REVIEW. 
183 
than as constituting a given volume of positively deleterious matter. 
Hence extremely minute quantities taken into the system are capable of 
producing very extensive mischief.” 
Mr. Coiidy goes on to say that— 
“ The detection of organic matter in water had long presented serious 
difficulties to chemists, who were obliged to have recourse to very tedious 
methods, based on the estimation of the amount of nitrogen and carbon 
contained in the deposit formed by the evaporation of the water submitted 
to examination. Having for many years been in the habit of using the 
alkaline permanganates for the removal of organic impurities from certain 
'liquid substances, which, as a manufacturing chemist, I was engaged in 
making, I had my attention early directed to tlie part which tiiose salts 
were capable of performing in tiie purification of water. After satisfying 
myself that the action of tliose substances could with certainty be relied on 
for the detection and practical estimation of varying quantities of organic 
matter, in the year 1856 I communicated my method to several of our 
leading chemists, who verified my experiments and reported favorably of the 
advantages of my method.” 
“But the action of the permanganates is not limited merely to the testing 
of water for organic impurities; the properties possessed by those sub¬ 
stances, of rapidly decomposing organic matter, and making manifest to the 
eye their effects, render them admirably suited to the purijicalion of water 
employed for drinking, cooking, and general domestic purposes. Com- 
])osed of oxygen in combination with manganese, the mildest and most 
wholesome of the metals, and one or other of the alkalies, the alkaline per¬ 
manganates can hardly be supposed capable of proving injurious even when, 
from haste or carelessness, a trace of them in solution or a minute portion 
of binoxide of manganese in suspension may remain in the water treated; 
for it has recently been shown that manganese is one of the normal con¬ 
stituents of the blood, and that in some of the very healthiest races of men, 
such as the Scotch, who are fed to a great extent on oats, a cereal which 
contains that metal, it is always present in the body. Indeed, it is ex¬ 
tremely probably that manganese is a requisite constituent of the human 
frame, and that its entire absence is not conducive to health. The nature 
of the reaction which takes place. between those compounds and organic 
matter is, moreover, such, that when they are used with caution, and not in 
excess, the whole of the metallic ingredient present is separated by preci¬ 
pitation in the solid form, leaving in the water only the alkali which had 
been in combination with it. xis most waters, by reason of a certain 
portion of carbonic acid which they contain, hold in solution, in the form 
of bicarbonate, a small quantity of carbonate of lime, the presence of this 
free alkali is rather an advantage than the contrary, since by neutralizing 
the excess of carbonic acid it converts the more soluble bicarbonate into a 
less soluble carbonate, which then subsides as a deposit, leaving an alkaline 
carbonate in its place.” 
vS * * % 
“ The importance of using only soft water in pharmaceutical operations 
is admitted on all hands. Medical men, in prescriptions requiring water, 
uniformly order aqua pura or aqua destillata. But there is one very im¬ 
portant purpose to which water is now very extensively put in surgery, 
namely, ‘ water dreasings,’ in connection with which sufficient attention is 
seldom paid to the quality of the M^ater employed. Miss Nightingale, with 
that practical tact which distinguishes all her observations on hospital 
economy and the management of the sick, has well pointed out the preju¬ 
dicial effects produced by the use of impure water for dressing wounds, as 
