Aprtlis, 1875J 



NATURE 



^11 



f ACCIDENTAL EXPLOSIONS * 



II. 

 'TTHERE is no doubt whatever that a veiy considerable propor- 

 -*- lion of the accidents which occur to persons using petroleum 

 lamps are really traceable to the erroneous behef, which is still 

 so very prevalent, in the exploske character of these liquids. 

 The fact that they and their vapours are simply inflammable, 

 and that the latter requires to be mixed with a large volume of 

 air before their ignition can be accompanied by explosive effects, 

 is so slowly reahsed, that in public prints petroleum is still often 

 spoken of as an explosive substance. The popular belief in the 

 explosiveness of these simply inflammable liquids contrasts 

 strangely with the fact that many explosions have been brought 

 about by the careless employment of candles or other naked 

 flames in premises where the volatile varieties have been stored, 

 or where the operation of transferring the hquid from one vessel 

 to another for purposes of sale is carried on, the result being the 

 ignition of the explosive m^Xnre frodiiccd by the volatilisation of 

 the spir t and its diffusion through the air. This fact does indeed 

 tend to discourage the hope that the proportion of accidental 

 explosions of gii iifo~d'dt-y which are apparently due to ignorance 

 may become very greatly diminished by keeping its explosive 

 properties before the minds of those using it. 



The lecturer then referred tothe legislative restrictions in connec- 

 tion with the transfer, storage, and sale of petroleum and petroleum 

 oils. The danger arising more especially from the transport and 

 storage of inipcrfcitly refined oils under designations which apply 

 to the properly refined and therefore safe petroleum- or coal-oils, 

 which do not demand special precautions for their safe storage 

 and use, and are consequently not subject to any restrictive or 

 precautionary regulations, renders the application of the existing 

 legal regulations to the inspection of petrojeum-c//.f imported into 

 England of special importance. Referring to the io-cAXtA flashing- 

 test described in the Act of Parliament, Prof. Abel thinks it un- 

 doubtedly desirable, in the framing of any future Act, that this 

 test should be carefully reconsidered, as well as the question 

 whether some narrow limit below 100° F. may not reasonably, 

 and without incurring any increased risk, be fixed within which 

 the flashing point of an oil [i.e. the temperature at which it 

 evolves vapour) may range.t 



The liability of oil or spirit to leak from casks or barrels even 

 of the best construction, consequent upon the rough usage to which 

 these are un.ivoidably subjected when transferred from store to 

 ship or carriage, and the reverse, need scarcely be pointed out. But 

 even in the absence of leakage from the openings of the barrels, 

 or from any accidental point of escape, evaporation or diffusion 

 of the volatile petroleum will occur through the wood itself of 

 which they are constructed, especially in the warm holds of ships 

 or in stores exposed to the sun, even though the precautionary 

 mea.sure is frequently adopted of rinsing the barrel out before 

 use with a solution of glue. It is evident that the object of im- 

 parting an impervious coating to the interior of the barrel can 

 thus be only very imperfectly attained, and that, even if it were, 

 the alternations of temperature to which the barrels must be 

 exposed must in course of time open up places for escape by 

 leakage or evaporation. 



The dangers resulting from the escape cf petroleum spirit or 

 its vapour from receptacles in vs hich it is kept, in confined spaces, 

 where little or no ventilation exists, has been but too frequently 

 exemplified by explosions more or less violent, followed by fires 

 in localities where it is stored or handled, or in the holds of 

 vessels in which it is transported. Accidents of such kinds have 

 been due either to carelessness in transferring petroleum from 

 one vessel to another, in a shop or store in which a light has 

 been burning at the time, or to a light being carried into or a 

 match struck in a store where vapour has been escaping until it 

 has formed an explosive mixture with the air. The lecturer had 

 a vivid recollection of an accident of this kind which he witnessed 

 at the Royal College of Chemistry in 1847. Mr. C. B. Mans- 

 field, who was then engaged in his important researches on the 

 composition of coal-tar naphtha, which led a few years after\vards 

 to his sad untimely death, was engaged at one extremity of a low 



* Abstract of a lecture delivered at the Royal lostitution, March 12, 

 by Prof. F. A. Abel, F.R.S. Continued from p. 439. 



