7 £4 14 oo. .
Cs. } Ferment-Theory of Nitrification. 269
haps have been dragged over mechanically from No. 8 by all, and during this time air was drawn from the furnacehe
 current of air. box and purified as before. The contents of the bottles
A second series of tests was made upon Nos, 8, 9, and were then tested for nitrites and nitrates, but no reaction
10, to see which of them gave the weakest reaction, was obtained in either case. To make sure that the ab-25
 c.c. of liquid being taken from each bottle and diluted sence of the reaction was. not due to any interference
with pure water to the volume of 100 c.c. before applying caused by the presence of the peat or the chemicals, a
the test. Itappeared again that No. 10 gave the strongest resh portion of liquid was taken from each of the bottles ;
-eation, and that No. 8 gave the weakest. Roughly esti- znough nitrate of potash to amount to 0-001 grm. of N;Og
mated, the strength of the reactions from jars Nos. 10,9, was added, and the test for nitrites and nitrates was
and 8 were to one another as 5:2: 1. applied in the usual way : reactions were now obtained
It may here be said that humus was employed in these 'mmediately in every instance.
experiments for the sake of testing the old observation of In the light of the fa@s observed by Schlésing, the
Millon,* who noticed that ammonium salts are changed natural inference from the results of these experiments is
0 nitrates when in conta@ with oxidising humus, and that the formation of nitrates or nitrites in bottles Nos. 7
who argued that the chemical action, originated by the !o 10 of the first series of experiments was due to the precoming
 together of humus and oxygen, was communicated sence of living organisms which the peat had harboured,
io the ammonium compound. In his own words—* The and that the absense of nitrification in the other series of
oxidation of the humic acid is the cause of the oxidation sxperiments is to be attributed to the destruction of the
of the ammonia.” . ‘erment-germs by the hot acid with which the peat em-In
 so far as the foregoing experiments go, we have >loyed in these experiments had been treated. Itis to be
manifestly a striking confirmation of the accuracy of >bserved, moreover, that the formation of nitrogen oxides
Millon's work. But on repeating the experiments—with n the bottles Nos. 7 to 10 is in nowise out of accord with
:he difference that the bog-earth was henceforth exhausted :he important fa& observed by Warington, that darkness*
with hot, strong, muriatic acid, before proceeding to wash .s essential to the aétion of the nitrifying germs, for alit
 with water —no such results as the foregoing were ob- hough my bottles were not shielded from diffused dayrained.
 For example, in a second series of trials, arranged light, the mixtures of peat and water which they conlike
 the first, the contents of bottles Nos. 1 to 6 wers tained were practically dark coloured muds, not ill-fitted
identically the same as before, only that the amount of to shelter the germs from the light.
.iquid was now 150 c.c. instead of 250 c.c. No. 7 con- [tis possible of course that the colder weather which
tained the purified peat mixed with water; No. 8 wasthe prevailed during thelater trials may have had an influence
same as No. 7, plus a quantity of gypsum ; No. g was the upon their results: but if this be so, the fa& must be
same as No. 8, plus some ammonium chloride ; No. 10 counted as an additional argument in favour of the ferment
contained water alone; No. 11, purified peat, plus ammo- :heory. Moreover, it may fairly be inferred that if mere
nium chloride and ferric hydrate; No. 12, well-washed oxidation be all that is needed to induce nitrification, the
cotton rags, plus ammonium chloride and ferric hydrate; neating of the liquids by day in the third series of experi-No.
 13, purified peat, plus ammonium chloride ; No. 14, ments would have been sufficient; thoughboth the strong
pure water ; No. 15, pure water, the same, namely, which heat and the cooling of the bottles by night would have
had already done service (as No. 11) in the first series of tended to prevent the growth of living organisms.
sxperiments. In the interest of the ferment theory, it would have
The weather (O&ober 13, 1877) being too cold to permit been well to control the negative results above given by
:he keeping open of a window, the current of air, purified trials with mixtures of the purified peat and carbonate of
as before, was drawn from the cold-air box of the hot-air ‘ime, for peat which has been treated with muriatic acid
furnace used for warming the laboratory. The current of has always a slight acid reaction, due I suppose to free
air passed this time in the direction from No. 1 to No. 15; 1umic acid, no matter how thoroughly it may have been
it was maintained constantly during ten days, and the washed with water, and it is to be supposed that this acid
:ontents of the bottles were then tested as before for peat, devoid withal of phosphatic and other saline matters,
nitrites and nitrates. But no reaction was obtained in is not favourable for the growth of the ferment. But, as
sither instance, with the exception of No. 12 (cotton rags, was said before, my experiments were made to test the
%c.), which gave a faint colouration of a not very satis- oxidising aion of certain chemicals, not to cultivate
fadory chara&er. After the application of the test, those living organisms. .
of the bottles which still contained a sufficiency of liquid It may be added that I have not as yet found any eviwere
 re-attached to the aspirator, and air was drawn dence that solutions of ammonium compounds can be
through them continually during another week, when the oxidised to nitrites or nitrates by means either of ferric
iest for nitrites and nitrates was again applied. But in
no case was there any reaction, with the exception of
bottle No. 8, whose contents gave a faint colouration.
Inasmuch as warm, and, at times, hot summer weather
nad prevailed during the term of the first series of experiments,
 while the out-door air was decidedly cool, and that
of the laboratory by no means very warm during the time
allotted to the second series, a third set of trials was
undertaken in December, 1877, in which the contents of the
sottles where heated artificially, That is to say, the
bottles were immersed in a large water-bath, which was
heated to from 70° to 80° C. during the progress of the
Experiment. :
In this third series, there were eight bottles containing
‘he purified peat, first by itself, then admixed with gypsum;
 with gypsum and ammonium chloride ; and with
ammonium chloride and ferric hydrate. One bottle contained
 washed cotton rags, ammonium chloride, and ferric
hydrate as before. The water-bath was heated during
working hours for a fortnight, perhaps a hundred hours in

The following statement has a certain interest for analysts as
yearing upon the stability of dilute solutions of ammonium chloride.
in February, 1877, it was noticed by my assistant, Mr. Lewis, that a
solution of ammonium chloride, which had been prepared ten or
:welve months previously for use in connection with Nessler's test,
by dissolving the salt at the rate of 3'15 grms. to the litre, now gave a
itrong reaction for nitrites, although freshly prepared solutions, made
n the same way from like materials, gave no reaction. The old
solution was contained in a glass stoppered vessel, which was about
aif fied by it, and it had been kept most of the time in a dark
cupboard.
A®ing on the supposition that the change of the ammonium salt to
1 nitrite had been caused by the growth of some fungus ia the liquid,
ind that such fungus might perhaps be present in other bottles in the
seighbourhood, I collected as many different specimens of moulds as
sould be found growing in the various saline solutions kept in the
laboratory, and, after rinsing with pure water, placed them in a series
»f half-gallon bottles, into which had been poured from halfto quarter
of dilute ammonium chloride, such as is used for Nesslerisimng, A
quantity of mother of vinegar also was placed in a similar bottle.
This series of bottles was left to stand during early autumn, ani
winter ina greenhouse, in a rather strong light, and the solutions wer :
rested from time to time, at intervals of three or four weeks, but no
reaction for nitrites or nitrates could ever be obtained from either o¢
the bottles. The experiments of Warington show that these trials
were vitiated by the strong light to which the bottles were exposed.
It is not altogether unlikely that different results would have been
-eached if the bottles had been kept in the dark.

* Kopp and Will's Fahresbericht der Chemie, 1860, xiii, 103, and
864, xvii.. 158,