

100 pounds (1 cu. ft. = 89.75 pounds).[A]

[A] An effort is now being made to standardise cylinders of 150 lbs.

capacity.

For small installations only one cylinder is necessary but it is always

preferable to connect more than one. When the flow of gas is rapid the

temperature of the liquid chlorine falls and reduces the pressure. The

effect of the fall in temperature, due to the latent heat of

evaporation, can be partially overcome by using a larger number of

cylinders; in addition a source of external heat should be provided that

will maintain the temperature of the cylinders at a minimum of 80 deg. F.

This is a "sine qua non" for successful operation. The effect of the

temperature upon the pressure in the cylinders is shown in Diagram VII.

[Illustration: DIAGRAM VII

CHLORINE GAS PRESSURES AT VARIOUS TEMPERATURES]

In practice it is found impossible to utilise all the gas contained in

the containers; when the cylinders are almost empty the pressure

necessary for the operation of the regulating device cannot be obtained

and full cylinders must be attached. When sufficient heat is provided

the weight of chlorine in the cylinder can be reduced to 1 - 1-1/2

pounds before the tank pressure becomes too low.

Liquid chlorine machines will operate, with ordinary care, for long

periods. The various parts are made of such metals as experience has

demonstrated to be best able to resist the corrosive action of the dry

gas and the apparatus is designed to prevent the access of moisture

which would otherwise produce corrosion and impede the flow of gas.

Stoppages are sometimes caused by brown deposits derived from

impurities in the liquid chlorine. These are primarily due to variations

in the graphite electrodes used in the electrolytic process for the

manufacture of chlorine from salt.

[Illustration: FIG. 8.--Dunwoodie Chlorinating Plant Treating

400,000,000 Gallons Per Day for New York City.]

To convey the dry gas from the apparatus to the point of application,

copper or iron pipes may be used; for aqueous solutions, flexible rubber

hose must be employed. Chlorine water is exceedingly active, chemically,

and rapidly attacks all the common metals; ordinary galvanised iron pipe

is eroded in a few days and should never be used.

Liquid chlorine, for water disinfection, possesses several marked

advantages over the ordinary bleach process.

(1) The sterilising agent is practically 100 per cent pure, the only

impurities being traces of carbon dioxide and air, and does not

deteriorate on storage; it will, in fact, keep almost indefinitely.

(2) Liquid chlorine practically eliminates all labour costs because of

the simplicity of the apparatus and the concentrated form of the

sterilising agent. The apparatus is so compact that all the cylinders

and regulating apparatus required for delivering 200 pounds of gas per

day can be placed in an area of about 50 square feet and it can

consequently be almost invariably accommodated in locations where the

trifling amount of attention required can be obtained without extra

cost.

(3) The sludge problem, inseparable from bleach installations, is

eliminated.

(4) Regulation of the dosage is simpler and consequently usually more

accurate. The dosing apparatus in bleach plants invariably tends to

choke and demands regular attention from intelligent operators; a

similar tendency in liquid chlorine machines is easily detected and

electrical devices can be installed to indicate automatically any

changes in the flow.

(5) The first cost is smaller. The cost of liquid chlorine machines

varies from $400, for the small manual control types, to $1,200, for the

automatic control types. The capital outlay is mainly determined by the

number of machines and accessories required and not, within certain

limits, by the capacity. One machine will deliver up to 200 pounds of

gas per day, an amount sufficient to treat 60,000,000 U. S. A. gallons

(50,000,000 Imp. gals.) at 0.40 p.p.m. of available chlorine. Unless

duplicate machines are installed for the higher rates, the first cost is

inversely proportional, though not directly so, to the volume of water

treated. It is in all cases less than the first cost of a bleach plant

of equal capacity, accuracy, and durability.

(6) Liquid chlorine installations usually tend to produce less

complaints as to tastes and odours. This is probably due, not to any

merit of the chlorine _per se_, but to a more accurate regulation of the

dosage and efficient distribution of the chlorine in the treated water.

The advantages ensuing from thorough admixture had only become partially

appreciated before liquid chlorine machines were fully developed and

they have been more fully utilised in the design of these later

installations.

Claims have also been made that liquid chlorine prevents "aftergrowths"

but no evidence can be adduced in support of this statement.

Aftergrowths have occurred at many places where this process is employed

and in this respect it possesses no advantage over hypochlorite

installations.

It is also claimed that one pound of liquid chlorine is more efficient,

as a germicide, than an equal weight of chlorine in the form of bleach.

Jackson[5] has stated that 1 pound of chlorine is equal to 9 pounds of

bleach; Kienle (_loc. cit._) that it was equal to 8 pounds of bleach,

whilst Huy claimed to have obtained an efficiency ratio of 1:10 at

Niagara Falls, N. Y. The conditions of the experiment were not

comparable however, in the last mentioned ratio. Catlett, at Wilmington,

N. C. (West[4]) obtained a better bacterial reduction with 1 pound of

liquid chlorine than with 6 pounds of bleach.

The efficiency ratio of chlorine to bleach has been reported upon by

West.[4] From 1910-1913 the mixed filter effluents of the Torresdale

plant at Philadelphia were treated with bleach but in November, 1913 the

liquid chlorine process was substituted. On comparing the results

obtained during the same months of the two periods it was found that, in

general, 1 pound of liquid chlorine gave a slightly higher percentage

purification than 6-7 pounds of bleach. Similar results were obtained at

the other Philadelphia plants. The figures published by West show that

the hypochlorite solutions used were abnormally strong (3.6-10.4 per

cent of available chlorine), a condition that would increase the

difficulty of extracting all the soluble hypochlorite. It was found

indeed, that, under the most advantageous conditions, only 87 per cent

of the available chlorine was extracted. The average chlorine content of

the bleach used during 1912-1913 was 36.1 per cent but the figures given

would indicate that at least 1.5 per cent, a reduction of 4.6 per cent

of the total, was lost during storage. It would seem not improbable that

the total loss under average conditions was not less than 20 per cent,

which would reduce the efficiency ratio to 1:4.8-5.6.

Hale[6] also made a comparison of the relative efficiency of liquid

chlorine and hypochlorite of lime at New York, and the earlier results

agreed with West's ratio of 1:6-7. An investigation showed that large

quantities of chlorine were not extracted from the bleach and when this

condition was rectified the total loss averaged only 4 per cent and the

results obtained were equal to those given by the liquid chlorine

machines. Hale's comparative figures are given in Table XXIII.

TABLE XXIII.--COMPARISON OF LIQUID CHLORINE WITH EFFICIENT USE OF

BLEACH--(HALE)

----------------+----------+-----------+------------+---------------

Treatment. | Water | Number of | Chlorine | Reduction

| Treated. | Samples. | p.p.m. | of B. coli.

----------------+----------+-----------+------------+---------------

Bleach | Croton | 84 | 0.27-0.36 | 93%

Liquid chlorine | Bronx | 84 | 0.27-0.36 | 93%

----------------+----------+-----------+------------+---------------

Hale concluded that, when efficiently used, the ratio of chlorine to

bleach required to produce equal bacterial purification, approached 1:3.

The results obtained by the author in Ottawa are similar to those of

Hale. During the earlier period of the bleach treatment a dosage of 1.5

p.p.m. of available chlorine was required to obtain satisfactory

purification but various improvements that were subsequently made

enabled the quantity to be reduced to 0.8 p.p.m. The same raw water

usually requires 0.75 to 0.80 p.p.m. of liquid chlorine to obtain the

same purification. The total losses in the Ottawa bleach plant averaged

6-8 per cent and based on these figures the efficiency ratio is

approximately 1:3.5.

Ratios as low as 1:3.5 can only be obtained by the supervision of a

chemist and this analytical control involves additional expense that

must be charged against the bleach process. No chemical analyses are

necessary for the control of liquid chlorine plants.

_Disadvantages of Liquid Chlorine Plants._ The main objection to the use

of liquid chlorine is that the slight leaks of gas occur occasionally

and unless removed by forced ventilation may produce a concentration of

chlorine that will injure the operators.

Pettenkofer and Lehmann[7] found that 0.001-0.005 per cent of chlorine

in air affected the respiratory organs; 0.04-0.06 per cent produced

dangerous symptoms, whilst concentrations exceeding 0.06 per cent

rapidly proved fatal.

The danger of gas leakages can be eliminated by placing the apparatus in

a small separate room provided with a fan and a ventilation duct. By the

liberal use of glass in the construction of the room, the operation of

the plant can be seen at all times without entering the chamber.

A portion of the liquid chlorine apparatus is made of glass and is

consequently easily fractured. Duplicates of the glass parts should be

kept in stock to prevent interrupting the supply of gas; a duplicate

machine is also advisable in large installations.

_Cost of Treatment._ Prior to the outbreak of war in 1914, liquid

chlorine sold at 10-11 cents per pound in small quantities and for 8-9

cents per pound in large shipments. In 1917 the price was 18-20 cents

per pound for small quantities and 15 cents upwards for large contracts.

Canadian prices are 25 per cent higher.

The amount of chlorine required for satisfactory disinfection (see

Chapter III) depends upon the nature of the water and the cost of

treatment varies accordingly. In the majority of plants the cost varies

from 25-90 cents per million gallons.

_Popularity of Process._ Since 1913, when the first commercial liquid

chlorine machines were used, the popularity of this process has

increased in a most remarkable manner. In 1913 over 1,700 million

gallons per day were treated with hypochlorite; in 1915, 1,000 million

gallons per day were treated with liquid chlorine and an approximately

equal amount with hypochlorite; in January 1918, the amounts were 3,500

million gallons per day (liquid chlorine) and 500 million gallons per

day (hypochlorite).

This wonderful development has been largely due to the intrinsic merits

of the process and the reliability of the machines manufactured although

it has been indirectly assisted by the excessive cost of hypochlorite

during 1915-1916.

Liquid chlorine machines are being used for the purification of water on

the Western Front of the European battlefield. The outfit is a mobile

one and consists of a rapid sand filter, liquid chlorine apparatus, a

small storage tank and solution tanks. Owing to the limited contact

period available a large dosage of chlorine is employed and the excess

afterwards removed by the addition of a solution of sodium thiosulphate.

_Chlorine Water._ Marshall[8] has proposed the use of chlorine water for

the sterilisation of water for troops. The solution is contained in

ampoules which are of two sizes, one for water carts and the other for

water bottles of one quart capacity.

The coefficient of solubility of chlorine, from 10 deg.-41 deg. C. is _C_ =

3.0361 - 0.04196_t_ + 0.0001107_t_^{2}; when _t_ = 10 deg. C. 1 c.cm. of

water absorbs 2.58 c.cms. of chlorine or 8.2 m.gr., a quantity

sufficient to give a concentration of 1 p.p.m. in 8 litres of water.

Marshall has stated that, when pure materials are used, chlorine water

is stable but the author is unable to confirm this. A saturated solution

of chlorine in distilled water lost over 50 per cent of its available

chlorine content when stored for five days in the dark at 70 deg. F. The

chlorine present as hypochlorous acid increased slightly but the

quantity never exceeded very small proportions. Chlorine solutions

decompose in accordance with the equation, Cl_{2} + H_{2}O = 2HCl + O.

Although chlorine water appears to be of little value because of its

instability there appears to be no reason why chlorine hydrate should

not be successfully employed. The hydrate was first prepared by

Faraday[9] by passing chlorine into water surrounded by a freezing

mixture. A thick yellow magma resulted from which the crystals of

chlorine hydrate were separated by pressing between filter paper at 0 deg.

