Stubb!;^. — Coud iictivit ij of A>/i/P()iis Sohif/niis of Ciirhoii-dioxidc . 23 

 (c.) The temperature was now raised again. 



The conductivity increased regularly with the temperature up to about 

 5|°, when a remarkable variation made itself manifest. The conductivity 

 first went down, and then suddenly rose, to the extent of over 2 cm. in the 

 bridge-reading. This was repeated several times, the fluctuations gradu- 

 ally diminishing, the conductivity eventually assuming a constant value, 

 much higher than would have been assumed if following the same law of 

 variation as from 0° to 5°. This is shown in a graph by a vertical line 

 at 5|°. (During the fluctuations referred to the somid in the telephone 

 was most interesting ; the decrease in bridge-reading was fairly slow and 

 uniform, but the increase was mstantaneous, the telephone suddenly sound- 

 ing a very loud note, and requiring the sliding contact to be moved a good 

 deal higher before again being quiet.) 



During the decomposition of the hydrate the indicated gauge-pressure 

 rose by half an atmosphere. This is explained by the fact that the hydrate 

 was formed at a higher pressure (25 atmospheres), and when it decomposed 

 would yield an excess of COg. 



From 5J° to 8° the conductivity continued to increase much in the same 

 way as before, but then a break occurred, the conductivity thereafter in- 

 creasing considerably more slowly with the temperature. 



In lowering the temperature from 11° to 0° the conductivity obeyed 

 the latter law of variation. It was therefore assumed that the solution 

 remained as such, no change to hydrate form, with the corresponding pheno- 

 mena, having taken place. 



At (6), about 0°, the conductivity suddenly began to fall at an abnormal 

 rate, eventually assuming the value given for 0°. This was taken to indi- 

 cate that the formation of the hydrate had taken place. 



The remaining part of the experiment (from c) was conducted several 

 hours later. The pressure was in the meantime 20| atmospheres, not 

 having been relieved after the evolution of the excess of CO2. This will 

 doubtless explain why the conductivity from 5|° to 8° was in this case 

 slightly greater than in the former part of the experiment. 



It was found here that there was no definite and sudden rise of con- 

 ductivity, as there had been before. The graph of the conductivity is a 

 continuous curve, almost a straight line, merging at 8° into the ordinary 

 solution conductivity graph. Thus it seems that the abrupt change is 

 characteristic only of those conditions under which a kind of stress exists 

 in the hydrate, owing to its having been formed at a higher pressure than 

 exists when it is about to decompose. 



F. Temperature lowered to 0° ; and, after bridge-reading had indi- 

 cated formation of hydrate, pressure lowered to 15 atmospheres. Thus 

 there would be in existence at 15 atmospheres a hydrate formed at 



