Nitroglycerin

Nitric esters or organic nitrates contain the nitrate radical, -O-N02, attached to a carbon atom, or, to express the same idea in a different way, they contain the nitro group, -N02, attached to an oxygen atom which is attached to a carbono In nitro compounds, strictly so called, the nitro group is attached directly to a carbon; in nitroamines or nitramines it is attached to an amino nitrogen atom, that is, to a nitrogen which is attached to a carbono In the nitric esters and in the nitroamines alike, a single atom stands between the nitro group and the carbon atom of the organic molecule. Substances of the two classes are alike in their most characteristic reaction, namely, they are formed by the reversible nitration of alcohoIs and amines respectively.
During the nitration of glycerin by the action of strong nitric acid or of strong mixed acid upon it, nitro groups are introduced in pIace of three of the hydrogen atoms of the originaI molecule. There is therefore a certain propriety in thinking of the product as anitra compound, and a reasonable warrant far the common practice of calling it by the name of trinitroglycerin or, more commonly, of nitroglycerin. The hydrogen atoms which are replaced were attached to oxygen atoms; the product is really a nitric ester, and its proper name is glyceryl trinitrate. Similarly, the substances which are commonly called nitroglycol, nitrostarch, nitrosugar, nitrolactose, nitrocotton, etc., are actually nitric esters.
The physical properties of the nitric esters resemble in a generaI way the physical properties of the alcohols from which they are derived. Thus, methyl and ethyl nitrate, Iike methyl and ethyl alcohol, are volatile liquids; nitroglycerin is a viscous oil, more viscous and less volatile than gIycol dinitrate as glycerin is more viscous and less volatile than gIycol. Nitrocellulose from fibrous cellulose yields a tough and plastic colloid, but nitrostarch remains from the evaporation of its solutions as a mass which is brittle and friable.


Properties:
IUPAC NAME: 1,2,3-trinitroxypropane
OTHER NAME: 1,3-dinitrooxypropan-2-yl nitrate, propane-1,2,3-triyl trinitrate
MOLECULAR FORMULA: C3H5N3O9
MOLAR MASS: 227,09 g/mol
SHOCK SENSITIVITY: high
FRICTION SENSITIVITY: high
EXPLOSIVE VELOCITY: 7700 m/s

Nitroglycerin was first prepared late in the year 1846 or early in 1847 by the Italian chemist Ascanio Sobrero (1812 1888) who was at the time professor of Applied Chemistry at the University of Torino. Sobrero, was authorized to practice medicine and had studied in Paris and Giessen, returning to Torino in 1845 where he equipped a laboratory. The earliest printed account of nitroglycerin appears in a letter which Soberro wrote to Pelouze and which Pelouze caused to be published in L'Institut of February 15, 1847. In the same month Sobero presented to the Academy of Torina a paper in which he described nitroglycerin, nitromannite, and nitrated lactose. Later in the year he presented another paper before the chemistry section of the Ninth Italian Scientific Congress at Venice.
Sobero found that , if concentrated nitric acid or strong mixed acid is added to glycerin, a violent reaction ensues and red fumes are evolved, but that, if syrupy glycerin is added to a mixture of sulfuric acid and nitric acid, with strict controls the results are entirely different. The glycerin dissolves, and the solution when poured into water gives an oily precipitate of nitroglycerin.
For many years Sobrero kept in his laboratory and guarded jealously a sample of the original nitroglycerin which he had prepared in 1847. In 1886 he washed this material with a dilute solution of sodium bicarbonate and took it to the Nobel-Avigliana factory, of which he was a consultant, where he gave verbal testimony of its authenticity and where it has since been stored in one of the magazines.
Nitroglycerin was the first, and is still one of the most widely produced nitrate ester. It is used in dynamites, nitroglycerine is absorbed in fine wood meal or other powdered absorbent. This process prevents the microbubbles from forming and stabilizes the liquid. The nitroglycerine is also thickened or gelantinized by the addition of a small percentage of nitrocellulose. This process assists in preventing "weeping" (exhuding) or settling out of the absorbent material. Because settling does occur, boxes of stored nongelled dynamites are turned over at regular intervals to reverse the settling flow.

Glycerin (glycerol)[20] is a by-product of soap manufacture; it's a viscous liquid, colorless and odorless when pure, and possessing a sweet taste. It is hygroscopic, will absorb more than half its own weight of moisture from the air, and does not evaporate. It varies in color from pale yellow to dark brown, generally has a faint odor resembling that of burnt sugar, and yields a nitroglycerin of a pale yellow or pale brown color.
Nitroglycerin is formed and remains in solution if glycerin is added to a large excess of strong nitric acid. Heat is evolved, and cooling is necessary. The nitroglycerin is thrown out as a heavy oil when the solution is diluted with water. The yield of the trinitrate may be improved by the addition to the nitric acid of dehydrating agents such as phosphorus pentoxide, calcium nitrate, or strong sulfuric acid.

Nitroglycerin begins to decompose at temperatures as low as 50°C or 60°C. At a temperature of about 135°C the decomposition of nitroglycerin is so rapid as to cause the liquid to become of a strongly reddish color, owing to the absorption of the nitrous fumes resulting from that which is decomposed; and at a temperature of about 145°C the evolution of decomposition products is so rapid that, at atmospheric pressures, ebullition begins, and the liquid "boils" strongly. This "boiling" is due in part to the evolution of decomposition products (mainly oxides of nitrogen and water vapor) and in part to the actual volatilization of nitroglycerin itself.