Gunpowder. 
Method of 
choosing 
gunpowder, 
Deseription 
of the E- 
prouvette 
for deter. 
mining the 
trength of 
588 
Carbonic acid . . . . 40.8 = 87 cubic inches 
Carbonic oxide 12.9= 42 
S RPP? PL WH ay 19.1 40.6 . 
Total. 169.6 : 
Now Mr Robins found that 27 grains of powder ge- 
nerated a8 much air’as made +’, of an atmosphere in’a 
space equal to 520 cubic inches. This at the pressure 
of the atmosphere, which was at the time equal to 30 
inches, would make 34.6 cubic inches. ‘The increased 
temperature which the receiver got by the explosion, 
might reduce; this to 30 or 31. We find from our cal- 
culation that 126.7 of gunpowder generates 169.6 cubic 
inches of gas, Then as 126.7: 27:: 169.6 : 35.7 cu- 
bie inches; which is only three cubic inches different 
from, Mr Robins’ experiment.. This might arise from 
his powder not consisting of proper proportions. 
In the present improved state of chemical science, 
when the nature of the bodies constituting gunpowder 
are so well understood, as well as the compounds re- 
sulting from their action-on each other, the proportions 
above given "may be’taker as'the best for practice. The 
charcoal should, ‘in particular, not be less in proportion 
tothe nitre, as the smallest portion less than a whole 
atom would be the same as to leave out the wholeatom, 
in which case there would be no carbonic oxide form- 
ed, . If, for instance, instead of the proportions 95.5 
nitre, 16.2 charcoal, and 15 sulphur, the carbon was 
16, then there would be 4.2 of carbon ‘left in the re« 
siduum, and no carbonic oxide would be formed ; since 
bodies cannot unite but in definite proportions. 
The reason why carbonic oxide is formed during 
the decomposition of nitre by charcoal, will be obvious 
from nitric acid having five atoms of oxygen. Four of 
these unite with two of ¢arbon to form two atoms of 
carbonic acid, while the odd atom of oxygen is com- 
pelled to take another atom of carbon to form carbonic . 
oxide, The writer of this article found the presence of 
the latter substance a fatal objection to getting pure 
carbonic acid by deflagrating nitre with charcoal. 
The goodness of gunpowder is known to those ex- 
perienced in it by its appearance. It: should not be 
strictly black, but of azure grey inclining to red. | The 
grains should appear uniform, both to the eye and to 
the touch. If some rub to powder sooner than others, 
it shows ‘that the mass is not;wellomixed, + 
When it is fired on clean paper, or on a clean board; 
it should not soil it, or leave black spots. The smoke 
arising from it will form a circle: or | ring, more or less 
perfect as the explosion:is more’ or less rapid, and is 
a good test of its strength: 
The best and most certain test of the strength of 
gunpowder is the eprouvetie.. This is a machine in 
which the powder acts against a-weight in order to 
raise it to a given height, The powder in these ma- 
chines, however, acts by a sudden impulse, and not as 
it acts ina gun, which is by gradual pressure durin 
the whole time the charge is passing through the barrel. 
Hence the common powder powers are very imperfect, 
and have been long deemed insufficient. The French 
method of trying powder is more to be depended upon, 
but it is more tedious, and takes up too much time for 
practice. 
Each of the magazines for powder have a small 
mortar, exactly of the same size, and capable of con- 
taining a ball of 73 inches in diameter. The mor- 
tar is elevated to an angle of 45°; and when the pow- 
der is of the required strength, 3 ounces of it is ca- 
* See the Deseription of this Plate at the end of the Volume 
GUNPOWDER. 
pable of projecting the ball of the above'size 55 French Gur 
fathoms. Naat hea tet Eablet 
“Mr Robins proposed a much more certain apparatus 
for trying the Taestigtda of powder, which has since been 
executed and reduced to practice by Dr Hutton. | It is 
founded on the principle that the momentum of the °! &™ 
gun and the charge must be equal; or that the force Rows 
the powder, which is equally exerted w both, wi 
generate velocities in-each, which will be inversely as 
their quantities of matter. Thus, if the weight of the: 
charge were 1, that of the gun being 100, then their: 
velocities will be reciprocally as these numbers. For 
this purpose, Dr Hutton’s machine consists of a brass|P&4TE 
cannon of about one inch bore.* » It:is:suspended im CCL 
such,a way, that the arch of its recoil can be easily ascers Fi8: 1%! 
tained. The gun is generally charged with two ounces : 
of powder. The arch of; recoil gives the velocity 
with which it is propelled, and hence the force of a 
given quantity of powder. No: wadding is used in this 
me the powder being merely collected into as 
compact a mass as possible. In these experiments, it 
should always be ascertained whether the whole of the 
pemebenaees . .” Ys lorie yummie 
e strength of powder might be very conveniently 
and correctly ascertained, by: firing a bullet into some 
uniform medium, such as’ sand or clay.» The medium 
may first be tried, by letting a ball fall from a given 
height into it, and observing the depth to which it has 
penetrated. _ Since these depths are the spaces through 
which the ball has to lose motion, which is sup= 
posed to have been uniformly they will there« 
fore be as the squares of their velocities. Hence; 
when the space has been determined by the falling 
body of which the velocity was known ; the first ve- 
locity of the projected body may be determined, the 
space through which it has penetrated ‘known, — 
-_ Since the force of gunpowder is exerted in a manner 
Pe spr an ema air, which is ana- 
ogous to the action of a spring, there appears nothing 
more to be nae ahi the pee of elastic 
fluid set free, and its temperature, to know what is its ve~ 
locity of expansion when no matter has to be moved, 
Mr Robins first ascertained the apery air formed 
by a given quantity of wder, and then supposed 
that this inutic flusd ph re to a heat ent ‘to 
redness, by the explosion of gunpowder. He also found 
by experiment, how much the volume.of'a given bulk 
of air was increased by a red heat. The first produc- 
tion of air gave him. a force of about 244 atmospheres, 
or that the original volume ‘of gunpowder was multi- 
plied by that number... The red heat he found would 
multiply this volume by about 4.1. This gave about 
1000 times for the increase of volume. The force 
of its first action would therefore equal so many atmo-« 
spheres, or 1000 x 15 pounds upon a'square inch, When 
this force begins to move, it decreases with the dilatation; 
and exactly in the same ratio. _Mr Robins not only as- 
certained the velocity given to. the bullet by a given 
weight of powder, but he fired the powder alone, which 
having no weight to move, would expand itself with 
the greatest valeciog He found that, under these cir- 
cumstances, the velocity of expansion was 7000 feet in 
one second, we 
In these experiments, the charge, at a small distance, Prats — 
was fired at a piece of wood, constituting the bob of a ccLxxxrm 
ndulum. This ulum had a ribbon attached to Fig. 12. — 
it, which was slightly held between two surfaces, so 
that when the pendulum vibrated, the length of the 
the str 
