CHAPTER III.
Nitro-Glycerin Considered in
its Chemical Details.
Glycerin, the base of Nitro-Glycerin, is produced from most of the fixed oils and solid fats by the process of saponification, that is, by treating these fatty bodies with an alkali, or other metallic oxide, in presence of water, or with water itself at a high temperature. For many years the Glycerin of commerce was produced from olive oil, by boiling, in the presence of water, litharge, which yielded the well known lead plaster or diachylon, and a sweetish liquid, which by evaporation of the water, was found to be Glycerin; thus procured, however, it was apt to be contaminated with lead, and therefore very objectionable for medical purposes. The sources whence it is now procured, are, the alkaline mother liquor of the soap works, when the soap is separated by common salt: also the residue of the manufacture of stearic acid for candles, by heating neutral fats with water or with steam, (Tilghmann’s process): and the action of muriatic acid on castor oil. It is apt to be contaminated with sulphuric acid, oxalic acid, lead, and more generally with uncrystallizable sugars. The demand has vastly increased of late years for medical purposes, elastic sponge, and retaining moisture in tobacco, print works, as a preserving agent, and for floating compasses, etc., etc.
The following are the synonyms of Nitro-Glycerin; Nitrate of Oxide of Lipyl, (Berzelius); Glonoin, Mono-Nitro-Glycerin, Di-Nitro-Glycerin, Tri-Nitro-Glycerin, (Liecke)—Symbol, (C₆H₅,) O³, 3NO⁵; (Hydrogen = 1, Oxygen = 8,) the equivalent or atomic weight is 147.
Pure Nitro-Glycerin is nearly colorless; usually, however, owing to coloring matter contained in the Glycerin used in its manufacture, it is of a light yellow-tinted color, oily, without odor, but having an aromatic taste, Sp. Gr. 1.6 at 60°F, very insoluble in water; mixes with alcohol (one part to four parts) and ether; it separates from the alcoholic solution by the addition of water. A vinous taste is perceptible to the tongue, the maxillary glands are stimulated, and in a few minutes the individual who has tasted it from a pin’s point for the first time, is conscious of a persistent, throbbing headache. Slightly touching, it with the hands produces a like effect; after a few days of frequent handling, however, the system becomes less susceptible to these effects, and workmen constantly employed in its manufacture are not affected by it. It is poisonous, a small quantity being sufficient to kill a dog, (Sobrero). It decomposes at 320°F, giving out red vapors, and explodes at a higher temperature, or by concussion or percussion, crashing the containing vessel; it ignites by flame, and burns without explosion, yielding a light ethereal flame of considerable volume.
Pure Nitro-Glycerin may be kept for a year unchanged, (De Vrij). The writer has exposed it to frost, sun and rain, for three years, and found it unchanged. Unless perfectly pure, however, it rapidly changes, becoming of an orange yellow color, evolving fumes, and seems to become a wholly differing compound, being difficult, when thus changed, to congeal, except at a much lower temperature than 45°F, and is more readily exploded.
It very easily decomposes by drying in a warm room with rarefied air, (Williamson).
It is instantly decomposed when dissolved in alcohol, by adding an alcoholic solution of caustic potash, the reaction being so violent as to eject the mixture from the test tube.
Nitro-Glycerin in contact with the following salts: nitrates of lime, cobalt, soda, barytes and potash; chlorides of calcium, of barium; perchloride of iron, carbonate of lime, sulphates of potash, lime and soda, was found unchanged after a year’s exposure.
Incompatibles: nitrate of silver precipitates black oxide of silver; nitrate of copper gives a precipitate of peroxide of copper, the Nitro-Glycerin remaining, however, bright and apparently unchanged. In a solution of nitrate of mercury, there appears a white film, a bubble of protoxide of azote, apparently adherent to the Nitro-Glycerin. Muriate of ammonia seems to divide the Nitro-Glycerin into two liquids, a light film supernatant, and the heavier liquid subjacent. The action of chloride of mercury (calomel) is but very slight. Protochloride of tin forms a precipitate of peroxide of tin, the residuary Nitro-Glycerin reflecting light powerfully, and as brightly as a diamond. Bichromate of potash is partly reduced to chromate. Sulphate of copper forms a very slight precipitate of oxide of copper, with apparently no change in the residuary Nitro-Glycerin. Sulphate of iron decomposes it, giving a voluminous precipitate, with evolution of nitrous fumes. Sulphuret of ammonia decomposes it, with precipitation of sulphur. Acetate of lead, chlorine water, ferridcyanide of potassium, cyanide of potassium, sulphocyanide of potassium, and of mercury, nitroprusside of sodium decompose it, also the sulphurets of iron, and potassium.
