Carbon 15.62 15.86 per cent.
Hydrogen 2.40 2.20 "
Nitrogen 17.90 18.50 "
Oxygen … 63.44 "
The above analysis is by Beckerheim. Sauer and Adou give the nitrogen as 18.35 to 10.54 per cent. by Dumas' method; but I have never found any difficulty in obtaining percentages as high as 18.46 by the use of Lunge's nitrometer. The decomposition products by explosion are shown by the following equation—
2C_{3}H_{5}(NO_{3}){3} = 6CO{2} + 5H_{2}O + 6N + O;
that is, it contains an excess of 3.52 per cent. of oxygen above that required for complete combustion; 100 grms. would be converted into—
Carbonic Acid (CO_{2}) 58.15 per cent.
Water 19.83 "
Oxygen 3.52 per cent.
Nitrogen 18.50 "
The volume of gases produced at 0° and 760 mm., calculated from the above, is 714 litres per kilo, the water being taken as gaseous. Nitro-glycerine is decomposed differently if it is ignited as dynamite (i.e., kieselguhr dynamite), and if the gases are allowed to escape freely under a pressure nearly equal to that of the atmosphere. Sarrau and Vieille obtained under these conditions, for 100 volumes of gas—
NO 48.2 per cent.
CO 35.9 "
CO_{2} 12.7 "
H 1.6 per cent.
N 1.3 "
CH_{4} 0.3 "
These conditions are similar to those under which a mining charge, simply ignited by the cap, burns away slowly under a low pressure (i.e., a miss fire). In a recent communication, P.F. Chalon (Engineering and Mining Journal, 1892) says, that in practice nitro-glycerine vapour, carbon monoxide, and nitrous oxide, are also produced as the result of detonation, but he attributes their formation to the use of a too feeble detonator.
Nitro-glycerine explodes very violently by concussion. It may be burned in an open vessel, but if heated above 250° C. it explodes. Professor C.E. Munroe gives the firing point as 2O3°-2O5° C., and L. de Bruyn[A] states its boiling point as 185°. He used the apparatus devised by Horsley. The heat of formation of nitro-glycerine, as deduced from the heat of combustion by M. Longuinine, is 432 calories for 1 grm.; and the heat of combustion equals 1,576 cals. for 1 grm. In the case of nitro-glycerine the heat of total combustion and the heat of complete decomposition are interchangeable terms, since it contains an excess of oxygen. According to Dr W.H. Perkin, F.R.S.,[B] the magnetic rotation of nitro-gylcerine is 5,407, and that of tri-methylene nitrate, 4.769 (diff. = .638). Dr Perkin says: "Had nitro-glycerine contained its nitrogen in any other combination with oxygen than as -O-NO_{2}, as it might if its constitution had been represented as C_{3}H_{2}(NO_{2}){3}(OH){3}, the rotation when compared with propyl nitrate (4.085) would be abnormal."
[Footnote A: Jour. Soc. Chem. Ind., June 1896, p. 471.]