The manufacture of nitro-glycerine is based upon the reaction which takes place when glycerine is brought in contact with nitric acid and which may be represented by
C3H5O3H3+3HONO2= C3H5(NO2)3O3+3H2O
in which one molecule of glycerine being acted upon by three molecules of nitric acid yields one molecule of tri-nitro-glycerine and three molecules of water. Three of the atoms of hydrogen in the glycerine being replaced by the three atoms of nitryl (NO2). in the three molecules of nitric acid.
It is believed to be possible to produce three different nitro-glycerines. By replacing one atom of hydrogen in the glycerine by one atom of nitryl the mono-nitro-glycerine is formed, having the formula C3H5NO2H2O3. By replacing two of the atoms of hydrogen by two of nitryl the di-nitro-glycerine is produced, having the formula C3H5(NO2)HO3.
By replacing the three atoms, we get the tri-nitro-glycerine given in the reaction above.
It is believed also that the tri-nitro-glycerine is the only one of these compounds which is stable and that many of the accidents which have been caused by nitro- glycerine have been due to the presence of these other compounds in the tri-nitro-glycerine.
To produce pure nitro-glycerine it is necessary that we should use the purest, most concentrated glycerine and the purest, strongest nitric acid. The presence of any fatty impurities in the glycerine gives rise to the decomposition and spontaneous explosion of the nitro glycerine, hence the necessity of purity. It is difficult to obtain anhydrous glycerine and anhydrous nitric acid, hence it is the custom to use the most concentrated articles to be obtained and to mix with them some substance which will absorb the water and thus render them anhydrous. The importance of using an exsiccating substance is further shown, if we refer to the reaction, by the fact that water is one of the products of the reaction and hence if we were to start with anhydrous glycerine and nitric acid, after a portion of the glycerine has been converted the water formed will have so diluted the remainder that there is danger of the lower nitro-substitution products being formed.
Concentrated sulphuric acid is used as the exsiccating substance and it is added in sufficient quantity to combine not only with the water contained in the original substances but also with all the water formed during the operation. But in using the sulphuric acid another element of danger is introduced. The sulphuric acid removes the water by entering into chemical combination with it, a hydrate of sulphuric acid being formed, and this combination is attended with the development of heat. If the temperature is raised somewhat there is danger of the nitro-glycerine being exploded or if an explosion does not result the glycerine will be wasted by being converted into oxalic acid and other products, which may render the nitro-glycerine unstable. Hence it is necessary to keep the mixture cool while the conversion is taking place and in the process of manufacture this is effected by means to be described.
I have thus attempted to state as briefly as possible the rationale of the operations in the manufacture of nitro-glycerine. I will now describe some of the processes employed.
Sobrero, the discoverer of nitro-glycerine, proposed the following process for its manufacture; one half oz. of anhydrous glycerine is poured with constant stirring into a mixture of two ozs. of concentrated sulphuric acid and one oz. of fuming nitric acid of Sp. Gr. 1.52, the temperature of the mixture being kept below 25°C. by external cooling with ice, and as the oily drops begin to form on the surface, the mixture is poured with constant stirring into fifty ozs. of cold water. Nitroglycerine then separates and may be purified by washing and drying in small portions, in a vapor bath. (Liebe, Arch. Pham. ciii, 158; civ, 282.)
De Vrij's process differs from the above only in the proportion of the acid used and in the fact that the sulphuric acid was added after the mixture of the glycerine with the nitric acid had been effected.
The Mowbray process as used at North Adams and in a much improved form at Newport, is simply an adaptation of the Sobrero process to the commercial manufacture.
Many of you are familiar with the process, yet you will pardon me if I call your attention to it again in order to compare it with the processes which are afterwards to be described. The acids are first mixed in the proportions of one part of nitric acid (Sp. Gr. 1.45) to two pts. of sulphuric acid (Sp. Gr. 1.8) and cooled.* The operation is conducted, in the words of Prof. Hill, as follows.
