Nitroglycerine powder

Gallwitz (Ref 16) reports the following data on the influence of the heat of explosion upon the bore wear. With a nitroglycerine powder containing no solvent and giving a heat of explosion of 950 kcal, the barrel stands up to 1700 rounds while with a similar powder giving a heat of explosion of 820 kcal, it withstands 3500 rounds. The reduction of the calorific value of the powder by 130 kcal therefore doubles the useful life of the barrel... 

Further reduction of the calorific value of nitroglycerine powder proved to be impossible. But by using nitrodiglycol instead of nitroglycerine, a powder was obtained with a heat of explosion of 690 kcal, which prolonged the life of the barrel considerably, i.e. to 15,000-17,000... 

Of course, not enough nitroglycerine was available for wartime. Experiments took an extremely favorable course so that in 1939 the production of nitroglycerine powder was given up, and only diglycol powder was produced. 

The very high flame temperature of the above mentioned mixtures is noteworthy. In the majority of smokeless nitrocellulose or nitroglycerine powders it is considerably lower 2000-3000°K. 

As can be seen, the gelatinous explosives of the Nobelite type, safe in the presence of methane, contain a small amount of calcium nitrate solution. Calcium nitrate was added to Nobelites to reduce the temperature of the flame of explosion. After World War I, small quantities of calcium nitrate in the form of a concentrated aqueous solution were added to the milled nitroglycerine powder (from the post-war surplus) used as a rock explosive. This was done to counteract dustiness e.g. Nitro-glycerinpulver 1 explosive had the following composition ... 

Ingredients Ammonium nitrate powder Ammonal Ammon gelatine dynamite Ammon gelignite Semi-gelatine Nitroglycerine powder... 

IV. Nitroglycerine powders. They contain ca. 10% nitroglycerine which is not gelatinized. The density is ca. 1.0. A typical example is Polar Viking. Its sheathed Eq. S. Explosive is Unifrax. 

Nitroglycerine powder—completely or almost completely wholly colloidal—is less porous, therefore more difficult to ignite than nitrocellulose powder and requires a stronger priming. 

Nitroglycerine powder—cordite—gives a better proportion of more completely oxidized products. 

The heat of explosion depends chiefly on the composition of the powder, e.g. in nitrocellulose powder on the content of nitrogen in the nitrocellulose and in nitroglycerine powder on the content of the nitroglycerine. 

FtG. 185. Gas volume and heat of explosion of nitroglycerine powder as a function of the proportion of nitroglycerine in the powder [17]. 

Generally speaking, nitroglycerine powders give a higher heat of explosion, so that the temperature of their products is higher than that in nitrocellulose powders. 

This means that nitroglycerine powders are more erosive (greater bore wear) (p. 548) and more flashy (p. 544). 

Non-explosive substance (e.g. vaseline) are added to nitroglycerine powders to reduce the heat of explosion and the temperature of the flash. The addition of cool explosives such as nitroguanidine has the same effect. 

In the German Army nitroglycerine powders (double base powders) possessed the following calorific values 1250, 1150, 950 and 820 kcal/kg. 

Nitrocellulose powder is more sensitive to friction than nitroglycerine powder, although the latter is more sensitive to impact (due to the presence of nitroglycerine). 

Nitroglycerine powder Ballistite, 1.3 mm thick circles laid perpendicularly to the tube axis 1.53 7445-7615... 

Nitrocellulose and nitroglycerine powders should properly be called slightly smoky the name smokeless is inexact. The smoke from nitrocellulose and nitroglycerine powders is composed chiefly of water vapour. Shots from small arms or cannons of small calibre are slightly smoky or almost smokeless. Conversely guns of heavy calibre often give a considerable amount of smoke. The presence of metal torn off from inside the barrel and from the driving band in the products of combustion of the propellant is a partial cause of smoke. 

On heating nitroglycerine powder of a ballistite type to a temperature of 95°C in a Dewar vessel without a stabilizer, de Bruin [58] obtained the following data on temperature rise ... 

The test for nitroglycerine powders at a temperature of 120°C (nitroglycerine powders cannot withstand higher temperatures) here the same conditions apply as in the test for nitrocellulose powders, viz. appearance of the nitrogen oxides after a lapse of at least 45 min and no explosion for 5 hr. The same test can be carried out in the presence of methyl violet test papers. Decoloration of the paper should not occur before 30 min. 

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