THE ADDITION OF CARBON TO POWDERS WITH A NITROCELLULOSE AND NITROGLYCERIN BASE.

BY CAPT. MONNI,

Translated from the Moni teur Scientit~que, August, 19o8, BY

W. J. W I L L I A M S , F.I.C.

THE results obtained by the use of the new nitro-powders in fire-arms have caused their rapid adoption by all armies and navies. Generally speaking, these powders consist either of a mixture of nitroglycerin and nitrocellulose or of nitrocellulose alone. It is needless to describe the properties of nitro-powders, for they are well known; it need be said only that from the economic and ballistic points of view, the addition of nitro- glycerin offers advantages. But practical use has shown that these powders erode the bore of the pieces to such a degi~ee that after a limited number of rounds they become useless. This harmful effect, which increases with the length of the weapon, is augmented in proportion to the quantity of nitroglycerin con- tained in the powder, and when it is taken into consideration that the products of the decomposition of these nitro-powders are all the same, the cause of this fact must be sought in the temperat,wc of the decomposition of nitroglycerin, which is far higher than that of nitrocellulose. Moreover, the decomposition-products of nitroglycerin contain a great excess of carbon dioxide, which removes carbon from the metal. In view of this rapid attack, the Governments which have adopted powders with a nitro- glycerin base, find themselves under the necessity of either aban- doning their advantages or eliminating their drawbacks.

Italy chose the second method, and made a series of experi- ments to attain this end. For ten years I was detached to the Government factory of Fontana L4r6 and put in charge of the experiments conducted by distinguished chemists. I do not in- ~end to detail a l l tha t was done, but I can show the grounds by which I arrived at the solution of the problem.

It is fmown that the Italian Army and Navv make considerable I I I

I I2 \V. J. WiLl,ra~s.

use of balistite, which is a mixture of equal parts of nitroglycerin and nitrocellulose. This mixture is brought by a special method to a nitration of 12 per cent., which corresponds almost exactly to a 9-nitrocellulose. The respective molecular weights are

Nitroglycerin, C3Hs(O.NO2)3 = 227

Nitrocellulose, C~4HaOn(O.NO2)9= I053

Balistite then is composed of one molecule of nitrocellulose and 4.64 molecules (4.64 X 227 ~--- lO53) of nitroglycerin.

The equation for the decomposition of nitroglycerin is well known: it is written

C3H~(ONO2)3= 3CO2 + 2.5H20 + 1.5N2+o.2502

It is different with nitrocellulose--its decomposition varies ac- cording to conditions and because it is composed of a mixture of products of higher or lower nitration. The following equation appears to be most in accordance with the facts

C24I-Ia On (O. NO2) 9 = 8CO2 + ~ 6CO + 6H20 + 9- 5H2 + 4.5N~

These decompositions being granted, then the products of the decomposition of balistite are

4.64CaHs(O.NO2)a + C2,HalOn (O-N%) 9

= 2 1 .9CO2 + i 6 C O + 19.92H20 + 7 . I8H2+ I 1 .46N=

or in round numbers

22CO2+ 16CO + 2oH20 + 7H2+ I 1.5N2

CALCULATION OF THE HEAT DISENGAGED AT CONSTANT VOLUME.

Heat of formation of i molecule CO 2 .............. 94 Calories

Heat of formation of i molecule CO .............. 25.8 Calories

Heat of formation of i molecule H20 ............. 58.2 Calories

Heat of formation of i molecule C3Hs(O.NO~)3 .... 98 Calories

Heat of formation of i molecule C~4H~IOn(O.NO2)9. 609 Calories

Hence the result is

22 X 9 4 + I6X25.8 + 2oX 58.2--4.64 X 9 8 - - 6 o 9 = 2 5 8 I Calories.

If the gases are produced at constant pressure, then 258I Calories are disengaged. To find the heat at constant volume,

A D D I T I O N OF C A R B O N TO POWDERS. I I 3

there must be added to this figure the number of Calories equiv- alent to the work of the expansion of the gas.

L : the work , L = pv kilogl a m m e t r e s . P = lO335 k i l o g r a m m e t r e s per squa re met re . V = ( 2 2 + I 6 + 2 o + 7 + ! 1 . 5 ) ~2.32I =17o7 .48 litres.

L = ! ° ' 335 >( ~7°7'48 =41 . 5 Calories. 425

The sum 2581 + 41.5 = 2 6 2 2 . 5 Calories for a molecular weight equal to

22 X 4 4 + I 6 X 2 8 + 2 0 X I 8 + 7 >(2 + I I . 5 X 2 8 = 2 I I 2 .

For each kilog'ramme of powder then, there are

2632. 5 - = 1242 Calories + ~ 7 7 7 . 4 8 = 808 l i t res of gas.