"The apparatus used for this purpose, at the Station, is shown on the Plate. An elevation, section and plan are given, the lettering being the same in the three.
A, A, A, A, A, A, are wooden troughs placed around the brick chimney D, D. In these troughs are the earthen-ware pitchers a, a, a - - - a which contain the acid mixture. On the shelf B, above the pitchers, are the bottles b, b, b, - - - - - b which contain the glycerine. The bottles are loosely closed by wooden stoppers with broad, rounded tops. Through holes in these stoppers, pass loosely the rubber tubes c, c, c, c, which reach to the bottom of the bottles and carry small glass jets at their outer ends. Conical wooden plugs e, e, e, e, are placed in the holes through the stoppers, alongside the rubber tubes.
The steam pipe G passes along the shelves B, B, just behind the glycerine bottles. The air-main F passes under the shelf B, and carries on its under side a number of small short pipes or jets; (two for each pitcher,) to which are attached the rubber tubes d, d, d, d, which bang over the pitchers. In these rubber tubes are inserted glass tubes, long enough to extend to the bottom of the acid pitchers. In the elevation, these tubes are out of the pitchers, but in the section they are in place as if in use.
The troughs are made tight to hold the ice water with which the pitchers are surrounded. Partitions, with openings at the bottoms, cut off the corners of the troughs, forming clear spaces f, f, f, f. These spaces contain water only, as the partitions keep out the ice. These water spaces are convenient as affording opportunities for quickly emptying a pitcher into water if it becomes necessary. In one corner of each trough is placed a pipe, through which the water may be drawn off into the escape E, when the operation is finished.
The pitchers stand on narrow strips, which raise them off the bottom about two inches, thus giving the cold water free access all about them, and when in position are well under the overhanging hoods C1,C2. These hoods are flat wooden boxes, wide at the bottoms and drawn in at the tops, where they fit against openings in the chimney D, D. In the lower part of the chimney, on the floor below, is placed a grate and fire door (not shown in drawing).
Each pitcher receives 18 to 20 pounds of the acid mixture (according to the strength of the latter). All are then set in place in the troughs, covered with glass plates, surrounded with ice and water and allowed to stand until completely cooled. Into each bottle is put two pounds of glycerine.
When the acid in the pitcher has fallen to the temperature of the surrounding ice water, the covers are removed from the pitchers and the air-tubes passed through holes in the hoods down into them. Through these air-tubes a strong current of air is forced by means of a pump driven by steam. This current of air keeps the contents of the pitchers in continual agitation. The air for the pump is drawn through sulphuric acid to render it perfectly dry, and just before it enters the air-main over the troughs, it is thoroughly cooled. The cooling arrangement is made of ten coils of small tin pipe, which are surrounded by ice, (or better, ice and salt). These coils are so arranged as to give an extensive cooling surface without impeding the current.
As soon as the air-current has been turned on, the flow of the glycerine is begun. Each rubber tube c is a siphon, which is started by suction through a glass tube inserted in the outer end. As soon as the glycerine runs freely, the suction tube is withdrawn, and a fine pointed glass jet put in its place. The glycerine runs from this jet in a fine stream directly into the pitcher under it. In cold weather the glycerine may become too thick to flow easily. To overcome this, the bottles of glycerine are warmed by passing steam through the pipe behind them until the glycerine is sufficiently thin.
The glycerine dropping into the acid mixture is rapidly acted on and converted into nitro-glycerine."
When the whole of the glycerine has run into the acid mixture, the mixture of acids and nitro-glycerine are poured into a large wooden tub filled with water and the nitro-glycerine is washed until all traces of the acids are removed.
Nobel's Process.
In Nobel's process a large leaden cylinder capable of holding 200 litres is placed inside a wooden cylinder. Cold water circulates in the space between the two, and also, through a leaden worm coiled up in the inside of the leaden cylinder. The charge of acid is placed in the converter, and a leaden pipe with a perforated nozzle introduces the glycerine into the center of the acids. Inside of this pipe is another which brings in the compressed air so that the glycerine is forced into the acid mixture under a considerable pressure and the mixing is very intimate and rapidly effected.