C. The hydrate prepared by Faraday was found to have the composition

represented by the formula Cl.5H_{2}O but later investigators have shown

that more concentrated hydrates can be prepared. Roozeboom[10] prepared

a hydrate represented by the formula Cl.4H_{2}O and Forcrand[11] one

containing only 3-1/2 molecules of water (Cl_{2}.7H_{2}O). Chlorine

hydrate separates into chlorine gas and chlorine water at 9.6 deg. C. in

open vessels and at 28.7 deg. C. in closed vessels. Pedler[12] has shown

that when the ratio of Cl_{2}:H_{2}O is 1:64 or greater, the mixture of

chlorine hydrate and water exhibits great stability and can be exposed

to tropical sunlight for several months without decomposition.

Cl_{2}.64H_{2}O contains 5.8 per cent of chlorine and about 8. c.cms.

would be required to give a concentration of 1 p.p.m. in 110 Imp.

gallons of water, the usual capacity of a military water cart.

BIBLIOGRAPHY

[1] Nesfield. Public Health, 1903, =15=, 601.

[2] Darnall. J. Amer. Pub. Health Assoc., 1911, =1=, 713.

[3] Kienle. Proc. Amer. Waterworks Assoc., 1913, 274.

[4] West. J. Amer. Waterworks Assoc., 1914, =1=, 400-446.

[5] Jackson. Proc. Amer. Waterworks Assoc., 1913.

[6] Hale. Proc. N. J. San. Assoc., 1914.

[7] Pettenkofer and Lehmann. Munich Acad., 1887.

[8] Marshall. Conv. Amer. Elect. Chem. Soc., 1917. Eng. and Contr.,

1918, =49=, 40.

[9] Faraday. Q. J. S., =15=, 71.

[10] Roozeboom. Rec. Trav. Chim., 1885, =3=, 59.

[11] Forcrand. Comp. rend., 1902, =134=, 991.

[12] Pedler. J. C. S., 1890, =83=, 613.

CHAPTER VIII

ELECTROLYTIC HYPOCHLORITES AND CHLORINE

Since 1889 when Webster first proposed the use of electrolysed sea-water

as a disinfectant, various attempts have been made to introduce

electrolytic hypochlorites for the bactericidal treatment of water and

sewage. Two of these preparations were named Hermite fluid, and

electrozone (c.f. page 5). Sodium hypochlorite, made by passing chlorine

into solutions of caustic soda, or by the decomposition of bleach by

sodium carbonate, has also been used and preparations of this character

have been sold under such names as Eau de Javelle, Labarraque solution,

chloros, and chlorozone. These solutions contain mixtures of sodium

hypochlorite and sodium chloride together with some free alkali.

Chlorozone was the name given by Count Dienheim-Brochoki to a number of

preparations patented in 1876 and subsequently down to 1885. They were

produced by passing air and chlorine into solutions of caustic soda.

Lunge and Landolt[1] have shown that the air introduced is without

effect and that the advantages claimed for chlorozone are illusory.

The earliest electrolytic installation on this continent was operated at

Brewster, N. Y., in 1893 and since that date several plants have been

erected where local conditions conduced to economical operation.

When a uni-directional current of electricity is passed through a

solution of sodium chloride, the salt is dissociated and the components

liberated, NaCl = Na + Cl. If the elements are not separated, the

chlorine combines with the sodium hydrate, formed by the action of the

sodium on the water, to form sodium hypochlorite. The equations 2Na +

2H_{2}O = 2NaOH + H_{2}, and 2NaOH + Cl_{2} = NaOCl + NaCl + H_{2}O show

that only one-half of the chlorine produced is found as hypochlorite;

the other half reforming sodium chloride.

Several types of electrolysers have been used for the production of

hypochlorites and chlorine but only two are suitable for water-works

purposes: in one, the cathodic and anodic products recombine in the main

body of the electrolyte; in the other, the diaphragm process, they are

separated as removed and the final products are chlorine gas and a

solution containing caustic soda and some undecomposed salt.

Until a few years ago the non-diaphragm process was the only one used

for water treatment and it will consequently be discussed first.

_Non-diaphragm Process._ The theoretical voltage required for the

decomposition of sodium chloride is 2.3 but when the products recombine

in the electrolyte, side reactions occur which increase the minimum

voltage to 3.54. On this basis one kilowatt hour gives 272 ampere hours

and as one ampere hour is theoretically capable of producing 1.33 grams

of chlorine, 1.21 kilowatt hours are necessary for the production of 1

pound of chlorine by the decomposition of 1.65 pounds of salt.

Charles Watt (1851) discovered this process and was the first to

recognize the necessary conditions which are (1) insoluble electrodes,

(2) low temperature of electrolyte, and (3) rapid circulation of

electrolyte from the cathode to the anode. The control of the

temperature is very important, for as it increases, side reactions occur

with the formation of chlorates, and the efficiency is decreased.

The non-diaphragm cells used in Europe (Haas and Oettel, Kellner,

Hermite, Vogelsand, and Mather and Platt) have been described by

Kershaw.[2] In the Haas and Oettel electrolyser the electrodes are

composed of carbon but in the other types at least one electrode is made

from platinum or a platinum alloy. The Dayton electrolyser, which is the

cell most familiar in North America, is shown in Fig. 9.

[Illustration: FIG. 9.--Dayton Electrolytic Cell.]

The outer cell is made of soapstone and is approximately 2-1/2 feet long

and 2 feet wide. The main electrodes consist of four pieces of Atcheson

graphite connected together by screws and metal strips to which is

attached a clamp for connecting electrical terminals. Circulation of the

brine is produced by glass baffle plates and secondary electrodes placed

one inch apart between the main electrodes. The cell is intended to be

used at 110-volts pressure but by wiring two cells in series a 220-volt

circuit may be employed. An inlet and outlet are provided at each end of

the tank to permit the direction of the flow to be periodically reversed

for the purpose of removing the lime deposit from the graphite plates.

The salt solution is prepared in wooden tanks from coarse clean salt

(ground rock salt is unsuitable), containing as little iron as possible,

in the proportion of 50 pounds to 100 gallons of water. After passing

through a gravel or other suitable filter the brine solution is carried

by brass pipes to the electrolyser. The rate of flow is adjusted to the

temperature of the hypochlorite solution leaving the cell but under

normal conditions it is stated that the cell described will pass 40

gallons per hour with a consumption of 70 amperes and produce 2-1/2

pounds of chlorine per hour. This is equal to 8 pounds of salt and 3.08

kilowatt hours per pound of chlorine. After the cells have been operated

for several months the efficiency usually falls and 10-11 pounds of salt

and 3.5-3.7 kilowatt hours are required for the production of one pound

of chlorine. The concentration of the hypochlorite solution is usually

about 6 grams per litre.

Rickard[3] stated that by cooling the Dayton cell with ice 1 pound of

chlorine could be produced from 2.65 kilowatt hours and 6.9 pounds of

sodium chloride; without cooling the figures were 3.62 kilowatt hours

and 7.2 pounds of salt. Based on the figures that have been obtained

from mature cells, the efficiency of the Dayton cell as compared with

those described by Kershaw is as follows:

------------------+----------------------+----------------------

| SALT. | POWER.

| PER POUND OF AVAILABLE CHLORINE.

Type of Cell. +----------+-----------+----------+-----------

| Pounds. | Per Cent | Kilowatt | Efficiency

| | Consumed. | Hours. | Per Cent.

------------------+----------+-----------+----------+-----------

Haas and Oettel | 10.7 | 15.4 | 3.8 | 31.9

Kellner | 7.5 | 22.0 | 2.75 | 43.9

Hermite | 11.2 | 14.5 | 2.87 | 42.2

Mather and Platt | .... | .... | 2.75 | 43.9

Dayton | 10.0 | 16.5 | 3.6 | 33.6

Theoretical | 1.65 | 100.0 | 1.21 | 100.0

------------------+----------+-----------+----------+-----------

The cost of production depends upon local conditions: if alternating

current is available at $30 per horse-power per annum, and low-grade

salt can be obtained for $5 per ton the cost of 1 pound of chlorine

would be

-----------------+----------------------------

| COST (CENTS) PER POUND OF

| AVAILABLE CHLORINE.

Type of Cell. +--------+----------+--------

| Salt. | Current. | Total.

-----------------+--------+----------+--------

Haas and Oettel | 2.67 | 1.97 | 4.64

Kellner | 1.87 | 1.43 | 3.30

Hermite | 2.80 | 1.49 | 4.29

Dayton | 2.50 | 1.92 | 4.42

-----------------+--------+----------+--------

The electrical and chemical efficiencies of the Haas and Oettel and

Dayton cells, which contain carbon electrodes, are smaller than those

containing platinum electrodes but for water sterilisation the carbon

cells have been found to be more suitable. To prevent the action of

magnesium salts on the platinum electrodes it is necessary to use a

higher grade of salt or to provide means of purification. Because of the

absence of a base and the presence of chlorides, electrolytic

hypochlorite cannot be stored for more than a few hours without

appreciable loss of titre. Unless used for the treatment of the effluent

of a filter plant operated at a fairly constant rate a small storage

tank is necessary to compensate for the irregular demand and to provide

the head required by orifice feed boxes. Small variations can be made by

regulating the flow through the cells but large ones are not compatible

with efficiency, which is the highest under a constant load.

Claims have been made that electrolytic hypochlorite is more efficient

as a germicide than bleach when compared on the basis of their available

chlorine content but no evidence of it has been produced. Bleach

contains an excess of base, which retards the germicidal action, and

electrolytic hypochlorite contains an excess of sodium chloride, which

accelerates it (Race[4]) but the ultimate effect is the same with both.

This is shown in Table XXIV.

TABLE XXIV.[A]--COMPARISON OF BLEACH WITH ELECTROLYTIC HYPOCHLORITE

----------------+-------------------++-------------------

| BLEACH. || ELECTROLYTIC

| || HYPOCHLORITE.

+-------------------++-------------------

Contact Period. | Available Chlorine. Parts Per Million.

+---------+---------++---------+---------

| 0.4 | 0.6 || 0.4 | 0.6

----------------+---------+---------++---------+---------

Nil | 182 | ... || ... | ...

10 minutes | 130 | 10 || 120 | 8

1 hour | 66 | 1 || 60 | 0

2 hours | 3 | 0 || 1 | 0

3-1/2 hours | 0 | 0 || 0 | 0

----------------+---------+---------++---------+---------

[A] Results are B. coli per 10 c.cms.

Electrolytic hypochlorite has a greater germicidal velocity than bleach

but the difference is so small as to be of no practical importance.

Rabs[5] experimented with various hypochlorites but was unable to find

any appreciable differences in their germicidal action.

If electrical power can be obtained at a very low cost, or if the cost

is merely nominal, as it is when there is an appreciable difference

between the normal consumption and the peak load upon which the rate is

based, the electrolytic hypochlorite method offers some advantages but

in the great majority of plants it cannot economically compete with

bleach. The instability of the liquor and cell troubles have also

prevented the process being generally utilised. Baltimore and Cincinnati

experimented with this method but did not adopt it. Winslow[6] has

reported that, owing to the difficulty in obtaining bleach since the

outbreak of war, Petrograd has used electrolytic hypochlorite made from

salt.

_Diaphragm Process._ The various types of diaphragm cells that have been

commercially operated are of two varieties: (1) cells with submerged

diaphragms and (2) cells in which the electrolyte comes in contact with

one face only of an unsubmerged diaphragm.

The Le Sueur, Gibbs, Crocker, Billiter-Siemens, Nelson, and

Hargreaves-Bird cells are of the submerged diaphragm variety. The Nelson

cell has been operated for some time at the filtration plant at Little

Falls, N. J. The cells are fed with brine solution previously purified

by the addition of soda ash and have given fairly successful results

although the cost of maintenance is comparatively high. Tolman[7] has

reported that several towns in West Virginia use a bleach solution

prepared by absorbing chlorine, manufactured by the Hargreaves-Bird

process, in lime water; the solution contains about 1.95 per cent of

available chlorine.