2.112 2 . I 1 2

Calculation of the Temperature of Combustion. Let t be the temperature, q the quantity of heat, and c the specific heat be- tween zero and t ° ; then

t = q 6

Mallard and Le Chatelier give the following values'

For CO 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . c ~ 6 . 2 6 + o . o o 3 7 t calories For H20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . c ~ 5,61 + o.oo 33 t calories For o the r gases . . . . . . . . . . . . . . . . . . . . . . . c = 4.8o + o.0006 t calories

If these figures a r e applied to the quantities of gas g'iven above, we get

For 22CO2 . . . . . . . . . . . . . . . . . . . . . . . . . . Q = 2 2 X 6 . 2 6 + 2 2 Xo.oo37 t For 2oH20. . c 2 = 2 o X 5 . 6 1 + 2 o X o . o o 3 3 t For 16CO+ 7H2+ I1 .5N 2 . . . . . . . . . c a = 3 4 , S X 4 ; 8 o + 3 4 5 >(0.o006 t

c = 4 1 5 . 5 i + o . 1 6 8 I t

Introducing these values into the equation

t = q c

then

o .168 I t=+4I 5.51t-- 2622. 5 = o

- -415 .5I q'- ]/1415.512+4 X 26-'22. 5 XO. Z68I t =

X o . i 6 8 i

VOL. C L X V I I , No. 998-- 9

2902 ° C.

I I 4 W . J . WILLIAMS.

It remains then to find a m e a n s of diminishing the effect of this considerably high temperature.. T h i s e f fec t is m o re intense the longer the gas remains in the metallic tube (bore ) ; that is, the g rea te r the diameter and length . . . . . . . . .

As a long series o f trials has shown, the simplest method is to add a certain quant i ty o f carbon to the balistite, which, at the tempera ture under consideration, t ransforms all the carbon di- oxide into twice its volume of carbon monoxide. Theoretically, 22 X I2 ~---264 Gm. of carbon are required to reduce the 22 molecules of carbon dioxide (CO2) , fo rmed on firing 2 I I 2 Gin. of balistite, into carbon monoxide ( C O ) . Th en the explosion produces

('0 6oCO+20H20+TH2+II.5N2, molecular weight=2376

I f it be admit ted that the oxygen of the wate r can also be combined with carbon, then 20 atoms more of carbon can be used and the gases become

(fl) 8oCO+27H2+IL5N2, molecular weight =26x6

I f the case is studied in detail, the calculation of the ex- plosion is

FOR E Q U A T I O N a

Heat disengaged at constant volume for i kg. exptosive . . . . . . . . . 7x6 Calories Volume Of gas produced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 925 litres Temperature o f explosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i . . . . . 2278 o

FOR E Q U A T I O N j;[

Heat disengaged at constant volume for x kg. explosive . . . . . . . . . 407 Calories Volume of gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ioi i litres Temperature of explosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1565 °

Does this reduction of tempera ture actually take place in practice ? I will show. by the results of experiments how closely these theoretical forecasts are verified.

But it must be borne in mind that equal quantities of balistite and of these carbonated powders do not possess the same ex- plosive ~orce. They give

f 2 9 o 2 \ For balistite . . . . fl= 8o8~x + ~ 3 ) = 9 3 9 7 atmospheres per kg.

\ 2 7 3 . , "

A D D I T I O N OF C A R B O N TO P O W D E R S . I 1 5

F o r powder 3 . . . . f3 = 1 Ol I ( I + 1565"~ = 6804 atmospheres per kg. \ 2 7 3 /

For a content of carbon increasing up to T 9 per cent. (as in formula fl) the volume of the gaseous products formed increases, but does not compensate for the diminution of temperature. To obtain the same explosive force the charge of powder must be augmented.

A series of experiments proved this was the case. It is necessary to calculate the charges required to obtain the same initial velocity of the projectile at the muzzle of the gun with balilstite containing variable amounts of carbon. The results are

Percentage of carbon in the ballstite Charge

o ioo

2. 5 IO 3 5 I 0 9 7 '5 I I 2 8 I I 3 9 1 1 5

Percentage of carbonin the balistite

IO II

I3 I5 I9

Charge

116. 5 z i 8

I 23 ~37

The data were very difficult to obtain for percentages above 15.

Certain calorimetric determinations were made which are only valuable for comparison. Thus it was found

Percentage Rise of ,i Percentage [ of carbon in Charge of carbon in ' Charge Rise of

temperature the balistite temperature the balistite L

r o i o o 45° °

2. 5 I O 3 44 ° z z I 1 8 I 34 .~° 5.o IO 9 42 .6 ° 13 I 2 2 33 ° 7.5 zz2 39 ° (z) I5 z23 3o.3 ° 8 I I 3 3 7 . 6 ° (2) 19 I 3 7 3 I ° 9 I z 5 3 6 ' 3 ° I

It is obvious that the values found for the rise of temperature decrease progressively and in a very notable degree in proportion as the temperature (sic; charge) increases.