The acid mixture is obtained by dissolving one part of KNO3 in three and a half parts of H2SO4 of Sp. Gr. 1.8. The mixture is cooled down to 0° C. when the whole of the potash separates out as K2SO4 after the reaction.
H2SO4+2KNO3=K2SO4+2HNO3
and there remains a mixture of the strongest nitric and sulphuric acids After the conversion of the glycerine is complete, it is run into the washing tanks and finally treated with three per cent. of Na, CO, By this apparatus one thousand kilos. of nitro-glycerine are made per day at Paulille, in Southern France.
In 1876 the Noble process was used, with some slight modifications, at 14 factories.
Date of foundation |
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1865 | Vinterduken, near Stockholm, | Sweden |
1866 | Christiana, | Norway |
1865 | Krümmel, near Hamburg, | Germany |
1868 | Zamky, near Prague, | Austria |
1872 | Schlebuch, near Cologne, | Germany |
1874 | Presburg, | Hungary |
1872-3 | Isleten, canton of Uri, | Switzerland |
1872-3 | A vigliana, near Turin, | Italy |
1872 | Galdacano, near Bilbao, | Spain |
1873-4 | Trafaria, near Lisbon, | Portugal |
1871 | Ardeer, near Glasgow, | Scotland |
1870-71 | Paulille, near Port-Vendres, | France |
1868 | San Francisco, |
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1873 | New York. |
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Since then, the Scottish works have been removed to Stevenson. These factories produced in 1874, three and a half million kilogrammes of dynamite. The most important factory is that of Kriimmel, where the product is six hundred thousand kilogrammes. The factories at Zamky, Stevenson and San Francisco, follow with an annual yield of from four hundred thousand to five hundred thousand kilos.
At Stevenson, the nitric acid is made by the ordinary process, which consists in heating potassic or sodic nitrate in large retorts with sulphuric acid, and condensing the nitric acid, which is given off; or else it is absorbed by concentrated sulphuric acid and the mixture used for making nitro-glycerine.
At this factory the mixture of nitro-glycerine and mixed acids is run off from the convertor into settling tanks and when the nitro-glycerine has settled, the acids are drawn off and used for making nitric acid. The nitro-glycerine is then run into the washing tank and washed as usual.
I am indebted to Mr. Alex. Cuthbert the manager of the Stevenson works, for a copy of the tests which are applied to the glycerine used by them; and also, for a copy of the Government test for nitro-glycerine mixtures.
Essentials of Glycerine Used By Nobel's Explosive Company, Glasgow.
"For our own purpose glycerine, when diluted with twice its bulk of pure water, should give no precipitate with ammonia, even after standing for some time. There should be no precipitate with ammonia and oxalate of ammonia, Nitrate of silver added to it ought not to make it milky. Hypo-nitric acid passed through it might not to curdle it. The smell, if there is any at all, ought not to be unpleasant nor the color dark.
Complete solubility in water shows freedom, in some degree, from oil or fat. Precipitates with ammonia, show iron and alumina; with oxalate of ammonia, lime; with nitrate of silver, chlorides: curdling with hyponitric acid shows presence of fatty acids (oleic, margaric and palmitic), all of which are objectionable, and shows imperfect decomposition of the fat or oil from which the glycerine has been made, and also, defective distillation. A bad smell indicates decomposition in the still, and a dark color indicates charring. Both of these are caused either by too little steam in the still, or by too high a temperature in it. The distillation to be good must be effected in an atmosphere of super-heated steam at a temperature of 500° to 600° Fah., rather less than more. But the concentration of the distilled glycerine must be effected in so called vacuum pans, in the same way that sugar liquors are concentrated. Any over-heating during this operation is sure to cause decomposition that will injuriously affect the yield of nitro-glycerine."