The diaphragms in both the submerged and unsubmerged types are usually

constructed either with asbestos paper or cloth, placed in such a manner

as to divide the cells into two separate compartments: the anodic, into

which the brine is fed and where the chlorine is produced; and the

cathodic, where caustic soda is formed.

By maintaining the liquor in the anodic compartment at a higher

elevation than in the cathodic one, the direction of flow is towards the

latter, but owing to osmosis and diffusion the separation is not

complete and a portion of the caustic soda passes the diaphragm and

produces hypochlorite with a consequent loss of efficiency and rapid

deterioration of the anodes. With the exception of the Billiter-Siemens

cell, the submerged diaphragm cells operate at not more than 85 per cent

efficiency and the cost of maintenance is usually high.

In the non-submerged diaphragm types the invasion of the anodic

compartment by caustic is much reduced and the efficiency and life

increased.

An electrolyser of the non-submerged diaphragm type is the Allen-Moore

cell which has been adopted by the Montreal Water and Power Co. This

has been described by Pitcher and Meadows.[8] The general lay-out of the

installation is shown in Fig. 10, and the essential features are: a salt

storage bin having a capacity of 40 tons; the brine saturating and

purifying apparatus; duplicate 15 horse-power motor-generator sets; four

chlorine cells; and the silver ejectors and distributing lines for

carrying the chlorine solution to the point of application.

[Illustration: FIG. 10--Brine Saturating and Purifying Equipment.]

The brine solution, which is prepared by passing water through the

saturators previously filled with salt, is delivered to the two concrete

reaction tanks where an amount of soda ash and caustic liquor sufficient

to combine with the calcium and magnesium salts is added, and the

mixture filtered through sand and stored in the purified brine tanks. To

prevent the formation of hypochlorites by the interaction of chlorine

and alkali, the alkalinity of the liquor is determined and sufficient

hydrochloric acid added to ensure an acidity of 0.01 per cent. The acid

brine is delivered at one end of the four cells (Fig. 11) each of which

is 7 feet long and 20-3/8 inches wide and consumes 600 amperes at 3.3

volts. The cell box is built of concrete and is provided with a

perforated wrought iron cathode box and graphite anode plates which are

separated by an unsubmerged asbestos paper diaphragm.

[Illustration: FIG. 11.--Sections of Allen-Moore Cell.]

Each cell has a capacity of 32 pounds of chlorine per day and the gas

flow is determined by measuring the volume of caustic soda produced in a

given period of time and calculating the weight from the volume and

concentration as determined by titration with standard acid; each gram

of NaOH is equal to 0.88 gram of chlorine. The efficiency of the cell is

obtained by dividing the number of grams of chlorine produced per hour

by the product of the current volume (in amperes) and the factor 1.33,

the theoretical production of chlorine for one ampere hour. The average

efficiency of the Montreal cells was found to be 93 per cent. The

installation comprises four cells, one being held in reserve, and the

annual cost of producing 90 pounds of chlorine per day is given as

$2,500. The details are:

Salt at $8.00 per ton, delivered $500.00

Power, 15 H.P., at $30.00 flat rate 450.00

Labour and superintendence 500.00

Interest at 6 per cent on capital cost 300.00

Depreciation, 15 per cent 750.00

---------

$2,500.00

cost per pound of chlorine = 7.6 cents.

The diaphragm cells, like the non-diaphragm ones, operate most

efficiently under a constant load; they are consequently suitable for

treating the effluent of filter plants.

Where very cheap electrical power can be obtained, the cost per pound of

available chlorine is less for the electrolytic method just described

than for liquid chlorine or chlorine obtained from bleach; but this

condition obtains in very few places. Mr. J. A. Meadows has suggested to

the author that the cost could be reduced by converting the chlorine gas

into hypochlorite and then adding dilute ammonia as in the chloramine

process (_vide_ page 115). The caustic liquor, usually run to waste from

the cathodic compartment, could be delivered into a feed box from which

it would be drawn off by the water injector used for dissolving the

chlorine gas.

BIBLIOGRAPHY

[1] Lunge and Landolt. Jour. Soc. Dyers and Colourists, Nov. 25, 1885.

[2] Kershaw. Jour. Soc. Chem. Ind., 1912, =31=, 54.

[3] Rickard. Quar. Bull. Ohio Board of Health, Oct.-Dec., 1904.

[4] Race. Jour. Amer. Waterworks Assoc., 1918, =5=, 63.

[5] Rabs. Hygienische Rundschau, 1901, 11.

[6] Winslow. Public Health Rpts. U. S. P. H. S., 1917, =32=, 2202.

[7] Tolman. Jour. Amer. Waterworks Assoc., 1917, =4=, 337.

[8] Pitcher and Meadows. Jour. Amer. Waterworks Assoc., 1917, =4=, 337.

CHAPTER IX

CHLORAMINE

Chloramine (NH_{2}Cl), a chemical compound in which one of the hydrogen

atoms of ammonia has been replaced by chlorine, was discovered by

Raschig[1] in 1907. Chloramine was prepared by cooling dilute solutions

of bleach and ammonia and adding the latter to the former contained in a

flask surrounded by a freezing mixture. The proportions were as the

equivalent weights of anhydrous ammonia and available chlorine

(approximately two parts by weight of chlorine to one part by weight of

ammonia). After gas evolution had ceased the mixture was saturated with

zinc chloride and the magma distilled under reduced pressure. The

distillate was a dilute solution of comparatively pure chloramine.

The first to notice the effect of ammonia on the germicidal value of

hypochlorites was S. Rideal[2] who noted that during the chlorination of

sewage, the first rapid consumption of chlorine was succeeded by a

slower action which continued for days in some instances, and was

accompanied by a germicidal action after free chlorine or hypochlorite

had disappeared. Rideal stated that: "It became evident that chlorine,

in supplement to its oxidising action, which had been exhausted, was

acting by substitution for hydrogen in ammonia and organic compounds,

yielding products more or less germicidal." On investigating the effect

of ammonia on hypochlorite it was found that the addition of an

equivalent of ammonia to electrolytic hypochlorite increased the

carbolic acid coefficient of 2.18, for one per cent available chlorine,

to 6.36 (nearly three times the value). Further experimental work showed

that the increase was due to the formation of chloramine.

The author, in 1915, during a series of experiments on the relative

germicidal action of hypochlorites, attempted to prepare the ammonium

salt by double decomposition of bleach and ammonium oxalate solutions.

Ca(OCl)_{2} + (NH_{4})_{2}C_{2}O_{4} = CaC_{2}O_{4} + 2NH_{4}OCl.

The velocity of the germicidal action of the solution was found to be

about ten times greater than the germicidal velocities of other

hypochlorites of equal concentrations, (Race[3]), and from a

consideration of the chemical formula of ammonium hypochlorite it

appeared probable that it would be very unstable and decompose into

chloramine, which Rideal had previously shown to have an abnormal

germicidal action, and water. NH_{4}OCl = NH_{2}CL + H_{2}O. After these

results have been confirmed, the effect of adding ammonia to bleach

solution was tried and it was found that 0.20 p.p.m. of available

chlorine and 0.10 p.p.m. of ammonia produced equally good results as

0.60 p.p.m. of chlorine only. Similar results were obtained on the

addition of ammonia to electrolytic hypochlorite.

Experiments made with a view to determining the most efficient ratios of

ammonia gave very surprising results: chlorine to ammonia ratios (by

weight) between 8:1 and 1:2 gave approximately the same germicidal

velocity.[3] The action of the ammonia on the oxidising power of bleach,

as measured by the indigo test, was also found to be disproportionate to

the amount added.

The oxidising action of various mixtures of bleach and ammonia as

measured by the rate of absorption of the available by the organic

matter in the Ottawa River water is shown in Table XXV.

TABLE XXV.--RATE OF ABSORPTION OF AVAILABLE CHLORINE

--------------------------+-----------------------------------

Ratio Chlorine / Ammonia | PERCENTAGE OF ORIGINAL FOUND AFTER

by Weight. +-----------+-----------+-----------

| 10 Mins. | 4 Hours. | 20 Hours.

--------------------------+-----------+-----------+-----------

Infinity (ammonia absent) | 66.8 | 40.0 | 25.1

8:1 | 83.2 | 77.8 | 67.3

4:1 | 97.2 | 94.7 | 88.5

2.7:1 | 98.3 | 96.5 | 92.8

2:1 | 99.8 | 98.2 | 96.2

--------------------------+-----------+-----------+-----------

The 8:1 ratio caused a marked reduction in the rate of absorption of the

chlorine whilst a 4:1 ratio was almost as active as the ratios

containing more ammonia.

At the time when the abnormal results were obtained with ammonium

hypochlorite and mixtures of bleach and ammonia, the phenomenon appeared

to be of scientific interest only and especially so as Rideal had

attributed the obnoxious tastes and odours, sometimes produced by

chlorination, to the formation of chloramines. During the winter of

1915-1916 the price of bleach, however, advanced to extraordinary

heights and the author then determined to try out the process on a

practical scale for the purification of water. A subsidiary plant

pumping about 200,000 Imperial gallons per day (240,000 U. S. A.

gallons) was found to be available for this purpose and the chloramine

process was substituted for the bleach method previously in operation.

The process was commenced by the addition of pure ammonia fort, in the

amount required to give a chlorine to ammonia ratio of 2:1, to the

bleach solutions in the barrels. The results were not in accordance with

those obtained in the laboratory and it was found that the samples of

bleach solutions received for analysis were far below the strength

calculated from the amount of dry bleach used. This experience was

repeated on subsequent days and the deficiency was found to increase on

increasing the ammonia dosage. Solutions of similar concentration were

then used in the laboratory with similar losses, and it was observed

that on the addition of ammonia a copious evolution of gas occurred. An

investigation showed that the ammonia and bleach must be mixed as dilute

solutions and prolonged contact avoided (_vide_ p. 127). Alterations

were accordingly made in the plant and the bleach and ammonia were

prepared as dilute solutions in separate vessels and allowed to mix for

only a few seconds before delivery to the suction of the pumps. This

method of application was instantaneously successful and results equal

to those obtained in the laboratory were at once secured. The dosage was

reduced until the bacteriological results were adversely affected and

continued at values slightly in excess of this figure (0.15 p.p.m.) for

a short period to prove that the process was reliable.

From a consideration of the work of Raschig and Rideal, it appeared that

the most efficient proportions of available chlorine and ammonia would

be two parts by weight of the former to one part of the latter and this

ratio was maintained during the run on the experimental plant. Lower

ratios of chlorine to ammonia were contra-indicated by the laboratory

experiments, which showed that the efficiency was not increased thereby

whilst higher ratios were left for future consideration.

The results obtained on the experimental plant, together with those

obtained on the main plant, where 24 million gallons per day were

treated with bleach only, are given in Tables XXVI, XXVII and XXVIII.

The two periods given represent the spring flood condition and that

immediately preceding it; these are respectively the worst and best

water periods. The results in both cases are from samples examined

approximately two hours after the application of the chemicals.

The cost data were calculated on the current New York prices of bleach

and ammonia.

TABLE XXVI.--COMPARISON OF HYPOCHLORITE AND CHLORAMINE TREATMENT

BACTERIOLOGICAL RESULTS

-----+------------------+----------------------+----------------------------

| RAW WATER. | TREATED WITH HYPO- | TREATED WITH HYPOCHLORITE

| | CHLORITE ALONE. | AND AMMONIA.

