lyo'.t] on Guncotton and Nitroglycerine. 443 



turt' was deduced. This factor having been determined, what is 

 known as the " silvered vessel test " was worked out at the Royal 

 Gunpowder Factory. In this test, of which the details will be 

 described presently, cordite is heated in a specially designed vessel at 

 80^ C, a temperature not too far removed from those to be met with 

 when cordite is stored under the worst service conditions, and the 

 number of hours heating at this temperature any given sample will 

 stand before it shows signs of active decomposition are ascertained. 

 Then, by means of an equation, containing the factor connecting rate 

 of increase of deterioration with rise in temperature, a calculation 

 can be made converting the hours of heating at 80° C. the sample 

 withstood, to years and fractions of a year it would stand at any given 

 temperature of storage, and therefore a knowledge is obtained of how 

 much longer it would be safe to store this cordite at any given tem- 

 perature. 



This test was applied to a considerable number of samples of 

 known age and thermal history. From these data and knowing the 

 number of hours at 80° C. that newly made cordite of good stability 

 will stand before showing signs of decomposition, the number of 

 hours that the different samples should stand the test were calculated. 

 When the samples were actually tested, the number of hours heating 

 at 80° C. they withstood, were in close agreement with the number of 

 hours it was calculated they should stand. 



The form of vessel in which the heating is carried out is the 

 well-known vacuum vessel of Sir James Dewar. A glass bulb silvered 

 externally, is enclosed in an outer bulb, silvered internally. The 

 space between the two is highly evacuated for the purpose of limiting 

 the dissipation of any heat evolved by exothermic changes on the 

 one hand, and on the other for the purpose of minimising the effect 

 of accidental slight changes in temperature of environment. 



In the centre of the inner bulb is situated the bulb of a thermo- 

 meter, the stem of which passes through a cork in the neck of the 

 vessel. A side tube is attached for the purpose of making observa- 

 tions on the colour of the gases evolved. For heating the vessel, a 

 bath is provided, with cylinders closed at the bottom, and wide 

 enough to admit the vessel to such a depth as the side tube will 

 permit. The bath is surrounded by insulating materials. The 

 vessels are packed in the cylinders with wool yarn, and the tops of 

 the cylinders are closed with felt discs, to exclude draughts. 



The bath is fitted with a gas regulator or other means for securing 

 that the temperature of the explosive is kept constant. 



The cordite is coarsely ground, and 50 grammes are used. 



Readings of the thermometer are taken at intervals, and the time 

 is noted when a rise of 2° C. in the temperature of the explosive 

 above the temperature of 80° C. occurs. At the same time, visual ob- 

 servations are made as to the colour of the column of gas in the side^ 

 tube, since it is found that previous to the rise in temperature occur-' 



