266 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
These grenades are occasionally partly filled with lead balls or other 
missiles, but usually the effect of the high explosive alone is depended 
upon. It seems readily practicable to carry and drop from aero- 
planes bombs weighing from 50 to 100 pounds. It is, of course, 
practicable to carry and drop much heavier ones from dirigibles. 
Experiments in our service have indicated that good accuracy can be 
secured in dropping grenades of suitavle form from heights at least 
as great as 2,000 feet. 
NITROGLYCERIN. 
One of the most powerful and commonly used explosives is nitro- 
glycerin, it being used alone or as forming the explosive element in 
dynamite. It is prepared by slowly running glycerin into a mixture 
of the strongest nitric and sulphuric acids, the whole being stirred 
and kept cool durmg the process of mixing. The reaction which 
takes place between the glycerin and the nitric acid is in a general 
way similar to that which takes place in the manufacture of gun- 
cotton. As the result of the reaction, NO, groups from the nitric 
acid replace hydrogen in the glycerin, and the previously harmless 
glycerin is thereby changed into the powerful and dangerous explo- 
sive nitroglycerin. Nitroglycerin is a rather dense oil-like liquid. 
When pure it is colorless, but as it appears in the market is usually 
pale yellow. It is somewhat poisonous, and one can be poisoned by 
it not only through the mouth but also by breathing its vapors or by 
allowing the liquid to touch the skin. <A drop of it touching the tip 
of the finger will usually soon produce a violent headache. * The 
chemical formula giving its reaction upon explosion is usually written 
40,H,(O.NO,),=12CO,+10H,O +6N,+0, 
As expressed in simpler language this means that four molecules of 
nitroglycerin, each composed of 3 atoms of carbon, 5 of hydrogen, 
3 of oxygen and nitric peroxide (NO,), become upon explosion 12 
molecules of carbon dioxide (CO,), 10 of water vapor (H,O), 6 of 
nitrogen, and 1 of oxygen. 
Gas developed.—The equation further shows that, in accordance with 
a general chemical law, a quantity of this explosive in grams equal to 
the number of units of molecular weight in the first member—that is, 
908 grams—will give 12 molecular volumes of carbon dioxide, 10 of 
water vapor—if that be assumed to behave like a perfect gas—6 of 
nitrogen, and 1 of oxygen, if measured at zero temperature and 
standard atmospheric pressure. As the molecular volumes of all 
gases are the same (22.32 liters) the total volume of gas developed 
by 908 grams of nitroglycerin is approximately 647 liters. That is, 
1 pound of nitroglycerin, which occupies approximately 16 cubic 
inches of space would develop approximately 340 cubic inches of gas 