The action of tin, iron, and lead, slowly decomposing the Nitro-Glycerin, especially in the presence of an acid, indicates that metals having an affinity for oxygen, are the most active in promoting decomposition, evolving at the same time nitrous fumes, or protoxide of nitrogen, whilst the residuary Nitro-Glycerin does not seem to be affected; with sulphuretted hydrogen, as with sulphuret of sodium, potassium and ammonium, the action is prompt, and if these reagents be added in sufficient quantity, the Nitro-Glycerin is wholly decomposed, sulphur being precipitated.
Ascagne Sobrero, the discoverer of Nitro-Glycerin, says: it may be prepared by slowly introducing syrupy Glycerin into a mixture of two volumes concentrated sulphuric acid to one volume of nitric acid, Sp. Gr. 1.4, dropping it in and rapidly cooling. It seems to dissolve in this mixture without any noticeable reaction, and by pouring it into water, the so formed Nitro-Glycerin separates from it. It is then washed several times in water, is next dissolved in ether, and after evaporation (dangerous work this) is finally purified over sulphuric acid.
De Vrij recommends dissolving 100 grammes of Glycerin Sp. Gr. 1.262 in 200 c. c. of hydrated nitric acid cooled to 14°F, taking care that the mixture never exceeds in temperature 32°F. When a homogeneous mixture has been obtained, 200 c. c. of strong sulphuric acid are added very gradually, taking especial care that the temperature of this mixture never rises above 32°F. The oily Nitro-Glycerin which floats on the surface is separated by a tap-funnel from the acid liquid (which yields more Nitro-Glycerin on being diluted with water) and is now dissolved in the smallest possible quantity of ether; this solution is shaken with water, until the water no longer reddens litmus; the ether evaporated (here take care!) and the remaining Nitro-Glycerin heated over the water-bath till its weight remains constant. Merck, of Darmstadt, the eminent operative chemist, found in following De Vrij’s method, whilst evaporating the ethereal solution, and before the temperature had reached 212°F, it was accompanied by a terrible explosion. An accident from the same cause occurred in the laboratory of Dr. E. Von Gorup-Besanez, and we find in “Comptes Rendus” an account of the effects of the explosion of only 10 drops of Nitro-Glycerin, which, by one of the pupils of that chemist, in his laboratory, were put into a small cast-iron saucepan, and heated with a Bunsen gas flame. The effect of the explosion was that the forty-six panes of glass of the windows of the laboratory were smashed to atoms, the saucepan was hurled through a brick wall, the stout iron stand on which the vessel had been placed was partly split, partly spirally twisted, and the tube of the Bunsen burner was split and flattened outwards. Fortunately, none of the three persons present in the laboratory at the time were hurt. When Nitro-Glycerin is caused to fall drop by drop on a thoroughly red hot iron plate, it burns off as gunpowder would do under the same conditions; but if the iron is not red hot, but yet hot enough to cause the Nitro-Glycerin to boil suddenly, an explosion takes place.
Nitro-Glycerin is decomposed by evaporation, even in vacuo, over sulphuric acid at ordinary temperatures (Railton), and when left to itself, frequently undergoes spontaneous decomposition; but when well purified, it may be kept for a long time without alteration (H. Watts); exhibits different properties, according to the manner in which it is prepared (Gladstone).
