NITRO or GLoNotx, An explosive substance discovered by Sobrero in 1846. 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 Nobel (q.v.) discovered means of controlling its ex plosive properties and devised a practical method of making it on a large commercial scale. Nitro glycerin is made by running from 210 to 230 pounds of pure glycerin into 1500 -;._ - pounds of mixed acids, consisting of three parts 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 aphis. This is accomplished by injecting the glycerin into the acid mixture, stirring the whole, and cooling it by means of cold water run through pipes which are coiled within the leaden vessel Cthe eon verter') in which the conversion is earried out. When all of the glycerin is converted into nitro glycerin, the entire charge of the converter i= run into a tank, where, on standing. the nitro glycerin separates in a layer on top of the acids. 'I'lle nitroglycerin is then off, wash ed with water until nearly free from acid, then with a dilute solution of sodium carbonate nntil it is neutral in reaction, and then run through a filter by which it is dried.
I Pure nitroglycerin is a colorless. odorless.
transparent oily liquid, but as made on a com mercial scale it is colored various shade, of yellow. I8olidified nitroglycerin melts at C. (46.1' F.). Its specific gravity in the liquid state is I.599; when frozen. 1.735. It gives otr vapors to a slight extent at the ordinary temperature, and it may be completely evapo rated by continuous exposure at a temperature of 70° C. (158° F.). It is soluble in methyl alcohol, ethyl alcohol, ether, benzene, uud many other organic liquids, but it is nearly insoluble in water. When the vapors of nitroglycerin are inhaled or the substance is taken into the stom ach, it prodnees 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 undecomposed va por of nitroglycerin, when the substance is ex ploded, seriously interferes with its use in tun nels, mines, and other eon fined places. The mut
mon antidote is black coffee. Pure nitroglycerin will keep indefinitely at comition temperatures; but if continuously exposed to temperatures above 45° C. (113° F.) it undergoes devompo sition, which progresses the more rapidly the higher the temperature. At 180° C. 1356' 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 rise to accidental explo sions of this It may be exploded by percussion, concussion, or fire, but 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 supposed when the name was given, a intro-substitution eompound, it has been shown by Berthelot to be a nitric ester. namely, the tri-nitrate of glye eryl 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 all explosive. Its largest uses are in the manufacture of dynamite. blasting gela tin, and some varieties of smokeless powders, notably cordite and ballistite. Medicinally. 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 rapid and fu gavions 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 1867. and its progress was at first slow, in the year 1900 there were manu factured here 35,482.917 pounds, of which amount 31,661.806 pounds were used in the manufacture of dynamite. blasting gelatin, and smokeless powder. Consult: Mowbray. Trinitro Glycerin, (New York. 1874) : Nobel, Roux, and Sa mut. Les explosifs modernes (Paris. 18761; Outtmann. The Manufacture of Explosives (New York, 1895). See EXPLOSIVES.