NITROGEN. 583 NITKOGLYCERIN. suli>liuric acid and fifed liimi nitrogen trioxide b.v (la^.-sing a luirent of dry air. The uitrogen penlu.ide tlius obtained is passed into a suitable receiver kept in a freezing ini.Kture; when a crystalline mass has formed in the reeeiver, the portion remaining liquid is decanted oil"; then the crystals are allowed to melt, the liquid is again caused to solidify, and any portion remain- ing liquid is again rejected. By repeating this operation several times, it is easy to obtain per- fectly pure nitrogen pcnto.xide. The colorless rhombic crystals of this substance may be pre- served very long by keeping out of contact ith the air and away from light. They nudt at about 30° C. and the lii[uid boils at about 45" ('., but slightly above this temperature the substance undergoes decomposition. If exposed for some time to the light the crystals melt and may de- compose with explosive violence. Nitrogen pent- oxide is the anhydride of nitric acid. The compounds of nitrogen with hydrogen in- clude ammonia, XH„ hydrazine, X-Ii,, and hydra- zoic acid, XjH. The most important of the com- pounds of nitrogen with the halogens is nitrogen tri-cliloride, XCr. which may be considered as ammonia iu which all the hydrogen has been re- placed by chlorine. It is pre])ared by jiassing chlorine gas into a warm solution of ammonium chloride. It is a yellowish, volatile, extremely ex- plosive, oily substance, which must be handled with extreme caution and the preparation of which should not be undertaken by any one not thoroughly accustomed to experimenting with dangerous substances. Its explosion may be brought about by the action of lieat or light, or by contact with phosphorus, turpentine, and other substances. NITROGLYCERIN, or Gloxoix, CAP, (XO, ),. An explosive substance discovered by Sobrero in 1840. Although Sobrero pointed out the possibilities of the substance as an explosive agent, it found no other than a lim- ited use, in dilute alcoholic solution, as a remedy for headache, under the name of 'glonoin.' Its use as an explosive remained undeveloped until 1862, when Alfred X'obel (q.v. ) discovered means of controlling its ex- plosive properties and devised a practical method of making it on a large commercial scale. X'itro- glycerin is made by running from 210 to 2.30 pounds of pure glycerin into l.iOO pounds of nii.xed acids, consisting of three |)arts by weight of concentrated sulphuric, and two parts by weight of concentrated nitric acid. As consider- able heat is set free by the reaction it is neces- sary that the glycerin should be added slowly and intimately mixed with the acids. Tliis is I accomplished by injecting the glycerin into the acid mixture, stirring the whole. an<l cooling it by means of cold water run through pipes which are coiled within the leaden vessel ("the con- verter' I in which the conversion is carried out. I When all of the glycerin is converted into nitro-
glycerin, the entire charge of the converter is
I run into a tank, where, on standing, the nitro- 1 glycerin separates in a layer on top of the I acids. The nitroglycerin is then drawn off. wash- ed with water until nearly free from acid, then with a dilute solution of sodium carbonate until it is neutral in reaction, and then run through a filter by which it is dried. Pure nitroglycerin is a colorless, odorless, transparent oily liquid, but as made on a com- mercial scale it is colored various shades of jellow. Solidified nitroglycerin melts at 8° U. (40.4° F.). Its specitic gravity in the liquid .state is 1.599; when frozen, 1.735. It gives off vapors to a slight extent at the ordinary temperature, and it may be eomi)letely evapo- rated bv continuous exposure at a temperature of 70° C. (158° F.). It is soluble in methyl alcohol, ethyl alcohol, ether, benzene, and many other organic liquids, but it is nearly insoluble in water, heu the vapors of nitroglycerin are inhaled or the substance is taken into the stom- ach, it produces most violent headaches. Some persons are so sensitive to its action that they are poisoned by it when nitroglycerin touches the skin. The production of imdecomposed va- por of nitroglycerin, when the substance is ex- ploded, seriously interferes with its use in tun- nels, mines, and other confined places. The com- mon antidote is black coffee. Pure nitroglycerin will keep indefinitely at connnon tem[)eratures; but if continuously exposed to temperatures above 45° C. (113° F.) it undergoes decompo- sition, which progresses the more rapidly the higher the temperature. At 180° C. (350"° F.) it explodes violently. It is also decomposed by contact with sulphuric acid, or with an alkali, and decomposition due to the presence of acid has repeatedly given rise to accidental explo- sions of this substance. It may be exploded by percussion, concussion, or fire. I)ut the surest and safest way of firing it is by exploding a detonator containing mercuric fulminate in con- tact with it. The name nitroglycerin, as applied to the substance discovered by Sobrero, is a misnomer, and conveys a false impression as to its accepted constitution; for instead of being, as stipposed when the name was given, a nitrosubstitution compound, it has been shown by Berthelot to be a nitric ester, namely, the trinitrate of glyc- eryl (C3H5O3), a radicle forming part of the molecule of glycerin. Nitroglycerin is used directly in 'shooting' oil wells to make them yield more freely, and in blasting under water; but its liquid state ren- ders it unsuitable and even dangerous for gen- eral use as an explosive. Its largest uses are in the manufacture of dynamite, blasting gela- tin, and some varieties of smokeless powders, notably cordite and ballistite. Jlcdicinally, ni- troglycerin is used in a weak dilution to re- duce arterial tension and relieve the heart of strain, by dilating the arterioles and capillaries. Its action is similar to, though less ra|)id and fu- gacious than that of amyl nitrate, and less per- sistent than that of the nitrite of sodium or potas- sium. It is employed in a certain type of asthma, in chorea, epilepsy, angina pectoris, and gas- tralgia. It has been recommended in certain forms of Bright's disease. Although the manu- facture of nitroglycerin did not begin in the United States until 1807, and its progress was at first slow, in the year 1900 there were manu- factured here 3.t,482.947 pounds, of which amount 31,661.800 pounds were used in the manufacture of dynamite, blasting gelatin, and smokeless powder. Consult: Mowliray. Trinitro- Ghicerin (Xew York. 1874) ; Nobel, Roux, and Sarrau, Lex explosifs modemes (Paris. 187fi> ; Guttmann. The Mniiiifncture of Explosives (New York, 1895). See Explosives.
