724

THE COLLIERY GUARDIAN.

October 8, 1916.

/ = 7,205; and mononitronapbthalene, 3-48 per cent.;
nitrate, 96-52 per cent.; t = 1,554 degs., / = 6,618.

Ammonium nitrate and mononitrotoluene :—Limit
mixture, mononitrotoluene, 9*95 per cent.; nitrate,
90-05 per cent.; t = 2,174 degs.; f = 8,632. Inter-
mediate mixtures, mononitrotoluene, 5*4 per cent.;
nitrate, 94*6 per cent.; t = 1,713 degs.; f = 7,156; and
mononitrotoluene, 3’67 per cent.; nitrate, 96*33 per
cent.; t = 1,518 degs.; f ~ 6,500.

Ammonium nitrate and binitronaphthalene, :—The
limit mixture corresponds to ordinary Favier No. 1
explosive, viz., 1 molecule of binitronaphthalene and 19
molecules of nitrate; t = 2,229 degs.; f — 8,650. Inter-
mediate mixtures, “ Grisounaphthalite Roche,” and
binitronaphthalene, 6*37 per cent.; nitrate, 93-63 per
cent.; t = 1,707 degs.; f ~ 7,067.

Ammonium nitrate and binitrotoluene :—Limit mix-
ture, binitrotoluene, 14'89 per cent.; nitrate, 85*11 per
cent.; t = 2,244 degs.; f = 8,677. Intermediate mix-
ture, binitrotoluene, 5*38 per cent.; nitrate, 94*62 per
cent.; t = 1,549 degs.; f — 6,546.

Examination of the curves (from which the t values
have been omitted to prevent complication) shows that,
for all the ingredients high in carbon and low in nitro
products, very small proportions of the combustible
ingredients must be taken in order to obtain explosives
with a detonation temperature of 1,500 to 1,900degs.,
and though in some instances the / values appear
interesting, the explosives are difficult to employ in
consequence of their great insensibility. For example,
the naphthalene mixture detonating at 1,500 degs. con-
tains only a little over 2 per cent, of naphthalene; and
mixtures of this kind would be certain to give rise to
numerous mis-fires in practice. On the other hand,
binitro- naphthalene and toluene mixtures are higher in
combustible, and furnish interesting explosives, “Grisou-
naphthalite Roche,” for example.

Fig. 2 gives the curves (up to complete-combustion
limit) obtained with more highly nitrated ingredients,
including trinitrotoluene, trinitronaphthalene, picric





Values of f.

3000°

9000

HOOP

7000

5000

1?3s‘

Content of ammonium nitrate.

BL

co

o

te delacombu -(ioo
mileteenCO

<o

J7

#7

wn

W41

Fig 3.—Trinitronaphthalene and Ammonium
Nitrate.

acid, endecanitrocellulose and nitroglycerine, the binitro-
naphthalene and toluene curves being added for the
sake of comparison.

Ammonium nitrate and trinitronaphthalene :—Limit
mixture, trinitronaphthalene, 16*61 per cent.; nitrate,
93*39 per cent.; t = 2,298 degs.; f = 8,710. Inter-
mediate mixtures, “ Grisounaphthalite couche ” without
saltpetre; t ~ 1,500 degs.; f = 6,388; and trinitro-
naphthalene, 7*59 per cent.; nitrate, 92*41 per cent.;
t = 1,681 degs.; / = 6,944.

Ammonium nitrate and trinitrotoluene :—Limit mix-
ture, trinitrotoluene, 21*30 per cent.; nitrate, 78*70 per
cent.; t = 2,352 degs.; f = 8,833. Intermediate mix-
tures, trinitrotoluene, 16-8 per cent.; nitrate, 83*2 per
cent.; t = 2,117 degs.; f — 8,205; and trinitrotoluene,
11-9 per cent.; nitrate, 88*1 per cent.; t = 1,837 degs.;
/ = 7,403.

Ammonium nitrate and picric acid .-—Limit mixture,
picric acid, 30*58 per cent.; nitrate, 69*42 per cent.;
t = 2,507 degs.; / = 8,932. Intermediate mixture,
picric acid, 15*17 per cent.; nitrate, 84*83 per cent.;
t = 1,833 degs.; / = 7,277.

Ammonium nitrate and endccanitrocellulosc :—
Endeca., 41*07 per cent.; nitrate, 58*93 per cent.;
t — 2,561 degs.; f9,076. Intermediate mixture,
Endeca., 19*23 per cent.; nitrate, 80*77 per cent.;
t = 1,825 degs.; / = 7,266.

Ammonium nitrate and nitroglycerine :—Since all the
mixtures give complete combustion, owing to the excess
of oxygen in both ingredients, it was only necessary to
select intermediate mixtures, nitroglycerine, 48*61 per
cent.; nitrate, 51*39 per cent.; t = 2,297 degs.;
f = 8,248; and nitroglycerine, 73*94 per cent.; nitrate,
26*06 per cent.; t = 2,881 degs.; f = 9,323. The values
for pure nitroglycerine are : t = 3,469 degs.; / — 10,084.