t .^s the law ^at present stands, an oil, the flashing-point of which is 

 declared to be 99° by the official inspector, must be condemned ; but another 

 operator may make the flashing-point of the same oil to be slightly above 

 ico". Practically, an oil with a flashing-point of 97* or 98' would be quite as 

 safe as one which answers to the test at 100°, in the hands of the same 

 operator 



room (38 feet long, about 30 feet wide, and lo feet high) in 

 converrting one of the most important of these products — ben- 

 zol— (which boils at 176° F.) into nitrobenzol in a capacious 

 retort, which suddenly cracked, and, yielding to the pressure of 

 its contents, allowed the warm liquid hydro-carbon to flow over 

 the operating table. There was a gas-flame burning at the other 

 extremity of the laboratory, and no other source of fire. Within 

 a very few minutes after the fracture of the vessel a sheet of flume 

 flashed from the gas-flame along the upper part of the room and 

 communicated to the table upon which the liquid had been 

 spilled. 



Among other "accidents" referred to'as arising from a similar 

 cause, was the recent explosion of the powder-laden barge in the 

 Regent's Canal. It was established by a sound chain of circum- 

 stantial evidence that this explosion must have been caused by 

 the ignition, in the cabin of the barge, of an explosive mixture of 

 air and of the vapour of petroleum, derived from the leakage of 

 certain packages of the spirit which were packed along with the 

 powder. 



It is impossible to protect heavy packages from rough usage, 

 in the processes of unloading ships or other vehicles ot convey- 

 ance ; it is therefore most important that means should be adopted 

 of thoroughly closing the vents of receptacles of petroleum-spirit 

 by such means as are capable of sustaining ordinary rough usage 

 without any injury to their efficiency, and that the improvement 

 of the nature and construction of the receptacles themselves be 

 seriously considered with the view of reducing the hability to 

 accidents resulting from the escape of the spirit or its vapours, 

 and the consequent creation of danger connected with the 

 transpoit and storage of these valuable illuminating materials. 



The fact that combustible, and especially inflammable, solid 

 substances, if of sufficiently low specific gravity, and reduced to 

 a sufficiently fine state of division to allow of their becoming and 

 remaining for a time suspended in air, may furnish mixtures with 

 the latter which partake of explosive character, scarcely needs to 

 be pointed out. The ignition of a particle of such a substance, 

 surrounded by atmospheric oxygen, will, under these conditions, 

 at once communicate to others immediately adjacent to it, and 

 if the particles of suspended solid matter be sufficiently nume- 

 rous and finely divided, the ignition will spread throughout the 

 mixture with a rapidity approaching that of a mixture of inflam- 

 mable vapour and air, the development of gaseous products and 

 heat being sufficiently rapid and considerable to produce explosive 

 effects, which may even be of violent character, their violence 

 being regulated by the nature and '.inflammability of the solid 

 substance, the proportion and state of division in which it is dis- 

 tributed through the air, the quantity of the mixture, and the 

 extent of its confinement. 



Explosions of an accidental nature produced in this way are 

 believed to have occurred in connection with operations in the 

 chemical laboratory ; but it was scarcely to be expected that the 

 first clearly authenticated cases of any importance should have 

 arisen out of the apparently harmless operation of grinding com. 



That a mixture of very fine flour and air will ignite with a flash 

 when light is applied to it, and produce in a very mild form the 

 species of explosion observed on applying a hght to licopodium 

 suspended in air, is not very difficult of demonstration, but it is 

 not easy to realise the possibility of the production of violent 

 explosive effects by the ignition of such a mixture even upon a 

 very large scale, though the rapidity of its ignition be acci- 

 dentally favoured by the warmth of the atmosphere. Cotton 

 mills have been known to be rapidly fired by the ignition of 

 cotton particles suspended in the air ; but, compared with flour, 

 cotton is very combustible. Flour when absolutely dry would 

 contain only about half its weight of carbon, and about six per 

 cent, of hydrogen, the remainder consisting of nitrogen and 

 mineral substances ; constituents which, by absorbing heat in- 

 stead of contributing to its development, must tend to reduce 

 the rapid combustibility of the substance. Yet the possibility of 

 very serious calamities arising out of the accidental ignition of a 

 mixture of flour- dust and air has been but too conclusively 

 demonstrated. 



Referring to a destructive explosion in some extensive steam 

 flour-mills in Glasgow in July 1S72, the lecturer said that its 

 origin was conclusively traced to the striking of fire by a pair of 

 millstones, through the stopping of the "feed," or supply of 

 grain to them, and the consequent friction of their bare surfaces 

 against each other, the result being the ignition of the mixture 

 of air and fine flour-dust surrounding the mill-stones. 



This ignition alone would not suffice to develop any violent 



