The Chemistry of Powder and Explosives - Sciencemadness Dot Org

NITROGLYCERIN 201
Thus, if 100 grams of glycerin is added with cooling to a solution
of 150 grams of phosphorus pcntoxide in the strongest nitric aeid,
phosphoric acid precipitates as a heavy syrupy layer and the
supernatant acid liquid on dilution yields about 200 grams of
nitroglycerin. The yield is substantially the same if the glyeerin
is first dissolved in the nitric acid alone and if the phosphorus'
pentoxide is added afterwards. One hundred grams of glycerin
in 500 grams of the strongest nitric aeid, 400 grams of anhydrous
FIGURE 53. Nitroglycerin Nitrator. (Courtesy E. I. du Pont de Nemours
and Company, Inc.)
calcium nitrate being added and the mixture allowed to stand for
some hours, gives on drowning and purification 220 grams of
nitroglycerin which contains about 10% of glyccvyl dinitrate.
All these methods arc too expensive, fur the excess of nitric
acid is lost or has to be recovered from dilute solution. A process
in which the nitroglyccrin comes out as a separate phase withaut
the spent acid being diluted is preferable—and it is indeed true
that the addition of strong sulfuric acid to a solution of glycerin
in strong nitric acid completes the cstcrifieation and causes the
nitroglycerin to separate out. Since the strongest nitric aeid is
expensive to manufacture, and since a mixture of less strong nitric
acid with oleum (sulfuric acid containing free sulfur trioxide)