+------------+-----+-----------+-----+----+------------+-----+----+----

|centimeter. | _B. |centimeter.| _B. | |centimeter. | _B. | |

+-----+------+coli_+-----+-----+coli_| +------------+coli_| |

| 1 | 3 | per | 1 | 3 | per | | 1 | 3 | per | |

| day | days | 100 | day |days | 100 | | day | days | 100 | |

| at | at | cc. | at | at | cc. | | at | at | cc. | |

| 37 deg. | 20 deg. | | 37 deg. | 20 deg. | | | 37 deg. | 20 deg. | | |

| C. | C. | | C. | C. | | | C. | C. | | |

-----+-----+------+-----+-----+-----+-----+----+-----+------+-----+----+----

Mar. | 44| 238| 35.7| 4 | 12 |<0.14|0.90| 4 | 12 |0.14 |0.22|0.11

15-31| | | | | | | | | | | |

April|3,099|14,408|195.5| 32 | 56 | 0.50|1.10| 33 |246 |0.74 |0.25|0.13

1-19 | | | | | | | | | | | |

-----+-----+------+-----+-----+-----+-----+----+-----+------+-----+----+----

Legend: (1) Available chlorine parts per million.

(2) Ammonia, parts per million.

TABLE XXVII

_Percentage Reduction_

-------+---------------------------------+--------------------------------

| HYPOCHLORITE ALONE. | HYPOCHLORITE AND AMMONIA.

+---------------+-------+---------+--------------+-------+---------

+------+--------+ Index | per +------+-------+ Index | per

| at | at |centi- | | at | at |centi- |

-------+------+--------+-------+---------+------+-------+-------+---------

Mar. | 90.9 | 95.8 | 99.9+ | 0.90 | 90.0 | 95.0 | 99.7| 0.22

15-31| | | | | | | |

April | 98.9 | 99.6 | 99.7 | 1.10 | 98.3 | 98.9 | 99.6| 0.25

1-19 | | | | | | | |

-------+------+--------+-------+---------+------+-------+-------+---------

TABLE XXVIII

_Cost Per Million Imperial Gallons_[A]

-----------+--------------+--------------

| Hypochlorite | Hypochlorite

| alone. | and ammonia.

-----------+--------------+--------------

Mar. 15-31 | $1.12 | $0.46

April | 1.26 | 0.54

-----------+--------------+--------------

[A] Calculated as Bleach at $3.80 per 100 pounds and aqua ammonia (26 deg.

Be.) at 5-1/2 cents per pound.

The results were so satisfactory that the author recommended the

adoption of the process on the main chlorinating plant but owing to

conditions imposed by the Provincial Board of Health the process was not

operated until February, 1917.

In place of ammonia fort, aqua ammonia (26 deg. Be.), containing

approximately 29 per cent of anhydrous ammonia, was used. The material

was first examined by the presence of such noxious substance as cyanides

and found to be very satisfactory.

[Illustration: FIG. 12.--Sketch of Ottawa Chloramine Plant.]

The general design of the plant is shown in Fig. 12. The bleach is mixed

in tank _A_ as a solution containing 0.3 to 0.6 per cent of available

chlorine and delivered to tanks _B_ and _D_, each of which has a

twenty-four-hour storage capacity. The ammonia solution is mixed and

stored in tank _B_ and contains 0.3-0.5 per cent of anhydrous ammonia.

The two solutions are run off into boxes _E_ and _F_ which maintain a

constant head on valves _V_ and _V'_ controlling the head on the

orifices. Both orifices discharge into a common feed box _G_ from which

the mixture is carried by the water injector _J_ through one of

duplicate feed pipes and discharged into the suction well through a

perforated pipe.

As tank _B_ was previously used as a bleach storage tank, the change

from hypochlorite alone to chloramine necessitated very little expense.

The treatment was commenced by gradually increasing the quantity of

ammonia, until a dosage of 0.12 p.p.m. was reached, and constantly

increasing the dosage of bleach, which was formerly 0.93 p.p.m. of

available chlorine. Owing to the restrictions imposed by the Provincial

authorities it has not been possible to maintain a dosage as low as that

indicated as sufficient by the experimental plants results, but some

interesting data have been obtained. Table XXIX shows the results

obtained from February to October, 1917, from the chloramine treatment

at Ottawa and also those obtained with liquid chlorine at Hull where the

same raw water is treated with 0.7-0.8 p.p.m. of chlorine.

TABLE XXIX.--CHLORAMINE RESULTS AT OTTAWA

---------+--------------+----------+--------+------------------+-------

1917 +------+-------+Turbidity.| Colour.+---------+--------+Per 100

| Raw | Tap | | | | |c.cms.

---------+------+-------+----------+--------+---------+--------+-------

Feb. | 268 | 0.88 | 3 | 40 | 0.57 | 0.05 | ....

Mar. 1-18| 250 | 0.96 | 4 | 40 | 0.32 | 0.11 | ....

Mar. 1-31| 643 | 0.43 | 4 | 40 | 0.47 | 0.14 | ....

April | 5228 | 0.34 | 31 | 32 | 0.56 | 0.10 | ....

May | 162 | <0.08 | 3 | 39 | 0.52 | 0.08 | ....

June | 114 | <0.08 | 3 | 41 | 0.51 | 0.08 | ....

July | 237 | 0.08 | 5 | 41 | 0.51 | 0.08 | 44.4

Aug. | 165 | 0.08 | 4 | 42 | 0.51 | 0.10 | 28.0

Sept. | 55 | <0.08 | 6 | 42 | 0.50 | 0.09 | 15.2

Oct. | 31 | 0.15 | 5 | 42 | 0.42 | 0.08 | 1.1

---------+------+-------+----------+--------+---------+--------+

Average | 211 | 0.22 | 7 | 40 | 0.51 | 0.09 |

---------+------+-------+----------+--------+---------+--------+-------

At the height of the spring floods the raw water contained 80 p.p.m. of

turbidity and over 500 _B. coli_ per c.cm. but 0.6 p.p.m. of chlorine

and 0.13 p.p.m. of ammonia reduced the _B. coli_ index in the tap

samples to 2.5 per 100 c.cms.; samples taken in Hull on the same day

(treated with 0.7-0.8 p.p.m. of liquid chlorine) gave a _B. coli_ index

of 26.7. Previous experiences in Ottawa has shown that a dosage of

approximately 1.5 p.p.m. of available chlorine is required to reduce the

_B. coli_ index to 2.0 per 100 c.cms. under similar physical and

bacteriological conditions.

During the period of nine months covered by the results in Table XXIX,

only five cases of typhoid fever were reported in which the evidence did

not clearly indicate that the infection had occurred outside the city.

The reduction in the bleach consumed during the same period effected a

saving of $3,200.

During one period of operation the hypochlorite dosage was gradually

reduced to ascertain what factor of safety was maintained with a dosage

of 0.5 p.p.m. of available chlorine and 0.06-0.08 p.p.m. of ammonia. The

results are shown in Diagram VIII. The percentage of samples of treated

water showing _B. coli_ in 50 c.cms. was calculated from the results of

the examination of 4-7 samples daily.

The results showed that it was possible to reduce the chlorine dosage to

0.25 p.p.m. with 0.06 p.p.m. of ammonia without adversely affecting the

bacteriological purity of the tap supply and fully confirmed the

experimental results previously obtained.

The lowest ratio of available chlorine to ammonia used during this test

was approximately 4:1. This is the ratio indicated by a consideration of

the theory of the reaction, and not 2:1 as was formerly stated

(Race[4]). If bleach is represented as Ca(OCl)_{2}, the equation

Ca(OCl)_{2} + 2NH_{3} = 2NH_{2}Cl + Ca(OH)_{2}

would indicate a ratio of 2:1; but only one molecule of Ca(OCl)_{2} is

produced from two molecules of bleach and the theoretical ratio is

therefore 4:1 (142:34),

2CaOCl_{2} = CaCl_{2} + Ca(OCl)_{2} and Ca(OCl)_{2} + 2NH_{3} =

Cl = 142 34

= 2NH_{2}Cl + Ca(OH)_{2}.

The chlorine to ammonia ratio is very important because of its influence

on the economics of the process (_vide_ p. 124).

[Illustration: DIAGRAM VIII

CHLORAMINE TREATMENT, OTTAWA]

All the laboratory and works results that have been obtained in Ottawa

indicate the importance of an adequate contact period. The superiority

of chloramine over other processes is due to the non-absorption of the

germicidal agent and to obtain the same degree of efficiency the contact

period must be increased as the concentration is decreased. For this

reason the best results will be obtained by chlorinating at the entrance

to reservoirs or under other conditions that will ensure several hours

contact. At Ottawa the capacity of the pipes connecting the pumping

station (point of chlorination) and the distribution mains provides a

contact period of one and a quarter hours but even better results would

be obtained if the contact period were increased.

The general results obtained during the use of chloramine at Ottawa in

1917 have shown that the aftergrowths noted during the use of

hypochlorite (see p. 56) have been entirely eliminated and that the _B.

coli_ content of the tap samples from outlying districts has been

invariably less than that of samples taken from taps near to the point

of application of the chloramine. At Denver, Col., where the chloramine

process has also been used, similar results were obtained[5]: four days

after the initiation of the chloramine treatment the aftergrowth count

on gelatine of the Capitol Hill reservoir dropped from 15,000 to 10 per

c.cm. The hypochlorite dosage was cut from 0.26-0.13 p.p.m. of available

chlorine and 0.065 p.p.m. of ammonia added.

_Economics of the Chloramine Process._ The chloramine process was

introduced at Ottawa for the purpose of obtaining relief from the effect

of the high price of bleach caused by the cessation of imports from

Europe in 1915. The results obtained with the experimental plant

indicated that, calculated on the prices current at the beginning of

1917, appreciable economies could be made. Although the reduction in the

chlorine dosage has not been as great as was anticipated, due to the

restrictions previously mentioned, the cost of sterilising chemicals in

1917 was $3,200 less than the cost of straight hypochlorite treatment.

During the latter part of 1917 the relative cost of bleach and ammonia

changed (see Diagram IX).

When calculated on the New York prices for January, 1918, the cost of

chloramine treatment in the United States would be greater than

hypochlorite alone unless a large reduction in the dosage could be

secured by very long contact periods. This condition is only temporary,

however, and the price of ammonia will probably gradually decline as

the plants for fixation of atmospheric nitrogen commence operations and

reduce the demand for the ammonia produced from ammoniacal gas liquor.

In Canada, the market conditions are still (1918) favourable to the

chloramine process: bleach is 25 per cent higher than the U.S.A. product

and ammonia can be obtained for one-half the New York prices.

[Illustration: DIAGRAM IX

BLEACH AND AMMONIA PRICES]

_Advantages of the Chloramine Process._ Although the market conditions

may, in some instances, be unfavourable to the chloramine process, the

method possesses certain advantages that more than offset a slight

possible increase in the cost of materials. The taste and odour of

chloramine is even more pungent than that of chlorine but since the

introduction of the process in Ottawa no complaints have been received.

Owing to the reduced dosage, slight proportional fluctuations in the

dosage do not produce the same variations in the amount of free chlorine

which is the usual cause of complaints. A public announcement that the

amount of hypochlorite has been reduced also has a psychological

effect upon the consumers and tends to reduce complaints due to

auto-suggestion.

The most important advantage of the process is the elimination of the

aftergrowth problem. At Denver, where the aftergrowth trouble is

possibly more acute than at any other city on the continent, it was

effectively banished by the use of chloramine. At Ottawa, the sanitary

significance of _B. coli_ aftergrowths is no longer of practical

interest because such aftergrowths have ceased to occur. Whatever may be

their opinion as to the sanitary significance of aftergrowths, all water

sanitarians will agree that the better policy is to prevent their

occurrence.

