CHLORATE OF POTASSIUM AS AN EXPLOSIVE
(Specially written for FIRE AND WATER.)
IN the number of FIRE AND WATER published on July 29, of last year, an editorial dealt at some length on the subject of “Chlorate of potassium as an explosive.” It was chiefly devoted to showing that an explosion which took place on May 12, 1899, at St. Helens. Lancashire, England, was not the result of the “ignition of a mixture of gas produced by the action of a high temperature upon the chlorate of potash, with atmospheric air,” as the London Fireman had it, but of frictionthe—high temperature which the British Government’s chief inspector of explosives blames having nothing to do with it. Since that article was written, the official report of the Government inspector—Col. Ford, C. B., of the Royal Engineers—lias been published. In this report is displayed the minimum of knowledge und the maximum of ignorance on the subject of the explosivein question.
The writer intimates that tlie explosion at St Helens was the first ever known to have occurred—presumably the English expert means the first ever known to have occurred in England on such a large scale. Smaller quantities (as lie ought to have known) have repeatedly been exploded in the ordinary compounding of prescriptions either by percussion,such as striking a sharp blow with a pestle, or by simply triturating them energetically. This lias taken place when the chlorate was handled alone, and also when it was being mixed with other substances, particularly such ns are easily oxidized—viz., organic bodies or inorganic bodies, such, for instance, as sulphur, antimony oxide, and the like. But, according to Col. Ford, it is only when mixed with substances such as these, that potassium chlorate will explode— unless it is subjected to high temperature. Readers of FIRE AND WATER will remember that an explosion of this sort took place last year, on the lower West Side of Manhattan. A mixture of potassium-chlorate and sodium-salicylate was being triturated, when suddenly an explosion occurred, causing considerable injury to the compounder, but not much damage from fire, because tlie quantity of material used was small.
The British inspector holds that all danger of explosives would have been avoided, if the potassiumchlorate had been stored in fireproof containers. Had that been done, the danger from fire following tlie explosion would certainly have been lessened, but that of further explosion from the kegs being jarred by the concussion, would certainly not have been removed. This danger was strongly in evidence. According to the London Fireman’s account of the fire, pubished at the time, the kegs, which were of wood and held fivehundred weight apiece of the stuff, were piled up in pyramidal form to a height of fifteen feet, one on top of the other. This pile, as l)r. Best, an expert chemist and manager of an adjoining chemical works states, collapsed under the influence of the flames. In collapsing, some of the kegs, at least, must have fallen down and struck against either the ground or each other. It is, therefore, well within the range of possibility that such concussion, without heat, except that caused by the impact, would produce an explosion, which again would have a similar effect upon the others—and so quickly as in the confusion and excitement of the moment to appear as one heavy detonation—and this nil the more probably, on account of the large amount of potassium-chlorate contained in each keg.
It was also stated that a proximate, if not the direct cause of the explosion was the complete saturation of the empty kegs and the wooden-bottomed coolers with the salt, into one of which, it is claimed, a single spark, “created by tlie friction of two casks.” fell, producing a fierce flame, which caused the chlorate to give off gas in great quantity, and when this gas was mixed with atmospheric air in a suitable proportion, tlie explosion was inevitable.
Of course, anything saturated with this salt will burn fiercely, particularly wooden vessels or tanks, or casks still containing quantities of it adhering to sides and bottom. So far, therefore, that part of tlie statement is correct, as is likewise that which says the “coolersburned with great intensity and gave off gas in great quantity ” Not so, however, tlie remainder of that statement—viz., that when the gas so given off was “mixed with atmospheric air in a suitable proportion,” it produced the “inevitable explosion.”
This theory is certainly open to criticism os follows: When chlorate of potassium is subjected to a certain temperature it is decomposed as under: 2 KCLO3/ heat = 2 KCL + 302 (potassium chlorate -theat – – potassium chlorate + oxygen—the gas given off being oxygen). Now this oxygen does not burn at all; it is si in ply a supporter of combustion. If oxygen did burn, why then that in the atmosphere would certainly be burning all the time, A mixture of air and oxygen cannot be exploded any more than atmospheric air itself can be. As oxygen gas is given off in such large quantities during the decomposition of potassium chlorate, and as it is a good supporter of combustion, it will readily be seen that a fire would make very much more rapid progress in an atmosphere consisting of oxygen than it wouid in an atmosphere of air which contains only about one-tifth of oxygen. That is the reason why such fires make very rapid progress. Theoretically, to cause an explosion some organic material would have to be present. In the case of the fire and explosion referred to, this would be represented by the casks (wood) themselves. It can also be assumed, judging from the quantity of the stuff in question, that it was the ordinary commercial kind, always more or less impure—-viz., mixed with bits of wood, paper, and other organic materials. If this were tlie case, an explosion could very readily have taken place.
M. D. COL. FORD’S REPORT.
Col. Ford in his report states that potassiumchlorate is not itself an explosive within the meaning of tlie Explosives act, having the property of detonating when mixed with sulphur or sulphide of antimony, and being thus externally used in detonating compositions which are explosives of a very sensitive character.
Had the colonel stated that potassium-chiorate, when uot subjected to trituration or friction in any shape, or to percussion, would not detonate, and so become an “explosive within the meaning of tlie British Explosives act,” his statement could have passed unscrutinized. Had he further added that it would he well to include that chemical under those explosives covered by the act, he would have made a sensible suggestion. But he did not. Hence he has laid himself open uot only to criticism, but to the charge eith r of negligence or ignorance.
Before lie made his report he visited the scene of the explosion, where no very probable explanation of the occurrence appeared to present itself, and a searching inquiry into tlie circumstances was thus rendered necessary. Evidence of experiments to detonate the chlorate was given, and iu view of the result it cannot lie doubted that an explosion of a small portion of the chlorate actually took place at St. Helens. This portion was doubtless raised very rapidly to the required temperature by the intense heat caused by tlie burning of tlie kegs in contact with other portions of the chlorate. Potassium-chlorate (he adds), if decomposed suddenly, will evolve at the temperature of decomposition about the same amount of gas as an equal weight of gunpowder. Comparing, therefore, the effects produced at St. Helens with those produced by an explosion of gunpowder, we find that similar effects might have been expected from an explosion of about five or six tons of gunpowder. In all probability, therefore, only about five to six tons of the chlorate exploded, a very small proportion of the 156 tons originally contained in the store. Tlie remainder was either decomposed or melted by the heat, or scattered in all directions by tlie explosion.
The question which arises is. whether potassiumchlorate, which lias now been found liable to explode under certain conditions, should be treated its an explosive within the meaning of the Explosives act, 1875. This is a question, however, which demands the fullest and most careful consideration, alike in the interests of the trade and of the public, and it is unnecessary for me to discuss it in this report. The
precautions additional to those already in force which should be adopted for the future in factories in which potassium-chlorate is made and stored are sufficiently indicated by the particulars of the present fire and subsequent explosion. It is obvious that, if, first, tlie kegs, secondly, the orystalizing tanks, and, lastly, the buildings had been of uninflammable materials this disaster could not have happened. All inflammable materials, therefore, as well as those liable toform an explosive mixture with the chlorate, should be rigidly excluded from the packages containing the chlorate and the tanks and buildings in which this portion of the manufacture is carried on. If the non-flammability of the kegs and the buildings in which the chlorate is stored is assured, it is unnecessary, in my opinion, to limit the amount of the chlorate to be kept, or to require that it be kept in an isolated building. [Ei FIRE AND WATER.