One prominent feature exhibited by the curves is the
small difference in the / value of all the mixtures, both at
1,500 and 1,900 degs., viz., about 200 at the former
temperature, and 300 to 400 at the latter. This makes
it difficult to foresee the possibility of discovering a new
mixture of this type with some other combustible
ingredient, to obtain a more powerful explosive than the
safety explosives now in use, whether such new mixture
contain two or more ingredients.

The second part of the investigation relates to mixtures
in which the main ingredient furnishes insufficient oxygen
to convert all the carbon present into carbon dioxide and
all the hydrogen into water. The examination was con-
fined to the mixtures of fig. 2, those of fig. 1 being of
merely slight interest in this connection. In all the
compounds the problem becomes singularly complicated
when the limit of complete combustion is exceeded,
owing to the uncertainty whether the products of
combustion will consist for the most part of C02 or CO,
whether of water vapour or hydrogen, and whether CH4
will be formed at all. The rule that, when the supply of
oxygen is insufficient, CO is produced first, and that the
remaining oxygen will go partly to form CO2 and partly
to form water, does not take into account the produc-
tion of CH4, which is not infrequently found in the
gases. Even the bomb test, with analysis of the pro-
ducts, is liable to cause error, since the gases may react
among themselves between the moment of detonation
and the time of analysis in the cooled condition. It wras
therefore decided to make a theoretical study of the
various decompositions possible, and to trace curves
corresponding to the maximum production of CO2,
maximum of CO, etc. With this object, different
formulae of decomposition were established for a mixture
with a high percentage of combustible ingredient, on the
basis of the admitted hypotheses, and the values of t and
f were calculated for each hypothesis, the intermediate
points thus obtained enabling the different curves to be
traced.

As an example, a mixture of ammonium nitrate and
trinitronaphthalene was employed, the proportion of the
latter being raised above the limit of complete combus-
tion (16*61 per cent.) to 24*72 per cent. The effect of
the explosion of this mixture was calculated in accord-
ance with four different assumptions : Maximum produc-
tion of CO2 (value of /' = 8,856, t' — 2,262 degs. Cent.);
maximum of CO (f2 = 8,455, t2 = 2,156 degs. Cent.);
production of CII4 and CO (/3 = 8,659, t3 =
2,321 degs. Cent.); production of CH4 and CO2 (/4 =
8,790, tA = 2,360 degs. Cent.). With a mixture of 35*4
per cent, of trinitronaphthalene and 64*6 per cent, of
nitrate, the calculation for a maximum of CO2 gives the
values : f = 9,027, t’ = 2,209 degs. Cent.; for maximum
CO : f2 = 8,093, t2 = 1,952 degs. Cent.; for CH4 and CO :
f;t = 8,668, t3 — 2,450 degs. Cent.; and for CH4 and CO2 :
/4 = 8,896, t4 ~ 2,512 degs. Cent. Again, with a mix-
ture of 52*28 per cent, of trinitronaphthalene and 47*72
per cent, of nitrate, the values are : For maximum CO2 :
f ~ 8,377, t' =-- 1,897 degs. Cent.; for maximum CO :
f2 — 7,516, t2 ~ 1,674 degs. Cent.; for CH4 and CO : /3
— 8,818, t3 = 2,817 degs. Cent.; and for CH4 and CO2 :
/4 — 9,000, t4 ~ 2,878 degs. Cent. When the proportion
of trinitronaphthalene is increased to 71*19 per cent., the
limit at which no CO2 can be formed without the simul-
taneous formation of CH4 is attained; and in this case
the value for / = 4,848, and that for t~ 1,295 degs.
Cent. Beyond this point the mixtures do not detonate
at all.

The curves relating to the foregoing mixtures are
plotted in fig. 3, and curves for the other mixtures
referred to above were also determined. In order to
ascertain which of them approximates most nearly to
practical results, the Trauzl test was applied to a number
of mixtures, starting with the complete-combustion mix-
tures, and comparing the dimensions of the cavities pro-
duced in the Trauzl blocks with the theoretical values of
f. That proportionality should exist between the two
results is evident from the discovery of Taffanel and
Dautriche that, for explosives containing an excess of
oxygen, decomposition in an enclosed space agrees
closely with the theoretical decomposition.

As a typical example, the limit mixture of nitrate and
binitronaphthalene (12*6 per cent.) may be taken, which
gives a cavity of 294-9 c.c. in the Trauzl block (the /
value of No. 1 Favier powder being 8,633). If now,
Roche “ grisounaphthalite ” (8-5 per cent, of binitro-
naphthalone) be considered, the calculated theoretical
value of / is about 7,700, whilst the calculated actual
value from the Trauzl test (cavity 269-5 c.c.) is
(259*5 X 8,633) -e 294*9 = 7,889, which may be regarded
as fairly close. Similarly, the limit mixture of trinitro-
toluene and nitrate gives the value of / as 8,833, the
cavity measuring 329 c.c.; and again, the mixture con-
taining 11*9 per cent, of trinitrotoluene, having the
calculated value / 7,403, gives the value 7,705, the
cavity measuring 287 c.c. With the binitrotoluenc
mixtures also, the results wore fairly close, the differ-
ences between the two calculations for f being only
200-300. It may therefore be assumed that the
theoretical calculations fairly represent the truth for
mixtures containing sufficient, or more than sufficient,
oxygen to furnish complete combustion into CO2.

