﻿106 Messrs. H. T. Tizard and D. R. Pye on the 



o£ carbon with oxygen. The exact conditions when this 

 occurs seems well worthy o£ further investigation. 



It is always necessary to clean out the cylinder carefully 

 after such a deposit has been formed, and before the next 

 experiment is made ; for, if not, abnormal results will be 

 obtained, and the " delay " before ignition occurs will be 

 very much shorter than is expected. To explain this it 

 does not appear to be necessary to attribute any special 

 " catalytic " activity to the carbon ; a simple physical ex- 

 planation seems to be sufficient. Such a deposit is known 

 to be a very bad conductor of heat. If left on the walls of 

 the piston and cylinder, we shall therefore have, on the next 

 compression, large portions of gas from which the heat 

 cannot get away quickly. Hence the ignition temperature 

 is lowered, and the explosion takes place more rapidly. 



XIII. Experiments on the self- ignition of mixtures of the 

 vapour of ethyl ether C 2 H 5 .O.C 2 H 5 gave very similar 

 results. The results of the experiments on the compression 

 of non-turbulent mixtures are shown in Table VIII. ; while 



Tuble VIII. 

 Ignition of mixtures of ether and air. Fan stationary. 

 Initial pressure (atmospheric) =I4'77 lb./sq. in. 

 Mean apparent value of "7" = 1*309. 

 Strength of mixture = 1 part ether to 15 of air by weight. 



No. of 



Compn. 



Initial 



Max. Compn. 



Max. temp. 



Delay 



Cooling 



expt. 



ratio. 



temp. 



pressure. 



7 = 1-309. 



obs. 



-a, 



Oi 



451 



25° C. 



105 lb./sq. in. 



201° C. 



No. ign. 



0-47 



c 2 



4-83 



24 



116 



211 



,, 



0-47 



°3 



502 



23 



121-5 „ 



214 



041 



— 



O! 



5-21 



23 



128 „ 



220 



030 



— 



C 5 



5-42 



23 



135 - 5 ,, 



226 



0-205 



— 



C 6 



5-63 



23 



143 



232 



012 



. — 



c~ 



5-82 



23 



149 



237 



0093 



— 



Cs 



6-03 



23 



155 



242-5 



0071 



— 



c 9 



0-56 



23 



172 



256 



035 



— 



Table X. shows the results when the fan was rotating at 

 full speed. No ignition was observed in experiments Qi 

 and C 2 in the first series, and in experiments D l5 D 2 , and D 7 

 in the second series. The details of the calculation of the 

 cooling factor corresponding to experiment C 2 are shown in 

 Table IX. The cooling curve was not so regular in the case 

 of Cj, but the mean value of the constant was the same, 



