MINING 383 



Taffanel, which form the subject of several reports. An experimental mine has now 

 been secured by the French Government at Commentry. In the United States, in 

 addition to the existing installation at Pittsburg, a drift at Bruceton, Pa., has been 

 equipped for experimental purposes, under the charge of the Bureau of Mines. It re- 

 mains to mention the gallery erected in 1908 at Babitz, near Segengottes, by the Vienna 

 Permanent Firedamp Committee, and the Frameries testing station of the Belgian Co- 

 mite de Grisou, since transferred to the neighbourhood of Charleroi, at which some im- 

 portant results have been achieved by Victor Watteyne and his collaborators. 



In the first instance the experiments at the large galleries were principally devoted to 

 demonstrating the inflammability and explosibility of mixtures of coal dust with air and 

 to testing the adequacy of certain suggested remedies such as water , deliquescent sub- 

 stances, and inert dust, and the arrangement of the same in zones, barriers, collapsible 

 troughs, etc. The possibility of producing a coal dust explosion in the absence of fire- 

 damp may be said to have been firmly established in IQIO. Latterly research has been 

 principally devoted to establishing the conditions that promote or hinder the full de- 

 velopment of explosions, as well as ascertaining their real nature. Amongst the points 

 considered have been the velocity, pressure, and temperature of explosion waves, the 

 relative inflammability of various dusts and their behaviour under certain conditions. 



One of the results of the British experiments has been to show conclusively that the 

 relative ignition temperatures of a series of coal dusts have no fixed relationship to the 

 percentage of volatile matter as usually determined. In determining the chemical con- 

 stitution of coal, the chemist has hitherto relied upon two different modes of procedure, 

 viz: (i) the action of solvents, and (2) fractional distillation. The method of fractional 

 distillation, as recently applied by Burgess and Wheeler, has afforded valuable results 

 which have led those authors to a definite conclusion as to the nature of coal. They 

 maintain that all coals contain at least two different types of compounds of different 

 degrees of ease of decomposition. They regard coal as a conglomerate consisting of 

 cellulose degradation products embedded in a cement of altered resins and gums. It is, 

 in their view, the latter which first distils by heat, yielding mainly the paraffin hydro- 

 carbons. The cellulose products are decomposed later, and, at a higher temperature, 

 yield proportionally large quantities of hydrogen. In the second Eskmeals report 

 strong evidence is adduced to show that the paraffin-yielding constituents are identical 

 with Bedson's pyridine extract, for it is proved that in the series investigated there is a 

 marked, although not rigid, relation between the ignition temperature of coal dusts and 

 the percentage that can be extracted by pyridine. Taffanel, Floch and Durr, describing 

 certain investigations undertaken at Lievin upon the oxidation and distillation of coal 

 dusts, found that at 700 degrees all the ethylene and four-fifths of the methane had al- 

 ready been expelled. These gases are also those which possess the greater heat of 

 combustion, that for ethylene being given by Taffanel as 341 calories, methane 213, 

 hydrogen 58, and carbon 68. It is interesting also to note that these same gases which 

 are most readily distilled from coal dust have the lowest " limit " value for inflammabili- 

 ty in air. As in other distillations the produits de teie differ markedly from the produits 

 de queue, and the danger of coal dust is vastly enhanced by the fact that the early 

 distillates are the more readily inflammable. 



The present feeling is that in stone dust lies the principal hope of a remedy. W. E. 

 Garforth, in delivering his presidential address before the Institution of Mining Engi- 

 neers on June 6, 1912, expressed the opinion that the dangers of explosion of coal dust 

 from electrical causes could be completely counteracted by the vigorous application of 

 this remedy. Investigations have shown that suitable diluents exist which satisfy the 

 considerations of health, efficiency and economy. At Altofts the cost of stone-dusting 

 was -^d. per ton raised. 



At the Clarence colliery, where an explosion occurred on September 3, 1912, the collap- 

 sible arrets-barrages (arresting barriers), proposed by Taffanel, failed to arrest the course of 

 the explosion, in the one instance in which they have been put to a test under actual work- 

 ing conditions. This failure however may have been due to the improper application of the 

 barriers, to the presence of firedamp, or to the exceptional slowness of the explosion. 