_Operation of Chloramine Process._ For the successful operation of the

chloramine process, the essential factors are low concentrations of the

hypochlorite and ammonia solutions. The author has found that

hypochlorite containing 0.3-0.5 per cent of available chlorine and

ammonia containing 0.3-0.5 per cent of anhydrous ammonia can be mixed in

a 4:1 or 8:1 ratio without appreciable loss in titre. Solutions of these

concentrations mixed in 4:1 ratio lost only 2-3 per cent of available

chlorine in fifteen minutes and less than 10 per cent in five hours. The

effect of mixing solutions containing 4.35 per cent of available

chlorine and 2.2 per cent of ammonia is shown in Table XXX.

The stability of chloramine is a function of the concentration and the

temperature and in practice it will be found advisable to determine in

the laboratory the maximum concentrations that can be used at the

maximum temperature attained by the water to be treated (cf. Muspratt

and Smith[6]).

According to Raschig[1] two competing reactions occur when ammonia is in

excess.

(1) NH_{2}Cl + NH_{3} = N_{2}H_{4}HCl hydrazine hydrochloride

and (2) 3NH_{2}Cl + 2NH_{3} = N_{2} + 3NH_{4}Cl.

When the excess of ammonia is large, as on the addition of ammonia fort,

the second reaction predominates and the yield of nitrogen gas is almost

quantitatively proportional to the quantity of available chlorine

present. As ammonium chloride has no germicidal action, and hydrazine a

carbolic coefficient of only 0.24 (Rideal), the formation of these

compounds should be avoided.

TABLE XXX.--LOSS ON MIXING HYPOCHLORITE AND AMMONIA

Hypochlorite containing 4.35 per cent available chlorine. Ammonia

contained 2.2 per cent NH_{3}

-----------------------------+-------------------------------------

| LOSS OF AVAILABLE CHLORINE AFTER

Ratio Chlorine to Ammonia by +--------------+----------+-----------

Weight. | Few Minutes. | 1 Hour. | 24 Hours.

-----------------------------+--------------+----------+-----------

| Per cent | Per cent | Per cent

6:1 | 19 | 19 | 19

4:1 | 24 | 25 | 25

2:1 | 45 | 47 | 47

1:1 | 91 | 91 | 92

1:2 | 20 | 28 | 65

-----------------------------+--------------+----------+-----------

The dosage of chloramine can be checked by titration of the available

chlorine (see p. 82) immediately after treatment or by the estimation of

the increment in the total ammonia (free and albuminoid). Routine

determinations of the latter made in Ottawa show that practically the

whole (90-95 per cent) of the added ammonia can be recovered by

distillation with alkaline permanganate and that 85-90 per cent is in

the "free" condition.

In operating the chloramine process it is important that the pipes used

for conveying the chloramine solution should be of ample dimensions and

provided with facilities for blowing out the lime that deposits from the

solution.

Ca(OCl)_{2} + 2NH_{3} = 2NH_{2}Cl + Ca(OH)_{2}.

The marked activity of chloramine as a chlorinating agent could be

predicated from its heat of formation, which is 8,230 calories. The

other possible chloramines should be even more active as the heat of

formation of these compounds are:

Dichloramine NHCl_{2} -- 36,780 calories.

Nitrogen trichloride NCl_{3} -- 65,330 calories.

Dichloramine is unknown but nitrogen chloride has been prepared and is a

highly explosive yellow oil that decomposes slowly when kept under water

in the ice box. NCl_{3} can be easily prepared by passing chlorine gas

into a solution of ammonium chloride and this process would suggest that

a method might be found of utilising chlorine and ammonia as gases for

the production of nitrogen trichloride as a germicide for water

chlorination. NH_{4}Cl + 3Cl_{2} = NCl_{3} + 4HCl.

The "available" chlorine content of the chloramines is double the actual

chlorine content as each atom of chlorine will liberate two atoms of

iodine from hydriodic acid.

NH_{2}Cl + 2HI = I_{2} + NH_{4}Cl.

NCl_{3} + 6HI = 3I_{2} + NH_{4}Cl + 2HCl.

HALAZONE

For the sterilisation of small individual quantities of water such as

are required by cavalry and other mobile troops bleach and acid sulphate

tablets have been usually employed. Such tablets have given fairly

satisfactory results but certain difficulties inherent to these

chemicals have made it desirable to seek other methods.

The subject was investigated by Dakin and Dunham,[7] who first tried

chloramine-T (sodium toluene-_p_-sulphochloramide). It was found that

heavily contaminated waters, and particularly those containing much

carbonates, required a comparatively high concentration of the

disinfectant: 40 parts per million of chloramine-T were necessary in

some cases and such an amount was distinctly unpalatable. By adding

tartaric acid or citric acid the effective concentration could be

reduced to 4 p.p.m. but the mixture could not be made into a tablet

without decomposition and a two-tablet system was deemed undesirable.

Toluene sulphodichloramines were next tried. Excellent bacteriological

results were obtained but the manufacture of tablets again presented

difficulties. When the necessary quantity of dichloramine was mixed with

what were assumed to be inert salts--sodium chloride for example--the

normal slow rate of decomposition was accelerated. The dichloramine, in

tablet form, was also found to be too insoluble to effect prompt

sterilisation.

The most suitable substance found by Dakin and Dunham was "halazone" or

_p_-sulphodichloraminobenzoic acid (Cl_{2}N.O_{2}S.C_{6}H_{4}.COOH).

This compound is easily prepared from cheap readily available materials

and was found to be effective and reasonably stable.

The starting point in the preparation of halazone is

_p_-toluenesulphonic chloride, a cheap waste product in the manufacture

of saccharine. By the action of ammonia, _p_-toluene sulphonamide is

produced and is subsequently oxidised by bichromate and sulphuric acid

to _p_-sulphonamidobenzoic acid. This acid, on chlorination at low

temperatures, yields _p_-sulphondichloraminobenzoic acid (halazone). The

reactions may be expressed as follows:

CH_{3} COOH COOH

/ \ / \ / \

| | --> | | --> | |

\ / \ / \ /

SO_{2}.NH_{3} SO_{2}.NH_{2} SO_{2}.NCl_{2}

Halazone is a white crystalline solid, sparingly soluble in water and

chloroform, and insoluble in petroleum. It readily dissolves in glacial

acetic acid from which it crystallizes in prisms (M.P. 213 deg. C.).

The purity of the compound can be ascertained by dissolving in glacial

acetic acid, adding potassium iodide, and titrating with thiosulphate;

0.1 gram should require 14.8 to 14.9 c.cms. of N/10 sodium thiosulphate.

Each chlorine atom in halazone is equivalent to 1 molecule of

hypochlorous acid and the "available" chlorine content is consequently

52.5 per cent or double the actual chlorine content.

>SO_{2}.NCl_{2} + 4HI = >SO_{2}.NH_{2} + 2HCl + 2I_{2}.

From the bacteriological results given by Dakin and Dunham it would

appear that 3 parts per million of halazone (1.5 p.p.m. available

chlorine) are sufficient to sterilise heavily polluted waters in thirty

minutes and that this concentration can be relied upon to remove

pathogenic organisms.

The formula recommended for the preparation of tablets is halazone 4 per

cent, sodium carbonate, 4 per cent (or dried borax 8 per cent), and

sodium chloride (pure) 92 per cent.

Halazone and halazone tablets, when tested in the author's laboratory on

the coloured Ottawa River water seeded with _B. coli_, have given rather

inferior results. With 1 tablet per quart, over six hours were required

to reduce a _B. coli_ content of 100 per 10 c.cms. to less than 1 per 10

c.cms. Clear well waters gave excellent results and large numbers of _B.

coli_ were reduced to less than 1 per 10 c.cms. in less than thirty

minutes. McCrady[A] has also obtained excellent results with various

strains of _B. coli_ seeded into the colourless St. Lawrence water.

[A] Private communication.

BIBLIOGRAPHY

[1] Raschig. Chem. Zeit., 1907, =31=, 926.

[2] Rideal. S. J. Roy. San. Inst., 1910, =31=, 33-45.

[3] Race. J. Amer. Waterworks Assoc., 1918, =5=, 63.

[4] Race. Eng. and Contr., 1917, =47=, 251.

[5] Contract Record. Aug. 15, 1917, 696.

[6] Muspratt and Smith. J. Soc. Chem. Ind., 1898, =17=, 529.

[7] Dakin and Dunham. Brit. Med. Jour., 1917, No. 2943, 682.

CHAPTER X

RESULTS OBTAINED

The object of adding chlorine or chlorine compounds to water is for the

purpose of destroying any pathogenic organisms that may be present. In a

few instances some collateral advantages are also obtained but, in

general, no other object is aimed at or secured.

Chlorination does not change the physical appearance of water; it does

not reduce or increase the turbidity nor does it decrease the colour in

an appreciable degree.

The chemical composition is also practically unaltered. When bleach is

used there is a proportionate increase in the hardness but the amount is

usually trifling and is without significance. During 1916 when the

Ottawa supply was entirely treated with bleach at the rate of 2.7 parts

per million (0.92 p.p.m. of available chlorine) the average increase in

the total hardness as determined by the soap method was 2.5 parts per

million.

When chlorine is added to prefiltered water, as an adjunct to

filtration, an increase in the number of gallons filtered per run has

been noted at some plants. This increase is not so great with rapid as

with slow sand filters but in some instances it has led to appreciable

economies.

Walden and Powell[1] of Baltimore, found that the addition of a quantity

of bleach equal to approximately 0.50 p.p.m. of available chlorine

enabled the alum to be reduced from 0.87 to 0.58 grain per gallon. The

percentage of water used in washing the filters was also reduced, from

4.1 per cent to 2.9 per cent, whilst the filter runs were increased on

the average by one hour and ten minutes. The net saving in coagulant

alone amounted to 30 cents per million gallons.

Clark and De Gage[2] found that the use of smaller amounts of coagulant

during the period of combined disinfection and coagulation resulted in

an increase of nearly 25 per cent in the quantity of water passed

through the filter between washings, and also in a material reduction of

the cost of chemicals, which averaged $2.62 per million gallons for

combined disinfection and coagulation as against $4.86 for coagulation

alone. The water used in these experiments was obtained from the

Merrimac River at Lawrence.

The effect of hypochlorite on the reduction of algae growths on slow sand

filters was first noticed by Houston during the treatment of the Lincoln

supply in 1905. Two open service reservoirs were fed with treated water

and were themselves dosed from time to time. "Previous to 1905 they

developed seasonally most abundant growths, but during the hypochlorite

treatment it was noticed that they remained bright, clear, and

remarkably free from growths" (Houston[3]).

Ellms,[4] of Cincinnati, has also noted the effect of hypochlorite on

algae. When the bleach was added to the coagulated water the destruction

of the plankton was not as satisfactory as had been anticipated and it

was found that large doses destroyed the coating of the sand particles

and rendered the filters less efficient. The use of bleach in the

filtered water basin was more successful and cleared it of troublesome

growths.

In 1916, during the treatment of the London Supply with bleach (dosage

0.5 p.p.m. of available chlorine), Houston made further observations on

this point. The Thames water, taken at Staines, had previously been

stored for considerable periods in reservoirs, but this necessitated

lifting the water by pumps which consumed large quantities of coal that

were urgently needed for national purposes. As a war measure, the

storage was eliminated and the water treated with hypochlorite at

Staines and allowed to flow by gravitation to the various works where

the slow sand filters are situated. The treatment resulted in a marked

reduction in the growths of algae, the reduction in the area of filters

cleaned in 1916 (June to September) as compared with 1915 being as

follows:

Percentage

Filter Works. Reduction

(Approximate).

