The Londonderry sifter. (South Londonderry, Vt.) 1883-19??, 1888-10-11
TESTING DRINKING WATER.

Unsatisfactory Results which Are some-
times Obtained Tests.
We are giving more and more attention
TO the purity of drinking water as 1t be-
comes more apparent that infection oral-
most every kind travels by water. II be-
comes OF the highest Importance to know
whether the tests usually resorted to for
the detection Of organic impurities are
trustworthy. II dangerous impurities
slip past these tests. they afford no pro-
lection against the transmission of dis.
ease germs, The Sanitarian prints pa.
per by DR.. j. A. Tanner, of Boston, giving
results of some of his experiments in this
direction, which may almost be called
startling.
DR.. Tanner declares boldly that the
chemical processes relied upon for testing
water are las apt to condemn good
water as they are to commend it, and to
commend an impure water when they
should condemn it," and his statements
go far to support his theory For example,
II 8 per cent. of milk or any beef extract
be added to a gallon of distilled water the
processes will condemn It as impure be.
cause it contains organic matter. Add a
rev million of disease germs to gallon
OF distilled water and none Of the pro-
ccsses will discover them, because the
quantity of organic matter is not large
enough. Yet the one mixture is entirely
harmless, and the other, if we accept the
germ theory, is dangerous. The combus-
ton process relies upon the proportions
found of carbon and nitrogen; the am.
monia process upon the presence of free
ammonia and albumoid ammonia; the
permanganate process upon the amount
OF oxygen required to oxidize the organic
matter. All of these tests are extremely
delicate, and slight inaccuracy is enough
TO cause an impure water to be rated as
pure, or the opposite.
The fact that they disagree wildly In
their results with the same water is
enough to shake faith in all of them. DR..
Tanner shows this by reference to the In.
vestigation conducted by Professor ].
Mallet for the national board of health
some years ago, with which he was con-
nected. Nineteen samples Of natural
water, believed from actual use to be
wholesome. were examined by these pro-
cesses. They agreed that ten were pot
able and three were not, but as to six, or
one-third of the number, they disagreed |
totally. Then nineteen samples were |
taken Of natural waters which there
seemed to be fair grounds for believing
have actually caused disease" But only |
four of these were rejected as unwhole-
some. as to nine, or one-half, there was
no agreement, and six, or one-third, were
pronounced wholesome by all the pro-
cesses. Then twenty samples were taken
of natural water Of doubtful but sus-
pected character, and as to these the re-
suits were really more unfavorable than
as to the waters known to be dangerous.
The most remarkable of all the tests
were with twenty samples of good water,
to which were added various pollutions,
such rs sewage from various sources,
black vomit and like offensive and poison
GUS substances. Only eight of these
samples less than half were condemned
by all the processes; as to nine the re-
ports did not agree, and three the pro-
cesses actually concurred in pronouncing
good Water, to which enough of weak
mixed sewage from large public sewer
had been added to create, it was believed,
serious danger of typhoid, was pro-
nounced to be Of great organic purity" by
two processes, and good" by the third.
A larger admixture Of the same sewage,
as much as per cent. was pronounced of
medium" quality by two processes, and
dad" by only one Even more striking
could be given Yet the same
processes condemned as impure the Lake
Drummond water from the Dismal
swamp, which is in part the water sup
ply of Portsmouth, Va, and the Cochitu-
ate of Boston, simply because Of the
presence of vegetable matter contributed
by leaves, roots, etc.-New York Tribune.