April 1,1871.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
781 
WATER ANALYSIS. 
the estimation of organic matter and 
NITRATES IN POTABLE WATERS * 
BY CHARLES EKIN, F.C.S., 
PRESIDENT OF THE BATH CHEMISTS’ ASSOCIATION. 
Whilst referring for details to the several me¬ 
moirs that treat of the subject, I propose to pass 
briefly in review the various methods now or lately 
in use for the estimation of organic matter in potable 
waters, and then to make a few remarks on the value 
to be attached to the presence of nitric acid. 
The old process of incineration, so far as the loss 
of weight bears any proportion to the amount of or¬ 
ganic matter, is now universally discarded, and no 
doubt rightly so, at the same time one is much helped 
in forming a judgment of the wholesomeness of a 
water by heating to redness the residue obtained by 
evaporation. If it blackens or has a decided empy- 
reumatic odour, there cannot be much doubt as to 
its character. 
The permanganate test, though not by any means 
to be relied upon by itself, sometimes gives valuable 
confirmatory evidence. The deoxidation may, how¬ 
ever, be due to the presence of a proto-salt of iron or 
of alkaline nitrites. If the latter, the bleaching 
takes place in a very few seconds, and it can con¬ 
sequently be at once distinguished and measured 
separately from the reducing effect occasioned by 
organic matter, which is always gradual. I find 
iron to be frequently present in waters which have 
passed through iron mains, and when we consider 
also how widely-distributed this metal is, it is mani¬ 
fest that we must be very careful to ascertain its 
absence before we attribute any bleaching of the 
permanganate to organic matter. All the strata, 
and therefore the springs in and about Bath, contain 
very appreciable quantities of iron; and where this 
is the case, the permanganate test is almost useless. 
Yet, notwithstanding this, Dr. Letheby, relying upon 
this method alone, undertakes to speak authorita¬ 
tively upon the purity of waters, as in the case of the 
samples sent up to him by the Bath Corporation a 
year or two ago. 
Frankland and Armstrongs method—although hi 
the hands of such excellent chemists as themselves 
it may yield good results—is altogether too elaborate 
and troublesome to come much into use, especially 
as the alternative process of AVanklyn offers so many 
advantages. The details of this latter process, which 
is now generally acknowledged to be the best yet de¬ 
vised, has been so thoroughly explained in AVanklyn 
and Chapman’s little treatise that I need not take up 
your time by dwelling on it here. Having had a 
tolerably extensive experience in working it, I can 
thoroughly indorse all that has been said in its 
favour as an improvement upon the older methods; 
but I hope the da}' - is not far distant when this even 
will be replaced by a process yet more satisfactory. 
Where sewage is present in a water, it is invari¬ 
ably accompanied by an abnormal quantity of chlo¬ 
rine, but the reverse by no means holds good. I 
find that the quantity of soluble chlorides varies so 
much in different strata, that the estimation of chlo¬ 
rine is quite useless as a comparative test between 
different waters; but it is certainly valuable when 
* This paper was read at a meeting of the Bath Che¬ 
mists’ Association, February 3rd. 
Third Series, No. 40. 
it is wished to examine the same water at different 
times. Thus, the Birmingham water last autumn 
was regarded with more than suspicion when it was 
found that the chlorine had increased in it from 
1*41 parts in 100,000, in May, to 7T4 parts in 
100,000, in August. 
Last autumn, too, the Bristol supply, generally so 
good, was found to be offensive, and to contain a 
good deal of ammonia, and Mr. Stoddart was re¬ 
quested to investigate the cause. Finding that the 
quantity of chlorine in the water had not increased 
above its normal rate, he was enabled at once to say 
that there was no contamination by sewage; and it 
was then found that, owing to the lowness of the 
water, and the exceptional summer, there was pre¬ 
sent in the reservoir a large accumulation of decom¬ 
posing diatoms, which had, no doubt, given rise to 
the impurity. 
Of the fermentation test by means of sugar I have 
had no experience, but I am not sanguine that it 
will be found of much practical use. 
The oxygen of atmospheric air is soluble in water 
in the proportion of one part to two of nitrogen; and 
if a less proportion than this is found, it may fairly 
be concluded that it has been used up in oxidating 
sewage or other organic matter present in the water. 
The estimation of the proportion of oxygen to 
nitrogen, in conjunction with Wanklyn’s plan, sel¬ 
dom leaves any doubt as to the character of a water. 
It has always been supposed that, with the excep¬ 
tion of the small proportion of nitric acid present in 
rain water, the nitric acid to be found in spring- and 
well-waters is to be referred to the oxidation of sew¬ 
age in some shape or other, but I have ascertained 
that this is by no means the case. In a paper read 
before the Chemical Society last month, I showed 
that the result of several analyses of rocks and 
fossils collected in this neighbourhood was to prove 
that they all contained nitric acid in greater or less 
quantity. Thus, grey chalk marl contained IT part 
of combined nitrogen in 1,000,000; Bath oolite, T3 
parts; fossils from the greensand, 2'23 parts; fossils 
from the lias, 3'6 parts; fossils from the fuller’s 
earth nearly 3 parts, and inferior oolite rock, which 
is almost entirely made of fossils, 7'6 parts. 
Although it is surprising that such soluble salts 
as nitrates, which probably resulted from the oxida¬ 
tion of organic beings that existed countless ages 
ago, should still be found in the different strata, it is 
not entirely without parallel. In one of the very 
first formations in which evidence of organic life is 
found, namely, in the Caithness Flags, Sir Roderick 
Murchison says that the bitumen found there is un¬ 
doubtedly due to the numerous fishes of the period, 
and this bitumen, when analysed by Dr. Hofmann, 
yielded 30 per cent, of organic matter and ammonia. 
We find, too, from Watts’s ‘Dictionary of Che¬ 
mistry,’ that such substances as fossil teeth still 
contain a large proportion of their original organic 
matter. 
Thus Rhinoceros teeth contained . 23 - 03 per cent. 
Elephas primig.enius . . . 15 6 „ 
Cave Bear. 23*45 „ 
Fish, Acrodus.2T7 „ 
Fish from the Chalk . . . ’54 ,, 
If then organic matter even can exist as Such, 
through indefinite time, we shall cease to wonder 
that salts, the result of the oxidation of organic 
matter, should also be found. 