Grand Junction (Hampton) 6

Grand Junction (Kew) 43

East London (Sunbury) 30

Kempton Park 33

West Middlesex 56

A portion of this reduction can probably be attributed to the

elimination of storage.

Chlorination, by decreasing the load on filter beds, has enabled the

rate of filtration to be increased in some cases. This increased

capacity, which would otherwise have necessitated additional filter

units, has been obtained without any further capital outlay. At

Pittsburg (Johnson[5]) the rate of filtration, after cleaning, was

increased 250,000 gallons each hour until the normal rate was reached;

restored beds were maintained at a 250,000 gallon rate for one week.

After the introduction of chlorination it was found possible to increase

the rates more rapidly without adversely affecting the purity of the

mixed filter affluents.

_Hygienic Results._ Evidence as to the actual reduction of the number of

such pathogenic germs as _B. typhosus_ in water supplies by chlorination

is most readily found in the death rates from typhoid fever in cities

that have no other means of water purification. In some cases this

evidence is necessarily of a circumstantial nature; in others it is

definite and conclusive.

Some of the earlier results of the effect of chlorination on typhoid

morbidity and mortality rates were compiled by Jennings[6] and others

have been published by Longley.[7] These data have been brought up to

date in Table XXXI and other statistics added.

TABLE XXXI.--EFFECT OF CHLORINATION ON TYPHOID RATES

AVERAGE TYPHOID DEATH RATE PER 100,000 POPULATION

----------------+-------------+--------------+--------------+-----------

City. | Commenced | BEFORE USING.| AFTER USING. |

|Chlorination.+-------+------+-------+------+ Percentage

----------------+-------------+-------+------+-------+------+-----------

Baltimore |June 1911 |1900-10| 35.2 |1912-15| 22.2 | 36

Cleveland |Sept. 1911 |1900-10| 35.5 |1912-16| 8.2 | 77

Des Moines |Dec. 1910 |1905-10| 22.7 |1911-13| 13.4 | 41

Erie |Mar. 1911 |1906-10| 50.6 |1912-14| 15.0 | 70

Evanston, Ill. |Dec. 1911 |1908-11| 29.0 |1912-13| 14.5 | 50

Jersey City |Sept. 1908 |1900-17| 18.7 |1909-16| 8.4 | 55

Kansas City, Mo.|Jan. 1911 |1900-10| 42.5 |1911-16| 14.2 | 66

Omaha, Neb. |May 1910 |1900-09| 22.5 |1911-16| 10.6 | 53

Trenton |Dec. 1911 |1907-11| 46.0 |1911-14| 28.7 | 35

Montreal |Feb. 1910 |1906-10| 40.0 |1911-16| 25.0 | 37

Toronto |Apr. 1911 |1906-10| 31.2 |1912-16| 7.8 | 75

Ottawa |Sept. 1912 |1906-10| 34.0 |1913-17| 17.0 | 50

----------------+-------------+-------+------+-------+------+-----------

The figures given in this table show the effect of chlorination only; no

other form of purification was used during the periods given, except at

Toronto where a portion of the supply has been subjected to filtration.

It will be seen that since chlorination was adopted the typhoid death

rates have been reduced by approximately 50 per cent and that the

averages for the period after treatment are almost invariably less than

20 per 100,000, a figure that a few years ago was regarded as

satisfactory. The average death rate for the last available year is 11

per 100,000, a result that is even more satisfactory and exceeds the

anticipations of the most optimistic of sanitarians.

A portion of the reduction in the typhoid rates is no doubt due to

improvements in general sanitary conditions but the reduction is much

greater than can be accounted for in that manner alone and in many

cases there was a sharp decline immediately following the commencement

of chlorination.

In a few instances there is evidence that chlorination has reduced the

typhoid rates of cities previously supplied with filtered water. Diagram

X, drawn from data supplied by Dr. West, of the Torresdale Filtration

Plant, shows the effect of disinfecting the filter effluents at

Philadelphia.

[Illustration: DIAGRAM X

TYPHOID IN PHILADELPHIA]

During the years 1909-10-11, when practically the whole of the city

supply was filtered, the average typhoid death rate was 18, but when the

water was also chlorinated, in 1914-15-16, the rate was only 7, a

reduction of 61 per cent.

The figures in Table XXXII show that the Torresdale filters, during

1915-16 were unable to adequately purify the water and that chlorination

was necessary.

TABLE XXXII.--CHLORINATION OF FILTER EFFLUENTS

(TORRESDALE)

----+---------+---------+----------+----------------------------------

| | | | BACTERIA PER CUBIC CENTIMETER.

| Oxygen | | +-----------------+----------------

| | | +---------+-------+---------+------

----+---------+---------+----------+---------+-------+---------+------

1915| 1.70 | 12 | 0.6 | 141 | 30 | 28 | 14

1916| 1.90 | 12 | Nil. | 88 | 23 | 38 | 11

====+=========+=========+==========+=========+=======+=========+======

| _B. coli communis_ |

| Per Cent Positive Tests. |

+----------------------+-------------------------+

| Untreated. | Treated. | Added Chlorine

+----------+-----------+------------+------------+ Parts Per

----+----------+-----------+------------+------------+----------------

1915| 66 | 24 | 5 | 0.3 | 0.18

1916| 49 | 16 | 7.4 | 1.9 | 0.15

----+----------+-----------+------------+------------+----------------

In Diagram XI the typhoid death rates of Columbus, Ohio, and New Orleans

are shown to exemplify conditions that have not been improved by

chlorination. The endemic condition of typhoid in Columbus was brought

to an abrupt conclusion by the installation and operation of the

softening and filter plant in September, 1908, and no further reduction

followed the introduction of chlorination in December, 1909.

In New Orleans the typhoid rate decreased on the inception of the new

water works system in 1909 and again after the installation of the

Carrollton filters in 1912. The product of the filtration plants has

always been above suspicion but aftergrowths occasionally developed and

the bacterial count then exceeded the United States Treasury standard.

To overcome this difficulty, hypochlorite was used in 1915, but, as was

anticipated, it had no effect on the typhoid rate. The high rate in New

Orleans is largely due to outside cases received for hospital treatment

and to other circumstances beyond the control of the water and sewerage

department.

In all the examples previously cited, the evidence as to the effect of

chlorination on typhoid mortality rates is circumstantial but, taken as

a whole, it is fairly conclusive. In the examples to be considered next

the evidence is more direct.

[Illustration: DIAGRAM XI

TYPHOID IN COLUMBUS AND NEW ORLEANS]

One of the most conclusive experiments as to the beneficial effect of

chlorination is that reported by Young[8] of Chicago. The water supply

of Chicago was obtained from Lake Michigan by means of intake pipes and

pumped to various parts of the city. The distribution system was divided

into four districts and, although there was a certain amount of mixing

along the borders, the water supplied to each district was substantially

separate. The rapid and progressive decline in the typhoid rate of

Chicago (from 19 in 1900 to 10.8 in 1911) subsequent to the diversion

of the city sewage from the lake, led to the assumption that water-borne

typhoid had ceased to be of any moment. Early in 1912, however,

permission was secured to chlorinate the supply of one district (No. 1)

and the treatment was continued until December when the solutions

commenced to freeze. Diagram XII shows the effect of the treatment on

the autumnal increase in District No. 1 as compared with the other three

districts. The autumnal increase was calculated from the excess of

typhoid incidence for July to November inclusive, over that for February

to June inclusive.

[Illustration: DIAGRAM XII

AUTUMNAL INCREASE IN TYPHOID, CHICAGO (Young)]

These results demonstrate in a most striking manner the beneficial

effect of chlorination. The general conditions, with the exception of

the raw water supply, were approximately the same in all four districts.

Diagram XIII shows that the raw water supply of District No. 1 was

slightly worse than any of the others, 21.8 per cent of the samples from

District No. 1 containing _B. coli_ in 1 c.cm. as compared with 21.0 per

cent in the most polluted supply of the other districts.

[Illustration: DIAGRAM XIII

B. COLI IN CHICAGO RAW WATER (Young)]

The results obtained at Ottawa are also conclusive. Following two

epidemics of typhoid fever in 1911 and 1912, caused by breaks in the

intake pipe, hypochlorite treatment was commenced and has been in

continuous operation until February, 1917, when chloramine treatment was

substituted. The dosage has been so regulated as to assure a high degree

of purity at all times in the water delivered to the mains and as

evidence of this it might be mentioned that the average _B. coli_ index

(calculated by Phelps' method) for the years 1916 and 1917 was only 0.27

per 100 c.cms. The typhoid rates for the five years preceding the

epidemic years and for a similar subsequent period are given in Diagram

XIV.

[Illustration: DIAGRAM XIV

TYPHOID IN OTTAWA]

The diagram shows that there has been a constant reduction in the city

typhoid rate since the last severe epidemic with the exception of the

year 1915. The high rate of that year was caused by a localised epidemic

started by polluted well water and spread by flies from an unsewered

area. This outbreak was the cause of about seven deaths registered

during that year (population 100,000).

The objection might be raised that if the reduction of the typhoid rate

were due to the water treatment, the decline should have been abrupt and

not a gradual one. It is probable that there has been practically no

water-borne typhoid in the city since chlorination was commenced but

this fact is masked by cases from other sources. During 1911 and 1912

over 3,500 cases of typhoid were reported, of which an appreciable

number would become carriers for various periods of time. As these

carriers decreased the number of cases infected by them would also

decrease and so account for a gradually declining death rate.

It might be further objected that the reduced typhoid rate is due to a

general improvement in the sanitary conditions. If the death rate from

causes other than typhoid can be regarded as a measure of the general

sanitary conditions it is obvious from the data in Table XXXIII that the

improvement in the typhoid rate is immeasurably greater than can be

ascribed to that cause.

TABLE XXXIII.--DEATH RATES IN OTTAWA BEFORE AND AFTER CHLORINATION

--------------------------+-------------------+---------------------

| RATE PER 100,000 | PERCENTAGE

Cause. +---------+---------+-----------+---------

| 1908-12 | 1913-17 | Reduction | Increase

--------------------------+---------+---------+-----------+---------

Total[A] | 14.90 | 14.78 | 1.2 | ...

Typhoid, total | 34[B] | 17 | 50.0 | ...

Typhoid, city | 26[B] | 8 | 69.2 | ...

Pneumonia | 100 | 107 | ... | 7.0

Tuberculosis | 133 | 138 | ... | 3.7

Diarrh[oe]a and Enteritis | 139 | 128 | 7.9 | ...

under 2 years | | | |

--------------------------+---------+---------+-----------+---------

[A] Rate per 1,000.

[B] 1906-10, epidemic years 1911-12 excluded.

One further objection might be made: that the raw water was not infected

during 1913-17 or infected to a smaller extent than during the previous

period. Attempts to isolate _B. typhosus_ from the raw water have

invariably been futile but their presence in 1914 might be inferred from

the fact that during the latter part of the summer of that year an

epidemic of typhoid fever occurred at Aylmer, a village that discharges

its sewage into the Ottawa River about six miles above the Ottawa

intake. Hull, situated on the opposite bank of the river and having a

population of 20,000, takes its water supply from the same channel that

supplies Ottawa but at a point a few hundred feet further down stream.

During November and December, 1914, some 200 cases of typhoid fever

(incidence 1,000 per 100,000) occurred in Hull as compared with 28 in

Ottawa. As the Ottawa intake is situated between the Hull intake and the

outlet of the Aylmer sewer it is incredible that the Ottawa raw water

was not also infected.