Heat Test for Nitro-Glycerine Mixtures.
"Experiments to ascertain whether a heat-test, similar to that adopted in the case of gun-cotton, could be applied to nitro-glycerine preparations of different kinds for the purpose of exercising control over the quality, in regard to stability, of commercial preparations of this class.
These experiments were carried on in the Chemical Establishment of the War Department, and embraced a trial of a large number of specimens, including samples that from time to time had been forwarded to the Committee for examination, and trade samples received from H. M. Inspector of Magazines.
The method of applying the test and the results obtained, are given in the following Memorandum from the War Department Chemist.
Woolwich, February 11th, 1874.
Secretary of Special Committee on Gun Cotton, &c.:
In accordance with the request of the Committee I have instituted a series of experiments with the view of ascertaining whether a heat-test, similar to that employed as a means of ascertaining whether the processes of purification have been sufficiently applied to gun-cotton, can be applied to nitro-glycerine preparations of different kinds, for the purpose of exercising control over the quality, in regard, to stability, of commercial preparations of this class.
As these preparations differ considerably from each other, both as regards the proportion of nitro-glycerine which they contain and as relates to the solid materials with which that substance is mixed, the most satisfactory course to be pursued in applying a heat-test for comparative purposes would at first sight appear to consist in extracting the nitro-glycerine itself from the preparation to be tested and applying the heat-test to the liquid, apart from the other ingredients of the preparation. I therefore instituted a number of experiments in this direction, but with unsatisfactory results. Mechanical means were found to be inapplicable to the separation from small samples (say one cartridge) of even those materials richest in nitro-glycerine sufficient of the liquid for purposes of testing; its extraction by means of a solvent was also found to be inexpedient, because the obstinate retention by the nitro-glycerine of small portions of the solvent used, was found likely to become a fruitful source of fallacious results. It was ascertained, moreover, that the period for which nitro-glycerine may be exposed to heat (150-160° F.) before it furnishes any indication of change by the disengagement of acid vapor, is very different when the liquid is heated by itself and when it is reduced to a state of division by absorption in some porous medium or by mixture with solid substances of inert character.
I therefore proceeded to apply to various samples of dynamite and other nitro-glycerine preparations, in their original condition, the heat-test described in detail in the official specification which governs the supply of compressed gun-cotton to H. M. Government.
An entire cartridge or half a cartridge of each sample (previously thawed, if frozen,) was rubbed up thoroughly, so as to furnish a uniform sample as pulverulent as it could be obtained. Fifty grains were then introduced into the test tube, pressed down firmly by means of a fiat-headed glass rod, and placed in the testing bath which was maintained at 160° F., the test being carried out in accordance with the directions laid down in the gun-cotton heat test.
The following results were obtained with samples which I have here distinguished by numbers, giving at the same time the percentage of nitro-glycerine in such as it had been estimated in.
Number of Sample | Percentage of Nitro Glycerine | Duration of exposure to 160° F. before the test paper was affected | Remarks |
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| Duplicate experiments |
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It was thought possible, before this series of experiments was carried out, that the proportion of nitro-glycerine, in a given sample, might considerably influence the results obtained, but it appears to be satisfactorily indicated by the comparative results furnished with samples 2, 4, 5 and 7 (as well as with others) that such is not the case at any rate to an extent to affect the value of the test as a comparative one.
The high results furnished by sample 13, were unquestionably to be ascribed to the presence of a large proportion of a substance (carbonate of soda) capable of neutralizing any acid liberated by the action of heat, and it is probable that some other high results observed in the series are ascribable to the same cause, as an alkaline (or earthy) carbonate is at any rate occasionally used as a protective constituent in the production of this class of preparations. There is no question that the keeping properties of a nitro-glycerine preparation are, at least in many cases, likely to be considerably improved by such a precautionary measure. The fact that the existence of such an ingredient as carbonate of soda, in a particular sample, has the effect of raising the test which would be furnished by that sample if the neutralizing material were not present, can therefore not, in my opinion, be considered to reduce the reliability of the test as a practical indication of the stability of the preparations examined.