Liecke in Dingler’s Polytechnical Journal, prescribes the following formulæ for manufacturing the three several preparations, Mono-Nitro-Glycerin, Di-Nitro-Glycerin and Tri-Nitro-Glycerin.
| Mono-Nitro-Glycerin: | ||||
| Glycerin 100 grammes. | ||||
| Nitric acid, Sp. Gr. 1.3, 200 grammes. | ||||
Dissolve the Glycerin in the nitric acid, and then add sulphuric acid 200 cubic centimeters.
| The product should be | C³H⁵O²H |  |
| O⁴ | ||
| NO⁴H |
Di-Nitro-Glycerin:
Sulphuric acid containing 1 eq. water, two volumes, nitric acid, Sp. Gr. 1.4, one volume; mix the above, lower the temperature to 32°F, or below, and drop into it
Glycerin, pure,one volume.
| Prod. | C³H⁵O²H | |
| O⁴ | ||
| 2NO⁴ |
| Tri-nitro-glycerin: | ||||
| Sulphuric Acid, 3.5 parts. | ||||
| Nitrate of Potash, 1 part. | ||||
cooled to 0°F, produces KO + 4SO³ + 6HO, from this the concentrated fuming Nitric acid is separated by decantation, and being maintained at 0°F,
Glycerin 0.8 parts is very gradually added,
| producing | C³H⁵O²NO⁴ | |
| O⁴ | ||
| 2NO⁴ |
From the above extracts of several of the most eminent chemists of the present day, the reader will glean, that in order to prepare this explosive, of uniform quality, invariable in composition, free from water, or any other impurity, it is not merely necessary to buy the best materials, but to have at command the means of verifying their purity before attempting its manufacture.
These points secured, viz: purity and strength of materials, i. e., glycerin free from sugar, fatty acid, saline impurities, and a mixture of Sulphuric Acid with Nitric Acid in due proportion, of due percentage of the respective acids, and not more water therein, nor in the glycerin, at one time of making, than another; the next point to command will be, that in combining the glycerin with the acids, when considerable heat is evolved, the heat thus evolved shall be absorbed rapidly, so as never under any circumstances whatever, to exceed a certain temperature. Sobrero names 32°F; otherwise, according to my experience, very differing nitro-glycerin will result from variation of temperature whilst mixing. Such products may be fatal to the miner, although only affecting the manufacturer in a pecuniary sense. I am led to emphasize these remarks from the fact that prospectuses have been issued to tempt contractors to buy apparatus in the one case, and offering to manufacture on the side of a railroad cutting, if required, in another case, by parties who have no experience in the manufacture, and who start in their new avocation, by deriding the care, outlay and precautions that their competitors have deemed it necessary to make, in order to secure a uniform, certain, and, for mining purposes, perfectly safe explosive; for as the product is to be handed over to the uneducated miner, who cannot estimate the risk he is subjected to even if such a course occurred to him, it does seem to me just and proper, that the controlling engineer, the intelligent contractor, and especially the operating miner who is to handle this explosive, should be advised, that under the term Nitro-Glycerin, very different substances, both as regards explosive force, and liability to spontaneous explosion, do result, unless extraordinary precautions are adopted in the selection of the crude materials, as well as securing uniformly low temperature throughout the process of making. Unless this be done, decomposition sets in and is indicated by the emanation of fumes, by the deepening of the light lemon tint to an orange yellow, and at this point, the miner should decline using it, and require the manufacturer to take his place, and the risks contingent on using it.
Since many of the accidents that have occurred with Nitro-Glycerin, have been traced to leakage from the containing vessel, notably the San Francisco accident, probably the Panama explosion, and undoubtedly the Titusville or Enterprise explosion, besides other cases where it leaked through the bottom of wagon and thence on to the springs, whose hammering caused an explosion, the discovery by Granger, [page 19], confirmed by the magazine explosion, [page 18], teach the importance of transporting this explosive in a solid state, that is, congealed; there is however another reason; decomposing Nitro-Glycerin will not solidify at 45°F, and the consumer has a ready and convenient test for the purity of this article, by seeing to it that he invariably purchases the explosive deliverable in a solid form. Another test is, when exploded, in a close tunnel, the fumes or decomposed gases should not inconvenience the miner.—Failing in either of these tests, it may fairly be rejected as an inferior article, or should be used up as speedily as possible, preferably by the manufacturer or his more experienced employees, rather than by a miner who may not be fully aware of the unnecessary risk to which he is exposed in handling impure Nitro-Glycerin.