In 1916 a liquid chlorine plant was installed in Hull, but in 1917,

owing to an accident, it was out of commission for a short period and at

least 100 cases of fever developed during the following month. During

the same period only two cases were reported in Ottawa and of these one

was obviously contracted outside the city.

In view of the preceding facts it must be granted that the improvement

in the typhoid rate of Ottawa can be definitely attributed to an

improvement in the water supply caused by chlorination.

The efficacy of chlorination to prevent and check epidemics of

water-borne typhoid has never been doubted. Innumerable instances could

be cited in which the prompt treatment of large public supplies has

promptly checked outbreaks that threatened to assume serious proportions

and there is no doubt that the extremely low typhoid morbidity rate on

the Western Front of the European battlefield is partially due to the

extensive and rigorous chlorination measures that have been instigated.

Prophylactic vaccination and the prompt isolation of typhoid carriers

have largely contributed to the wonderful results obtained but due

credit must also be given to the systematic purification and treatment

of water supplies. Similar results have been obtained at training camps

in Canada and in other countries by effective treatment with either

liquid chlorine or hypochlorite.

Since the inception of water chlorination in America in 1908, the merit

of the method has been very generally recognized throughout the

Continent but was regarded with scepticism in Europe, except as a

temporary expedient, until the results obtained by the military forces

compelled more general recognition. Before the war, chlorination of

water supplies in England was only practised in a few isolated and

relatively unimportant instances; in 1917, practically the whole supply

of London was chlorinated and at Worcester a similar treatment has been

recommended to enable the slow sand filters to be operated at higher

rates without reducing the quality of the water supplied to the

consumers.

_Use and Abuse of Chlorine._ Inasmuch as chlorination has no beneficial

effect on water except the reduction of the bacterial content it should

be used for this purpose only and under such conditions as permit the

operations to be under full control at all times. The supplies that can

be most efficiently and safely treated are those that are relatively

constant in chemical composition and bacterial pollution. Changes in

volume can be dealt with by automatic apparatus but sudden changes in

organic and bacterial content require a change of dosage that cannot be

made by any mechanical appliance. Long experience and accurate

meteorological records may in some cases enable those in charge of

chlorination plants to anticipate changes in the conditions of the water

supply, but it is always preferable to provide a positive method of

preventing sudden changes by using chlorination merely as an adjunct to

other processes of purification. Unpurified waters that are

objectionable on account of their bacterial content only are very rare,

as the cause that produces the bacterial pollution usually produces

other conditions that are equally objectionable though not so dangerous

to health. Sudden storms in summer, or sudden thaws in winter, usually

cause large increments in turbidity accompanied by soil washings that

often carry appreciable quantities of faecal matter into surface water

supplies. Lake supplies often suffer in the same manner and sewage,

which during normal conditions is carried safely away from water

intakes, obtains access to the supply. If the dosage is maintained at a

level sufficiently high to meet these abnormal conditions, complaints as

to taste and odour would ensue, and in general, such a practice is

impossible. Some supplies have been chlorinated successfully for years

but the principle of using chlorination as the first and last line of

defence cannot be recommended. Success can only be obtained by eternal

vigilance and the responsibility for results is more than water works

officials should be called upon to assume.

Chlorination is an invaluable adjunct to other forms of water

purification and it is not improbable that, in the future, filter plants

will be designed to remove aesthetic objections at the lowest possible

cost and that chlorination will be relied upon for bacterial reduction.

Chlorination is the simplest, most economical, and efficient process by

which the removal of bacteria can be accomplished and there is no valid

reason why it should not be used for that purpose.

The popularity of this process has suffered through the efforts of over

zealous enthusiasts who have been unable either to recognize its

limitations or to appreciate the fact that a domestic water supply

should be something more than a palatable liquid that does not contain

pathogenic organisms. Every system of water purification has its limited

sphere of utility and chlorination is no exception to the rule.

BIBLIOGRAPHY

[1] Weldon and Powell. Eng. Rec., 1910, =61=, 621.

[2] Clark and De Gage, 41st Annual Rpt. Mass. State B. of H. 1910.

[3] Houston. 12th Research Rpt. Metropolitan Water Board, London.

[4] Ellms. Eng. Rec., 1911, =63=, 388.

[5] Johnson. Eng. Rec., 1911, =64=, No. 16.

[6] Jennings. 8th Inter. Congr. Appl. Chem., =26=, 215.

[7] Longley. J. Amer. Waterworks Assoc., 1915, =2=, 679.

[8] Young. J. Amer. Public Health Assoc., 1914, =4=, 310.

APPENDIX

ESTIMATION OF CHLORINE IN CHLORINATED WATERS

REAGENTS. 1. Tolidine solution. One gram of _o_-tolidine, purified by

recrystallization from alcohol, is dissolved in 1 litre of 10 per cent

hydrochloric acid.

2. Copper sulphate solution. Dissolve 1.5 grams of copper sulphate and 1

c.cm. of concentrated sulphuric acid in distilled water and dilute the

solution to 100 c.cms.

3. Potassium bichromate solution. Dissolve 0.025 gram of potassium

bichromate and 0.1 c.cm. of concentrated sulphuric acid in distilled

water and dilute the solution to 100 c.cms.

PROCEDURE. Mix 1 c.cm. of the tolidine reagent with 100 c.cms. of the

sample in a Nessler tube and allow the solution to stand at least five

minutes. Small amounts of free chlorine give a yellow and larger amounts

an orange colour.

For quantitative determination compare the colour with that of standards

in similar tubes prepared from the solutions of copper sulphate and

potassium bichromate. The amounts of solution for various standards are

indicated in the following table:

PREPARATION OF PERMANENT STANDARDS FOR CONTENT OF CHLORINE

--------------------+-------------------+-----------------------

Chlorine. | Solution of | Solution of

| Copper Sulphate. | Potassium Bichromate.

Parts per million. | c.cms. | c.cms.

--------------------+-------------------+-----------------------

0.01 | 0.0 | 0.8

.02 | 0.0 | 2.1

.03 | 0.0 | 3.2

.04 | 0.0 | 4.3

.05 | 0.4 | 5.5

.06 | 0.8 | 6.6

.07 | 1.2 | 7.5

.08 | 1.5 | 8.7

.09 | 1.7 | 9.0

.10 | 1.8 | 10.0

.20 | 1.9 | 20.0

.30 | 1.9 | 30.0

.40 | 2.0 | 38.0

.50 | 2.0 | 45.0

--------------------+-------------------+-----------------------

[Illustration: DIAGRAM XV]

[Illustration: DIAGRAM XVI]

