1881.] Existence of Ice and other Bodies in the Solid State. 289 



the cooler parts of the tube, whilst the unvolatilised portion of the salt 

 shrank away from the sides of the tube and clung tenaciously in the 

 form of a solid mass to the bulb of the thermometer, which rose con- 

 siderably above 300° 0., the mercury of the thermometer shooting up 

 to the top of the stem. After slight cooling the air was let in, and 

 under the increased pressure thus produced the salt attached to the 

 bulb of the thermometer at once melted and began to boil, cracking 

 the tube at the same time. 



The experiment was next varied as follows : — 



About the same quantity of chloride was placed in the tube A, fig. 3, 

 as before, and heated by the full flame of a Bunsen's burner. The lamp 

 was applied during the whole of this experiment, and the size of the 

 flame kept constant throughout. The mercuric chloride first liquefied 

 and then boiled at 303° under ordinary pressure, and whilst the salt 

 was still boiling the pressure was gradually reduced to 420 millims., 

 when the boiling point slowly fell to 275°, at which point the mercuric 

 chloride suddenly began to solidify, and at 270° was completely solid, 

 the pressure then being 376 millims. When solidification was complete 

 the pump was stopped working, but the heat still continued to the 

 same extent as before. The salt then rose rapidly to temperatures 

 above that at which a thermometer could be used, but not the least 

 sign of fusion was observed. From the completion of the solidification 

 to the end of the experiment the pressure remained at about 350 

 millims. 



The above experiment, which was repeated three times, shows, 

 therefore, that when the pressure is gradually reducsd from the 

 ordinary pressure of the atmosphere to 420 millims., and the boiling 

 point simultaneously from 303° to 275°, the salt solidifies while it is 

 still boiling and in contact with its own hot liquid, notwithstanding 

 that it is being strongly heated at the same time ; and that, after 

 solidification is complete at 270°, the temperature then rises far above 

 the ordinary boiling point (303°) of the substance without producing 

 any signs of fusion. Under ordinary circumstances, mercuric chloride 

 melts at 288° and re-solidifies at 270 — 275°, i.e., at a temperature 

 identical with that at which it solidifies under diminished pressure, as- 

 above described. 



The solid mercuric chloride obtained on solidification under the 

 combined influence of diminished pressure, and the application of a 

 strong heat had a peculiar appearance, quite different to that pro- 

 duced when the substance is allowed to solidify in the ordinary way. 

 It appeared to consist of a mass of pearly leaflets closely packed 

 together round the bulb of the thermometer. 



Any final explanation of these phenomena is reserved until further 

 experiments have been made. 