It is true that neither the charge nor the rise of temperature follows the percentage of carbon exactly; but that is because in

I I6 W . J . WILLIAMS."

manufacturing on the small scale, it is impossible to avoid all the defects which influence the ballistic properties of the explosive. Moreover, the last two results (I and 2) do not really contradict each other; if the temperatures are considered in relation to the weights of the explosive which would contain the same quantity of nitrated products, the temperature for 2 would be 29.5 °, lower than that found for I.

In proof of the fact that the carbon actually reacts, as in the equations given, it is well to emphasize the fact that during the explosion there is neither smoke nor residue produced. Hence the inference is strong that carbon determines the quantity and the nature of the products of explosion.

Must it not be concluded from these results that balistite, and all powders which produce a large proportion of carbon dioxide, act upon the steel of the muzzle of the gun by removing its carbon ?

To answer this question, an apparatus was constructed, analogous to that described by Vieille (M6m. des poudres et salp&tres, vol. xi) to measure the erosion. Vieille, in his ex- periments, always used the same weight of powder. But in this way an exact expression of the damage done by different powders cannot be obtained. It is preferable, and more logical, to experi- ment with such quantities of powder as give the same ballistic effect, while keeping the other factors which may influence the result as constant as possible. Hence the powders are granulated so that the duration of combustion shall be the same for all. The following results were obtained:

Atmospheres Erosion O r d i n a r y ba l i s t i t e . . . . . . . . . . . . . . . . . . . . . . . . . . 34~3 0.3038 Grn. Ba l i s t i t e w i t h 11 .28% c a r b o n . . . . . . . . . . . . . . 3768 o .3048 Gin.

Vieille found that with the same pow.der the erosion is pro- portional to the pressure developed in the gun:

Atmospheres Erosion O r d i n a r y ba l i s t i t e . . . . . . . . . . . . . . . . . . . . . . . . . . 2162 .3038 Gin. Balistite with i i .28% c a r b o n . . . . . . . . . . . . . . . 2366 o . I 4 6 I Gin. O r d i n a r y ba l i s t i t e . . . . . . . . . . . . . . . . . . . . . . . . . . ~3 I3 0 .3874 Gin. Ba l i s t i t e w i t h 8 .00% c a r b o n . . . . . . . . . . . . . . . . 2323 o .21o8 Gin. Ba l i s t i t e w i t h 11 .28% c a r b o n . . . . . . . . . . . . . . 2543 o . i 73o Gm.

It is seen, that in spite of a heavier charge of carbonated products and in spite of higher pressure, the erosion is less.

A D D I T I O N OF CARBON I'O POWDERS. I 17

The following comparative experiments were made:

Atmospheres Erosion Balis t i te w i t h 8 % ca rbon . . . . . . . . . . . . . . . . . . . i ,o5o o;oo4x Gm. Balis t i te w i t h ix~28% ca rbon . . . . . . i . . . . . . . 911 o.oo31 Gm. Black p o w d e r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i ,o77 o .o ix8 Gm. Rot tenc i le r p o w d e r . . . . . . . . . . . . . . . . . . . . . . . . i ,o2o o.oxo0 Gm. Smokeless p o w d e r . . . . . . . . . . . . . . . . . . . . . . . . . 1,438 o . o i i o Gm.

These results need no comment. But this point may be in- sisted on; if, as Vieille assures us, it is admitted that erosion is produced in the same manner in the apparatus for measuring the erosion as it is in fire-arms, the results prove that carbonated balistite is the least erosive of the explosives.

But, it may be asked, what guarantees can be offered for carbonated balistite from the chemical, physical, and ballistic points of view? The only answer is that these are the same as for ordinary balistite, i.e., it is easily and conveniently manufac- tured, it offers considerable resistance to variations of tempera- ture and humidity, and its ballistic effect is constant; its com- bustion is a little slower. Both in economy and in practical re- sults, it corresponds to what was sought.

My official position prevents my going into detail concerning the experiments made to determine the best proportion of the components, the general properties of the powder, and the method of making it suitable for different weapons. The Italian patent is open to the public and any one can study the process.

An interesting question, from the practical point of view, is the use of carbonated balistite as a sporting powder. In fact its production is one-half more economical than that o f the com- mercial powders made for this purpose, and there is no fear that the guns will be deteriorated.

Those who have used balistite as a sporting powder and have not obtained the expected results, may claim that it would have been just the same notwithstanding the addition of carbon. But it is easy to r~fute this objection. Once its chief fault, the erosive property, is eliminated, the rest is only a comparatively simple question of granulating the powder.

Carbonated balistite can be sold at a price as advantageous for the merchant as for the manufacturer. It is sufficient to say that the cost of production should not exceed 5 fr. 5o ($I.IO), and that the charge is about one-third of the equivalent charge of black powder.