Table III contains details as to the lines of experiments, the strengths of the
solutions, and results of titration for the percentage of available chlorine in the
solutions ( a) soon after they were made, (b) a week later, and (c) 16 days later. It
will be seen that a 10 per cent solution keeps better after 16 days and loses compa
-
ratively smaller quantities of the chlorine than solutions of higher strengths.
Lower strengths are not to be preferred, from the point of view of bulk.
TABLE IV.
Results of Bacteriological Examination.
Sample.
Lactose fermenters in ? c.c.
Total count.
Nature of the colonies.
28th July 1919.
Adyar water . . . 0.01 c.c. and upwards . . .
Countless
(on nutrient agar.)
Bacilli and a few spores.
Flask which received 5 c.c. of
Bleaching powder test solu-
tion.
15 c.c. and upwards . . .
950 per c.c.
(on nutrient agar.)
Majority were spore
bearers.
Flask which received 6 c.c. of
Bleaching powder test solu-
tion.
30 c.c. and upwards . . .
540 per c.c.
(on nutrient agar.)
Do.
12th August 1919.
Adyar water . . . 0.1 c.c. and upwards . . .
650
(on McConkey's agar.)
Lactose fermenters.
Sample from flask which re
-ceived 5 c.c.
60 c.c. and upwards . . .
10
(on McConkey's agar.)
Do.
Sample from flask which re-
ceived 6 c.c.
None in 60 c.c. . . .
Nil
(on McConkey's agar.)
Nil.
Table IV gives the results of the bacteriological examination of untreated
Adyar water and the same treated with the proper dosage of the above solution
16 days' old. The proper dosage was determined by the field-test advocated by
Prof. Sims Woodhead. The bactericidal power of the stored solution was thus
found to have been maintained unimpaired.
From these experiments the following conclusions are justifiable:
—
( 1 ) A t e n p e r c e n t s o l u t i o n o f B l e a c h i n g p o w d e r c a n b e p r e p a r e d a n d s t o r e d
for a fortnight and perhaps longer, without the available chlorine diminishing in
quantity to any appreciable extent.
(2) Exposure of the solution to diffuse light does not appear to affect its
bactericidal properties.
(3) The solution even when stored in bottles without stoppers, does not lose
its available chlorine content to any marked degree.
(4) It is effective as a bactericidal agent and can be relied upon for water
sterilisation.
About the close of the year under report, a churning apparatus for preparing
solutions of Bleaching powder in bulk was made ready on the model of churns used
in Mesopotamia and it was found to yield a very satisfactory product. It has just
now been lent to the Municipal Council of Kumbakonam for use in connexion
with the chlorination of tanks and wells during the ensuing Mahamakham festival.
(4) Research Work in connexion with the Experimental Filter Installation.
In January of the year Major J. Cunningham I.M.S. and M.R.Ry. T. N. S.
Raghavachari, B.A., contributed a paper to the Indian Science Congress held at
Nagpur, entitled "Observations on the purification of water by filtration." This
paper embodied the results of research work conducted at the Institute between
1913 and 1919.
In February Major Morison, I.M.S., who had made a special study of the
questions relating to water purification both at Poona and in Mesopotamia,
happened to visit Madras and advantage was taken of his presence to discuss
certain important factors connected with the research work carried out at the
Guindy Experimental Filter Installation.