224 SIR ANDREW NOBLE: RESEARCHES ON EXPLOSIVES. 



If the figures given in these tables be carefully examined, it will be observed that 

 in the three explosives the transformation on firing appears in all to follow the 

 same general laws. 



Thus in all three there is, with increase of pressure, at first a slight increase, 

 afterwards a steady decrease in the volume of permanent gases produced. 



This increase in the total gases is much less marked with cordite, and in the case 

 of M.D. and nitrocellulose there is practically a steady decrease in the volume of 

 the total gases. 



In all three explosives there is, with increased pressure, a large increase in the 

 volume of carbonic anhydride and a large decrease in the volume of carbonic 

 monoxide. 



In the case of hydrogen, this decrease of volume with increase of pressure is very 

 great, while with methane, the percentage which with low pressures is quite 

 insignificant, very rapidly increases and at the highest density is from twenty to 

 thirty times greater than the lowest density. 



There are some variations in the percentages of nitrogen and H 2 O, but on the 

 whole these constituents may be considered to be nearly constant. 



The units of heat with a slight decline at first afterwards increase and somewhat 

 rapidly at the highest pressures. 



But the changes which take place under different pressures are more readily 

 appreciated if the observations are graphically recorded by means of curves. 



Accordingly in Plate 5 I have given for three explosives the pressures in tons per 

 sq. inch and in atmospheres, deduced from the experiments under consideration, 

 and which pressures vary from about 3 tons per sq. inch (457 atmospheres) to (in 

 the case of Mark I cordite) 53 tons per sq. inch (8078 atmospheres). 



It will be observed also that from densities of about 0'25 upwards the curve 

 expressing the relation of pressure to density, both in the Mark I cordite and in the 

 M.D., differs inappreciably from a straight line. This remark also appears to be, in 

 some degree, corroborated by an experiment I once made at a density of unity, and 

 which gave a pressure of about 112* tons per sq. inch (17,070 atmospheres). 



With nitrocellulose there appears, at high densities, to be a tendency to detonate, 

 from which tendency Mark I cordite appears to be free. By way of showing the 

 enormous superiority of the new explosives as regards potential energy, I have added 

 to Plate 5 the curve showing the relation of pressure to density of fired gunpowder. 



In Plate 6 there are three sets of curves : (l) The changes in the volumes of the 

 permanent gases due to increase of density ; (2) The changes in the volumes of the 

 total gases which do not differ very greatly from those of the permanent gases ; and 

 (3) The changes in the units of heat at different densities (water fluid). 



It may be noted that, while at pressures under 20 tons per sq. inch the heat 



* On the occasion referred to, I was not sure that the pressure might not be higher, as there was 

 considerable friction between the piston and the cylinder, due to compression of the gauge. 