There appear to be strong grounds for ascribing the high results furnished by No. 8 sample to a protective action exerted by the paraffin which existed in that particular preparation. I am, however, unable to speak with decision on this point, which could only be satisfactorily determined by experimenting with preparations made up of one and the same batch of nitro-glycerine, with and without the addition of paraffin, but in all other respects alike.
Some considerable experience in the application of the heat-test to samples of the various nitro-glycerine preparations of commerce is indispensable before a decided opinion can be given as to the minimum duration of exposure to 160° F., which a sample should sustain before any reaction is produced upon the test paper. The results obtained with samples 1, 3, 9, 10, 11, 16, 17 and 18 (of which there was not one possessing exceptional characters) appear, however, to indicate that samples of dynamite, &c., should sustain exposure to 160° F. (in the manner specified) for not less than 5 to 6 minutes before producing any action upon the test paper.
(Signed) F. A. Abel.
Apparatus Required.
1. A spherical glass vessel, Fig. 4, about 8 inches diameter (a) filled with water to within a quarter of an inch of the edge, having a loose cover of sheet tin or copper about 7 inches square (b), rests on a tripod stand about 14 inches high (c), covered with coarse ironwire gauze (e), and surrounded with a screen of thin sheet copper (d). Within this is placed an argand burner (f) with glass chimney. Over the glass globe is placed a common green paper lamp shade (mu). The cover (b) has 5 holes arranged as seen in Fig. 5; No. 5 to receive the thermometer; No. 1, the regulator; No. 4, a small funnel; and Nos. 2 and 3, test tubes containing the gun-cotton to be tested. Around holes 2 and 3 on the under side of the cover are soldered 3 pieces of brass wire with points slightly converging (Fig. 6 turned upside down), these, acting as springs, allow the test tubes to be easily placed in position and removed.
2. Scheibler's temperature regulator.
3. Two cells of Le Clanche's battery, No. 1.
4. A few yards of insulated copper wire.
5. Test tubes about 1 inch diameter and not less than 5 inches long.
6. Glass rod with a flat head, of sufficient length to reach to the bottom of the test tubes.
7. Corks, fitting the test tubes and carrying an arrangement for holding the test paper (a thin glass tube passing through the centre of the cork, drawn out and terminating in a platinum wire hook, Fig. 7).
8. A thermometer with range not less than 300 to 212° Fahrenheit.
9. A minute clock.
Materials Required.—The test paper is prepared as follows :-45 grains of white starch are added to 81 ounces of water, and the mixture is stirred and heated to boiling; 15 grains of iodide of potassium are dissolved in 8½ ounces of water. The two solutions are thoroughly mixed together. Strips or sheets of white Swedish filter paper are dipped in the solution thus prepared; they are then allowed to drain and dry. The dimensions of the pieces of test paper used, are about 1/2 inch by 5/8 inch. The paper should be preserved in a well-stoppered or corked bottle.
Preparation of Samples for Testing.—Half a cartridge of the material (or about 500 grains, if it is not supplied in the form of cartridges,) is thoroughly rubbed up together so as to furnish a very uniform sample. If the material is frozen, it should first be thawed.
