Sec. II. Of Nitrate of Soda.
This salt has been recommended in lieu of nitre, for preparing certain fire-works; but we confess, we can see no particular advantage in using it. It has the property of attracting humidity from the air, and on that account is rendered unfit for the manufacture of gunpowder. This salt is composed of nitric acid and soda. It was formerly called cubic nitre. It may be formed, very readily, by saturating nitric acid with soda, and evaporating the solution. It crystallizes in rhomboidal prisms. It may be formed more economically, by mixing together the solutions of nitrate of lime and sulphate of soda, filtering the mixture, and evaporating the filtered liquor. It will be sufficient to observe, that it deliquesces, or absorbs moisture, and in the fire, that its phenomena are the same as those of nitre. It does not melt so readily.
Used in the same proportion as nitre, it will form a gunpowder, which soon, however, spoils by exposure. It will, like nitre, communicate a yellow colour to the flame of alcohol. Experiments were made with this salt, with the view to the fabrication of gunpowder, by MM. Bottée and Riffault. Their conclusions, as we have stated, may be seen in their work on gunpowder. Professor Proust says, that five parts of nitrate of soda, with one of charcoal, and one of sulphur, will burn three times as long as common powder, so as to form an economical composition for fire-works.
The cubic nitre, and the nitrum flammans were known, and so called, by the older chemists. The former we have seen, is the nitrate of soda, and the latter, is a combination of nitric acid and ammonia. Nitrate of soda, consists of 6.75 acid + 3.95 soda.
Nitrate of ammonia possesses the property of exploding; and, when exposed to a temperature of about six hundred degrees, is decomposed, furnishing the nitrous oxide, called also the protoxide of azote, and exhilarating gas, besides water. Nitrate of ammonia is composed of 6.75 acid + 2.13 ammonia + 1.125 water.
Sec. III. Of Chlorate of Potassa.
This salt, formerly called hyperoxymuriate of potassa, is used for sundry preparations, and especially for experimental fire-works. It is prepared by dissolving one part of carbonate of potassa in six parts of water, and saturating it with chlorine, formerly called oxymuriatic acid gas. This operation is usually performed in a Woulfe's apparatus. The gas, as it proceeds from the retort or gas bottle, is brought in contact with, and passes through, the fluid. It is formed by pouring liquid muriatic acid on the black oxide of manganese, or by pouring sulphuric acid on a mixture of muriate of soda, and the black oxide. When the saturation is nearly complete, crystals fall down. These being dissolved in boiling water, and the solution allowed to stand, pure chlorate of potassa will be formed.
This salt is composed of 9.5, chloric acid, and 6 potassa; and chloric acid is formed of 28.87, chlorine, and 32.28, oxygen. It is to the oxygen in the salt, that its particular properties in fire-works are to be ascribed.
This salt is decomposed by all combustible bodies, and detonations generally accompany the decomposition. Hence it is used in a variety of experiments, some of which we will give.
Three parts of the salt and one of sulphur detonate when rubbed in a mortar. The same mixture, struck with a hammer on an anvil, produces a loud explosion. Phosphorus detonates with this salt either by trituration or percussion. The quantity of each should not exceed a grain. Treated in the same manner with almost all the metals, the same effect takes place. Cinnabar, antimony, pyrites, &c. produce the same effect. Nitric acid, poured on a mixture of this salt with phosphorus, produces flashes of fire. A mixture of the chlorate and white sugar, when touched with sulphuric acid, immediately inflames. Hence it is used in the preparation of pocket lights; the mixture being put on a common sulphur match, and immersed in sulphuric acid. The same preparation of sugar and chlorate of potassa, put over a tube used for firing artillery, will set fire to the priming fuse, by dropping on it sulphuric acid. Owing to this effect, M. Gassicourt (Archives des Découvertes), recommended a similar mixture for discharging cannon by means of this acid. As it contains a large quantity of oxygen, that gas may be obtained from it by distillation. Light decomposes it. It should, therefore, be excluded from the light.
As this salt, when mixed with inflammable substances, detonates when struck with a hammer, it has been used for the purpose of inflaming gunpowder without the use of the flint and steel. There are several formulæ given for the purpose. We remarked, when treating of the general theory of fire-works, that the Rev. Alexander Forsyth discovered a new kind of gunpowder, which inflames merely by percussion; that the gun-lock, which he contrived, was calculated for firing cannon, as well as musquetry; that it was so contrived as to hold forty primings of such powder; and that the act of raising the cock primes the piece. In his composition, each charge of priming contains no more than one-eighth of a grain of chlorate of potassa. Since that period, it appears, that the lock, as well as the powder, has been improved, although neither of them is in general use. Thenard, (Traité de Chimie, tome ii, p. 559, troisième édition), has given a formula for preparing a priming powder of this salt, adapted to the new lock, which is made by mixing it with 0.55 of nitrate of potassa, 0.33 of sulphur, 0.17 of the raspings of peach-wood passed through a fine sieve, and 0.17 of lycopodium, or puffball. (See Inflammable Powder.)
This salt also produces powerful effects with charcoal and sulphur. Three parts of it, with half a part of sulphur, and half a part of charcoal powder, produce most violent explosions. Two persons, in 1788, lost their lives by it. If this mixture be thrown into concentrated sulphuric acid, a brilliant flame is produced. Such mixtures, we are informed, will explode spontaneously. It should not, for that reason, be kept prepared. Chlorate of potassa has been used in the place of nitre, for the manufacture of gunpowder, in consequence of its decomposition by charcoal. From its explosive effects, M. Berthollet was induced to propose it as a substitute for nitre. The proportions used by Chaptal, (Chimie Appliqué aux Arts, tome iv, p. 198), are six parts of chlorate of potassa, one of sulphur, and one of charcoal. They are to be mixed in a marble mortar with a wooden pestle. The first experiment was made at Essone, in France, in 1788. No sooner, however, had the workmen begun to triturate the mixture, than it exploded with violence, and killed two persons.
The force of this gunpowder is greater than that of the common sort; but the danger of preparing it, and even of using it, is so great, that these circumstances will always prevent its introduction. A salt, containing so much oxygen, and so loosely combined, that even the slightest friction, in contact with inflammable bodies, will separate it, must, of necessity, prevent its use in that way.
The experiments, which were made at the arsenal at Paris, on the 27th of April, 1793, comparing the effects of muriated powder, and the superfine common powder, have given us the following results:
1st. By the eprouvette of Darcy, consisting of a cannon, which, being suspended to the extremity of a bar of iron, described by its recoil an arc, of which the degrees can be measured.
| Recoil. | |||
| 2 drachms | muriatic powder, | 15 deg. | 2/20 |
| 2—— | do do moistened, | 14— | 1/20 |
| 2—— | common powder, | 10— | 7/20 |
| 2—— | common powder, | 10— |
|