NAME INDEX

Adams, 66, 82

Bassenge, 9

Baxter, 4

Berge, 9

Berthollet, 1

Bevan, 29

Bonjean, 36

Bray, 24

Breteau, 26

Bucholtz, 5

Catlett, 99

Clark, 53, 133

Comte, 47

Cross, 29

Cruikshank, 3

Dakin, 22, 28, 129

Darnall, 89

Davy, 1

DeGage, 53, 133

DeMorveau, 3

Dibden, 6

Dienert, 48

Dienheim-Brochoki, 105

Dowell, 24

Dunbar, 6

Dunham, 129

Dupre, 5

Dusch, 4

Ellms, 34, 83, 84, 133

Elmanovitsch, 36

Elsner, 6

Evans, 84

Faraday, 103

Fischer, 16

Forcrand, 103

Fuller, G. W., 11

Gascard, 47

Griffen, 17, 79

Haberkorn, 5

Hale, 80, 100

Harrington, 34, 65

Hauser, 83, 84

Hedallen, 17, 79

Heise, 36

Henry, 2

Hermite, 5

Hewlett, 9

Hooker, 72

Horrocks, 48

Houston, 8, 59, 71, 133

Hsu, 21

Jackson, 91, 99

Jakowkin, 26

Jennings, 135

Johnson, 11, 134

Jordan, H. E., 57

Kanthack, 6

Kauffman, 9

Kellerman, 7

Kershaw, 107

Kienle, 65, 66, 90, 99

Kimberly, 7

Klein, 5

Koch, 4

Kolessnikoff, 16

Kranejuhl, 7

Kuhn, 5

Kurpjuivat, 7

Landolt, 105

Langar, 10

Laroche, 47

Lavoisier, 1, 15

Leal, 16

Lehmann, 101

LeRoy, 83

Letton, 64

Longley, 43, 135

Lunge, 105

Lyon, 24

Marshall, 102

Massy, 48

Meadows, 112, 114

McCrady, 130

McGowan, 8

McLintock, 5

Mohler, 31

Mohr, 79

Moor, 9

Muspratt, 126

Nesfield, 8, 89

Nissen, 30

Norton, 21

Novey, 23

Noyes, 24

Ornstein, 90

Orticoni, 36

Pedler, 103

Percy, 3

Pettenkofer, 101

Phelps, 7, 17, 82

Pitcher, 112

Plucker, 10

Powell, 132

Pratt, 7

Proskauer, 6, 16

Rabs, 110

Race, 36, 110, 116

Raschig, 115

Rickard, 108

Rideal, E. K., 84

Rideal, S., 6, 9, 21, 22, 60, 115, 116

Roscoe, 5

Roozeboom, 103

Rouquette, 36

Ruffer, 5

Sandman, 56

Scheele, 1, 15

Schroder, 4

Schuder, 10

Schumacher, 7

Schumburg, 10

Schwann, 4

Schwartz, 7

Semmelweiss, 4

Sickenberger, 9

Smeeton, 53

Smith, 126

Tennant, 2

Thomas, 53, 56

Thresh, 87

Tiernan, 92

Tolman, 111

Traube, 9

Valeski, 36

Von Loan, 90

Walden, 132

Walker, 87

Wallace, 92

Wallis, 83

Warouzoff, 16

Watt, 2, 3, 15, 106

Webster, 5, 105

Wesbrook, 31, 44, 53

West, 91, 99, 136

Whittaker, 31

Winkler, 84

Winogradoff, 16

Winslow, 110

Woodhead, 7

Woolf, 5

Young, 138

Zirn, 6

SUBJECT INDEX

Absorption of chlorine by water, 35

Abuse of chlorination, 144

Acids, effect of, 19, 21

Action of chlorine, 16

Admixture, effect of, 39

Aftergrowths, 55

accelerated growth, 58

_B. coli_ in, 57

effect of liquid chlorine, 99

views as to nature of, 56

Algae, effect of chlorine on, 133

Alkalies, effect of, 19, 20

Allen-Moore cell, 111

Ammonia, and chlorine, 24

and sodium hypochlorite, 114

effect on bleach, 21

effect on oxidising action, 21

soda process, 2

Antichlors, 86

Antiseptics, early work on, 3

chlorine as an, 50

Application of chlorine, point of, 43

Auto-suggestion, 62

_B. cholerae_ suis, 31

_B. cloacae_, 31

_B. coli_, aftergrowths, 57

in sewage, 6, 7

in water, 9, 28, 31

standard, 46

viability of, 52, 55

_B. cuticularis_, 53

_B. faecalis alkaligenes_, 31

_B. enteritidis_, 31

_B. enteritidis sporogenes_, 53

_B. lactis aerogenes_, 31

_B. subtilis_, 53

_B. tetani_, 9

_B. typhosus_, 9, 10, 30, 31

Bacteria surviving chlorination, 50

aftergrowths, 55

nature of, 53

spores, 57

Benzidine, 83

Bleach, analysis of solution, 79

as deodourant, 3, 6

as sewage disinfectant, 6, 7

at Adrian, 11

at Boonton, 11, 16

at Bubbly Creek, 11

composition, 14

decomposition of, 25

discovery, 2

germicidal velocity, 20, 21

hydrolysis, 18, 19

production, 3

stability of, 17

toxic action, 22

treatment, 72

control of, 78

cost, 86

dosage regulation, 75

in France, 78

losses in, 81

mixing tank, 73

plant design, 72

storage tank, 75

Brest experiments, 5

Carnallite, 1

Chicago, typhoid rate, 138

Chloramine, 114

at Denver, 124, 126

at Ottawa, 28, 116

contact period, 123

cost of, 124

decomposition of, 126

experimental results, 119

germicidal power, 116

operation of process, 126

plant design, 120

preparation of, 115

ratio of chlorine and ammonia, 116, 122

tastes and odours, 28, 64, 117

toxic action, 22, 29

Chlorides, effect of, 20

Chlorine, and ammonia, 24, 25

discovery of, 1

disinfection, effect of pabulum, 4

general reactions, 28

hydrate, 103

detection of, 81

effect on flowers, 68

estimation of, 81

in sanitary work, 4

medicinal dose, 67

oxygen equivalent, 23

liquid, 89

advantages of, 97

cost of treatment, 101

disadvantages of, 101

germicidal efficiency, 99

machines, 89

peroxide, 9

water, 102

corrosion of pipes, 69

damage to seeds, 68

decomposition of, 15

heat of formation, 27

Chlorometer, 84

Chloros, 8

Chlorozone, 105

Colour, effect on dosage, 33

Columbus, typhoid rates, 137

Complaints, 62

Contact period, effect on dosage, 44

effect on taste, 43

usual practice, 45

Cost of bleach plant, 85

bleach treatment, 86

liquid chlorine treatment, 101

Crossness experiments, 5

Dayton cell, 107

DeChlor filters, 87

Denver, chloramine treatment, 124, 126

Dichloramine, 128

Disinfectants, 50

Disinfection, early views of, 3

Dosage, 30

determination of, 46

effect of, admixture, 39

colour, 33

contact period, 43

initial contamination, 32

light, 45

oxidisable matter, 32

standard of purity, 30, 32

temperature, 34, 36

turbidity, 45

for military work, 48

regulation of bleach, 75

relation to oxygen absorbed, 36

tanks, 75

Eau de Javelle, 3, 47

Electrical conductivity of treated water, 70

Electrolysed sea water, 5

Electrolytic hypochlorite, 2, 104

Bradford, 5

Brest, 5

Brewster, 6, 105

cost of, 113

Electrolytic hydrochlorite, Crossness, 5

discovery of, 3

diaphragm cells, 110

early use of, 5

efficiency of, 109

Havre, 5

non-diaphragm cells, 106

Electrozone, Brewster, 6

Maidenhead, 6

Tonetta Creek, 6

Filter effluents, chlorination of, 34

Filters, effect on beds, 60

effect on runs, 132

Fish, effect on, 8, 67, 68

Germicidal velocity, effect of acids, 21

alkalies, 20

ammonia, 21

chlorides, 20

Guildford, chlorination at, 9

Haas and Oettel cell, 108

Halazone, 128

Hardness, effect of chlorine on, 132

Havre experiments, 5

Hermite fluid, 5

Hexamethyl-_p_-aminotriphenylmethane, 83

Historical, 1

Hooghly River, 7

Hydrazine, 126

Hydrogen peroxide, 24

Hydrolysis of hypochlorites, effect of, acids, 19

alkalies, 19

chlorides, 20

Hygienic results, 134

Hypochlorous acid, 17

decomposition of, 24, 25, 26

hydrolytic constant, 18

Initial contamination, effect on dosage, 32

Intestinal organisms, viability of, 52

Iodoform taste, 65

Iron salts, effect on dosage, 33

Jersey City, court case, 11, 16

Kellner cell, 108

Labarraque solution, 105

Leavitt-Jackson machine, 91

Leblanc process, 2

Light, effect on dosage, 45

Lincoln, chlorination at, 8, 59

Liquid chlorine, advantages of, 97

and tastes, 65

effect of temperature on, 95

machines, 89

dry feed, 94

E. B. G. Co., 91

Leavitt-Jackson, 91

operation of, 95

Wallace and Tiernan, 92

L'Orient, experiments at, 5

M. agilis, 53

Maidstone, use of bleach at, 8

Margin of safety for taste and odour, 64

Material for bleach plants, 74

Military work, bleach method for, 78

chlorine water, 103

dosage for, 47, 48, 78

early European, 10

liquid chlorine, 102

typhoid reduction, 143

use of chlorine in, 8

Mixing tank for bleach, 73

Moisture, effect on chlorine gas, 16

Montreal, dosage at, 34

electrolytic cells, 112

Nascent oxygen hypothesis, 17

Nelson cell, 111

Neva River, 36

New Orleans, typhoid rates, 137

New York, bacteria surviving treatment, 53

bleach efficiency, 100

liquid chlorine plant, 97

Nitrites, effect on dosage, 33

Nitrogen trichloride, 24, 128

Odours, effect of contact period on, 43

nature of, 63

Ottawa, aftergrowths at, 57

bleach plant efficiency, 100

chloramine plant, 120

chloramine results, 121

sludge trouble, 65

typhoid rates, 140

Oxidisable matter, effect on dosage, 32, 36

Oxychloride, Guildford, 9

Middlekerke, 9

Ostend, 9

Ozone, 24

Philadelphia and chlorination, 136

Pipe corrosion, 69

Pittsburg report, 71

Plumbo solvency, 71

_P. mirabilis_, 31

Potassium permanganate, 23

Puerperal fever in Vienna, 4

Pumps, for admixture, 41

Red Bank, sewage disinfection at, 7

Reversed ratio of counts, 54

Sewage disinfection at Baltimore,

Berlin, 7

Boston, 7

Brewster, 6

Hamburg, 6

Maidenhead, 6

Sludge, as cause of complaints, 65

Sodium bisulphite, 86

Sodium chloride, deposits, 1

decomposition of, 106

Sodium hypochlorite, 105

decomposition of, 26

effect of ammonia on, 21

hydrolysis of, 26

Sodium thiosulphate, 87

Standard of purity, 30

Storage tanks, 75

Sulphuretted hydrogen, 33

Sylvine, 1

Tannin, 67

Tastes, effect of contact period on nature of, 63

Temperature, effect on absorption of chlorine, 35, 38

bleach deterioration, 72

dosage, 34, 36

germicidal velocity, 38

pressure of liquid chlorine, 96

tastes and odours, 66

Thermophylic organisms, 54

Tolidine, 82

Toxic action of chlorine, 22, 29

Turbidity, effect on dosage, 45

effect of chlorine on, 132

Use of chlorination, 144

Water mains, disinfection of, 8

Well water, 7

Worcester, chlorination at, 11

Worthing experiments, 5

Subjects Related to this Volume

For convenience a list of the Wiley Special Subject Catalogues, envelope

size, has been printed. These are arranged in groups--each catalogue

having a key symbol. (See Special Subject List Below.) To obtain any of

these catalogues, send a postal using the key symbols of the Catalogues

desired.

_List of Wiley Special Subject Catalogues_

=1--Agriculture. Animal Husbandry. Dairying. Industrial Canning

and Preserving.=

=2--Architecture. Building. Masonry.=

=3--Business Administration and Management. Law.

Industrial Processes:= Canning and Preserving; Oil and Gas

Production; Paint; Printing; Sugar Manufacture; Textile.

CHEMISTRY

=4A= General; Analytical, Qualitative and Quantitative; Inorganic;

Organic.

=4B= Electro- and Physical; Food and Water; Industrial; Medical

and Pharmaceutical; Sugar.

CIVIL ENGINEERING

=5A= Unclassified and Structural Engineering.

=5B= Materials and Mechanics of Construction, including: Cement

and Concrete; Excavation and Earthwork; Foundations;

Masonry.

=5C= Railroads; Surveying.

=5D= Dams; Hydraulic Engineering; Pumping and Hydraulics;

Irrigation Engineering; River and Harbor Engineering;

Water Supply.

(Over)

=5E= Highways; Municipal Engineering; Sanitary Engineering;

Water Supply. Forestry. Horticulture, Botany and Landscape

Gardening.

=6=--Design. Decoration. Drawing: General; Descriptive Geometry;

Kinematics; Mechanical.

ELECTRICAL ENGINEERING--PHYSICS

=7=--General and Unclassified; Batteries; Central Station Practice;

Distribution and Transmission; Dynamo-Electro Machinery;

Electro-Chemistry and Metallurgy; Measuring Instruments

and Miscellaneous Apparatus.

=8=--Astronomy. Meteorology. Explosives. Marine and Naval

Engineering. Military. Miscellaneous Books.

MATHEMATICS

=9=--General; Algebra; Analytic and Plane Geometry; Calculus;

Trigonometry; Vector Analysis.

MECHANICAL ENGINEERING

=10A= General and Unclassified; Foundry Practice; Shop Practice.

=10B= Gas Power and Internal Combustion Engines; Heating and

Ventilation; Refrigeration.

=10C= Machine Design and Mechanism; Power Transmission; Steam

Power and Power Plants; Thermodynamics and Heat Power.

=11=--Mechanics.

=12=--Medicine. Pharmacy. Medical and Pharmaceutical Chemistry.

Sanitary Science and Engineering. Bacteriology and Biology.

MINING ENGINEERING

=13=--General; Assaying; Excavation, Earthwork, Tunneling, Etc.;

Explosives; Geology; Metallurgy; Mineralogy; Prospecting;

Ventilation.

+---------------------------------------------------------------------+

| Additional Transcriber's Notes: |

| |

| * The original symbol in Table XIV (a circled +) has been changed |

| to [也. |

| * Some formulas have been spaced out for better readability. |

| * Some minor typographical errors have been corrected (including |

| indicators for references and missing diacritical marks from |

| German words). |

| * In-line multi-line formulas have been changed to in-line single- |

| line formulas, if necessary with the addition of brackets. |

| * Inconsistencies in spelling, hyphenation, lay-out or formatting |

| have not been corrected, except in the following cases: |

| * Bassenege, Schemmelweiss, Langar and Kanthdack in the name index|

| have been changed to Bassenge, Semmelweiss, Langer and Kanthack |

| as in the text. |

| * Heisse, Jordon, Tonnetta Creek and Horrock's have been changed |

| to Heise, Jordan, Tonetta Creek and Horrocks's, respectively, as|

| elsewhere in the text. |

| * Page 35: N^{1} and N^{2} in formula changed to N_{1} and N_{2} |

| as elsewhere. |

| * Page 7: Hadallen changed to Hedallen as elsewhere in the text. |

| * Changes made to the text: |

| * Page 17: --> changed to <=> in chemical formula as described in |

| the text. |

| * Page 26: H^{.} + HCO_{3} changed to H^{.} + HCO_{3}'. |

| * Page 26: chlor-ions changed to chlorine ions. |

| * Page 54: Gention Violet changed to Gentian Violet. |

| * Page 103: Footnote marker [11] inserted (missing in original). |

| * The author called Kurpjuivut, Kurjuivut and Kurpjuivat in various |

| places in the text is probably called Kurpjuweit. The author |

| called Schumburg and Schumberg in the text is called Schumberg. |

| The book contains references to both Zaleski and Elmanovitsch |

| and Valeski and Elmanovitsch; Zaleksi is probably correct. |

| * Other remarks: |

| * Footnote on Page 119: fraction unclear in the original, |

| presented here as 5-1/2. |

| * Page 134: affluents should probably be effluents. |

| * In the original work, there is no TABLE XXII between TABLE XXI |

| and XXIII. |

+---------------------------------------------------------------------+