Application of the Test.—The thermometer is fixed so as to be inserted through the lid of the glass globe into the water (which is to be steadily maintained at a temperature of 160° Fahrenheit) to a depth of 21 inches. 50 grains of the sample to be tested, are inserted into the test tube and gently pressed down to the bottom, with a flat headed glass rod. The test tube is then inserted through the perforation in the cover and is immersed in the hot water to the depth of 2/ inches, the tube being closed with a loosely fitting cork. A test paper is fixed on the lower extremity of the glass rod, so that, when inserted into the tube, it will be in a vertical position. A drop of distilled water containing 10 per cent. of pure glycerine is applied to the upper edge of the test paper, the quantity used being only sufficient to moisten about half of the paper; the first cork is then taken out of the test tube and replaced by the cork holding the glass rod and test paper, keeping the test paper as near the top of the test tube as possible until the tube has been immersed for about 5 or 6 minutes. A ring of moisture will, about this time, be deposited in the test tube a little above the cover of the bath; the glass rod must then be lowered until the lower margin of the moistened part of the paper is on a level with the bottom of the ring of moisture in the tube; the paper is now closely watched. The test is complete when a very faint brown coloration makes its appearance at the line of boundary between the dry and moist part of the paper. The interval of time between the first insertion of the tube containing the sample in the water at 160° and the first appearance of discoloration on the paper, constitutes the test."
Works at Vonges.
The manufacture of nitro-glycerine is carried on by the French government at the powder mills at Vonges, in the eastern part of the country, about thirty miles from Dijon. The factory consists of six light frame buildings about thirty feet long, fifteen feet high, well lighted by six windows on the front which extend nearly to the ground The buildings stand along the side of a stream with earth embankments behind each building and earth traverses between the buildings. The buildings are used as follows.
No. 1. For mixing the acids.
No. 2. For mixing the glycerine and sulphuric acid.
No. 3. For making dynamite.
No. 4. For washing the nitro-glycerine.
No. 5. For making nitro-glycerine.
No. 6. For making nitro-glycerine.
Besides these there is an old shed near No. 1 where the mixtures are cooled.
In No. 1 the nitric and sulphuric acids are mixed in equal proportions by weight.
The apparatus used consists of a semi-cylindrical trough, Fig. 8., of iron lined with lead, about 1 meter long and 40 cm. in diameter. The trough is surrounded by an iron jacket. Water is kept circulating in the space between in order to keep the mixture cool. When the apparatus is in use it is covered with a semi-cylindrical iron cover, lined with lead, to prevent loss by spattering. A shaft running the length of the trough and turned from the outside by a crank, is armed with paddles which, when the shaft is turned, mix the acids together very intimately. A leaden tube at the bottom allows the acid to run off into carboys. The apparatus rests on a light iron frame.
The acids are now carried in the carboys to the cooling shed where they are immersed up to their necks in troughs of cold water and allowed to remain till thoroughly cooled. The cooling shed is open on all sides to admit of the ready circulation of the air but covered on top to shield the acids from the influence of the sun.
In the next building the glycerine is mixed with concentrated sulphuric acid, by means of a similar apparatus to the one described above, in the proportion of one hundred kilos of the glycerine to three hundred and twenty kilos of the acid. This mixture stored in carboys is then removed to the cooling shed.
We will now turn to the converting rooms. Here the earthern pots Fig. 9. used for the conversion of the glycerine, twenty in number, are ranged in two rows elevated on a platform about a meter high, with about a meter space between the rows. The pots are of about eighty three litres in capacity. They are closed with leaden covers sealed with sulphuric acid to prevent the exposure of the entire surface of the mixture to the atmosphere, for this would permit the absorption of the aqueous vapor in the atmosphere which would result in the dilution of the acid and endanger the safety of the process or at least render the yield less. As however during the operation fumes may be generated which will exert pressure, a vent Fig. 10 must be provided. This is secured by fitting into the cover two pieces of lead pipe 4 cm. in diameter and 5 cm. long. Around each of these outlets another piece of pipe 6 cm. wide and 4 cm. long, is fastened to the outside of the lid, thus making an annular space which may be filled with strong sulphuric acid to act as a seal. A leaden cap fits over the inner tube and a curved leaden tube about ½ cm. in diameter leads from the top of the cap, and permits the nitrous fumes to escape into the air.
The object of this apparently complicated device is as follows. When the action is going on quietly the small tubes are of sufficiently large dimensions to permit the gases generated to escape freely but if through any cause a large volume of gas is generated the pressure will cause the caps to be lifted and the entire area of the 4 cm. pipe will then be exposed, thus furnishing, without any harm being done, a sufficiently large opening for the escape of the gas.
