294 
ON THE DETERMINATION OF ORGANIC MATTER IN WATER. 
if not entirely of animal origin, being drained, with the water of streams, from 
manured land or percolating through the soil with other constituents of sewage. 
A glance for a moment at such a consideration, remembering also that these 
substances are constantly undergoing oxidation by exposure of the water which 
contains them to the influence of the air, will furnish sufficient evidence of the 
fact that the nature of the organic constituents of water must differ in each 
particular instance. 
It follows from this that all the processes which have hitherto been in use for 
the determination of the substances classed as “organic matters,’’ fail entirely 
of their object. 
In the first place they do not indicate what they pretend,—the aggregate 
weight of carbonaceous matter ; or, if that were possible, they make no distinc¬ 
tion between such as is comparatively harmless (i.e. non-nitrogenous) and that 
which is in the highest degree poisonous. 
An account of experiments with a view to improvement in this direction will 
be found further on. 
Determination of Organic Matter by Ignition .—The original process for the es¬ 
timation of organic matters consisted in the evaporation to dryness of a known 
quantity of the water under examination, taking the weight of the dry residue 
and again weighing after exposure to a dull red-heat. By this means, it is plain, 
other loss occurs than that which is alone due to carbonaceous matters, inas¬ 
much as ammoniacal salts would be expelled together with a certain amount of 
water, hydrochloric acid, from magnesium salts principally, and carbonic acid 
from carbonates. 
And this plan was adopted until comparatively recently, when analysts came 
to appreciate more accurately the extremely unsatisfactory and misguiding na¬ 
ture of the results so obtained. 
The first improvement consisted in the addition of a known quantity of car¬ 
bonate of soda previous to evaporation ; then, when the weight of the residue 
is ascertained, this weight is simply deducted. If it be intended to evaporate a 
quart of water, about four or five grains of fused carbonate of soda should 
be ctdded. The drying of the residue must be completed in an air bath, the 
temperature of which should be maintained for an hour at 280°, or not exceed¬ 
ing 300° Fahr.; a careful weighing is then made and the organic matter is burnt 
off at a red heat barely visible in daylight. 
After the residue has been ignited, the saline mass is covered with two or 
three ounces of a solution of carbonic acid in distilled water. The contents of 
the crucible must then be again evaporated to dryness, and the residue main¬ 
tained for an hour at the same temperature as that employed in the original 
desiccation. Another careful weighing must then be made. 
In this manner a result will be arrived at which is certainly less inaccurate 
than that obtained without the use of the carbonate of soda, but even here 
error will arise from various causes. For example, should the water contain 
nitrates or nitrites resulting from the oxidation of nitrogenous substances, the 
organic matters in the residue will, on ignition, effect their more or less com¬ 
plete decomposition. 
Use of Permanganate of Potash. —Attempts have been made at different 
times to apply to the purposes of water-analysis, the well-known property pos¬ 
sessed by permanganate of yielding oxygen to all oxidizable substances. The 
process founded upon this reaction, although undoubtedly leading to fallacious 
conclusions, has been in extensive use ; it will therefore be necessary to describe 
it. 
A solution of permanganate is prepared, such that 10,000 water-grain 
measures shall, in an acidulated solution, exert an oxidizing power equal to one 
grain of oxygen. For this purpose 3*95 grains of pure crystallized permanga- 