On the other hand, the explosive mixtures which are
low in oxygen do not develop the same force as they
would if containing sufficient oxygen for complete com-
bustion. For example, whereas a mixture of binitro-
naphthalene and nitrate, containing 12-50 per cent, of
the former ingredient, gives, in the Trauzl test, the
f value 8,633, this value falls progressively to 1,469 as
the proportion is increased to 57-67 per cent. With
biiiitrotoluone, 14*89 per cent, gives f = 8,692, whilst
53-22 per cent, gives only / = 5.484. With picric acid,
30-58 per cent, gives f = 8,933; 74-11 per cent, gives
f — 7,763; and 100 per cent., f = 6,870. In the case of
endecanitrocellulose, 41-07 per cent, gives / = 9,020;
87-72 per cent, f — 8,245; and 100 per cent., / = 8,031.

The results of the Trauzl tests are plotted as curves in

fig. 4, in which the absciss® represent the percentage of
ammonium nitrate, and the ordinates the dimensions of
the cavities formed in the block; whilst the correspond-
ing values for / are given at the side, picric acid being
taken as the basis. To enable a comparison to be drawn
it was necessary to establish a common basis to which
the whole could be referred, since the theoretical values
of / do not always correspond to the size of cavity pro-
duced. For instance, the most powerful mixture of
picric acid and nitrate gives a cavity of 393-3 c.c.,
whereas / = only 8,933; whilst the corresponding tri-
nitrotoluene mixture gives a cavity of 329 c.c., the value
of / being 8,833. Whereas the theoretical / value of the
two only differs by 1-1 per cent., the difference in the
Trauzl test is over 16 per cent. The theoretical / value

11000

200~

100

•100

2000

20

100%

Content of ammonium nitrate.

193.3

Li.r^te d«!» comOust »n

V CO^pttlt

l\

I \

I •

rc CO

a 5

PS
o
o

O (896i) Acde pic. ique
in
o
‘to
fl
a
5

Fig. 4.—Results of Trauzl Tests.

Values of f on picric acid basis.

of picric acid being 8,964 (Sarrau), this value was taken
as the equivalent of the 302-5 c.c. cavity produced in
the Trauzl block.

Comparison of the two sets of / values shows that the
differences are small in the case of the less powerful
explosives, but large in the high explosives. For example,
the actual / value for the most powerful picric acid
mixture is 11,654, as compared with 8,933, that for
endecanitrocellulose being 11,168, instead of 9,020. These
differences are attributable to the effect of the high
velocity of detonation of these explosives, in consequence
of which the results obtained w’ith them in the Trauzl
test do not always correspond to the results they furnish
in practical use. This is the reason why, in the United
States, for example, the ballistic mortar is employed as
a check test.

Two principal conclusions may be drawn from these
experiments, namely, that, with regard to mixtures con-
taining an excess of oxygen and having a low detonation
temperature, suitable for fiery mines, idle force developed
is much about the same in all cases, whilst those which
might perhaps develop the highest force are of such
composition that, by reason of their lack of sensitiveness,
it would be risky to recommend their employment. On
the other hand, the mixtures too low in oxygen to ensure
the whole of the carbon present being converted into
CO2, are all less powerful than mixtures of the same type
giving complete combustion without any excess of
oxygen; it would therefore be advantageous—provided
circumstances permitted—to add a source of oxygen in
sufficient quantity to give complete combustion.

Mr. Consul Spencer Dickson, H.M. Representative at
Rosario, says the import of coal rose from 83,500 tons in
1898 to 358,000 tons in 1908. The average import during
the last six years has been 346,000 tons. The figures for
1913 are 424,000 tons. Competition threatened from the
United States during the Welsh coal strike. Quite recently
a German coal company established itself in Rosario; it
imported Welsh coal, and the effect was to lower local prices
rather than to bring in foreign competition ; the company
is at present commercially inactive through lack of supply.

H.M. Consul at Batouin (Mr. P. Stevens) reports, with
reference to a notice in a recent issue of the Board of Trade.
Journal relative to the coal industry of the Caucasus in
1914, that, owing to the exceedingly inferior product
obtained, the only coal deposit that has ever been worked in
the Caucasus has never been profitable. This deposit exists
at Tkvibuli, and, except locally, there is no demand for the
coal won from the mines as it is considered not to be worth
the cost of transport. The industry, therefore, is unlikely
to attain commercial importance. Other coal deposits in
the Caucasus are situated at Olti and near Tchartala. in both
of winch localities very rich varieties, somewhat similar to
Welsh coal, are stated to exist. The Olti coal mines, how-
ever, cannot be advantageously worked until cheap and easy
means of transport to and from the district is provided. The
coal field at Tchartala is not very far distant from Poti, to
which port a narrow gauge railway could be constructed
without much difficulty, but in this case lack of capital has
precluded the exploitation of the mines.