The remainder of the apparatus consists of a bent lever for raising the covers of the pots which lets into two upright iron bars which are erected beside each pot, and of lead siphons for running off the acids and nitro-glycerine.
To make the nitro-glycerine forty-two kilos of the mixture of glycerine and sulphuric acid and fifty-six kilos of the mixed acids are poured into the pot, both of the mixtures having been thoroughly cooled. The cover is then put on, and the action is left to go on over-night.
You will please observe how unlike this process is to any other suggested. Here the mixture is surrounded by the atmosphere solely, whereas, in all other processes, the mixture is kept cool by being surrounded with ice or with cold water. In other processes the mixture is continually agitated by a current of air or by some mechanical means while here the materials are allowed to mix quietly together. And finally while in the other processes the glycerine is added in small quantities to the acids and the process has to be closely watched to prevent accidents, here the whole of the glycerine is added at once to the acids and the operation is left to itself. Yet this operation seems to be with-out danger for not a single accident has occurred since 1871, when the manufacture was begun at this place by this method. Besides the freedom from danger this process gives a larger yield of nitro-glycerine than any other and the product is very pure.
The comparative yield is shown in the following table.
Champion and Pellet’s process 1 kilo. of gly. yields 1.2 to 1.3 kilo. of n. gly
Girard, Millot and Vogt’s process 1 kilo. of gly. yields 1.3 kilo. of n. gly
Mowbray’s process at Newport 1 kilo. of gly. yields 1.6 kilo. to 1.5 kilo. of n. gly
Process at Vonges 1 kilo. of gly. yields 1.8 kilo. of n. gly
Theoretical yield 1 kilo. of gly. yields 2.46 kilo of n. gly
Hill obtained by the action of the strongest nitric acid on anhydrous glycerine 1.96, 1.89 and 2.03 parts of nitro-glycerine from 1 of glycerine. De Vrij obtained by the same process 1.84 parts of nitroglycerine.
The following table shows the relative amounts of acid used in various processes.
| Nitric | Sulphuric | Glycerine |
De Vrij | 200 pts. | 200 pts. | 100 pts. |
Sobrero | 200 pts. | 400 pts. | 100 pts. |
Siebe | 200 pts. | 400 pts. | 100 pts. |
Champion | 226 pts. | 426 pts. | 100 pts. |
Paeger & Betram | 266 pts. | 533 pts. | 100 pts. |
Hill | 300 pts. | 600 pts. | 100 pts. |
Vonges | 280 pts. | 600 pts. | 100 pts. |
Theory requires | 206 pts. |
| 100 pts. |
After the operation of converting the glycerine is completed, the mixture is siphoned off and conveyed in earthern vessels to the washing room where it is thrown into water to remove the acid, the last traces of the acids being neutralized by carbonate of magnesia. It is then allowed to settle and is stored in the magazine.
When used for making dynamite it is conveyed to the dynamite building. Here the infusorial silica, previously dried and sifted, is spread out on a low wooden table covered with lead. The nitro-glycerine is poured upon it, and then a workman with a rolling pin incorporates the mass thoroughly. After the whole is incorporated the dynamite is squeezed in a large, wooden cylindrical vessel, having a perforated bottom, and provided with a plunger by which any excess of nitro-glycerine is squeezed out. The vessel is suspended vertically upon trunions so that it may be readily overturned and emptied. The dynamite is now ready for cartridges. Three kinds of dynamite are made at Vonges.
No. 1 contains 75 per cent. of nitro-glycerine.
No. 2 contains 50 per cent. of nitro-glycerine.
No. 3 contains 30 per cent. of nitro-glycerine.
Two to three per cent, of carbonate of magnesia are added to the dynamite as a precautionary measure to neutralize any traces of acid remaining in the nitro-glycerine.